Function _mi_vsnprintf

system/lib/mimalloc/src/libc.c:222–343

#define MI_NEXTC()  c = *in; if (c==0) break; in++;

int _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args) {
  if (buf == NULL || bufsize == 0 || fmt == NULL) return 0;
  buf[bufsize - 1] = 0;
  char* const end = buf + (bufsize - 1);
  const char* in = fmt;
  char* out = buf;
  while (true) {
    if (out >= end) break;
    char c;
    MI_NEXTC();
    if (c != '%') {
      if (c == '\\') {
        MI_NEXTC();
        switch (c) {
        case 'e': mi_outc('\x1B', &out, end); break;
        case 't': mi_outc('\t', &out, end); break;
        case 'n': mi_outc('\n', &out, end); break;
        case 'r': mi_outc('\r', &out, end); break;
        case '\\': mi_outc('\\', &out, end); break;
        default: /* ignore */ break;
        }
      }
      else if ((c >= ' ' && c <= '~') || c=='\n' || c=='\r' || c=='\t' || c=='\x1b') { // output visible ascii or standard control only
        mi_outc(c, &out, end);
      }
    }
    else {
      MI_NEXTC();
      char   fill = ' ';
      size_t width = 0;
      char   numtype = 'd';
      char   numplus = 0;
      bool   alignright = true;
      if (c == '+' || c == ' ') { numplus = c; MI_NEXTC(); }
      if (c == '-') { alignright = false; MI_NEXTC(); }
      if (c == '0') { fill = '0'; MI_NEXTC(); }
      if (c >= '1' && c <= '9') {
        width = (c - '0'); MI_NEXTC();
        while (c >= '0' && c <= '9') {
          width = (10 * width) + (c - '0'); MI_NEXTC();
        }
        if (c == 0) break;  // extra check due to while
      }
      if (c == 'z' || c == 't' || c == 'L') { numtype = c; MI_NEXTC(); }
      else if (c == 'l') {
        numtype = c; MI_NEXTC();
        if (c == 'l') { numtype = 'L'; MI_NEXTC(); }
      }

      char* start = out;
      if (c == '%') {
        mi_outc('%', &out, end);
      }
      else if (c == 's') {
        // string
        const char* s = va_arg(args, const char*);
        mi_outs(s, &out, end);
      }