| 1 | /********************************************************************* |
| 2 | * Filename: base64.c |
| 3 | * Author: Brad Conte (brad AT bradconte.com) |
| 4 | * Copyright: |
| 5 | * Disclaimer: This code is presented "as is" without any guarantees. |
| 6 | * Details: Implementation of the Base64 encoding algorithm. |
| 7 | *********************************************************************/ |
| 8 | |
| 9 | /*************************** HEADER FILES ***************************/ |
| 10 | #include <stdlib.h> |
| 11 | #include "base64.h" |
| 12 | |
| 13 | /****************************** MACROS ******************************/ |
| 14 | #define NEWLINE_INVL 76 |
| 15 | |
| 16 | /**************************** VARIABLES *****************************/ |
| 17 | // Note: To change the charset to a URL encoding, replace the '+' and '/' with '*' and '-' |
| 18 | static const BYTE charset[]={"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"}; |
| 19 | |
| 20 | /*********************** FUNCTION DEFINITIONS ***********************/ |
| 21 | BYTE revchar(char ch) |
| 22 | { |
| 23 | if (ch >= 'A' && ch <= 'Z') |
| 24 | ch -= 'A'; |
| 25 | else if (ch >= 'a' && ch <='z') |
| 26 | ch = ch - 'a' + 26; |
| 27 | else if (ch >= '0' && ch <='9') |
| 28 | ch = ch - '0' + 52; |
| 29 | else if (ch == '+') |
| 30 | ch = 62; |
| 31 | else if (ch == '/') |
| 32 | ch = 63; |
| 33 | |
| 34 | return(ch); |
| 35 | } |
| 36 | |
| 37 | size_t base64_encode(const BYTE in[], BYTE out[], size_t len, int newline_flag) |
| 38 | { |
| 39 | size_t idx, idx2, blks, blk_ceiling, left_over, newline_count = 0; |
| 40 | |
| 41 | blks = (len / 3); |
| 42 | left_over = len % 3; |
| 43 | |
| 44 | if (out == NULL) { |
| 45 | idx2 = blks * 4 ; |
| 46 | if (left_over) |
| 47 | idx2 += 4; |
| 48 | if (newline_flag) |
| 49 | idx2 += len / 57; // (NEWLINE_INVL / 4) * 3 = 57. One newline per 57 input bytes. |
| 50 | } |
| 51 | else { |
| 52 | // Since 3 input bytes = 4 output bytes, determine out how many even sets of |
| 53 | // 3 bytes the input has. |
| 54 | blk_ceiling = blks * 3; |
| 55 | for (idx = 0, idx2 = 0; idx < blk_ceiling; idx += 3, idx2 += 4) { |
| 56 | out[idx2] = charset[in[idx] >> 2]; |
| 57 | out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)]; |
| 58 | out[idx2 + 2] = charset[((in[idx + 1] & 0x0f) << 2) | (in[idx + 2] >> 6)]; |
| 59 | out[idx2 + 3] = charset[in[idx + 2] & 0x3F]; |
| 60 | // The offical standard requires a newline every 76 characters. |
| 61 | // (Eg, first newline is character 77 of the output.) |
| 62 | if (((idx2 - newline_count + 4) % NEWLINE_INVL == 0) && newline_flag) { |
| 63 | out[idx2 + 4] = '\n'; |
| 64 | idx2++; |
| 65 | newline_count++; |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | if (left_over == 1) { |
| 70 | out[idx2] = charset[in[idx] >> 2]; |
| 71 | out[idx2 + 1] = charset[(in[idx] & 0x03) << 4]; |
| 72 | out[idx2 + 2] = '='; |
| 73 | out[idx2 + 3] = '='; |
| 74 | idx2 += 4; |
| 75 | } |
| 76 | else if (left_over == 2) { |
| 77 | out[idx2] = charset[in[idx] >> 2]; |
| 78 | out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)]; |
| 79 | out[idx2 + 2] = charset[(in[idx + 1] & 0x0F) << 2]; |
| 80 | out[idx2 + 3] = '='; |
| 81 | idx2 += 4; |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | return(idx2); |
| 86 | } |
| 87 | |
| 88 | size_t base64_decode(const BYTE in[], BYTE out[], size_t len) |
| 89 | { |
| 90 | BYTE ch; |
| 91 | size_t idx, idx2, blks, blk_ceiling, left_over; |
| 92 | |
| 93 | if (in[len - 1] == '=') |
| 94 | len--; |
| 95 | if (in[len - 1] == '=') |
| 96 | len--; |
| 97 | |
| 98 | blks = len / 4; |
| 99 | left_over = len % 4; |
| 100 | |
| 101 | if (out == NULL) { |
| 102 | if (len >= 77 && in[NEWLINE_INVL] == '\n') // Verify that newlines where used. |
| 103 | len -= len / (NEWLINE_INVL + 1); |
| 104 | blks = len / 4; |
| 105 | left_over = len % 4; |
| 106 | |
| 107 | idx = blks * 3; |
| 108 | if (left_over == 2) |
| 109 | idx ++; |
| 110 | else if (left_over == 3) |
| 111 | idx += 2; |
| 112 | } |
| 113 | else { |
| 114 | blk_ceiling = blks * 4; |
| 115 | for (idx = 0, idx2 = 0; idx2 < blk_ceiling; idx += 3, idx2 += 4) { |
| 116 | if (in[idx2] == '\n') |
| 117 | idx2++; |
| 118 | out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4); |
| 119 | out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2); |
| 120 | out[idx + 2] = (revchar(in[idx2 + 2]) << 6) | revchar(in[idx2 + 3]); |
| 121 | } |
| 122 | |
| 123 | if (left_over == 2) { |
| 124 | out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4); |
| 125 | idx++; |
| 126 | } |
| 127 | else if (left_over == 3) { |
| 128 | out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4); |
| 129 | out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2); |
| 130 | idx += 2; |
| 131 | } |
| 132 | } |
| 133 | |
| 134 | return(idx); |
| 135 | } |