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#include <limits.h>
#include <stdbool.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
static bool print(const char* data, size_t length) {
const unsigned char* bytes = (const unsigned char*) data;
for (size_t i = 0; i < length; i++)
if (putchar(bytes[i]) == EOF)
return false;
return true;
}
// for %d and %x.
static const char* itoa(unsigned int num, char* str, unsigned int base) {
int cou = 0; // nt
if (num == 0) { // 0
str[cou] = '0';
str[++cou] = '\0';
return str;
}
while (num)
{
unsigned int rem = (num % base);
// brings the number up to ascii 0 + the digit
if (rem > 9) {
str[cou] = rem + '7'; // 7 = 55 + 10(A) = 65
} else {
str[cou] = rem + '0';
}
num /= base;
++cou;
}
// reverse the string
size_t start = 0;
size_t end = cou - 1;
while (start < end) {
char temp = str[start];
str[start] = str[end];
str[end] = temp;
++start;
--end;
}
str[cou] = '\0';
return str;
}
// have no idea if there's a better way to do this. for %lx
static const char* itoa_u64(unsigned long long num, char* str, int base) {
size_t cou = 0; // nt
if (num == 0) { // 0
str[cou] = '0';
str[++cou] = '\0';
return str;
}
while (num)
{
unsigned long long rem = num % base;
// brings the number up to ascii 0 + the digit
if (rem > 9) {
str[cou] = rem + '7'; // 7 = 55 + 10(A) = 65
} else {
str[cou] = rem + '0';
}
num /= base;
++cou;
}
// reverse the string
size_t start = 0;
size_t end = cou - 1;
while (start < end) {
char temp = str[start];
str[start] = str[end];
str[end] = temp;
++start;
--end;
}
str[cou] = '\0';
return str;
}
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.
return -1;
}
if (!print(format, amount))
return -1;
format += amount;
written += amount;
continue;
}
const char* format_begun_at = format++;
if (*format == 'c') {
format++;
char c = (char) va_arg(parameters, int /* char promotes to int */);
if (!maxrem) {
// TODO: Set errno to EOVERFLOW.
return -1;
}
if (!print(&c, sizeof(c)))
return -1;
written++;
} else if (*format == 'd') {
format++;
char str[20]; // probably a long enough buffer
unsigned int d = va_arg(parameters, unsigned int);
itoa(d, str, 10);
size_t len = strlen(str);
if (maxrem < len) {
// TODO: Set errno to EOVERFLOW.
return -1;
}
if (!print(str, len))
return -1;
written += len;
} else if (*format == 'x') {
format++;
char str[20]; // probably a long enough buffer
unsigned int d = va_arg(parameters, unsigned int);
itoa(d, str, 16);
size_t len = strlen(str);
if (maxrem < len) {
// TODO: Set errno to EOVERFLOW.
return -1;
}
if (!print(str, len))
return -1;
written += len;
} else if (*format == 'l') { // for %lx and others that start with l
format++;
if (*format == 'x') {
format++;
char str[20]; // probably a long enough buffer
unsigned long long d = va_arg(parameters, unsigned long long);
itoa_u64(d, str, 16);
size_t len = strlen(str);
if (maxrem < len) {
// TODO: Set errno to EOVERFLOW.
return -1;
}
if (!print(str, len))
return -1;
written += len;
}
} 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.
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.
return -1;
}
if (!print(format, len))
return -1;
written += len;
format += len;
}
}
va_end(parameters);
return written;
}
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