tor-browser

base64.c (7027B)

---

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "plbase64.h"
#include "prlog.h" /* For PR_NOT_REACHED */
#include "prmem.h" /* for malloc / PR_MALLOC */

#include <string.h> /* for strlen */

static unsigned char *base = (unsigned char *)"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static void encode3to4(const unsigned char* src, unsigned char* dest) {
 PRUint32 b32 = (PRUint32)0;
 PRIntn i, j = 18;

 for (i = 0; i < 3; i++) {
   b32 <<= 8;
   b32 |= (PRUint32)src[i];
 }

 for (i = 0; i < 4; i++) {
   dest[i] = base[(PRUint32)((b32 >> j) & 0x3F)];
   j -= 6;
 }

 return;
}

static void encode2to4(const unsigned char* src, unsigned char* dest) {
 dest[0] = base[(PRUint32)((src[0] >> 2) & 0x3F)];
 dest[1] = base[(PRUint32)(((src[0] & 0x03) << 4) | ((src[1] >> 4) & 0x0F))];
 dest[2] = base[(PRUint32)((src[1] & 0x0F) << 2)];
 dest[3] = (unsigned char)'=';
 return;
}

static void encode1to4(const unsigned char* src, unsigned char* dest) {
 dest[0] = base[(PRUint32)((src[0] >> 2) & 0x3F)];
 dest[1] = base[(PRUint32)((src[0] & 0x03) << 4)];
 dest[2] = (unsigned char)'=';
 dest[3] = (unsigned char)'=';
 return;
}

static void encode(const unsigned char* src, PRUint32 srclen,
                  unsigned char* dest) {
 while (srclen >= 3) {
   encode3to4(src, dest);
   src += 3;
   dest += 4;
   srclen -= 3;
 }

 switch (srclen) {
   case 2:
     encode2to4(src, dest);
     break;
   case 1:
     encode1to4(src, dest);
     break;
   case 0:
     break;
   default:
     PR_NOT_REACHED("coding error");
 }

 return;
}

/*
* PL_Base64Encode
*
* If the destination argument is NULL, a return buffer is
* allocated, and the data therein will be null-terminated.
* If the destination argument is not NULL, it is assumed to
* be of sufficient size, and the contents will not be null-
* terminated by this routine.
*
* Returns null if the allocation fails.
*/

PR_IMPLEMENT(char*)
PL_Base64Encode(const char* src, PRUint32 srclen, char* dest) {
 if (0 == srclen) {
   size_t len = strlen(src);
   srclen = len;
   /* Detect truncation. */
   if (srclen != len) {
     return (char*)0;
   }
 }

 if ((char*)0 == dest) {
   PRUint32 destlen;
   /* Ensure all PRUint32 values stay within range. */
   if (srclen > (PR_UINT32_MAX / 4) * 3) {
     return (char*)0;
   }
   destlen = ((srclen + 2) / 3) * 4;
   dest = (char*)PR_MALLOC(destlen + 1);
   if ((char*)0 == dest) {
     return (char*)0;
   }
   dest[destlen] = (char)0; /* null terminate */
 }

 encode((const unsigned char*)src, srclen, (unsigned char*)dest);
 return dest;
}

static PRInt32 codetovalue(unsigned char c) {
 if ((c >= (unsigned char)'A') && (c <= (unsigned char)'Z')) {
   return (PRInt32)(c - (unsigned char)'A');
 } else if ((c >= (unsigned char)'a') && (c <= (unsigned char)'z')) {
   return ((PRInt32)(c - (unsigned char)'a') + 26);
 } else if ((c >= (unsigned char)'0') && (c <= (unsigned char)'9')) {
   return ((PRInt32)(c - (unsigned char)'0') + 52);
 } else if ((unsigned char)'+' == c) {
   return (PRInt32)62;
 } else if ((unsigned char)'/' == c) {
   return (PRInt32)63;
 } else {
   return -1;
 }
}

static PRStatus decode4to3(const unsigned char* src, unsigned char* dest) {
 PRUint32 b32 = (PRUint32)0;
 PRInt32 bits;
 PRIntn i;

 for (i = 0; i < 4; i++) {
   bits = codetovalue(src[i]);
   if (bits < 0) {
     return PR_FAILURE;
   }

