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#include <stdbool.h>
#include <shared/mem.h>
#include <shared/printf.h>
struct out_state {
void (*back)(void *, const char *, size_t);
void *backarg;
int written;
};
static int output(struct out_state *os, const char *buf, size_t len) {
if (len) os->back(os->backarg, buf, len);
os->written += len;
return os->written;
}
static void output_c(struct out_state *os, char c) {
output(os, &c, 1);
}
struct mods {
char fill_char;
size_t field_width;
};
static void pad(struct out_state *os, struct mods *m, size_t len) {
for (size_t i = 0; len + i < m->field_width; i++)
output(os, &m->fill_char, 1);
}
static void output_uint(struct out_state *os, struct mods *m, unsigned long long n) {
// TODO static assert sizeof(unsigned long long) <= 8
char buf[20];
size_t pos = sizeof(buf);
if (!n) {
buf[--pos] = '0';
} else while (n) {
unsigned long long q = n / 10, r = n % 10;
buf[--pos] = r + '0';
n = q;
}
pad(os, m, sizeof(buf) - pos);
output(os, buf + pos, sizeof(buf) - pos);
}
int __printf_internal(const char *fmt, va_list argp,
void (*back)(void*, const char*, size_t), void *backarg)
{
const char *seg = fmt; /* beginning of the current non-modifier streak */
struct out_state os = {
.back = back,
.backarg = backarg,
};
for (;;) {
char c = *fmt++;
if (c == '\0') {
return output(&os, seg, fmt - seg - 1);
}
if (c != '%') continue;
output(&os, seg, fmt - seg - 1);
struct mods m = {
.fill_char = ' ',
.field_width = 0,
};
for (bool modifier = true; modifier;) {
c = *fmt++;
switch (c) {
case '0':
m.fill_char = '0';
break;
default:
modifier = false;
break;
}
}
while ('0' <= c && c <= '9') {
m.field_width *= 10;
m.field_width += c - '0';
c = *fmt++;
}
// TODO length modifiers
switch (c) {
unsigned long n, len;
case 'c':
output_c(&os, va_arg(argp, int));
break;
case 's':
const char *s = va_arg(argp, char*);
if (s) {
len = strlen(s);
pad(&os, &m, len);
output(&os, s, len);
} else {
pad(&os, &m, 0);
}
break;
case 'x':
n = va_arg(argp, unsigned long);
len = 1;
while (n >> (len * 4) && (len * 4) < (sizeof(n) * 8))
len++;
pad(&os, &m, len);
while (len-- > 0) {
char h = '0' + ((n >> (len * 4)) & 0xf);
if (h > '9') h += 'a' - '9' - 1;
output_c(&os, h);
}
break;
case 'u':
n = va_arg(argp, unsigned long);
output_uint(&os, &m, n);
break;
case '%':
output(&os, "%", 1);
break;
}
seg = fmt;
}
}
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