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#include <lcq/pit/utils.h>
enum vsnprintf_mode {
VSNPRINTF_MODE_NORMAL,
VSNPRINTF_MODE_FLAGS,
VSNPRINTF_MODE_WIDTH,
VSNPRINTF_MODE_PRECISION,
VSNPRINTF_MODE_LENGTH_MOD,
VSNPRINTF_MODE_CONVERSION_SPEC
};
#define SCRATCH_LEN 256
#define WRITE(c) { buf[idx++] = c; if (idx >= len - 1) goto done; }
#define WRITE_SCRATCH(c) { scratch[sidx++] = c; if (sidx >= SCRATCH_LEN) goto error; }
int pit_libc_string_vsnprintf(char *buf, size_t len, char *format, va_list ap) {
// vsnprintf
size_t idx = 0;
size_t flen = pit_libc_string_strlen(format);
size_t fidx = 0;
enum vsnprintf_mode mode = VSNPRINTF_MODE_NORMAL;
size_t sidx = 0;
char scratch[SCRATCH_LEN] = {0};
char length_mod = 0;
for (; fidx < flen && idx < len - 1; ++fidx) {
char c = format[fidx];
sidx = 0;
switch (mode) {
case VSNPRINTF_MODE_NORMAL:
if (c == '%') {
mode = VSNPRINTF_MODE_FLAGS;
} else WRITE(c);
break;
case VSNPRINTF_MODE_FLAGS:
case VSNPRINTF_MODE_WIDTH:
case VSNPRINTF_MODE_PRECISION:
case VSNPRINTF_MODE_LENGTH_MOD:
switch (c) {
case 'l': length_mod = 'l'; mode = VSNPRINTF_MODE_CONVERSION_SPEC; continue;
}
// fallthrough
case VSNPRINTF_MODE_CONVERSION_SPEC:
switch (c) {
case '%': WRITE('%'); mode = VSNPRINTF_MODE_NORMAL; break;
case 'd': {
long arg = 0;
if (length_mod == 'l') arg = va_arg(ap, long); else arg = va_arg(ap, int);
if (arg == 0) { WRITE('0') }
else {
if (arg < 0) { WRITE('-'); arg = -arg; }
while (arg != 0) { WRITE_SCRATCH('0' + (char) (arg % 10)); arg /= 10; }
while (sidx > 0) { WRITE(scratch[sidx - 1]); sidx -= 1; }
}
mode = VSNPRINTF_MODE_NORMAL;
break;
}
case 'f': {
double arg = 0.0;
if (length_mod == 'l')
arg = va_arg(ap, double);
else
arg = va_arg(ap, double);
long wholepart = (long) arg;
double fracpart = arg - (double) wholepart;
if (wholepart == 0) { WRITE('0') }
else {
while (wholepart != 0) { WRITE_SCRATCH('0' + (char) (wholepart % 10)); wholepart /= 10; }
while (sidx > 0) { WRITE(scratch[sidx - 1]); sidx -= 1; }
}
WRITE('.');
for (int i = 0; i < 6; ++i) {
fracpart *= 10.0;
wholepart = (long) fracpart;
fracpart -= (double) wholepart;
WRITE('0' + (char) wholepart);
}
mode = VSNPRINTF_MODE_NORMAL;
break;
}
case 's': {
char *arg = va_arg(ap, char *);
while (*arg != 0) { WRITE(*arg); arg += 1; }
mode = VSNPRINTF_MODE_NORMAL;
break;
}
default: goto error;
}
break;
}
}
done:
buf[idx] = 0;
return (int) idx;
error:
return -1;
}
int pit_libc_string_snprintf(char *buf, size_t len, char *format, ...) {
va_list ap;
va_start(ap, format);
int ret = pit_libc_string_vsnprintf(buf, len, format, ap);
va_end(ap);
return ret;
}
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