FENIX_libc/stdio/printf.c
2020-02-11 23:23:27 -06:00

107 lines
1.9 KiB
C
Executable file

#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);
}