text: /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 4 -*- */
  /* vi: set expandtab shiftwidth=4 tabstop=4: */
  /**
   * \file modp_b64.c
   * <PRE>
   * MODP_B64 - High performance base64 encoder/decoder
   * http://code.google.com/p/stringencoders/
   *
   * Copyright &copy; 2005, 2006, 2007  Nick Galbreath -- nickg [at] modp [dot] com
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   *   Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   *
   *   Redistributions in binary form must reproduce the above copyright
   *   notice, this list of conditions and the following disclaimer in the
   *   documentation and/or other materials provided with the distribution.
   *
   *   Neither the name of the modp.com nor the names of its
   *   contributors may be used to endorse or promote products derived from
   *   this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * This is the standard "new" BSD license:
   * http://www.opensource.org/licenses/bsd-license.php
   * </PRE>
   */
  
  /* public header */
  #include "modp_b64.h"
  
  /*
   * If you are ripping this out of the library, comment out the next
   * line and uncomment the next lines as approrpiate
   */
  //#include "config.h"
  
  /* if on motoral, sun, ibm; uncomment this */
  /* #define WORDS_BIGENDIAN 1 */
  /* else for Intel, Amd; uncomment this */
  #undef WORDS_BIGENDIAN
  
  #include "modp_b64_data.h"
  
  #define BADCHAR 0x01FFFFFF
  
  /**
   * you can control if we use padding by commenting out this
   * next line.  However, I highly recommend you use padding and not
   * using it should only be for compatability with a 3rd party.
   * Also, 'no padding' is not tested!
   */
  #define DOPAD 1
  
  /*
   * if we aren't doing padding
   * set the pad character to NULL
   */
  #ifndef DOPAD
  #undef CHARPAD
  #define CHARPAD '\0'
  #endif
  
  int modp_b64_encode(char* dest, const char* str, int len) {
      int i;
      const uint8_t* s = (const uint8_t*) str;
      uint8_t* p = (uint8_t*) dest;
  
      /* unsigned here is important! */
      /* uint8_t is fastest on G4, amd */
      /* uint32_t is fastest on Intel */
      uint32_t t1, t2, t3;
  
      for (i = 0; i < len - 2; i += 3) {
          t1 = s[i];
          t2 = s[i + 1];
          t3 = s[i + 2];
          *p++ = e0[t1];
          *p++ = e1[((t1 & 0x03) << 4) | ((t2 >> 4) & 0x0F)];
          *p++ = e1[((t2 & 0x0F) << 2) | ((t3 >> 6) & 0x03)];
          *p++ = e2[t3];
      }
  
      switch (len - i) {
      case 0:
          break;
      case 1:
          t1 = s[i];
          *p++ = e0[t1];
          *p++ = e1[(t1 & 0x03) << 4];
          *p++ = CHARPAD;
          *p++ = CHARPAD;
          break;
      default: /* case 2 */
          t1 = s[i];
          t2 = s[i + 1];
          *p++ = e0[t1];
          *p++ = e1[((t1 & 0x03) << 4) | ((t2 >> 4) & 0x0F)];
          *p++ = e2[(t2 & 0x0F) << 2];
          *p++ = CHARPAD;
      }
  
      *p = '\0';
      return (int)(p - (uint8_t*)dest);
  }
  
  #ifdef WORDS_BIGENDIAN   /* BIG ENDIAN -- SUN / IBM / MOTOROLA */
  int modp_b64_decode(char* dest, const char* src, int len) {
      int i;
      if (len == 0) {
          return 0;
      }
  
  #ifdef DOPAD
      /* if padding is used, then the message must be at least
         4 chars and be a multiple of 4.
         there can be at most 2 pad chars at the end */
      if (len < 4 || (len % 4 != 0)) {
          return -1;
      }
      if (src[len - 1] == CHARPAD) {
          len--;
          if (src[len - 1] == CHARPAD) {
              len--;
          }
      }
  #endif  /* DOPAD */
  
      int leftover = len % 4;
      int chunks = (leftover == 0) ? len / 4 - 1 : len / 4;
  
      uint8_t* p = (uint8_t*) dest;
      uint32_t x = 0;
      uint32_t* destInt = (uint32_t*) p;
      uint32_t* srcInt = (uint32_t*) src;
      uint32_t y = *srcInt++;
      for (i = 0; i < chunks; ++i) {
          x = d0[y >> 24 & 0xff] | d1[y >> 16 & 0xff] |
              d2[y >> 8 & 0xff] | d3[y & 0xff];
  
