1 /* ----------------------------------------------------------------------- * 2 * 3 * Copyright 2005-2008 H. Peter Anvin - All Rights Reserved 4 * 5 * Permission is hereby granted, free of charge, to any person 6 * obtaining a copy of this software and associated documentation 7 * files (the "Software"), to deal in the Software without 8 * restriction, including without limitation the rights to use, 9 * copy, modify, merge, publish, distribute, sublicense, and/or 10 * sell copies of the Software, and to permit persons to whom 11 * the Software is furnished to do so, subject to the following 12 * conditions: 13 * 14 * The above copyright notice and this permission notice shall 15 * be included in all copies or substantial portions of the Software. 16 * 17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 18 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 19 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 20 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 21 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 22 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 23 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 24 * OTHER DEALINGS IN THE SOFTWARE. 25 * 26 * ----------------------------------------------------------------------- */ 27 28 /* 29 * unbase64.c 30 * 31 * Convert a string in base64 format to a byte array. 32 */ 33 34 #include <string.h> 35 #include <base64.h> 36 37 static const unsigned char _base64chars[] = 38 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; 39 40 size_t unbase64(unsigned char *buffer, size_t bufsiz, const char *txt) 41 { 42 unsigned int bits = 0; 43 int nbits = 0; 44 char base64tbl[256]; 45 int i; 46 char v; 47 size_t nbytes = 0; 48 49 memset(base64tbl, -1, sizeof base64tbl); 50 51 for (i = 0; _base64chars[i]; i++) { 52 base64tbl[_base64chars[i]] = i; 53 } 54 55 /* Also support filesystem safe alternate base64 encoding */ 56 base64tbl['.'] = 62; 57 base64tbl['-'] = 62; 58 base64tbl['_'] = 63; 59 60 while (*txt) { 61 if ((v = base64tbl[(unsigned char)*txt]) >= 0) { 62 bits <<= 6; 63 bits += v; 64 nbits += 6; 65 if (nbits >= 8) { 66 if (nbytes < bufsiz) 67 *buffer++ = (bits >> (nbits - 8)); 68 nbytes++; 69 nbits -= 8; 70 } 71 } 72 txt++; 73 } 74 75 return nbytes; 76 } 77