include/uv.h

/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

/* See https://github.com/joyent/libuv#documentation for documentation. */

#ifndef UV_H
#define UV_H
#ifdef __cplusplus
extern "C" {
#endif

#ifdef _WIN32
  /* Windows - set up dll import/export decorators. */
# if defined(BUILDING_UV_SHARED)
    /* Building shared library. */
#   define UV_EXTERN __declspec(dllexport)
# elif defined(USING_UV_SHARED)
    /* Using shared library. */
#   define UV_EXTERN __declspec(dllimport)
# else
    /* Building static library. */
#   define UV_EXTERN /* nothing */
# endif
#elif __GNUC__ >= 4
# define UV_EXTERN __attribute__((visibility("default")))
#else
# define UV_EXTERN /* nothing */
#endif

#include "uv-errno.h"
#include "uv-version.h"
#include <stddef.h>

#if defined(_MSC_VER) && _MSC_VER < 1600
# include "stdint-msvc2008.h"
#else
# include <stdint.h>
#endif

#if defined(_WIN32)
# include "uv-win.h"
#else
# include "uv-unix.h"
#endif

/* Expand this list if necessary. */
#define UV_ERRNO_MAP(XX)                                                      \
  XX(E2BIG, "argument list too long")                                         \
  XX(EACCES, "permission denied")                                             \
  XX(EADDRINUSE, "address already in use")                                    \
  XX(EADDRNOTAVAIL, "address not available")                                  \
  XX(EAFNOSUPPORT, "address family not supported")                            \
  XX(EAGAIN, "resource temporarily unavailable")                              \
  XX(EAI_ADDRFAMILY, "address family not supported")                          \
  XX(EAI_AGAIN, "temporary failure")                                          \
  XX(EAI_BADFLAGS, "bad ai_flags value")                                      \
  XX(EAI_BADHINTS, "invalid value for hints")                                 \
  XX(EAI_CANCELED, "request canceled")                                        \
  XX(EAI_FAIL, "permanent failure")                                           \
  XX(EAI_FAMILY, "ai_family not supported")                                   \
  XX(EAI_MEMORY, "out of memory")                                             \
  XX(EAI_NODATA, "no address")                                                \
  XX(EAI_NONAME, "unknown node or service")                                   \
  XX(EAI_OVERFLOW, "argument buffer overflow")                                \
  XX(EAI_PROTOCOL, "resolved protocol is unknown")                            \
  XX(EAI_SERVICE, "service not available for socket type")                    \
  XX(EAI_SOCKTYPE, "socket type not supported")                               \
  XX(EALREADY, "connection already in progress")                              \
  XX(EBADF, "bad file descriptor")                                            \
  XX(EBUSY, "resource busy or locked")                                        \
  XX(ECANCELED, "operation canceled")                                         \
  XX(ECHARSET, "invalid Unicode character")                                   \
  XX(ECONNABORTED, "software caused connection abort")                        \
  XX(ECONNREFUSED, "connection refused")                                      \
  XX(ECONNRESET, "connection reset by peer")                                  \
  XX(EDESTADDRREQ, "destination address required")                            \
  XX(EEXIST, "file already exists")                                           \
  XX(EFAULT, "bad address in system call argument")                           \
  XX(EFBIG, "file too large")                                                 \
  XX(EHOSTUNREACH, "host is unreachable")                                     \
  XX(EINTR, "interrupted system call")                                        \
  XX(EINVAL, "invalid argument")                                              \
  XX(EIO, "i/o error")                                                        \
  XX(EISCONN, "socket is already connected")                                  \
  XX(EISDIR, "illegal operation on a directory")                              \
  XX(ELOOP, "too many symbolic links encountered")                            \
  XX(EMFILE, "too many open files")                                           \
  XX(EMSGSIZE, "message too long")                                            \
  XX(ENAMETOOLONG, "name too long")                                           \
  XX(ENETDOWN, "network is down")                                             \
  XX(ENETUNREACH, "network is unreachable")                                   \
  XX(ENFILE, "file table overflow")                                           \
  XX(ENOBUFS, "no buffer space available")                                    \
  XX(ENODEV, "no such device")                                                \
  XX(ENOENT, "no such file or directory")                                     \
  XX(ENOMEM, "not enough memory")                                             \
  XX(ENONET, "machine is not on the network")                                 \
  XX(ENOPROTOOPT, "protocol not available")                                   \
  XX(ENOSPC, "no space left on device")                                       \
  XX(ENOSYS, "function not implemented")                                      \
  XX(ENOTCONN, "socket is not connected")                                     \
  XX(ENOTDIR, "not a directory")                                              \
  XX(ENOTEMPTY, "directory not empty")                                        \
  XX(ENOTSOCK, "socket operation on non-socket")                              \
  XX(ENOTSUP, "operation not supported on socket")                            \
  XX(EPERM, "operation not permitted")                                        \
  XX(EPIPE, "broken pipe")                                                    \
  XX(EPROTO, "protocol error")                                                \
  XX(EPROTONOSUPPORT, "protocol not supported")                               \
  XX(EPROTOTYPE, "protocol wrong type for socket")                            \
  XX(ERANGE, "result too large")                                              \
  XX(EROFS, "read-only file system")                                          \
  XX(ESHUTDOWN, "cannot send after transport endpoint shutdown")              \
  XX(ESPIPE, "invalid seek")                                                  \
  XX(ESRCH, "no such process")                                                \
  XX(ETIMEDOUT, "connection timed out")                                       \
  XX(ETXTBSY, "text file is busy")                                            \
  XX(EXDEV, "cross-device link not permitted")                                \
  XX(UNKNOWN, "unknown error")                                                \
  XX(EOF, "end of file")                                                      \
  XX(ENXIO, "no such device or address")                                      \
  XX(EMLINK, "too many links")                                                \

#define UV_HANDLE_TYPE_MAP(XX)                                                \
  XX(ASYNC, async)                                                            \
  XX(CHECK, check)                                                            \
  XX(FS_EVENT, fs_event)                                                      \
  XX(FS_POLL, fs_poll)                                                        \
  XX(HANDLE, handle)                                                          \
  XX(IDLE, idle)                                                              \
  XX(NAMED_PIPE, pipe)                                                        \
  XX(POLL, poll)                                                              \
  XX(PREPARE, prepare)                                                        \
  XX(PROCESS, process)                                                        \
  XX(STREAM, stream)                                                          \
  XX(TCP, tcp)                                                                \
  XX(TIMER, timer)                                                            \
  XX(TTY, tty)                                                                \
  XX(UDP, udp)                                                                \
  XX(SIGNAL, signal)                                                          \

#define UV_REQ_TYPE_MAP(XX)                                                   \
  XX(REQ, req)                                                                \
  XX(CONNECT, connect)                                                        \
  XX(WRITE, write)                                                            \
  XX(SHUTDOWN, shutdown)                                                      \
  XX(UDP_SEND, udp_send)                                                      \
  XX(FS, fs)                                                                  \
  XX(WORK, work)                                                              \
  XX(GETADDRINFO, getaddrinfo)                                                \
  XX(GETNAMEINFO, getnameinfo)                                                \

typedef enum {
#define XX(code, _) UV_ ## code = UV__ ## code,
  UV_ERRNO_MAP(XX)
#undef XX
  UV_ERRNO_MAX = UV__EOF - 1
} uv_errno_t;

typedef enum {
  UV_UNKNOWN_HANDLE = 0,
#define XX(uc, lc) UV_##uc,
  UV_HANDLE_TYPE_MAP(XX)
#undef XX
  UV_FILE,
  UV_HANDLE_TYPE_MAX
} uv_handle_type;

typedef enum {
  UV_UNKNOWN_REQ = 0,
#define XX(uc, lc) UV_##uc,
  UV_REQ_TYPE_MAP(XX)
#undef XX
  UV_REQ_TYPE_PRIVATE
  UV_REQ_TYPE_MAX
} uv_req_type;


/* Handle types. */
typedef struct uv_loop_s uv_loop_t;
typedef struct uv_handle_s uv_handle_t;
typedef struct uv_stream_s uv_stream_t;
typedef struct uv_tcp_s uv_tcp_t;
typedef struct uv_udp_s uv_udp_t;
typedef struct uv_pipe_s uv_pipe_t;
typedef struct uv_tty_s uv_tty_t;
typedef struct uv_poll_s uv_poll_t;
typedef struct uv_timer_s uv_timer_t;
typedef struct uv_prepare_s uv_prepare_t;
typedef struct uv_check_s uv_check_t;
typedef struct uv_idle_s uv_idle_t;
typedef struct uv_async_s uv_async_t;
typedef struct uv_process_s uv_process_t;
typedef struct uv_fs_event_s uv_fs_event_t;
typedef struct uv_fs_poll_s uv_fs_poll_t;
typedef struct uv_signal_s uv_signal_t;

/* Request types. */
typedef struct uv_req_s uv_req_t;
typedef struct uv_getaddrinfo_s uv_getaddrinfo_t;
typedef struct uv_getnameinfo_s uv_getnameinfo_t;
typedef struct uv_shutdown_s uv_shutdown_t;
typedef struct uv_write_s uv_write_t;
typedef struct uv_connect_s uv_connect_t;
typedef struct uv_udp_send_s uv_udp_send_t;
typedef struct uv_fs_s uv_fs_t;
typedef struct uv_work_s uv_work_t;

/* None of the above. */
typedef struct uv_cpu_info_s uv_cpu_info_t;
typedef struct uv_interface_address_s uv_interface_address_t;


typedef enum {
  UV_RUN_DEFAULT = 0,
  UV_RUN_ONCE,
  UV_RUN_NOWAIT
} uv_run_mode;


/*
 * Returns the libuv version packed into a single integer. 8 bits are used for
 * each component, with the patch number stored in the 8 least significant
 * bits. E.g. for libuv 1.2.3 this would return 0x010203.
 */
UV_EXTERN unsigned int uv_version(void);

/*
 * Returns the libuv version number as a string. For non-release versions
 * "-pre" is appended, so the version number could be "1.2.3-pre".
 */
UV_EXTERN const char* uv_version_string(void);


/*
 * All functions besides uv_run() are non-blocking.
 *
 * All callbacks in libuv are made asynchronously. That is they are never
 * made by the function that takes them as a parameter.
 */

/*
 * Returns the default loop.
 */
UV_EXTERN uv_loop_t* uv_default_loop(void);

