Created
May 12, 2015 04:15
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Simple fgetc implementation in Go
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| package main | |
| import ( | |
| "fmt" | |
| "os" | |
| "syscall" | |
| ) | |
| type File struct { | |
| file *os.File | |
| buf []byte | |
| off int | |
| end int | |
| flags int | |
| } | |
| func main() { | |
| file, err := Open("idk.c") | |
| if err != nil { | |
| panic(err) | |
| } | |
| defer file.Close() | |
| var c byte | |
| for { | |
| c, err = file.FGetC() | |
| if err != nil { | |
| break | |
| } | |
| fmt.Printf("%c", c) | |
| } | |
| } | |
| func Open(name string) (*File, error) { | |
| file, err := os.Open(name) | |
| if err != nil { | |
| return nil, err | |
| } | |
| buf, err := syscall.Mmap(-1, 0, syscall.Getpagesize(), | |
| syscall.PROT_READ|syscall.PROT_WRITE, | |
| syscall.MAP_PRIVATE|syscall.MAP_ANONYMOUS) | |
| if err != nil { | |
| file.Close() | |
| return nil, err | |
| } | |
| return &File{file, buf, 0, 0, 0}, nil | |
| } | |
| func (f *File) Close() error { | |
| err := syscall.Munmap(f.buf) | |
| if err != nil { | |
| return err | |
| } | |
| return f.file.Close() | |
| } | |
| func (f *File) Read() (int, error) { | |
| f.off = -1 | |
| n, err := f.file.Read(f.buf[0:]) | |
| f.end = n | |
| return n, err | |
| } | |
| // Returns one byte from the file. | |
| func (f *File) FGetC() (byte, error) { | |
| // (re)fill our buffer if needed. | |
| if f.off >= f.end { | |
| _, err := f.Read() | |
| if err != nil { | |
| return 0, err | |
| } | |
| } | |
| f.off++ | |
| return f.buf[f.off], nil | |
| } |
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