happz/ducky

/*
 * The Minimal snprintf() implementation
 * Copyright (c) 2013 Michal Ludvig <michal@logix.cz>
 *
 * This is a minimal snprintf() implementation optimised
 * for embedded systems with a very limited program memory.
 * mini_snprintf() doesn't support _all_ the formatting
 * the glibc does but on the other hand is a lot smaller.
 * Here are some numbers from my STM32 project (.bin file size):
 *      no snprintf():      10768 bytes
 *      mini snprintf():    11420 bytes     (+  652 bytes)
 *      glibc snprintf():   34860 bytes     (+24092 bytes)
 * Wasting nearly 24kB of memory just for snprintf() on
 * a chip with 32kB flash is crazy. Use mini_snprintf() instead.
 */

#include <stdarg.h>

static unsigned int
mini_strlen(const char *s)
{
    unsigned int len = 0;
    while (s[len] != '\0') len++;
    return len;
}

static char *_putc(char ch, char *pbuffer, char *buffer, unsigned int buffer_len)
{
  if ((unsigned int)((pbuffer - buffer) + 1) >= buffer_len)
      return 0;
  *(pbuffer++) = ch;
    *(pbuffer) = '\0';
  return pbuffer;
}

static char *_puts(char *s, unsigned int len, char *pbuffer, char *buffer, unsigned int buffer_len)
{
    unsigned int i;

    if (buffer_len - (pbuffer - buffer) - 1 < len)
        len = buffer_len - (pbuffer - buffer) - 1;

    /* Copy to buffer */
    for (i = 0; i < len; i++)
        *(pbuffer++) = s[i];
    *(pbuffer) = '\0';

  return pbuffer;
}

static unsigned int
mini_utoa(unsigned int value, unsigned int radix, unsigned int uppercase,
     char *buffer, unsigned int zero_pad)
{
    char    *pbuffer = buffer;
    int    negative = 0;
    unsigned int    i, len;

    /* No support for unusual radixes. */
    if (radix > 16)
        return 0;

    /* This builds the string back to front ... */
    do {
        int digit = value % radix;
        *(pbuffer++) = (digit < 10 ? '0' + digit : (uppercase ? 'A' : 'a') + digit - 10);
        value /= radix;
    } while (value > 0);

    for (i = (pbuffer - buffer); i < zero_pad; i++)
        *(pbuffer++) = '0';

    if (negative)
        *(pbuffer++) = '-';

    *(pbuffer) = '\0';

    /* ... now we reverse it (could do it recursively but will
     * conserve the stack space) */
    len = (pbuffer - buffer);
    for (i = 0; i < len / 2; i++) {
        char j = buffer[i];
        buffer[i] = buffer[len-i-1];
        buffer[len-i-1] = j;
    }

    return len;
}

int
mini_vsnprintf(char *buffer, unsigned int buffer_len, char *fmt, va_list va)
{
    char *pbuffer = buffer;
    char bf[24];
    char ch;

    while ((ch=*(fmt++))) {
        if ((unsigned int)((pbuffer - buffer) + 1) >= buffer_len)
            break;
        if (ch!='%')
            pbuffer = _putc(ch, pbuffer, buffer, buffer_len);
        else {
            char zero_pad = 0;
            char *ptr;
            unsigned int len;

            ch=*(fmt++);

            /* Zero padding requested */
            if (ch=='0') {
                ch=*(fmt++);
                if (ch == '\0')
                    goto end;
                if (ch >= '0' && ch <= '9')
                    zero_pad = ch - '0';
                ch=*(fmt++);
            }

            switch (ch) {
                case 0:
                    goto end;

                case 'd': {
          int i = va_arg(va, int);
          unsigned int u = (unsigned int)(i >= 0 ? i : -i);

          if ((unsigned int)i != u)
            pbuffer = _putc('-', pbuffer, buffer, buffer_len);

                    len = mini_utoa(u, 10, 0, bf, zero_pad);
                    pbuffer = _puts(bf, len, pbuffer, buffer, buffer_len);
                  }
                    break;

                case 'u':
          len = mini_utoa(va_arg(va, unsigned int), 10, 0, bf, zero_pad);
          pbuffer = _puts(bf, len, pbuffer, buffer, buffer_len);
          break;

                case 'x':
                case 'X':
                    len = mini_utoa(va_arg(va, unsigned int), 16, (ch=='X'), bf, zero_pad);
                    pbuffer = _puts(bf, len, pbuffer, buffer, buffer_len);
                    break;

                case 'c' :
                    pbuffer = _putc((char)(va_arg(va, int)), pbuffer, buffer, buffer_len);
                    break;

                case 's' :
                    ptr = va_arg(va, char*);
                    pbuffer = _puts(ptr, mini_strlen(ptr), pbuffer, buffer, buffer_len);
                    break;

        case 'C':
          ptr = va_arg(va, char *);
          len = va_arg(va, unsigned int);
          pbuffer = _puts(ptr, len, pbuffer, buffer, buffer_len);
          break;

                default:
                    pbuffer = _putc(ch, pbuffer, buffer, buffer_len);
                    break;
            }
        }
    }
end:
    return pbuffer - buffer;
}


int
mini_snprintf(char* buffer, unsigned int buffer_len, char *fmt, ...)
{
    int ret;
    va_list va;
    va_start(va, fmt);
    ret = mini_vsnprintf(buffer, buffer_len, fmt, va);
    va_end(va);

    return ret;
}