/*
 * Initializes a uv_loop_t structure.
 */
UV_EXTERN int uv_loop_init(uv_loop_t* loop);

/*
 * Closes all internal loop resources.  This function must only be called once
 * the loop has finished it's execution or it will return UV_EBUSY.  After this
 * function returns the user shall free the memory allocated for the loop.
 */
UV_EXTERN int uv_loop_close(uv_loop_t* loop);

/*
 * Allocates and initializes a new loop.
 * NOTE: This function is DEPRECATED (to be removed after 0.12), users should
 * allocate the loop manually and use uv_loop_init instead.
 */
UV_EXTERN uv_loop_t* uv_loop_new(void);

/*
 * Cleans up a loop once it has finished executio and frees its memory.
 * NOTE: This function is DEPRECATED (to be removed after 0.12). Users should use
 * uv_loop_close and free the memory manually instead.
 */
UV_EXTERN void uv_loop_delete(uv_loop_t*);

/*
 * Returns size of the loop struct, useful for dynamic lookup with FFI
 */
UV_EXTERN size_t uv_loop_size(void);

/*
 * This function runs the event loop. It will act differently depending on the
 * specified mode:
 *  - UV_RUN_DEFAULT: Runs the event loop until the reference count drops to
 *    zero. Always returns zero.
 *  - UV_RUN_ONCE: Poll for new events once. Note that this function blocks if
 *    there are no pending events. Returns zero when done (no active handles
 *    or requests left), or non-zero if more events are expected (meaning you
 *    should run the event loop again sometime in the future).
 *  - UV_RUN_NOWAIT: Poll for new events once but don't block if there are no
 *    pending events. Returns zero when done (no active handles
 *    or requests left), or non-zero if more events are expected (meaning you
 *    should run the event loop again sometime in the future).
 */
UV_EXTERN int uv_run(uv_loop_t*, uv_run_mode mode);

/*
 * This function checks whether the reference count, the number of active
 * handles or requests left in the event loop, is non-zero.
 */
UV_EXTERN int uv_loop_alive(const uv_loop_t* loop);

/*
 * This function will stop the event loop by forcing uv_run to end
 * as soon as possible, but not sooner than the next loop iteration.
 * If this function was called before blocking for i/o, the loop won't
 * block for i/o on this iteration.
 */
UV_EXTERN void uv_stop(uv_loop_t*);

/*
 * Manually modify the event loop's reference count. Useful if the user wants
 * to have a handle or timeout that doesn't keep the loop alive.
 */
UV_EXTERN void uv_ref(uv_handle_t*);
UV_EXTERN void uv_unref(uv_handle_t*);
UV_EXTERN int uv_has_ref(const uv_handle_t*);

/*
 * Update the event loop's concept of "now". Libuv caches the current time
 * at the start of the event loop tick in order to reduce the number of
 * time-related system calls.
 *
 * You won't normally need to call this function unless you have callbacks
 * that block the event loop for longer periods of time, where "longer" is
 * somewhat subjective but probably on the order of a millisecond or more.
 */
UV_EXTERN void uv_update_time(uv_loop_t*);

/*
 * Return the current timestamp in milliseconds. The timestamp is cached at
 * the start of the event loop tick, see |uv_update_time()| for details and
 * rationale.
 *
 * The timestamp increases monotonically from some arbitrary point in time.
 * Don't make assumptions about the starting point, you will only get
 * disappointed.
 *
 * Use uv_hrtime() if you need sub-millisecond granularity.
 */
UV_EXTERN uint64_t uv_now(const uv_loop_t*);

/*
 * Get backend file descriptor. Only kqueue, epoll and event ports are
 * supported.
 *
 * This can be used in conjunction with `uv_run(loop, UV_RUN_NOWAIT)` to
 * poll in one thread and run the event loop's event callbacks in another.
 *
 * Useful for embedding libuv's event loop in another event loop.
 * See test/test-embed.c for an example.
 *
 * Note that embedding a kqueue fd in another kqueue pollset doesn't work on
 * all platforms. It's not an error to add the fd but it never generates
 * events.
 */
UV_EXTERN int uv_backend_fd(const uv_loop_t*);

/*
 * Get the poll timeout. The return value is in milliseconds, or -1 for no
 * timeout.
 */
UV_EXTERN int uv_backend_timeout(const uv_loop_t*);


/*
 * Should prepare a buffer that libuv can use to read data into.
 *
 * `suggested_size` is a hint. Returning a buffer that is smaller is perfectly
 * okay as long as `buf.len > 0`.
 *
 * If you return a buffer with `buf.len == 0`, libuv skips the read and calls
 * your read or recv callback with nread=UV_ENOBUFS.
 *
 * Note that returning a zero-length buffer does not stop the handle, call
 * uv_read_stop() or uv_udp_recv_stop() for that.
 */
typedef void (*uv_alloc_cb)(uv_handle_t* handle,
                            size_t suggested_size,
                            uv_buf_t* buf);

/*
 * `nread` is > 0 if there is data available, 0 if libuv is done reading for
 * now, or < 0 on error.
 *
 * The callee is responsible for closing the stream when an error happens.
 * Trying to read from the stream again is undefined.
 *
 * The callee is responsible for freeing the buffer, libuv does not reuse it.
 * The buffer may be a null buffer (where buf->base=NULL and buf->len=0) on
 * EOF or error.
 */
typedef void (*uv_read_cb)(uv_stream_t* stream,
                           ssize_t nread,
                           const uv_buf_t* buf);
typedef void (*uv_write_cb)(uv_write_t* req, int status);
typedef void (*uv_connect_cb)(uv_connect_t* req, int status);
typedef void (*uv_shutdown_cb)(uv_shutdown_t* req, int status);
typedef void (*uv_connection_cb)(uv_stream_t* server, int status);
typedef void (*uv_close_cb)(uv_handle_t* handle);
typedef void (*uv_poll_cb)(uv_poll_t* handle, int status, int events);
typedef void (*uv_timer_cb)(uv_timer_t* handle);
typedef void (*uv_async_cb)(uv_async_t* handle);
typedef void (*uv_prepare_cb)(uv_prepare_t* handle);
typedef void (*uv_check_cb)(uv_check_t* handle);
typedef void (*uv_idle_cb)(uv_idle_t* handle);
typedef void (*uv_exit_cb)(uv_process_t*, int64_t exit_status, int term_signal);
typedef void (*uv_walk_cb)(uv_handle_t* handle, void* arg);
typedef void (*uv_fs_cb)(uv_fs_t* req);
typedef void (*uv_work_cb)(uv_work_t* req);
typedef void (*uv_after_work_cb)(uv_work_t* req, int status);
typedef void (*uv_getaddrinfo_cb)(uv_getaddrinfo_t* req,
                                  int status,
                                  struct addrinfo* res);
typedef void (*uv_getnameinfo_cb)(uv_getnameinfo_t* req,
                                  int status,
                                  char* hostname,
                                  char* service);

typedef struct {
  long tv_sec;
  long tv_nsec;
} uv_timespec_t;


typedef struct {
  uint64_t st_dev;
  uint64_t st_mode;
  uint64_t st_nlink;
  uint64_t st_uid;
  uint64_t st_gid;
  uint64_t st_rdev;
  uint64_t st_ino;
  uint64_t st_size;
  uint64_t st_blksize;
  uint64_t st_blocks;
  uint64_t st_flags;
  uint64_t st_gen;
  uv_timespec_t st_atim;
  uv_timespec_t st_mtim;
  uv_timespec_t st_ctim;
  uv_timespec_t st_birthtim;
} uv_stat_t;


/*
* This will be called repeatedly after the uv_fs_event_t is initialized.
* If uv_fs_event_t was initialized with a directory the filename parameter
* will be a relative path to a file contained in the directory.
* The events parameter is an ORed mask of enum uv_fs_event elements.
*/
typedef void (*uv_fs_event_cb)(uv_fs_event_t* handle,
                               const char* filename,
                               int events,
                               int status);

typedef void (*uv_fs_poll_cb)(uv_fs_poll_t* handle,
                              int status,
                              const uv_stat_t* prev,
                              const uv_stat_t* curr);

typedef void (*uv_signal_cb)(uv_signal_t* handle, int signum);


typedef enum {
  UV_LEAVE_GROUP = 0,
  UV_JOIN_GROUP
} uv_membership;


/*
 * Most functions return 0 on success or an error code < 0 on failure.
 */
UV_EXTERN const char* uv_strerror(int err);
UV_EXTERN const char* uv_err_name(int err);


#define UV_REQ_FIELDS                                                         \
  /* public */                                                                \
  void* data;                                                                 \
  /* read-only */                                                             \
  uv_req_type type;                                                           \
  /* private */                                                               \
  void* active_queue[2];                                                      \
  UV_REQ_PRIVATE_FIELDS                                                       \

/* Abstract base class of all requests. */
struct uv_req_s {
  UV_REQ_FIELDS
};


/* Platform-specific request types */
UV_PRIVATE_REQ_TYPES


/*
 * uv_shutdown_t is a subclass of uv_req_t
 *
 * Shutdown the outgoing (write) side of a duplex stream. It waits for
 * pending write requests to complete. The handle should refer to a
 * initialized stream. req should be an uninitialized shutdown request
 * struct. The cb is called after shutdown is complete.
 */
UV_EXTERN int uv_shutdown(uv_shutdown_t* req,
                          uv_stream_t* handle,
                          uv_shutdown_cb cb);

struct uv_shutdown_s {
  UV_REQ_FIELDS
  uv_stream_t* handle;
  uv_shutdown_cb cb;
  UV_SHUTDOWN_PRIVATE_FIELDS
};


#define UV_HANDLE_FIELDS                                                      \
  /* public */                                                                \
  void* data;                                                                 \
  /* read-only */                                                             \
  uv_loop_t* loop;                                                            \
  uv_handle_type type;                                                        \
  /* private */                                                               \
  uv_close_cb close_cb;                                                       \
  void* handle_queue[2];                                                      \
  UV_HANDLE_PRIVATE_FIELDS                                                    \

/* The abstract base class of all handles.  */
struct uv_handle_s {
  UV_HANDLE_FIELDS
};

/*
 * Returns size of various handle types, useful for FFI
 * bindings to allocate correct memory without copying struct
 * definitions
 */
UV_EXTERN size_t uv_handle_size(uv_handle_type type);

/*
 * Returns size of request types, useful for dynamic lookup with FFI
 */
UV_EXTERN size_t uv_req_size(uv_req_type type);

