diff options
Diffstat (limited to 'base64.c')
| -rw-r--r-- | base64.c | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/base64.c b/base64.c new file mode 100644 index 0000000..5e89808 --- /dev/null +++ b/base64.c @@ -0,0 +1,135 @@ +/********************************************************************* +* Filename: base64.c +* Author: Brad Conte (brad AT bradconte.com) +* Copyright: +* Disclaimer: This code is presented "as is" without any guarantees. +* Details: Implementation of the Base64 encoding algorithm. +*********************************************************************/ + +/*************************** HEADER FILES ***************************/ +#include <stdlib.h> +#include "base64.h" + +/****************************** MACROS ******************************/ +#define NEWLINE_INVL 76 + +/**************************** VARIABLES *****************************/ +// Note: To change the charset to a URL encoding, replace the '+' and '/' with '*' and '-' +static const BYTE charset[]={"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"}; + +/*********************** FUNCTION DEFINITIONS ***********************/ +BYTE revchar(char ch) +{ + if (ch >= 'A' && ch <= 'Z') + ch -= 'A'; + else if (ch >= 'a' && ch <='z') + ch = ch - 'a' + 26; + else if (ch >= '0' && ch <='9') + ch = ch - '0' + 52; + else if (ch == '+') + ch = 62; + else if (ch == '/') + ch = 63; + + return(ch); +} + +size_t base64_encode(const BYTE in[], BYTE out[], size_t len, int newline_flag) +{ + size_t idx, idx2, blks, blk_ceiling, left_over, newline_count = 0; + + blks = (len / 3); + left_over = len % 3; + + if (out == NULL) { + idx2 = blks * 4 ; + if (left_over) + idx2 += 4; + if (newline_flag) + idx2 += len / 57; // (NEWLINE_INVL / 4) * 3 = 57. One newline per 57 input bytes. + } + else { + // Since 3 input bytes = 4 output bytes, determine out how many even sets of + // 3 bytes the input has. + blk_ceiling = blks * 3; + for (idx = 0, idx2 = 0; idx < blk_ceiling; idx += 3, idx2 += 4) { + out[idx2] = charset[in[idx] >> 2]; + out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)]; + out[idx2 + 2] = charset[((in[idx + 1] & 0x0f) << 2) | (in[idx + 2] >> 6)]; + out[idx2 + 3] = charset[in[idx + 2] & 0x3F]; + // The offical standard requires a newline every 76 characters. + // (Eg, first newline is character 77 of the output.) + if (((idx2 - newline_count + 4) % NEWLINE_INVL == 0) && newline_flag) { + out[idx2 + 4] = '\n'; + idx2++; + newline_count++; + } + } + + if (left_over == 1) { + out[idx2] = charset[in[idx] >> 2]; + out[idx2 + 1] = charset[(in[idx] & 0x03) << 4]; + out[idx2 + 2] = '='; + out[idx2 + 3] = '='; + idx2 += 4; + } + else if (left_over == 2) { + out[idx2] = charset[in[idx] >> 2]; + out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)]; + out[idx2 + 2] = charset[(in[idx + 1] & 0x0F) << 2]; + out[idx2 + 3] = '='; + idx2 += 4; + } + } + + return(idx2); +} + +size_t base64_decode(const BYTE in[], BYTE out[], size_t len) +{ + BYTE ch; + size_t idx, idx2, blks, blk_ceiling, left_over; + + if (in[len - 1] == '=') + len--; + if (in[len - 1] == '=') + len--; + + blks = len / 4; + left_over = len % 4; + + if (out == NULL) { + if (len >= 77 && in[NEWLINE_INVL] == '\n') // Verify that newlines where used. + len -= len / (NEWLINE_INVL + 1); + blks = len / 4; + left_over = len % 4; + + idx = blks * 3; + if (left_over == 2) + idx ++; + else if (left_over == 3) + idx += 2; + } + else { + blk_ceiling = blks * 4; + for (idx = 0, idx2 = 0; idx2 < blk_ceiling; idx += 3, idx2 += 4) { + if (in[idx2] == '\n') + idx2++; + out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4); + out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2); + out[idx + 2] = (revchar(in[idx2 + 2]) << 6) | revchar(in[idx2 + 3]); + } + + if (left_over == 2) { + out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4); + idx++; + } + else if (left_over == 3) { + out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4); + out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2); + idx += 2; + } + } + + return(idx); +} |