text: /*
   * Copyright 2012-2014 Luke Dashjr
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the standard MIT license.  See COPYING for more details.
   */
  
  #ifndef WIN32
  #include <arpa/inet.h>
  #else
  #include <winsock2.h>
  #endif
  
  #include <stdbool.h>
  #include <stddef.h>
  #include <stdint.h>
  #include <string.h>
  #include <sys/types.h>
  
  #include "libbase58.h"
  
  bool (*b58_sha256_impl)(void *, const void *, size_t) = NULL;
  
  static const int8_t b58digits_map[] = {
      -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
      -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
      -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
      -1, 0, 1, 2, 3, 4, 5, 6,  7, 8,-1,-1,-1,-1,-1,-1,
      -1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,
      22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,
      -1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,
      47,48,49,50,51,52,53,54, 55,56,57,-1,-1,-1,-1,-1,
  };
  
  typedef uint64_t b58_maxint_t;
  typedef uint32_t b58_almostmaxint_t;
  #define b58_almostmaxint_bits (sizeof(b58_almostmaxint_t) * 8)
  static const b58_almostmaxint_t b58_almostmaxint_mask = ((((b58_maxint_t)1) << b58_almostmaxint_bits) - 1);
  
  bool se_b58tobin(void *bin, size_t *binszp, const char *b58, size_t b58sz)
  {
      size_t binsz = *binszp;
      const unsigned char *b58u = (void*)b58;
      unsigned char *binu = bin;
      size_t outisz = (binsz + sizeof(b58_almostmaxint_t) - 1) / sizeof(b58_almostmaxint_t);
      b58_almostmaxint_t outi[outisz];
      b58_maxint_t t;
      b58_almostmaxint_t c;
      size_t i, j;
      uint8_t bytesleft = binsz % sizeof(b58_almostmaxint_t);
      b58_almostmaxint_t zeromask = bytesleft ? (b58_almostmaxint_mask << (bytesleft * 8)) : 0;
      unsigned zerocount = 0;
      
      if (!b58sz)
          b58sz = strlen(b58);
      
      for (i = 0; i < outisz; ++i) {
          outi[i] = 0;
      }
      
      // Leading zeros, just count
      for (i = 0; i < b58sz && b58u[i] == '1'; ++i)
          ++zerocount;
      
      for ( ; i < b58sz; ++i)
      {
          if (b58u[i] & 0x80)
              // High-bit set on invalid digit
              return false;
          if (b58digits_map[b58u[i]] == -1)
              // Invalid base58 digit
              return false;
          c = (unsigned)b58digits_map[b58u[i]];
          for (j = outisz; j--; )
          {
              t = ((b58_maxint_t)outi[j]) * 58 + c;
              c = t >> b58_almostmaxint_bits;
              outi[j] = t & b58_almostmaxint_mask;
          }
          if (c)
              // Output number too big (carry to the next int32)
              return false;
          if (outi[0] & zeromask)
              // Output number too big (last int32 filled too far)
              return false;
      }
      
      j = 0;
      if (bytesleft) {
          for (i = bytesleft; i > 0; --i) {
              *(binu++) = (outi[0] >> (8 * (i - 1))) & 0xff;
          }
          ++j;
      }
      
      for (; j < outisz; ++j)
      {
          for (i = sizeof(*outi); i > 0; --i) {
              *(binu++) = (outi[j] >> (8 * (i - 1))) & 0xff;
          }
      }
      
      // Count canonical base58 byte count
      binu = bin;
      for (i = 0; i < binsz; ++i)
      {
          if (binu[i])
              break;
          --*binszp;
      }
      *binszp += zerocount;
      
      return true;
  }
  
  static
  bool my_dblsha256(void *hash, const void *data, size_t datasz)
  {
      uint8_t buf[0x20];
      return b58_sha256_impl(buf, data, datasz) && b58_sha256_impl(hash, buf, sizeof(buf));
  }
  
  int se_b58check(const void *bin, size_t binsz, const char *base58str, size_t b58sz)
  {
      unsigned char buf[32];
      const uint8_t *binc = bin;
      unsigned i;
      if (binsz < 4)
          return -4;
      if (!my_dblsha256(buf, bin, binsz - 4))
          return -2;
      if (memcmp(&binc[binsz - 4], buf, 4))
          return -1;
      
      // Check number of zeros is correct AFTER verifying checksum (to avoid possibility of accessing base58str beyond the end)
      for (i = 0; binc[i] == '\0' && base58str[i] == '1'; ++i)
      {}  // Just finding the end of zeros, nothing to do in loop
      if (binc[i] == '\0' || base58str[i] == '1')
          return -3;
      
      return binc[0];
  }
  
  static const char b58digits_ordered[] = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
  
  bool se_b58enc(char *b58, size_t *b58sz, const void *data, size_t binsz)
  {
      const uint8_t *bin = data;
      int carry;
      ssize_t i, j, high, zcount = 0;
      size_t size;
      
      while (zcount < binsz && !bin[zcount])
          ++zcount;
      
      size = (binsz - zcount) * 138 / 100 + 1;
      uint8_t buf[size];
      memset(buf, 0, size);
      
      for (i = zcount, high = size - 1; i < binsz; ++i, high = j)
      {
          for (carry = bin[i], j = size - 1; (j > high) || carry; --j)
          {
              carry += 256 * buf[j];
              buf[j] = carry % 58;
              carry /= 58;
          }
      }
      
      for (j = 0; j < size && !buf[j]; ++j);
      
      if (*b58sz <= zcount + size - j)
      {
          *b58sz = zcount + size - j + 1;
          return false;
      }
      
      if (zcount)
          memset(b58, '1', zcount);
      for (i = zcount; j < size; ++i, ++j)
          b58[i] = b58digits_ordered[buf[j]];
      b58[i] = '\0';
      *b58sz = i + 1;
      
      return true;
  }
  
  bool se_b58check_enc(char *b58c, size_t *b58c_sz, uint8_t ver, const void *data, size_t datasz)
  {
      uint8_t buf[1 + datasz + 0x20];
      uint8_t *hash = &buf[1 + datasz];
      
      buf[0] = ver;
      memcpy(&buf[1], data, datasz);
      if (!my_dblsha256(hash, buf, datasz + 1))
      {
          *b58c_sz = 0;
          return false;
      }
      
      return se_b58enc(b58c, b58c_sz, buf, 1 + datasz + 4);
  }
  