/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-â
âvi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :viâ
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ¡
â Copyright 2020 Justine Alexandra Roberts Tunney                              â
â                                                                              â
â Permission to use, copy, modify, and/or distribute this software for         â
â any purpose with or without fee is hereby granted, provided that the         â
â above copyright notice and this permission notice appear in all copies.      â
â                                                                              â
â THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                â
â WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                â
â WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             â
â AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         â
â DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        â
â PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               â
â TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             â
â PERFORMANCE OF THIS SOFTWARE.                                                â
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ
                             â             âââ
                       ââââââââ     â     ââââââââââ
                â    ââââ  âââ    ââââââ    âââââââ         âââ
            ââââââ   ââââ   ââââ           ââââââ         âââââââ
             ââââââ  âââââ  ââââ         âââââââââââ    ââââââââ
      ââââ      ââââ   ââââââââ                ââââ âââââââââââ   ââââââââ
   âââââââ    â   âââââ   ââ                          âââ âââââ  âââââââââââ
  ââââ ââââ  âââ  âââ                                     âââââ âââââ    âââââ
   ââ  âââââââââ        VARIABLE LENGTH INTEGER DECODING        âââ  âââ â  â
       ââââââ                                                    ââââââââ
        âââ                                                         */
#include "libc/fmt/leb128.h"
#include "libc/macros.internal.h"

/**
 * Decodes array to signed integer w/ zig-zag encoding.
 *
 * @param p is array
 * @param n is byte length of array
 * @param o optionally receives decoded integer
 * @return bytes decoded or -1 on error
 * @see zleb64()
 */
int unzleb64(const char *p, size_t n, int64_t *o) {
  int c;
  size_t i;
  uint64_t u, t;
  i = 0;
  u = 0;
  do {
    if (i == n) return -1;
    c = p[i] & 255;
    t = c & 127;
    if (i < 10) {
      t <<= i * 7;
      u |= t;
    }
    ++i;
  } while (c & 128);
  if (o) *o = (u >> 1) ^ -(u & 1);
  return i;
}
