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