banan-os/libc/printf_impl.cpp

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#include <BAN/Traits.h>
#include <BAN/Math.h>
#include <ctype.h>
#include <errno.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
#define BAN_PRINTF_PUTC(c) \
do \
{ \
if (putc_fun((c), data) == EOF) \
return -1; \
written++; \
} while (false)
struct format_options_t
{
bool alternate_form { false };
bool zero_padded { false };
bool left_justified { false };
bool show_plus_sign_as_space { false };
bool show_plus_sign { false };
int width { -1 };
int percision { -1 };
};
template<BAN::integral T>
static void integer_to_string(char* buffer, T value, int base, bool upper, const format_options_t options)
{
int width = 1;
bool zero_padded = options.zero_padded;
if (options.percision != -1)
{
width = options.percision;
zero_padded = false;
}
else if (options.width != -1)
width = options.width;
auto digit_char = [](int digit, bool upper)
{
if (digit < 10)
return '0' + digit;
return (upper ? 'A' : 'a') + (digit - 10);
};
bool sign = false;
int offset = 0;
if (value < 0)
{
sign = true;
buffer[offset++] = digit_char(-(value % base), upper);
value = -(value / base);
}
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if (value == 0 && width > 0)
buffer[offset++] = '0';
while (value)
{
buffer[offset++] = digit_char(value % base, upper);
value /= base;
}
int prefix_length = 0;
if (sign || options.show_plus_sign || options.show_plus_sign_as_space)
prefix_length++;
if (base == 8 && options.alternate_form)
prefix_length++;
if (base == 16 && options.alternate_form)
prefix_length += 2;
while (offset < width - prefix_length)
buffer[offset++] = (zero_padded ? '0' : ' ');
if (sign)
buffer[offset++] = '-';
else if (options.show_plus_sign)
buffer[offset++] = '+';
else if (options.show_plus_sign_as_space)
buffer[offset++] = ' ';
if (base == 8 && options.alternate_form)
buffer[offset++] = '0';
if (base == 16 && options.alternate_form)
{
buffer[offset++] = 'x';
buffer[offset++] = '0';
}
for (int i = 0; i < offset / 2; i++)
{
char temp = buffer[i];
buffer[i] = buffer[offset - i - 1];
buffer[offset - i - 1] = temp;
}
buffer[offset++] = '\0';
}
template<BAN::floating_point T>
static void floating_point_to_string(char* buffer, T value, bool upper, const format_options_t options)
{
int percision = 6;
if (options.percision != -1)
percision = options.percision;
int offset = 0;
// Add sign if needed
if (value < (T)0.0)
{
buffer[offset++] = '-';
value = -value;
}
else if (options.show_plus_sign)
buffer[offset++] = '+';
else if (options.show_plus_sign_as_space)
buffer[offset++] = ' ';
// Round last digit
value += (T)0.5 * BAN::Math::pow<T>(10.0, -percision);
// Add integer part of the decimal
if (value < (T)1.0)
{
buffer[offset++] = '0';
value *= (T)10.0;
}
else
{
int exponent = (int)BAN::Math::log10<T>(value);
T magnitude = BAN::Math::pow<T>(10, exponent);
value /= magnitude;
for (int i = 0; i <= exponent; i++)
{
int digit = 0;
for (; digit < 10; digit++)
if (value < digit + 1)
break;
buffer[offset++] = '0' + digit;
value -= (T)digit;
value *= (T)10.0;
}
}
// We are done if the decimal part is not written
if (percision == 0 && !options.alternate_form)
{
buffer[offset++] = '\0';
return;
}
buffer[offset++] = '.';
// Add the 'percision' digits after decimal point
for (int i = 0; i < percision; i++)
{
int digit = 0;
for (; digit < 10; digit++)
if (value < digit + 1)
break;
buffer[offset++] = '0' + digit;
value -= (T)digit;
value *= (T)10.0;
}
buffer[offset++] = '\0';
}
template<BAN::floating_point T>
static void floating_point_to_exponent_string(char* buffer, T value, bool upper, const format_options_t options)
{
int percision = 6;
if (options.percision != -1)
percision = options.percision;
int offset = 0;
// Add sign if needed
if (value < (T)0.0)
{
buffer[offset++] = '-';
value = -value;
}
else if (options.show_plus_sign)
buffer[offset++] = '+';
else if (options.show_plus_sign_as_space)
buffer[offset++] = ' ';
// Calculate which number to put as exponent
int exponent = 0;
if (value != (T)0.0)
{
exponent = (int)floorl(BAN::Math::log10<T>(value));
value /= BAN::Math::pow<T>(10.0, exponent);
}
// Add first numbers before 'e'