          if (x >= BADCHAR) {
              return -1;
          }
          *destInt = x << 8;
          p += 3;
          destInt = (uint32_t*)p;
          y = *srcInt++;
      }
  
      switch (leftover) {
      case 0:
          x = d0[y >> 24 & 0xff] | d1[y >> 16 & 0xff] |
              d2[y >>  8 & 0xff] | d3[y & 0xff];
          if (x >= BADCHAR) {
              return -1;
          }
          *p++ = ((uint8_t*)&x)[1];
          *p++ = ((uint8_t*)&x)[2];
          *p = ((uint8_t*)&x)[3];
          return (chunks + 1) * 3;
  #ifndef DOPAD
      case 1:  /* with padding this is an impossible case */
          x = d3[y >> 24];
          *p = (uint8_t)x;
          break;
  #endif
      case 2:
          x = d3[y >> 24] * 64 + d3[(y >> 16) & 0xff];
          *p = (uint8_t)(x >> 4);
          break;
      default:  /* case 3 */
          x = (d3[y >> 24] * 64 + d3[(y >> 16) & 0xff]) * 64 +
              d3[(y >> 8) & 0xff];
          *p++ = (uint8_t)(x >> 10);
          *p = (uint8_t)(x >> 2);
          break;
      }
  
      if (x >= BADCHAR) {
          return -1;
      }
      return 3 * chunks + (6 * leftover) / 8;
  }
  
  #else /* LITTLE  ENDIAN -- INTEL AND FRIENDS */
  
  int modp_b64_decode(char* dest, const char* src, int len) {
      int i;
      if (len == 0) {
          return 0;
      }
  
  #ifdef DOPAD
      /*
       * if padding is used, then the message must be at least
       * 4 chars and be a multiple of 4
       */
      if (len < 4 || (len % 4 != 0)) {
          return -1;    /* error */
      }
      /* there can be at most 2 pad chars at the end */
      if (src[len - 1] == CHARPAD) {
          len--;
          if (src[len - 1] == CHARPAD) {
              len--;
          }
      }
  #endif
  
      int leftover = len % 4;
      int chunks = (leftover == 0) ? len / 4 - 1 : len / 4;
  
      uint8_t* p = (uint8_t*) dest;
      uint32_t x = 0;
      uint32_t* destInt = (uint32_t*) p;
      const uint32_t* srcInt = (const uint32_t*) src;
      uint32_t y = *srcInt++;
      for (i = 0; i < chunks; ++i) {
          x = d0[y & 0xff] |
              d1[(y >> 8) & 0xff] |
              d2[(y >> 16) & 0xff] |
              d3[(y >> 24) & 0xff];
  
          if (x >= BADCHAR) {
              return -1;
          }
          *destInt = x ;
          p += 3;
          destInt = (uint32_t*)p;
          y = *srcInt++;
      }
  
  
      switch (leftover) {
      case 0:
          x = d0[y & 0xff] |
              d1[(y >> 8) & 0xff] |
              d2[(y >> 16) & 0xff] |
              d3[(y >> 24) & 0xff];
  
          if (x >= BADCHAR) {
              return -1;
          }
          *p++ = ((uint8_t*)(&x))[0];
          *p++ = ((uint8_t*)(&x))[1];
          *p = ((uint8_t*)(&x))[2];
          return (chunks + 1) * 3;
          break;
  #ifndef DOPAD
      case 1:  /* with padding this is an impossible case */
          x = d0[y & 0xff];
          *p = *((uint8_t*)(&x)); // i.e. first char/byte in int
          break;
  #endif
      case 2: // * case 2, 1  output byte */
          x = d0[y & 0xff] | d1[y >> 8 & 0xff];
          *p = *((uint8_t*)(&x)); // i.e. first char
          break;
      default: /* case 3, 2 output bytes */
          x = d0[y & 0xff] |
              d1[y >> 8 & 0xff ] |
              d2[y >> 16 & 0xff];  /* 0x3c */
          *p++ = ((uint8_t*)(&x))[0];
          *p = ((uint8_t*)(&x))[1];
          break;
      }
  
      if (x >= BADCHAR) {
          return -1;
      }
  
      return 3 * chunks + (6 * leftover) / 8;
  }
  
  #endif  /* if bigendian / else / endif */
  