93 lines
1.9 KiB
C
93 lines
1.9 KiB
C
#include <limits.h>
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#include <stdbool.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <string.h>
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static bool print(const char* data, size_t length) {
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const unsigned char* bytes = (const unsigned char*) data;
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for (size_t i = 0; i < length; i++)
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if (putchar(bytes[i]) == EOF)
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return false;
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return true;
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}
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int printf(const char* restrict format, ...) {
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va_list parameters;
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va_start(parameters, format);
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int written = 0;
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while (*format != '\0') {
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size_t maxrem = INT_MAX - written;
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if (format[0] != '%' || format[1] == '%') {
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if (format[0] == '%')
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format++;
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size_t amount = 1;
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while (format[amount] && format[amount] != '%')
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amount++;
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if (maxrem < amount) {
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// TODO: Set errno to EOVERFLOW.
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return -1;
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}
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if (!print(format, amount))
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return -1;
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format += amount;
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written += amount;
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continue;
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}
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const char* format_begun_at = format++;
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if (*format == 'c') {
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format++;
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char c = (char) va_arg(parameters, int /* char promotes to int */);
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if (!maxrem) {
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// TODO: Set errno to EOVERFLOW.
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return -1;
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}
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if (!print(&c, sizeof(c)))
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return -1;
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written++;
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} else if (*format == 's') {
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format++;
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const char* str = va_arg(parameters, const char*);
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size_t len = strlen(str);
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if (maxrem < len) {
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// TODO: Set errno to EOVERFLOW.
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return -1;
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}
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if (!print(str, len))
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return -1;
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written += len;
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} else if (*format == 'x') {
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format++;
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int c = va_arg(parameters, int);
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c = c == 10 ? 17 : c;
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if (!maxrem) {
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// TODO: Set errno to EOVERFLOW.
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return -1;
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}
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if (!print("0x", &c))
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return -1;
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written++;
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} else {
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format = format_begun_at;
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size_t len = strlen(format);
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if (maxrem < len) {
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// TODO: Set errno to EOVERFLOW.
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return -1;
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}
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if (!print(format, len))
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return -1;
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written += len;
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format += len;
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}
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}
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va_end(parameters);
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return written;
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}
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