/*
 * Returns non-zero if the handle is active, zero if it's inactive.
 *
 * What "active" means depends on the type of handle:
 *
 *  - A uv_async_t handle is always active and cannot be deactivated, except
 *    by closing it with uv_close().
 *
 *  - A uv_pipe_t, uv_tcp_t, uv_udp_t, etc. handle - basically any handle that
 *    deals with I/O - is active when it is doing something that involves I/O,
 *    like reading, writing, connecting, accepting new connections, etc.
 *
 *  - A uv_check_t, uv_idle_t, uv_timer_t, etc. handle is active when it has
 *    been started with a call to uv_check_start(), uv_idle_start(), etc.
 *
 *      Rule of thumb: if a handle of type uv_foo_t has a uv_foo_start()
 *      function, then it's active from the moment that function is called.
 *      Likewise, uv_foo_stop() deactivates the handle again.
 *
 */
UV_EXTERN int uv_is_active(const uv_handle_t* handle);

/*
 * Walk the list of open handles.
 */
UV_EXTERN void uv_walk(uv_loop_t* loop, uv_walk_cb walk_cb, void* arg);


/*
 * Request handle to be closed. close_cb will be called asynchronously after
 * this call. This MUST be called on each handle before memory is released.
 *
 * Note that handles that wrap file descriptors are closed immediately but
 * close_cb will still be deferred to the next iteration of the event loop.
 * It gives you a chance to free up any resources associated with the handle.
 *
 * In-progress requests, like uv_connect_t or uv_write_t, are cancelled and
 * have their callbacks called asynchronously with status=UV_ECANCELED.
 */
UV_EXTERN void uv_close(uv_handle_t* handle, uv_close_cb close_cb);


/*
 * Constructor for uv_buf_t.
 * Due to platform differences the user cannot rely on the ordering of the
 * base and len members of the uv_buf_t struct. The user is responsible for
 * freeing base after the uv_buf_t is done. Return struct passed by value.
 */
UV_EXTERN uv_buf_t uv_buf_init(char* base, unsigned int len);


#define UV_STREAM_FIELDS                                                      \
  /* number of bytes queued for writing */                                    \
  size_t write_queue_size;                                                    \
  uv_alloc_cb alloc_cb;                                                       \
  uv_read_cb read_cb;                                                         \
  /* private */                                                               \
  UV_STREAM_PRIVATE_FIELDS

/*
 * uv_stream_t is a subclass of uv_handle_t
 *
 * uv_stream is an abstract class.
 *
 * uv_stream_t is the parent class of uv_tcp_t, uv_pipe_t and uv_tty_t.
 */
struct uv_stream_s {
  UV_HANDLE_FIELDS
  UV_STREAM_FIELDS
};

UV_EXTERN int uv_listen(uv_stream_t* stream, int backlog, uv_connection_cb cb);

/*
 * This call is used in conjunction with uv_listen() to accept incoming
 * connections. Call uv_accept after receiving a uv_connection_cb to accept
 * the connection. Before calling uv_accept use uv_*_init() must be
 * called on the client. Non-zero return value indicates an error.
 *
 * When the uv_connection_cb is called it is guaranteed that uv_accept will
 * complete successfully the first time. If you attempt to use it more than
 * once, it may fail. It is suggested to only call uv_accept once per
 * uv_connection_cb call.
 */
UV_EXTERN int uv_accept(uv_stream_t* server, uv_stream_t* client);

/*
 * Read data from an incoming stream. The callback will be made several
 * times until there is no more data to read or uv_read_stop is called.
 * When we've reached EOF nread will be set to UV_EOF.
 *
 * When nread < 0, the buf parameter might not point to a valid buffer;
 * in that case buf.len and buf.base are both set to 0.
 *
 * Note that nread might also be 0, which does *not* indicate an error or
 * eof; it happens when libuv requested a buffer through the alloc callback
 * but then decided that it didn't need that buffer.
 */
UV_EXTERN int uv_read_start(uv_stream_t*,
                            uv_alloc_cb alloc_cb,
                            uv_read_cb read_cb);

UV_EXTERN int uv_read_stop(uv_stream_t*);


/*
 * Write data to stream. Buffers are written in order. Example:
 *
 *   uv_buf_t a[] = {
 *     { .base = "1", .len = 1 },
 *     { .base = "2", .len = 1 }
 *   };
 *
 *   uv_buf_t b[] = {
 *     { .base = "3", .len = 1 },
 *     { .base = "4", .len = 1 }
 *   };
 *
 *   uv_write_t req1;
 *   uv_write_t req2;
 *
 *   // writes "1234"
 *   uv_write(&req1, stream, a, 2);
 *   uv_write(&req2, stream, b, 2);
 *
 */
UV_EXTERN int uv_write(uv_write_t* req,
                       uv_stream_t* handle,
                       const uv_buf_t bufs[],
                       unsigned int nbufs,
                       uv_write_cb cb);

/*
 * Extended write function for sending handles over a pipe. The pipe must be
 * initialized with ipc == 1.
 * send_handle must be a TCP socket or pipe, which is a server or a connection
 * (listening or connected state).  Bound sockets or pipes will be assumed to
 * be servers.
 */
UV_EXTERN int uv_write2(uv_write_t* req,
                        uv_stream_t* handle,
                        const uv_buf_t bufs[],
                        unsigned int nbufs,
                        uv_stream_t* send_handle,
                        uv_write_cb cb);

/*
 * Same as `uv_write()`, but won't queue write request if it can't be completed
 * immediately.
 * Will return either:
 * - >= 0: number of bytes written (can be less than the supplied buffer size)
 * - < 0: negative error code
 */
UV_EXTERN int uv_try_write(uv_stream_t* handle,
                           const uv_buf_t bufs[],
                           unsigned int nbufs);

/* uv_write_t is a subclass of uv_req_t */
struct uv_write_s {
  UV_REQ_FIELDS
  uv_write_cb cb;
  uv_stream_t* send_handle;
  uv_stream_t* handle;
  UV_WRITE_PRIVATE_FIELDS
};


/*
 * Used to determine whether a stream is readable or writable.
 */
UV_EXTERN int uv_is_readable(const uv_stream_t* handle);
UV_EXTERN int uv_is_writable(const uv_stream_t* handle);


/*
 * Enable or disable blocking mode for a stream.
 *
 * When blocking mode is enabled all writes complete synchronously. The
 * interface remains unchanged otherwise, e.g. completion or failure of the
 * operation will still be reported through a callback which is made
 * asychronously.
 *
 * Relying too much on this API is not recommended. It is likely to change
 * significantly in the future.
 *
 * Currently this only works on Windows and only for uv_pipe_t handles.
 *
 * Also libuv currently makes no ordering guarantee when the blocking mode
 * is changed after write requests have already been submitted. Therefore it is
 * recommended to set the blocking mode immediately after opening or creating
 * the stream.
 */
UV_EXTERN int uv_stream_set_blocking(uv_stream_t* handle, int blocking);


/*
 * Used to determine whether a stream is closing or closed.
 *
 * N.B. is only valid between the initialization of the handle
 *      and the arrival of the close callback, and cannot be used
 *      to validate the handle.
 */
UV_EXTERN int uv_is_closing(const uv_handle_t* handle);


/*
 * uv_tcp_t is a subclass of uv_stream_t
 *
 * Represents a TCP stream or TCP server.
 */
struct uv_tcp_s {
  UV_HANDLE_FIELDS
  UV_STREAM_FIELDS
  UV_TCP_PRIVATE_FIELDS
};

UV_EXTERN int uv_tcp_init(uv_loop_t*, uv_tcp_t* handle);

/*
 * Opens an existing file descriptor or SOCKET as a tcp handle.
 */
UV_EXTERN int uv_tcp_open(uv_tcp_t* handle, uv_os_sock_t sock);

/* Enable/disable Nagle's algorithm. */
UV_EXTERN int uv_tcp_nodelay(uv_tcp_t* handle, int enable);

/*
 * Enable/disable TCP keep-alive.
 *
 * `delay` is the initial delay in seconds, ignored when `enable` is zero.
 */
UV_EXTERN int uv_tcp_keepalive(uv_tcp_t* handle,
                               int enable,
                               unsigned int delay);

/*
 * Enable/disable simultaneous asynchronous accept requests that are
 * queued by the operating system when listening for new tcp connections.
 * This setting is used to tune a tcp server for the desired performance.
 * Having simultaneous accepts can significantly improve the rate of
 * accepting connections (which is why it is enabled by default) but
 * may lead to uneven load distribution in multi-process setups.
 */
UV_EXTERN int uv_tcp_simultaneous_accepts(uv_tcp_t* handle, int enable);

enum uv_tcp_flags {
  /* Used with uv_tcp_bind, when an IPv6 address is used */
  UV_TCP_IPV6ONLY = 1
};

/*
 * Bind the handle to an address and port.  `addr` should point to an
 * initialized struct sockaddr_in or struct sockaddr_in6.
 *
 * When the port is already taken, you can expect to see an UV_EADDRINUSE
 * error from either uv_tcp_bind(), uv_listen() or uv_tcp_connect().
 *
 * That is, a successful call to uv_tcp_bind() does not guarantee that
 * the call to uv_listen() or uv_tcp_connect() will succeed as well.
 */
UV_EXTERN int uv_tcp_bind(uv_tcp_t* handle,
                          const struct sockaddr* addr,
                          unsigned int flags);
UV_EXTERN int uv_tcp_getsockname(const uv_tcp_t* handle,
                                 struct sockaddr* name,
                                 int* namelen);
UV_EXTERN int uv_tcp_getpeername(const uv_tcp_t* handle,
                                 struct sockaddr* name,
                                 int* namelen);

/*
 * Establish an IPv4 or IPv6 TCP connection.  Provide an initialized TCP handle
 * and an uninitialized uv_connect_t*.  `addr` should point to an initialized
 * struct sockaddr_in or struct sockaddr_in6.
 *
 * The callback is made when the connection has been established or when a
 * connection error happened.
 */
UV_EXTERN int uv_tcp_connect(uv_connect_t* req,
                             uv_tcp_t* handle,
                             const struct sockaddr* addr,
                             uv_connect_cb cb);

/* uv_connect_t is a subclass of uv_req_t */
struct uv_connect_s {
  UV_REQ_FIELDS
  uv_connect_cb cb;
  uv_stream_t* handle;
  UV_CONNECT_PRIVATE_FIELDS
};