   b32 <<= 6;
   b32 |= bits;
 }

 dest[0] = (unsigned char)((b32 >> 16) & 0xFF);
 dest[1] = (unsigned char)((b32 >> 8) & 0xFF);
 dest[2] = (unsigned char)((b32) & 0xFF);

 return PR_SUCCESS;
}

static PRStatus decode3to2(const unsigned char* src, unsigned char* dest) {
 PRUint32 b32 = (PRUint32)0;
 PRInt32 bits;
 PRUint32 ubits;

 bits = codetovalue(src[0]);
 if (bits < 0) {
   return PR_FAILURE;
 }

 b32 = (PRUint32)bits;
 b32 <<= 6;

 bits = codetovalue(src[1]);
 if (bits < 0) {
   return PR_FAILURE;
 }

 b32 |= (PRUint32)bits;
 b32 <<= 4;

 bits = codetovalue(src[2]);
 if (bits < 0) {
   return PR_FAILURE;
 }

 ubits = (PRUint32)bits;
 b32 |= (ubits >> 2);

 dest[0] = (unsigned char)((b32 >> 8) & 0xFF);
 dest[1] = (unsigned char)((b32) & 0xFF);

 return PR_SUCCESS;
}

static PRStatus decode2to1(const unsigned char* src, unsigned char* dest) {
 PRUint32 b32;
 PRUint32 ubits;
 PRInt32 bits;

 bits = codetovalue(src[0]);
 if (bits < 0) {
   return PR_FAILURE;
 }

 ubits = (PRUint32)bits;
 b32 = (ubits << 2);

 bits = codetovalue(src[1]);
 if (bits < 0) {
   return PR_FAILURE;
 }

 ubits = (PRUint32)bits;
 b32 |= (ubits >> 4);

 dest[0] = (unsigned char)b32;

 return PR_SUCCESS;
}

static PRStatus decode(const unsigned char* src, PRUint32 srclen,
                      unsigned char* dest) {
 PRStatus rv;

 while (srclen >= 4) {
   rv = decode4to3(src, dest);
   if (PR_SUCCESS != rv) {
     return PR_FAILURE;
   }

   src += 4;
   dest += 3;
   srclen -= 4;
 }

 switch (srclen) {
   case 3:
     rv = decode3to2(src, dest);
     break;
   case 2:
     rv = decode2to1(src, dest);
     break;
   case 1:
     rv = PR_FAILURE;
     break;
   case 0:
     rv = PR_SUCCESS;
     break;
   default:
     PR_NOT_REACHED("coding error");
 }

 return rv;
}

/*
* PL_Base64Decode
*
* If the destination argument is NULL, a return buffer is
* allocated and the data therein will be null-terminated.
* If the destination argument is not null, it is assumed
* to be of sufficient size, and the data will not be null-
* terminated by this routine.
*
* Returns null if the allocation fails, or if the source string is
* not well-formed.
*/

PR_IMPLEMENT(char*)
PL_Base64Decode(const char* src, PRUint32 srclen, char* dest) {
 PRStatus status;
 PRBool allocated = PR_FALSE;

 if ((char*)0 == src) {
   return (char*)0;
 }

 if (0 == srclen) {
   size_t len = strlen(src);
   srclen = len;
   /* Detect truncation. */
   if (srclen != len) {
     return (char*)0;
   }
 }

 if (srclen && (0 == (srclen & 3))) {
   if ((char)'=' == src[srclen - 1]) {
     if ((char)'=' == src[srclen - 2]) {
       srclen -= 2;
     } else {
       srclen -= 1;
     }
   }
 }

 if ((char*)0 == dest) {
   /* The following computes ((srclen * 3) / 4) without overflow. */
   PRUint32 destlen = (srclen / 4) * 3 + ((srclen % 4) * 3) / 4;
   dest = (char*)PR_MALLOC(destlen + 1);
   if ((char*)0 == dest) {
     return (char*)0;
   }
   dest[destlen] = (char)0; /* null terminate */
   allocated = PR_TRUE;
 }

 status = decode((const unsigned char*)src, srclen, (unsigned char*)dest);
 if (PR_SUCCESS != status) {
   if (PR_TRUE == allocated) {
     PR_DELETE(dest);
   }

   return (char*)0;
 }

 return dest;
}