FENIX_libc/stdio/printf.c

#include <limits.h>
#include <stdbool.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>

static bool print(const char * str, size_t len) {
  const unsigned char * bytes = (const unsigned char *) str;

  for(size_t i = 0; i < len; i++) {
    if(putchar(bytes[i]) == EOF) {
      return false;
    }
  }

  return true;
}

int printf(const char * restrict format, ...) {
  va_list parameters;
  va_start(parameters, format);

  int written = 0;

  while(*format != '\0') {
    size_t maxrem = INT_MAX - written;

    if(format[0] != '%' || format[1] == '%') {
      if(format[0] == '%') {
	format++;
      }

      size_t amount = 1;

      while(format[amount] && format[amount] != '%') {
	amount++;
      }

      if(maxrem < amount) {
	/* TODO: Set errno to EOVERFLOW after implementing errno.h */
	return -1;
      }

      if(!print(format, amount)) {
	return -1;
      }

      format += amount;
      written += amount;
      continue;
    }

    const char * format_begun_at = format++;

    /* TODO: Implement all format specifiers (%g, %o, &c.) */
    if(*format == 'c') {
      format++;
      char c = (char) va_arg(parameters, int);

      if(!maxrem) {
	/* TODO: Set errno to EOVERFLOW after implementing errno.h */
	return -1;
      }

      if(!print(&c, sizeof(c))) {
	return -1;
      }

      written++;
    }
    else if(*format == 's') {
      format++;
      const char * str = va_arg(parameters, const char *);
      size_t len = strlen(str);

      if(maxrem < len) {
	/* TODO: Set errno to EOVERFLOW after implementing errno.h */
	return -1;
      }

      if(!print(str, len)) {
	return -1;
      }

      written += len;
    }
    else {
      format = format_begun_at;
      size_t len = strlen(format);

      if(maxrem < len) {
	/* TODO: Set errno to EOVERFLOW after implementing errno.h */
	return -1;
      }

      if(!print(format, len)) {
	return -1;
      }

      format += len;
    } 
  }

  va_end(parameters);

  return(written);
}