/*
 * UDP support.
 */

enum uv_udp_flags {
  /* Disables dual stack mode. */
  UV_UDP_IPV6ONLY = 1,
  /*
   * Indicates message was truncated because read buffer was too small. The
   * remainder was discarded by the OS. Used in uv_udp_recv_cb.
   */
  UV_UDP_PARTIAL = 2,
  /* Indicates if SO_REUSEADDR will be set when binding the handle.
   * This sets the SO_REUSEPORT socket flag on the BSDs and OS X. On other
   * UNIX platforms, it sets the SO_REUSEADDR flag.  What that means is that
   * multiple threads or processes can bind to the same address without error
   * (provided they all set the flag) but only the last one to bind will receive
   * any traffic, in effect "stealing" the port from the previous listener.
   */
  UV_UDP_REUSEADDR = 4
};

/*
 * Called after uv_udp_send(). status 0 indicates
 * success otherwise error.
 */
typedef void (*uv_udp_send_cb)(uv_udp_send_t* req, int status);

/*
 * Callback that is invoked when a new UDP datagram is received.
 *
 *  handle  UDP handle.
 *  nread   Number of bytes that have been received.
 *          0 if there is no more data to read. You may
 *          discard or repurpose the read buffer.
 *          < 0 if a transmission error was detected.
 *  buf     uv_buf_t with the received data.
 *  addr    struct sockaddr* containing the address of the sender.
 *          Can be NULL. Valid for the duration of the callback only.
 *  flags   One or more OR'ed UV_UDP_* constants.
 *          Right now only UV_UDP_PARTIAL is used.
 */
typedef void (*uv_udp_recv_cb)(uv_udp_t* handle,
                               ssize_t nread,
                               const uv_buf_t* buf,
                               const struct sockaddr* addr,
                               unsigned flags);

/* uv_udp_t is a subclass of uv_handle_t */
struct uv_udp_s {
  UV_HANDLE_FIELDS
  UV_UDP_PRIVATE_FIELDS
};

/* uv_udp_send_t is a subclass of uv_req_t */
struct uv_udp_send_s {
  UV_REQ_FIELDS
  uv_udp_t* handle;
  uv_udp_send_cb cb;
  UV_UDP_SEND_PRIVATE_FIELDS
};

/*
 * Initialize a new UDP handle. The actual socket is created lazily.
 * Returns 0 on success.
 */
UV_EXTERN int uv_udp_init(uv_loop_t*, uv_udp_t* handle);

/*
 * Opens an existing file descriptor or SOCKET as a udp handle.
 *
 * Unix only:
 *  The only requirement of the sock argument is that it follows the
 *  datagram contract (works in unconnected mode, supports sendmsg()/recvmsg(),
 *  etc.). In other words, other datagram-type sockets like raw sockets or
 *  netlink sockets can also be passed to this function.
 *
 * This sets the SO_REUSEPORT socket flag on the BSDs and OS X. On other
 * UNIX platforms, it sets the SO_REUSEADDR flag.  What that means is that
 * multiple threads or processes can bind to the same address without error
 * (provided they all set the flag) but only the last one to bind will receive
 * any traffic, in effect "stealing" the port from the previous listener.
 * This behavior is something of an anomaly and may be replaced by an explicit
 * opt-in mechanism in future versions of libuv.
 */
UV_EXTERN int uv_udp_open(uv_udp_t* handle, uv_os_sock_t sock);

/*
 * Bind to an IP address and port.
 *
 * Arguments:
 *  handle    UDP handle. Should have been initialized with `uv_udp_init`.
 *  addr      struct sockaddr_in or struct sockaddr_in6 with the address and
 *            port to bind to.
 *  flags     Indicate how the socket will be bound, UV_UDP_IPV6ONLY and
 *            UV_UDP_REUSEADDR are supported.
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_bind(uv_udp_t* handle,
                          const struct sockaddr* addr,
                          unsigned int flags);

UV_EXTERN int uv_udp_getsockname(uv_udp_t* handle,
                                 struct sockaddr* name,
                                 int* namelen);

/*
 * Set membership for a multicast address
 *
 * Arguments:
 *  handle              UDP handle. Should have been initialized with
 *                      `uv_udp_init`.
 *  multicast_addr      multicast address to set membership for
 *  interface_addr      interface address
 *  membership          Should be UV_JOIN_GROUP or UV_LEAVE_GROUP
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_set_membership(uv_udp_t* handle,
                                    const char* multicast_addr,
                                    const char* interface_addr,
                                    uv_membership membership);

/*
 * Set IP multicast loop flag. Makes multicast packets loop back to
 * local sockets.
 *
 * Arguments:
 *  handle              UDP handle. Should have been initialized with
 *                      `uv_udp_init`.
 *  on                  1 for on, 0 for off
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_set_multicast_loop(uv_udp_t* handle, int on);

/*
 * Set the multicast ttl
 *
 * Arguments:
 *  handle              UDP handle. Should have been initialized with
 *                      `uv_udp_init`.
 *  ttl                 1 through 255
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_set_multicast_ttl(uv_udp_t* handle, int ttl);


/*
 * Set the multicast interface to send on
 *
 * Arguments:
 *  handle              UDP handle. Should have been initialized with
 *                      `uv_udp_init`.
 *  interface_addr      interface address
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_set_multicast_interface(uv_udp_t* handle,
                                             const char* interface_addr);

/*
 * Set broadcast on or off
 *
 * Arguments:
 *  handle              UDP handle. Should have been initialized with
 *                      `uv_udp_init`.
 *  on                  1 for on, 0 for off
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_set_broadcast(uv_udp_t* handle, int on);

/*
 * Set the time to live
 *
 * Arguments:
 *  handle              UDP handle. Should have been initialized with
 *                      `uv_udp_init`.
 *  ttl                 1 through 255
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_set_ttl(uv_udp_t* handle, int ttl);

/*
 * Send data. If the socket has not previously been bound with `uv_udp_bind,`
 * it is bound to 0.0.0.0 (the "all interfaces" address) and a random
 * port number.
 *
 * Arguments:
 *  req       UDP request handle. Need not be initialized.
 *  handle    UDP handle. Should have been initialized with `uv_udp_init`.
 *  bufs      List of buffers to send.
 *  nbufs     Number of buffers in `bufs`.
 *  addr      struct sockaddr_in or struct sockaddr_in6 with the address and
 *            port of the remote peer.
 *  send_cb   Callback to invoke when the data has been sent out.
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_send(uv_udp_send_t* req,
                          uv_udp_t* handle,
                          const uv_buf_t bufs[],
                          unsigned int nbufs,
                          const struct sockaddr* addr,
                          uv_udp_send_cb send_cb);

/*
 * Receive data. If the socket has not previously been bound with `uv_udp_bind`
 * it is bound to 0.0.0.0 (the "all interfaces" address) and a random
 * port number.
 *
 * Arguments:
 *  handle    UDP handle. Should have been initialized with `uv_udp_init`.
 *  alloc_cb  Callback to invoke when temporary storage is needed.
 *  recv_cb   Callback to invoke with received data.
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_recv_start(uv_udp_t* handle,
                                uv_alloc_cb alloc_cb,
                                uv_udp_recv_cb recv_cb);

/*
 * Stop listening for incoming datagrams.
 *
 * Arguments:
 *  handle    UDP handle. Should have been initialized with `uv_udp_init`.
 *
 * Returns:
 *  0 on success, or an error code < 0 on failure.
 */
UV_EXTERN int uv_udp_recv_stop(uv_udp_t* handle);


/*
 * uv_tty_t is a subclass of uv_stream_t
 *
 * Representing a stream for the console.
 */
struct uv_tty_s {
  UV_HANDLE_FIELDS
  UV_STREAM_FIELDS
  UV_TTY_PRIVATE_FIELDS
};

/*
 * Initialize a new TTY stream with the given file descriptor. Usually the
 * file descriptor will be
 *   0 = stdin
 *   1 = stdout
 *   2 = stderr
 * The last argument, readable, specifies if you plan on calling
 * uv_read_start with this stream. stdin is readable, stdout is not.
 *
 * TTY streams which are not readable have blocking writes.
 */
UV_EXTERN int uv_tty_init(uv_loop_t*, uv_tty_t*, uv_file fd, int readable);

/*
 * Set mode. 0 for normal, 1 for raw.
 */
UV_EXTERN int uv_tty_set_mode(uv_tty_t*, int mode);

/*
 * To be called when the program exits. Resets TTY settings to default
 * values for the next process to take over.
 *
 * This function is async signal-safe on UNIX platforms but can fail with error
 * code UV_EBUSY if you call it when execution is inside uv_tty_set_mode().
 */
UV_EXTERN int uv_tty_reset_mode(void);

/*
 * Gets the current Window size. On success zero is returned.
 */
UV_EXTERN int uv_tty_get_winsize(uv_tty_t*, int* width, int* height);

/*
 * Used to detect what type of stream should be used with a given file
 * descriptor. Usually this will be used during initialization to guess the
 * type of the stdio streams.
 * For isatty() functionality use this function and test for UV_TTY.
 */
UV_EXTERN uv_handle_type uv_guess_handle(uv_file file);

/*
 * uv_pipe_t is a subclass of uv_stream_t
 *
 * Representing a pipe stream or pipe server. On Windows this is a Named
 * Pipe. On Unix this is a UNIX domain socket.
 */
struct uv_pipe_s {
  UV_HANDLE_FIELDS
  UV_STREAM_FIELDS
  int ipc; /* non-zero if this pipe is used for passing handles */
  UV_PIPE_PRIVATE_FIELDS
};

/*
 * Initialize a pipe. The last argument is a boolean to indicate if
 * this pipe will be used for handle passing between processes.
 */
UV_EXTERN int uv_pipe_init(uv_loop_t*, uv_pipe_t* handle, int ipc);

/*
 * Opens an existing file descriptor or HANDLE as a pipe.
 */
UV_EXTERN int uv_pipe_open(uv_pipe_t*, uv_file file);

/*
 * Bind the pipe to a file path (UNIX) or a name (Windows.)
 *
 * Paths on UNIX get truncated to `sizeof(sockaddr_un.sun_path)` bytes,
 * typically between 92 and 108 bytes.
 */
UV_EXTERN int uv_pipe_bind(uv_pipe_t* handle, const char* name);

