/********************************************************************* * 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); }