Minimal scanf() implementation for embedded projects. All this happiness 150 lines :)

Recently I had the opportunity to implement firmware for systems with limited resources (6502,8080). No one expects speed from them, so the amount of addressable memory has become the main limitation.

I looked around the internet for some stripped down scanf() implementations but none I really liked. Then I decided to develop my own minimal scanf()/sscanf().

I did not implement this tool in strict accordance with the standard. Rather, it parodies functions from glibc.

Supported control characters:

%c  - matches a character or a sequence of characters
%s  - matches a sequence of non-whitespace characters (a string) 
%[] - matches a non-empty sequence of character from set of characters. 
%d  - matches a decimal integer. 
%u  - same as %d (You can enable ignoring the sign. nostd)

Mechanisms are also implemented:

// ?  - control characters
// @  - any character
// .. - etc

%12..0? - max field width modifier
%*?     - input suppression
%[@..]  - read selected characters (ranges are not supported)
%[^@..] - read until a character is encountered

NOTE: The return value is different from glibc! My implementation counts the number of parameters processed.

NOTE: The standard implementation of scanf is stream-based and has fifo. This is a very demanding mechanism. The buffer has been simplified to be able to return a single character. This allows you to emit NOT reading the delimiter character. Works a little differently.

It's completely standalone without any external dependencies. This implementation does not use memory allocation.

C_SSCANF // Comment out `#define` in order to use code like `scanf`
LENSCANS // The number of characters processed in the `%[]` construct

NOTE: Don't make LENSCANS too big. This affects performance.

Count one character (not expecting a delimiter). Returns a character directly. Redefine this function to read from UART.

int getch()

The function of reading and returning sibyl to the emitted stream. c_getch returns a character from the buffer, or a result getch().

The function c_getbackch allows you to write to the buffer. Returns false if there is nothing in the buffer, or true if there is no value in the buffer.

char c_getch()
bool c_getbackch(char b)

// "%d %*d %2u %c %s %[^$] %d"
in: -9 5 20 asd-   en d$ 3
imp:  D=-9 U=20 C=a S=sd- SS=en d  test=3  R=7
ref:  D=-9 U=20 C=a S=sd- SS=en d  test=3  R=5

test:

clear && gcc *.c -I ./ && ./a.out

Project inspired by the work of mini-printf