/*
 * Connect to the UNIX domain socket or the named pipe.
 *
 * Paths on UNIX get truncated to `sizeof(sockaddr_un.sun_path)` bytes,
 * typically between 92 and 108 bytes.
 */
UV_EXTERN void uv_pipe_connect(uv_connect_t* req,
                               uv_pipe_t* handle,
                               const char* name,
                               uv_connect_cb cb);

/*
 * Get the name of the UNIX domain socket or the named pipe.
 *
 * A preallocated buffer must be provided. The len parameter holds the
 * length of the buffer and it's set to the number of bytes written to the
 * buffer on output. If the buffer is not big enough UV_ENOBUFS will be
 * returned and len will contain the required size.
 */
UV_EXTERN int uv_pipe_getsockname(const uv_pipe_t* handle,
                                  char* buf,
                                  size_t* len);

/*
 * This setting applies to Windows only.
 * Set the number of pending pipe instance handles when the pipe server
 * is waiting for connections.
 */
UV_EXTERN void uv_pipe_pending_instances(uv_pipe_t* handle, int count);

/*
 * Used to receive handles over ipc pipes.
 *
 * First - call `uv_pipe_pending_count`, if it is > 0 - initialize handle
 * using type, returned by `uv_pipe_pending_type` and call
 * `uv_accept(pipe, handle)`.
 */
UV_EXTERN int uv_pipe_pending_count(uv_pipe_t* handle);
UV_EXTERN uv_handle_type uv_pipe_pending_type(uv_pipe_t* handle);

/*
 * uv_poll_t is a subclass of uv_handle_t.
 *
 * The uv_poll watcher is used to watch file descriptors for readability and
 * writability, similar to the purpose of poll(2).
 *
 * The purpose of uv_poll is to enable integrating external libraries that
 * rely on the event loop to signal it about the socket status changes, like
 * c-ares or libssh2. Using uv_poll_t for any other other purpose is not
 * recommended; uv_tcp_t, uv_udp_t, etc. provide an implementation that is
 * much faster and more scalable than what can be achieved with uv_poll_t,
 * especially on Windows.
 *
 * It is possible that uv_poll occasionally signals that a file descriptor is
 * readable or writable even when it isn't. The user should therefore always
 * be prepared to handle EAGAIN or equivalent when it attempts to read from or
 * write to the fd.
 *
 * It is not okay to have multiple active uv_poll watchers for the same socket.
 * This can cause libuv to busyloop or otherwise malfunction.
 *
 * The user should not close a file descriptor while it is being polled by an
 * active uv_poll watcher. This can cause the poll watcher to report an error,
 * but it might also start polling another socket. However the fd can be safely
 * closed immediately after a call to uv_poll_stop() or uv_close().
 *
 * On windows only sockets can be polled with uv_poll. On unix any file
 * descriptor that would be accepted by poll(2) can be used with uv_poll.
 */
struct uv_poll_s {
  UV_HANDLE_FIELDS
  uv_poll_cb poll_cb;
  UV_POLL_PRIVATE_FIELDS
};

enum uv_poll_event {
  UV_READABLE = 1,
  UV_WRITABLE = 2
};

/* Initialize the poll watcher using a file descriptor. */
UV_EXTERN int uv_poll_init(uv_loop_t* loop, uv_poll_t* handle, int fd);

/* Initialize the poll watcher using a socket descriptor. On unix this is */
/* identical to uv_poll_init. On windows it takes a SOCKET handle. */
UV_EXTERN int uv_poll_init_socket(uv_loop_t* loop,
                                  uv_poll_t* handle,
                                  uv_os_sock_t socket);

/*
 * Starts polling the file descriptor. `events` is a bitmask consisting made up
 * of UV_READABLE and UV_WRITABLE. As soon as an event is detected the callback
 * will be called with `status` set to 0, and the detected events set en the
 * `events` field.
 *
 * If an error happens while polling status, `status` < 0 and corresponds
 * with one of the UV_E* error codes. The user should not close the socket
 * while uv_poll is active. If the user does that anyway, the callback *may*
 * be called reporting an error status, but this is not guaranteed.
 *
 * Calling uv_poll_start on an uv_poll watcher that is already active is fine.
 * Doing so will update the events mask that is being watched for.
 */
UV_EXTERN int uv_poll_start(uv_poll_t* handle, int events, uv_poll_cb cb);

/* Stops polling the file descriptor. */
UV_EXTERN int uv_poll_stop(uv_poll_t* handle);


/*
 * uv_prepare_t is a subclass of uv_handle_t.
 *
 * Every active prepare handle gets its callback called exactly once per loop
 * iteration, just before the system blocks to wait for completed i/o.
 */
struct uv_prepare_s {
  UV_HANDLE_FIELDS
  UV_PREPARE_PRIVATE_FIELDS
};

UV_EXTERN int uv_prepare_init(uv_loop_t*, uv_prepare_t* prepare);

UV_EXTERN int uv_prepare_start(uv_prepare_t* prepare, uv_prepare_cb cb);

UV_EXTERN int uv_prepare_stop(uv_prepare_t* prepare);


/*
 * uv_check_t is a subclass of uv_handle_t.
 *
 * Every active check handle gets its callback called exactly once per loop
 * iteration, just after the system returns from blocking.
 */
struct uv_check_s {
  UV_HANDLE_FIELDS
  UV_CHECK_PRIVATE_FIELDS
};

UV_EXTERN int uv_check_init(uv_loop_t*, uv_check_t* check);

UV_EXTERN int uv_check_start(uv_check_t* check, uv_check_cb cb);

UV_EXTERN int uv_check_stop(uv_check_t* check);


/*
 * uv_idle_t is a subclass of uv_handle_t.
 *
 * Every active idle handle gets its callback called repeatedly until it is
 * stopped. This happens after all other types of callbacks are processed.
 * When there are multiple "idle" handles active, their callbacks are called
 * in turn.
 */
struct uv_idle_s {
  UV_HANDLE_FIELDS
  UV_IDLE_PRIVATE_FIELDS
};

UV_EXTERN int uv_idle_init(uv_loop_t*, uv_idle_t* idle);

UV_EXTERN int uv_idle_start(uv_idle_t* idle, uv_idle_cb cb);

UV_EXTERN int uv_idle_stop(uv_idle_t* idle);


/*
 * uv_async_t is a subclass of uv_handle_t.
 *
 * uv_async_send wakes up the event loop and calls the async handle's callback.
 * There is no guarantee that every uv_async_send call leads to exactly one
 * invocation of the callback; the only guarantee is that the callback function
 * is called at least once after the call to async_send. Unlike all other
 * libuv functions, uv_async_send can be called from another thread.
 */
struct uv_async_s {
  UV_HANDLE_FIELDS
  UV_ASYNC_PRIVATE_FIELDS
};

/*
 * Initialize the uv_async_t handle. A NULL callback is allowed.
 *
 * Note that uv_async_init(), unlike other libuv functions, immediately
 * starts the handle. To stop the handle again, close it with uv_close().
 */
UV_EXTERN int uv_async_init(uv_loop_t*,
                            uv_async_t* async,
                            uv_async_cb async_cb);

/*
 * This can be called from other threads to wake up a libuv thread.
 */
UV_EXTERN int uv_async_send(uv_async_t* async);


/*
 * uv_timer_t is a subclass of uv_handle_t.
 *
 * Used to get woken up at a specified time in the future.
 */
struct uv_timer_s {
  UV_HANDLE_FIELDS
  UV_TIMER_PRIVATE_FIELDS
};

UV_EXTERN int uv_timer_init(uv_loop_t*, uv_timer_t* handle);

/*
 * Start the timer. `timeout` and `repeat` are in milliseconds.
 *
 * If timeout is zero, the callback fires on the next tick of the event loop.
 *
 * If repeat is non-zero, the callback fires first after timeout milliseconds
 * and then repeatedly after repeat milliseconds.
 */
UV_EXTERN int uv_timer_start(uv_timer_t* handle,
                             uv_timer_cb cb,
                             uint64_t timeout,
                             uint64_t repeat);

UV_EXTERN int uv_timer_stop(uv_timer_t* handle);

/*
 * Stop the timer, and if it is repeating restart it using the repeat value
 * as the timeout. If the timer has never been started before it returns
 * UV_EINVAL.
 */
UV_EXTERN int uv_timer_again(uv_timer_t* handle);

/*
 * Set the repeat value in milliseconds. Note that if the repeat value is set
 * from a timer callback it does not immediately take effect. If the timer was
 * non-repeating before, it will have been stopped. If it was repeating, then
 * the old repeat value will have been used to schedule the next timeout.
 */
UV_EXTERN void uv_timer_set_repeat(uv_timer_t* handle, uint64_t repeat);

UV_EXTERN uint64_t uv_timer_get_repeat(const uv_timer_t* handle);


/*
 * uv_getaddrinfo_t is a subclass of uv_req_t
 *
 * Request object for uv_getaddrinfo.
 */
struct uv_getaddrinfo_s {
  UV_REQ_FIELDS
  /* read-only */
  uv_loop_t* loop;
  UV_GETADDRINFO_PRIVATE_FIELDS
};


/*
 * Asynchronous getaddrinfo(3).
 *
 * Either node or service may be NULL but not both.
 *
 * hints is a pointer to a struct addrinfo with additional address type
 * constraints, or NULL. Consult `man -s 3 getaddrinfo` for details.
 *
 * Returns 0 on success or an error code < 0 on failure.
 *
 * If successful, your callback gets called sometime in the future with the
 * lookup result, which is either:
 *
 *  a) err == 0, the res argument points to a valid struct addrinfo, or
 *  b) err < 0, the res argument is NULL. See the UV_EAI_* constants.
 *
 * Call uv_freeaddrinfo() to free the addrinfo structure.
 */
UV_EXTERN int uv_getaddrinfo(uv_loop_t* loop,
                             uv_getaddrinfo_t* req,
                             uv_getaddrinfo_cb getaddrinfo_cb,
                             const char* node,
                             const char* service,
                             const struct addrinfo* hints);

/*
 * Free the struct addrinfo. Passing NULL is allowed and is a no-op.
 */
UV_EXTERN void uv_freeaddrinfo(struct addrinfo* ai);


/*
* uv_getnameinfo_t is a subclass of uv_req_t
*
* Request object for uv_getnameinfo.
*/
struct uv_getnameinfo_s {
  UV_REQ_FIELDS
  /* read-only */
  uv_loop_t* loop;
  UV_GETNAMEINFO_PRIVATE_FIELDS
};