floating_point_to_string<T>(buffer + offset, value, upper, options);
offset = strlen(buffer);
// Add the exponent part
buffer[offset++] = (upper ? 'E' : 'e');
format_options_t exponent_options;
exponent_options.show_plus_sign = true;
exponent_options.zero_padded = true;
exponent_options.width = 3;
integer_to_string<int>(buffer + offset, exponent, 10, upper, exponent_options);
}
extern "C" int printf_impl(const char* format, va_list arguments, int (*putc_fun)(int, void*), void* data)
{
int written = 0;
while (*format)
{
if (*format == '%')
{
format_options_t options;
// PARSE FLAGS
bool flags_done = false;
while (!flags_done)
{
format++;
switch (*format)
{
case '#': options.alternate_form = true; break;
case '0': options.zero_padded = true; break;
case '-': options.left_justified = true; break;
case ' ': options.show_plus_sign_as_space = true; break;
case '+': options.show_plus_sign = true; break;
default:
flags_done = true;
break;
}
}
if (options.zero_padded && options.left_justified)
options.zero_padded = false;
// PARSE FIELD WIDTH
if (*format == '*')
{
options.width = va_arg(arguments, int);
format++;
}
else if (isdigit(*format) && *format != '0')
{
int width = 0;
while (isdigit(*format))
{
width *= 10;
width += *format - '0';
format++;
}
options.width = width;
}
// PARSE PERCISION
if (*format == '.')
{
format++;
int percision = 0;
if (isdigit(*format))
{
while (isdigit(*format))
{
percision *= 10;
percision += *format - '0';
format++;
}
}
else if (*format == '*')
{
percision = va_arg(arguments, int);
}
if (percision < 0)
percision = -1;
options.percision = percision;
}
// TODO: Lenght modifier
static char conversion[1024];
const char* string = nullptr;
switch (*format)
{
case 'd':
case 'i':
{
int value = va_arg(arguments, int);
integer_to_string<int>(conversion, value, 10, false, options);
string = conversion;
format++;
break;
}
case 'o':
{
unsigned int value = va_arg(arguments, unsigned int);
integer_to_string<unsigned int>(conversion, value, 8, false, options);
string = conversion;
format++;
break;
}
case 'u':
{
unsigned int value = va_arg(arguments, unsigned int);
integer_to_string<unsigned int>(conversion, value, 10, false, options);
string = conversion;
format++;
break;
}
case 'x':
case 'X':
{
unsigned int value = va_arg(arguments, unsigned int);
integer_to_string<unsigned int>(conversion, value, 16, *format == 'X', options);
string = conversion;
format++;
break;
}
case 'e':
case 'E':
{
double value = va_arg(arguments, double);
floating_point_to_exponent_string<double>(conversion, value, *format == 'E', options);
string = conversion;
format++;
break;
}
case 'f':
case 'F':
{
double value = va_arg(arguments, double);
floating_point_to_string<double>(conversion, value, *format == 'F', options);
string = conversion;
format++;
break;
}
case 'g':
case 'G':
// TODO
break;
case 'a':
case 'A':
// TODO
break;
case 'c':
{
conversion[0] = va_arg(arguments, int);
conversion[1] = '\0';
string = conversion;
format++;
break;
}
case 's':
{
string = va_arg(arguments, const char*);
format++;
break;
}
case 'C':
// TODO (depricated)
break;
case 'S':
// TODO (depricated)
break;
case 'p':
{
void* ptr = va_arg(arguments, void*);
options.alternate_form = true;
integer_to_string<uintptr_t>(conversion, (uintptr_t)ptr, 16, false, options);
string = conversion;
format++;
break;
}
case 'n':
{
int* target = va_arg(arguments, int*);
*target = written;
format++;
break;
}
case 'm':
{
// NOTE: this is a glibc extension
if (options.alternate_form)
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string = strerrorname_np(errno);
else
string = strerror(errno);
format++;
break;
}
case '%':
{
conversion[0] = '%';
conversion[1] = '\0';
string = conversion;
format++;
break;
}
default:
break;
}
if (string)
{
int len = strlen(string);
if (options.width == -1)
options.width = 0;
if (!options.left_justified)
for (int i = len; i < options.width; i++)
BAN_PRINTF_PUTC(' ');
while (*string)
{
BAN_PRINTF_PUTC(*string);
string++;
}
if (options.left_justified)
for (int i = len; i < options.width; i++)
BAN_PRINTF_PUTC(' ');
}
}
else
{
BAN_PRINTF_PUTC(*format);
format++;
}
}
return written;
}