banan-os/libc/stdio/printf.cpp

170 lines
2.9 KiB
C++

#include <limits.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
static bool print(const char* data, size_t len)
{
const unsigned char* bytes = reinterpret_cast<const unsigned char*>(data);
for(size_t i = 0; i < len; i++)
if (putchar(bytes[i]) == EOF)
return false;
return true;
}
static bool print_int(int value, size_t& out_len)
{
if (value == -2147483648)
{
if (!print("-2147483648", 11))
return false;
out_len = 11;
return true;
}
// Enough for any (32-bit) integer value
char buffer[11];
char* ptr = buffer + sizeof(buffer);
int len = 0;
bool sign = false;
if (value < 0)
{
sign = true;
value = -value;
}
while (value)
{
*(--ptr) = (value % 10) + '0';
value /= 10;
len++;
}
if (sign)
{
*(--ptr) = '-';
len++;
}
if (!print(ptr, len))
return false;
out_len = len;
return true;
}
static char bits_to_hex(unsigned char bits)
{
if (bits < 10)
return bits + '0';
return bits - 10 + 'a';
}
static bool print_ptr(void* ptr, size_t& out_len)
{
ptrdiff_t addr = reinterpret_cast<ptrdiff_t>(ptr);
char buffer[2 + sizeof(ptrdiff_t) * 2];
buffer[0] = '0';
buffer[1] = 'x';
size_t bytes = sizeof(ptrdiff_t);
for (size_t i = 1; i <= bytes; i++)
{
unsigned char byte = (addr >> ((bytes - i) * 8)) & 0xff;
buffer[i * 2 + 0] = bits_to_hex(byte >> 4);
buffer[i * 2 + 1] = bits_to_hex(byte & 0b1111);
}
if (!print(buffer, 2 + bytes * 2))
return false;
out_len = 2 + bytes * 2;
return true;
}
int printf(const char* __restrict format, ...)
{
va_list args;
va_start(args, format);
int written = 0;
while (*format)
{
size_t max_rem = INT_MAX - written;
if (format[0] != '%' || format[1] == '%')
{
if (format[0] == '%')
format++;
size_t len = 1;
while (format[len] && format[len] != '%')
len++;
if (!print(format, len))
return -1;
format += len;
written += len;
continue;
}
const char* format_start = format++;
if (*format == 'c')
{
format++;
char c = (char)va_arg(args, int);
if (!max_rem) // FIXME: EOVERFLOW
return -1;
if (!print(&c, sizeof(c)))
return -1;
written++;
}
else if (*format == 's')
{
format++;
const char* str = va_arg(args, const char*);
size_t len = strlen(str);
if (max_rem < len) // FIXME: EOVERFLOW
return -1;
if (!print(str, len))
return -1;
written += len;
}
else if (*format == 'd' || *format == 'i')
{
format++;
int value = va_arg(args, int);
size_t len;
if (!print_int(value, len))
return -1;
written += len;
}
else if (*format == 'p')
{
format++;
void* const ptr = va_arg(args, void*);
size_t len;
if (!print_ptr(ptr, len))
return -1;
written += len;
}
else
{
format = format_start;
size_t len = strlen(format);
if (max_rem < len) // FIXME: EOVERFLOW
return -1;
if (!print(format, len))
return -1;
written += len;
format += len;
}
}
va_end(args);
return written;
}