/*
 * Asynchronous getnameinfo.
 *
 * Returns 0 on success or an error code < 0 on failure.
 *
 * If successful, your callback gets called sometime in the future with the
 * lookup result.
 */
UV_EXTERN int uv_getnameinfo(uv_loop_t* loop,
                             uv_getnameinfo_t* req,
                             uv_getnameinfo_cb getnameinfo_cb,
                             const struct sockaddr* addr,
                             int flags);


/* uv_spawn() options */
typedef enum {
  UV_IGNORE         = 0x00,
  UV_CREATE_PIPE    = 0x01,
  UV_INHERIT_FD     = 0x02,
  UV_INHERIT_STREAM = 0x04,

  /* When UV_CREATE_PIPE is specified, UV_READABLE_PIPE and UV_WRITABLE_PIPE
   * determine the direction of flow, from the child process' perspective. Both
   * flags may be specified to create a duplex data stream.
   */
  UV_READABLE_PIPE  = 0x10,
  UV_WRITABLE_PIPE  = 0x20
} uv_stdio_flags;

typedef struct uv_stdio_container_s {
  uv_stdio_flags flags;

  union {
    uv_stream_t* stream;
    int fd;
  } data;
} uv_stdio_container_t;

typedef struct uv_process_options_s {
  uv_exit_cb exit_cb; /* Called after the process exits. */
  const char* file;   /* Path to program to execute. */
  /*
   * Command line arguments. args[0] should be the path to the program. On
   * Windows this uses CreateProcess which concatenates the arguments into a
   * string this can cause some strange errors. See the note at
   * windows_verbatim_arguments.
   */
  char** args;
  /*
   * This will be set as the environ variable in the subprocess. If this is
   * NULL then the parents environ will be used.
   */
  char** env;
  /*
   * If non-null this represents a directory the subprocess should execute
   * in. Stands for current working directory.
   */
  const char* cwd;
  /*
   * Various flags that control how uv_spawn() behaves. See the definition of
   * `enum uv_process_flags` below.
   */
  unsigned int flags;
  /*
   * The `stdio` field points to an array of uv_stdio_container_t structs that
   * describe the file descriptors that will be made available to the child
   * process. The convention is that stdio[0] points to stdin, fd 1 is used for
   * stdout, and fd 2 is stderr.
   *
   * Note that on windows file descriptors greater than 2 are available to the
   * child process only if the child processes uses the MSVCRT runtime.
   */
  int stdio_count;
  uv_stdio_container_t* stdio;
  /*
   * Libuv can change the child process' user/group id. This happens only when
   * the appropriate bits are set in the flags fields. This is not supported on
   * windows; uv_spawn() will fail and set the error to UV_ENOTSUP.
   */
  uv_uid_t uid;
  uv_gid_t gid;
} uv_process_options_t;

/*
 * These are the flags that can be used for the uv_process_options.flags field.
 */
enum uv_process_flags {
  /*
   * Set the child process' user id. The user id is supplied in the `uid` field
   * of the options struct. This does not work on windows; setting this flag
   * will cause uv_spawn() to fail.
   */
  UV_PROCESS_SETUID = (1 << 0),
  /*
   * Set the child process' group id. The user id is supplied in the `gid`
   * field of the options struct. This does not work on windows; setting this
   * flag will cause uv_spawn() to fail.
   */
  UV_PROCESS_SETGID = (1 << 1),
  /*
   * Do not wrap any arguments in quotes, or perform any other escaping, when
   * converting the argument list into a command line string. This option is
   * only meaningful on Windows systems. On unix it is silently ignored.
   */
  UV_PROCESS_WINDOWS_VERBATIM_ARGUMENTS = (1 << 2),
  /*
   * Spawn the child process in a detached state - this will make it a process
   * group leader, and will effectively enable the child to keep running after
   * the parent exits.  Note that the child process will still keep the
   * parent's event loop alive unless the parent process calls uv_unref() on
   * the child's process handle.
   */
  UV_PROCESS_DETACHED = (1 << 3),
  /*
   * Hide the subprocess console window that would normally be created. This
   * option is only meaningful on Windows systems. On unix it is silently
   * ignored.
   */
  UV_PROCESS_WINDOWS_HIDE = (1 << 4)
};

/*
 * uv_process_t is a subclass of uv_handle_t
 */
struct uv_process_s {
  UV_HANDLE_FIELDS
  uv_exit_cb exit_cb;
  int pid;
  UV_PROCESS_PRIVATE_FIELDS
};

/*
 * Initializes the uv_process_t and starts the process. If the process is
 * successfully spawned, then this function will return 0. Otherwise, the
 * negative error code corresponding to the reason it couldn't spawn is
 * returned.
 *
 * Possible reasons for failing to spawn would include (but not be limited to)
 * the file to execute not existing, not having permissions to use the setuid or
 * setgid specified, or not having enough memory to allocate for the new
 * process.
 */
UV_EXTERN int uv_spawn(uv_loop_t* loop,
                       uv_process_t* handle,
                       const uv_process_options_t* options);


/*
 * Kills the process with the specified signal. The user must still
 * call uv_close on the process.
 *
 * Emulates some aspects of Unix exit status on Windows, in that while the
 * underlying process will be terminated with a status of `1`,
 * `uv_process_t.exit_signal` will be set to signum, so the process will appear
 * to have been killed by `signum`.
 */
UV_EXTERN int uv_process_kill(uv_process_t*, int signum);


/* Kills the process with the specified signal.
 *
 * Emulates some aspects of Unix signals on Windows:
 * - SIGTERM, SIGKILL, and SIGINT call TerminateProcess() to unconditionally
 *   cause the target to exit with status 1. Unlike Unix, this cannot be caught
 *   or ignored (but see uv_process_kill() and uv_signal_start()).
 * - Signal number `0` causes a check for target existence, as in Unix. Return
 *   value is 0 on existence, UV_ESRCH on non-existence.
 *
 * Returns 0 on success, or an error code on failure. UV_ESRCH is portably used
 * for non-existence of target process, other errors may be system specific.
 */
UV_EXTERN int uv_kill(int pid, int signum);


/*
 * uv_work_t is a subclass of uv_req_t
 */
struct uv_work_s {
  UV_REQ_FIELDS
  uv_loop_t* loop;
  uv_work_cb work_cb;
  uv_after_work_cb after_work_cb;
  UV_WORK_PRIVATE_FIELDS
};

/* Queues a work request to execute asynchronously on the thread pool. */
UV_EXTERN int uv_queue_work(uv_loop_t* loop,
                            uv_work_t* req,
                            uv_work_cb work_cb,
                            uv_after_work_cb after_work_cb);

/* Cancel a pending request. Fails if the request is executing or has finished
 * executing.
 *
 * Returns 0 on success, or an error code < 0 on failure.
 *
 * Only cancellation of uv_fs_t, uv_getaddrinfo_t and uv_work_t requests is
 * currently supported.
 *
 * Cancelled requests have their callbacks invoked some time in the future.
 * It's _not_ safe to free the memory associated with the request until your
 * callback is called.
 *
 * Here is how cancellation is reported to your callback:
 *
 * - A uv_fs_t request has its req->result field set to UV_ECANCELED.
 *
 * - A uv_work_t or uv_getaddrinfo_t request has its callback invoked with
 *   status == UV_ECANCELED.
 *
 * This function is currently only implemented on UNIX platforms. On Windows,
 * it always returns UV_ENOSYS.
 */
UV_EXTERN int uv_cancel(uv_req_t* req);


struct uv_cpu_info_s {
  char* model;
  int speed;
  struct uv_cpu_times_s {
    uint64_t user;
    uint64_t nice;
    uint64_t sys;
    uint64_t idle;
    uint64_t irq;
  } cpu_times;
};

struct uv_interface_address_s {
  char* name;
  char phys_addr[6];
  int is_internal;
  union {
    struct sockaddr_in address4;
    struct sockaddr_in6 address6;
  } address;
  union {
    struct sockaddr_in netmask4;
    struct sockaddr_in6 netmask6;
  } netmask;
};

UV_EXTERN char** uv_setup_args(int argc, char** argv);
UV_EXTERN int uv_get_process_title(char* buffer, size_t size);
UV_EXTERN int uv_set_process_title(const char* title);
UV_EXTERN int uv_resident_set_memory(size_t* rss);
UV_EXTERN int uv_uptime(double* uptime);

typedef struct {
  long tv_sec;
  long tv_usec;
} uv_timeval_t;

typedef struct {
   uv_timeval_t ru_utime; /* user CPU time used */
   uv_timeval_t ru_stime; /* system CPU time used */
   uint64_t ru_maxrss;    /* maximum resident set size */
   uint64_t ru_ixrss;     /* integral shared memory size */
   uint64_t ru_idrss;     /* integral unshared data size */
   uint64_t ru_isrss;     /* integral unshared stack size */
   uint64_t ru_minflt;    /* page reclaims (soft page faults) */
   uint64_t ru_majflt;    /* page faults (hard page faults) */
   uint64_t ru_nswap;     /* swaps */
   uint64_t ru_inblock;   /* block input operations */
   uint64_t ru_oublock;   /* block output operations */
   uint64_t ru_msgsnd;    /* IPC messages sent */
   uint64_t ru_msgrcv;    /* IPC messages received */
   uint64_t ru_nsignals;  /* signals received */
   uint64_t ru_nvcsw;     /* voluntary context switches */
   uint64_t ru_nivcsw;    /* involuntary context switches */
} uv_rusage_t;

/*
 * Get information about OS resource utilization for the current process.
 * Please note that not all uv_rusage_t struct fields will be filled on Windows.
 */
UV_EXTERN int uv_getrusage(uv_rusage_t* rusage);

/*
 * This allocates cpu_infos array, and sets count.  The array
 * is freed using uv_free_cpu_info().
 */
UV_EXTERN int uv_cpu_info(uv_cpu_info_t** cpu_infos, int* count);
UV_EXTERN void uv_free_cpu_info(uv_cpu_info_t* cpu_infos, int count);

/*
 * This allocates addresses array, and sets count.  The array
 * is freed using uv_free_interface_addresses().
 */
UV_EXTERN int uv_interface_addresses(uv_interface_address_t** addresses,
  int* count);
UV_EXTERN void uv_free_interface_addresses(uv_interface_address_t* addresses,
  int count);

/*
 * File System Methods.
 *
 * The uv_fs_* functions execute a blocking system call asynchronously (in a
 * thread pool) and call the specified callback in the specified loop after
 * completion. If the user gives NULL as the callback the blocking system
 * call will be called synchronously. req should be a pointer to an
 * uninitialized uv_fs_t object.
 *
 * uv_fs_req_cleanup() must be called after completion of the uv_fs_
 * function to free any internal memory allocations associated with the
 * request.
 */

typedef enum {
  UV_FS_UNKNOWN = -1,
  UV_FS_CUSTOM,
  UV_FS_OPEN,
  UV_FS_CLOSE,
  UV_FS_READ,
  UV_FS_WRITE,
  UV_FS_SENDFILE,
  UV_FS_STAT,
  UV_FS_LSTAT,
  UV_FS_FSTAT,
  UV_FS_FTRUNCATE,
  UV_FS_UTIME,
  UV_FS_FUTIME,
  UV_FS_CHMOD,
  UV_FS_FCHMOD,
  UV_FS_FSYNC,
  UV_FS_FDATASYNC,
  UV_FS_UNLINK,
  UV_FS_RMDIR,
  UV_FS_MKDIR,
  UV_FS_RENAME,
  UV_FS_READDIR,
  UV_FS_LINK,
  UV_FS_SYMLINK,
  UV_FS_READLINK,
  UV_FS_CHOWN,
  UV_FS_FCHOWN
} uv_fs_type;

/* uv_fs_t is a subclass of uv_req_t */
struct uv_fs_s {
  UV_REQ_FIELDS
  uv_fs_type fs_type;
  uv_loop_t* loop;
  uv_fs_cb cb;
  ssize_t result;
  void* ptr;
  const char* path;
  uv_stat_t statbuf;  /* Stores the result of uv_fs_stat and uv_fs_fstat. */
  UV_FS_PRIVATE_FIELDS
};

UV_EXTERN void uv_fs_req_cleanup(uv_fs_t* req);

UV_EXTERN int uv_fs_close(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_open(uv_loop_t* loop, uv_fs_t* req, const char* path,
    int flags, int mode, uv_fs_cb cb);

UV_EXTERN int uv_fs_read(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    const uv_buf_t bufs[], unsigned int nbufs, int64_t offset, uv_fs_cb cb);

UV_EXTERN int uv_fs_unlink(uv_loop_t* loop, uv_fs_t* req, const char* path,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_write(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    const uv_buf_t bufs[], unsigned int nbufs, int64_t offset, uv_fs_cb cb);

UV_EXTERN int uv_fs_mkdir(uv_loop_t* loop, uv_fs_t* req, const char* path,
    int mode, uv_fs_cb cb);

UV_EXTERN int uv_fs_rmdir(uv_loop_t* loop, uv_fs_t* req, const char* path,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_readdir(uv_loop_t* loop, uv_fs_t* req,
    const char* path, int flags, uv_fs_cb cb);

UV_EXTERN int uv_fs_stat(uv_loop_t* loop, uv_fs_t* req, const char* path,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_fstat(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_rename(uv_loop_t* loop, uv_fs_t* req, const char* path,
    const char* new_path, uv_fs_cb cb);

UV_EXTERN int uv_fs_fsync(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_fdatasync(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_ftruncate(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    int64_t offset, uv_fs_cb cb);

UV_EXTERN int uv_fs_sendfile(uv_loop_t* loop, uv_fs_t* req, uv_file out_fd,
    uv_file in_fd, int64_t in_offset, size_t length, uv_fs_cb cb);

UV_EXTERN int uv_fs_chmod(uv_loop_t* loop, uv_fs_t* req, const char* path,
    int mode, uv_fs_cb cb);

UV_EXTERN int uv_fs_utime(uv_loop_t* loop, uv_fs_t* req, const char* path,
    double atime, double mtime, uv_fs_cb cb);

UV_EXTERN int uv_fs_futime(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    double atime, double mtime, uv_fs_cb cb);

UV_EXTERN int uv_fs_lstat(uv_loop_t* loop, uv_fs_t* req, const char* path,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_link(uv_loop_t* loop, uv_fs_t* req, const char* path,
    const char* new_path, uv_fs_cb cb);

/*
 * This flag can be used with uv_fs_symlink on Windows
 * to specify whether path argument points to a directory.
 */
#define UV_FS_SYMLINK_DIR          0x0001

/*
 * This flag can be used with uv_fs_symlink on Windows
 * to specify whether the symlink is to be created using junction points.
 */
#define UV_FS_SYMLINK_JUNCTION     0x0002

UV_EXTERN int uv_fs_symlink(uv_loop_t* loop, uv_fs_t* req, const char* path,
    const char* new_path, int flags, uv_fs_cb cb);

UV_EXTERN int uv_fs_readlink(uv_loop_t* loop, uv_fs_t* req, const char* path,
    uv_fs_cb cb);

UV_EXTERN int uv_fs_fchmod(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    int mode, uv_fs_cb cb);

UV_EXTERN int uv_fs_chown(uv_loop_t* loop, uv_fs_t* req, const char* path,
    uv_uid_t uid, uv_gid_t gid, uv_fs_cb cb);

UV_EXTERN int uv_fs_fchown(uv_loop_t* loop, uv_fs_t* req, uv_file file,
    uv_uid_t uid, uv_gid_t gid, uv_fs_cb cb);


enum uv_fs_event {
  UV_RENAME = 1,
  UV_CHANGE = 2
};


struct uv_fs_event_s {
  UV_HANDLE_FIELDS
  /* private */
  char* path;
  UV_FS_EVENT_PRIVATE_FIELDS
};


/*
 * uv_fs_stat() based polling file watcher.
 */
struct uv_fs_poll_s {
  UV_HANDLE_FIELDS
  /* Private, don't touch. */
  void* poll_ctx;
};

UV_EXTERN int uv_fs_poll_init(uv_loop_t* loop, uv_fs_poll_t* handle);

/*
 * Check the file at `path` for changes every `interval` milliseconds.
 *
 * Your callback is invoked with `status < 0` if `path` does not exist
 * or is inaccessible. The watcher is *not* stopped but your callback is
 * not called again until something changes (e.g. when the file is created
 * or the error reason changes).
 *
 * When `status == 0`, your callback receives pointers to the old and new
 * `uv_stat_t` structs. They are valid for the duration of the callback
 * only!
 *
 * For maximum portability, use multi-second intervals. Sub-second intervals
 * will not detect all changes on many file systems.
 */
UV_EXTERN int uv_fs_poll_start(uv_fs_poll_t* handle,
                               uv_fs_poll_cb poll_cb,
                               const char* path,
                               unsigned int interval);

UV_EXTERN int uv_fs_poll_stop(uv_fs_poll_t* handle);

/*
 * Get the path being monitored by the handle. The buffer must be preallocated
 * by the user. Returns 0 on success or an error code < 0 in case of failure.
 * On sucess, `buf` will contain the path and `len` its length. If the buffer
 * is not big enough UV_ENOBUFS will be returned and len will be set to the
 * required size.
 */
UV_EXTERN int uv_fs_poll_getpath(uv_fs_poll_t* handle, char* buf, size_t* len);


/*
 * UNIX signal handling on a per-event loop basis. The implementation is not
 * ultra efficient so don't go creating a million event loops with a million
 * signal watchers.
 *
 * Note to Linux users: SIGRT0 and SIGRT1 (signals 32 and 33) are used by the
 * NPTL pthreads library to manage threads. Installing watchers for those
 * signals will lead to unpredictable behavior and is strongly discouraged.
 * Future versions of libuv may simply reject them.
 *
 * Reception of some signals is emulated on Windows:
 *
 *   SIGINT is normally delivered when the user presses CTRL+C. However, like
 *   on Unix, it is not generated when terminal raw mode is enabled.
 *
 *   SIGBREAK is delivered when the user pressed CTRL+BREAK.
 *
 *   SIGHUP is generated when the user closes the console window. On SIGHUP the
 *   program is given approximately 10 seconds to perform cleanup. After that
 *   Windows will unconditionally terminate it.
 *
 *   SIGWINCH is raised whenever libuv detects that the console has been
 *   resized. SIGWINCH is emulated by libuv when the program uses an uv_tty_t
 *   handle to write to the console. SIGWINCH may not always be delivered in a
 *   timely manner; libuv will only detect size changes when the cursor is
 *   being moved. When a readable uv_tty_handle is used in raw mode, resizing
 *   the console buffer will also trigger a SIGWINCH signal.
 *
 * Watchers for other signals can be successfully created, but these signals
 * are never received. These signals are: SIGILL, SIGABRT, SIGFPE, SIGSEGV,
 * SIGTERM and SIGKILL.
 *
 * Note that calls to raise() or abort() to programmatically raise a signal are
 * not detected by libuv; these will not trigger a signal watcher.
 *
 * See uv_process_kill() and uv_kill() for information about support for sending
 * signals.
 */
struct uv_signal_s {
  UV_HANDLE_FIELDS
  uv_signal_cb signal_cb;
  int signum;
  UV_SIGNAL_PRIVATE_FIELDS
};

UV_EXTERN int uv_signal_init(uv_loop_t* loop, uv_signal_t* handle);

UV_EXTERN int uv_signal_start(uv_signal_t* handle,
                              uv_signal_cb signal_cb,
                              int signum);

UV_EXTERN int uv_signal_stop(uv_signal_t* handle);


/*
 * Gets load average.
 * See: http://en.wikipedia.org/wiki/Load_(computing)
 * Returns [0,0,0] on Windows.
 */
UV_EXTERN void uv_loadavg(double avg[3]);


/*
 * Flags to be passed to uv_fs_event_start.
 */
enum uv_fs_event_flags {
  /*
   * By default, if the fs event watcher is given a directory name, we will
   * watch for all events in that directory. This flags overrides this behavior
   * and makes fs_event report only changes to the directory entry itself. This
   * flag does not affect individual files watched.
   * This flag is currently not implemented yet on any backend.
   */
  UV_FS_EVENT_WATCH_ENTRY = 1,

  /*
   * By default uv_fs_event will try to use a kernel interface such as inotify
   * or kqueue to detect events. This may not work on remote filesystems such
   * as NFS mounts. This flag makes fs_event fall back to calling stat() on a
   * regular interval.
   * This flag is currently not implemented yet on any backend.
   */
  UV_FS_EVENT_STAT = 2,

  /*
   * By default, event watcher, when watching directory, is not registering
   * (is ignoring) changes in it's subdirectories.
   * This flag will override this behaviour on platforms that support it.
   */
  UV_FS_EVENT_RECURSIVE = 4
};


UV_EXTERN int uv_fs_event_init(uv_loop_t* loop, uv_fs_event_t* handle);

UV_EXTERN int uv_fs_event_start(uv_fs_event_t* handle,
                                uv_fs_event_cb cb,
                                const char* path,
                                unsigned int flags);

UV_EXTERN int uv_fs_event_stop(uv_fs_event_t* handle);

/*
 * Get the path being monitored by the handle. The buffer must be preallocated
 * by the user. Returns 0 on success or an error code < 0 in case of failure.
 * On sucess, `buf` will contain the path and `len` its length. If the buffer
 * is not big enough UV_ENOBUFS will be returned and len will be set to the
 * required size.
 */
UV_EXTERN int uv_fs_event_getpath(uv_fs_event_t* handle,
                                  char* buf,
                                  size_t* len);


/* Utility */

/* Convert string ip addresses to binary structures */
UV_EXTERN int uv_ip4_addr(const char* ip, int port, struct sockaddr_in* addr);
UV_EXTERN int uv_ip6_addr(const char* ip, int port, struct sockaddr_in6* addr);

/* Convert binary addresses to strings */
UV_EXTERN int uv_ip4_name(const struct sockaddr_in* src, char* dst, size_t size);
UV_EXTERN int uv_ip6_name(const struct sockaddr_in6* src, char* dst, size_t size);

/* Cross-platform IPv6-capable implementation of the 'standard' inet_ntop */
/* and inet_pton functions. On success they return 0. If an error */
/* the target of the `dst` pointer is unmodified. */
UV_EXTERN int uv_inet_ntop(int af, const void* src, char* dst, size_t size);
UV_EXTERN int uv_inet_pton(int af, const char* src, void* dst);

/* Gets the executable path */
UV_EXTERN int uv_exepath(char* buffer, size_t* size);

/* Gets the current working directory */
UV_EXTERN int uv_cwd(char* buffer, size_t* size);

/* Changes the current working directory */
UV_EXTERN int uv_chdir(const char* dir);

/* Gets memory info in bytes */
UV_EXTERN uint64_t uv_get_free_memory(void);
UV_EXTERN uint64_t uv_get_total_memory(void);

/*
 * Returns the current high-resolution real time. This is expressed in
 * nanoseconds. It is relative to an arbitrary time in the past. It is not
 * related to the time of day and therefore not subject to clock drift. The
 * primary use is for measuring performance between intervals.
 *
 * Note not every platform can support nanosecond resolution; however, this
 * value will always be in nanoseconds.
 */
UV_EXTERN extern uint64_t uv_hrtime(void);


/*
 * Disables inheritance for file descriptors / handles that this process
 * inherited from its parent. The effect is that child processes spawned by
 * this process don't accidentally inherit these handles.
 *
 * It is recommended to call this function as early in your program as possible,
 * before the inherited file descriptors can be closed or duplicated.
 *
 * Note that this function works on a best-effort basis: there is no guarantee
 * that libuv can discover all file descriptors that were inherited. In general
 * it does a better job on Windows than it does on unix.
 */
UV_EXTERN void uv_disable_stdio_inheritance(void);

/*
 * Opens a shared library. The filename is in utf-8. Returns 0 on success and
 * -1 on error. Call `uv_dlerror(uv_lib_t*)` to get the error message.
 */
UV_EXTERN int uv_dlopen(const char* filename, uv_lib_t* lib);

/*
 * Close the shared library.
 */
UV_EXTERN void uv_dlclose(uv_lib_t* lib);

/*
 * Retrieves a data pointer from a dynamic library. It is legal for a symbol to
 * map to NULL. Returns 0 on success and -1 if the symbol was not found.
 */
UV_EXTERN int uv_dlsym(uv_lib_t* lib, const char* name, void** ptr);

/*
 * Returns the last uv_dlopen() or uv_dlsym() error message.
 */
UV_EXTERN const char* uv_dlerror(const uv_lib_t* lib);

/*
 * The mutex functions return 0 on success or an error code < 0
 * (unless the return type is void, of course).
 */
UV_EXTERN int uv_mutex_init(uv_mutex_t* handle);
UV_EXTERN void uv_mutex_destroy(uv_mutex_t* handle);
UV_EXTERN void uv_mutex_lock(uv_mutex_t* handle);
UV_EXTERN int uv_mutex_trylock(uv_mutex_t* handle);
UV_EXTERN void uv_mutex_unlock(uv_mutex_t* handle);

/*
 * Same goes for the read/write lock functions.
 */
UV_EXTERN int uv_rwlock_init(uv_rwlock_t* rwlock);
UV_EXTERN void uv_rwlock_destroy(uv_rwlock_t* rwlock);
UV_EXTERN void uv_rwlock_rdlock(uv_rwlock_t* rwlock);
UV_EXTERN int uv_rwlock_tryrdlock(uv_rwlock_t* rwlock);
UV_EXTERN void uv_rwlock_rdunlock(uv_rwlock_t* rwlock);
UV_EXTERN void uv_rwlock_wrlock(uv_rwlock_t* rwlock);
UV_EXTERN int uv_rwlock_trywrlock(uv_rwlock_t* rwlock);
UV_EXTERN void uv_rwlock_wrunlock(uv_rwlock_t* rwlock);

/*
 * Same goes for the semaphore functions.
 */
UV_EXTERN int uv_sem_init(uv_sem_t* sem, unsigned int value);
UV_EXTERN void uv_sem_destroy(uv_sem_t* sem);
UV_EXTERN void uv_sem_post(uv_sem_t* sem);
UV_EXTERN void uv_sem_wait(uv_sem_t* sem);
UV_EXTERN int uv_sem_trywait(uv_sem_t* sem);

/*
 * Same goes for the condition variable functions.
 */
UV_EXTERN int uv_cond_init(uv_cond_t* cond);
UV_EXTERN void uv_cond_destroy(uv_cond_t* cond);
UV_EXTERN void uv_cond_signal(uv_cond_t* cond);
UV_EXTERN void uv_cond_broadcast(uv_cond_t* cond);

/*
 * Same goes for the barrier functions.  Note that uv_barrier_wait() returns
 * a value > 0 to an arbitrarily chosen "serializer" thread to facilitate
 * cleanup, i.e.:
 *
 *   if (uv_barrier_wait(&barrier) > 0)
 *     uv_barrier_destroy(&barrier);
 */
UV_EXTERN int uv_barrier_init(uv_barrier_t* barrier, unsigned int count);
UV_EXTERN void uv_barrier_destroy(uv_barrier_t* barrier);
UV_EXTERN int uv_barrier_wait(uv_barrier_t* barrier);

/* Waits on a condition variable without a timeout.
 *
 * Note:
 * 1. callers should be prepared to deal with spurious wakeups.
 */
UV_EXTERN void uv_cond_wait(uv_cond_t* cond, uv_mutex_t* mutex);
/* Waits on a condition variable with a timeout in nano seconds.
 * Returns 0 for success or UV_ETIMEDOUT on timeout, It aborts when other
 * errors happen.
 *
 * Note:
 * 1. callers should be prepared to deal with spurious wakeups.
 * 2. the granularity of timeout on Windows is never less than one millisecond.
 * 3. uv_cond_timedwait takes a relative timeout, not an absolute time.
 */
UV_EXTERN int uv_cond_timedwait(uv_cond_t* cond, uv_mutex_t* mutex,
    uint64_t timeout);

/* Runs a function once and only once. Concurrent calls to uv_once() with the
 * same guard will block all callers except one (it's unspecified which one).
 * The guard should be initialized statically with the UV_ONCE_INIT macro.
 */
UV_EXTERN void uv_once(uv_once_t* guard, void (*callback)(void));

/* Thread-local storage.  These functions largely follow the semantics of
 * pthread_key_create(), pthread_key_delete(), pthread_getspecific() and
 * pthread_setspecific().
 *
 * Note that the total thread-local storage size may be limited.
 * That is, it may not be possible to create many TLS keys.
 */
UV_EXTERN int uv_key_create(uv_key_t* key);
UV_EXTERN void uv_key_delete(uv_key_t* key);
UV_EXTERN void* uv_key_get(uv_key_t* key);
UV_EXTERN void uv_key_set(uv_key_t* key, void* value);

/*
 * Callback that is invoked to initialize thread execution.
 *
 * `arg` is the same value that was passed to uv_thread_create().
 */
typedef void (*uv_thread_cb)(void* arg);

UV_EXTERN int uv_thread_create(uv_thread_t* tid, uv_thread_cb entry, void* arg);
UV_EXTERN unsigned long uv_thread_self(void);
UV_EXTERN int uv_thread_join(uv_thread_t *tid);

/* The presence of these unions force similar struct layout. */
#define XX(_, name) uv_ ## name ## _t name;
union uv_any_handle {
  UV_HANDLE_TYPE_MAP(XX)
};

union uv_any_req {
  UV_REQ_TYPE_MAP(XX)
};
#undef XX


struct uv_loop_s {
  /* User data - use this for whatever. */
  void* data;
  /* Loop reference counting */
  unsigned int active_handles;
  void* handle_queue[2];
  void* active_reqs[2];
  /* Internal flag to signal loop stop */
  unsigned int stop_flag;
  UV_LOOP_PRIVATE_FIELDS
};


/* Don't export the private CPP symbols. */
#undef UV_HANDLE_TYPE_PRIVATE
#undef UV_REQ_TYPE_PRIVATE
#undef UV_REQ_PRIVATE_FIELDS
#undef UV_STREAM_PRIVATE_FIELDS
#undef UV_TCP_PRIVATE_FIELDS
#undef UV_PREPARE_PRIVATE_FIELDS
#undef UV_CHECK_PRIVATE_FIELDS
#undef UV_IDLE_PRIVATE_FIELDS
#undef UV_ASYNC_PRIVATE_FIELDS
#undef UV_TIMER_PRIVATE_FIELDS
#undef UV_GETADDRINFO_PRIVATE_FIELDS
#undef UV_GETNAMEINFO_PRIVATE_FIELDS
#undef UV_FS_REQ_PRIVATE_FIELDS
#undef UV_WORK_PRIVATE_FIELDS
#undef UV_FS_EVENT_PRIVATE_FIELDS
#undef UV_SIGNAL_PRIVATE_FIELDS
#undef UV_LOOP_PRIVATE_FIELDS
#undef UV_LOOP_PRIVATE_PLATFORM_FIELDS

#ifdef __cplusplus
}
#endif
#endif /* UV_H */