180 lines
6.0 KiB
C++
180 lines
6.0 KiB
C++
/*
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base64.cpp and base64.h
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Copyright (C) 2004-2008 René Nyffenegger
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This source code is provided 'as-is', without any express or implied
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warranty. In no event will the author be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this source code must not be misrepresented; you must not
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claim that you wrote the original source code. If you use this source code
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original source code.
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3. This notice may not be removed or altered from any source distribution.
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René Nyffenegger rene.nyffenegger@adp-gmbh.ch
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------------------------------
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This version has been modified (changed the interface + use another decoding algorithm
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inspired from https://stackoverflow.com/a/34571089 which was faster)
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*/
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#include "base64.h"
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#include <string.h>
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#include <vector>
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static const std::string base64_chars =
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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"abcdefghijklmnopqrstuvwxyz"
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"0123456789+/";
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static inline bool is_base64(unsigned char c) {
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return (isalnum(c) || (c == '+') || (c == '/'));
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}
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void base64_encode(std::string& result, const std::string& stringToEncode)
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{
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const unsigned char* bytes_to_encode = reinterpret_cast<const unsigned char*>
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(stringToEncode.size() > 0 ? &stringToEncode[0] : NULL);
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size_t in_len = stringToEncode.size();
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result.reserve(result.size() + in_len * 4 / 3 + 10);
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int i = 0;
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int j = 0;
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unsigned char char_array_3[3];
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unsigned char char_array_4[4];
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while (in_len--) {
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char_array_3[i++] = *(bytes_to_encode++);
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if (i == 3) {
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char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
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char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
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char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
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char_array_4[3] = char_array_3[2] & 0x3f;
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for(i = 0; (i <4) ; i++)
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result += base64_chars[char_array_4[i]];
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i = 0;
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}
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}
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if (i)
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{
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for(j = i; j < 3; j++)
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char_array_3[j] = '\0';
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char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
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char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
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char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
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char_array_4[3] = char_array_3[2] & 0x3f;
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for (j = 0; (j < i + 1); j++)
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result += base64_chars[char_array_4[j]];
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while((i++ < 3))
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result += '=';
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}
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}
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// old code from René Nyffenegger. This code is slower
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void base64_decode_old(std::string& result, const std::string& encoded_string) {
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size_t in_len = encoded_string.size();
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int i = 0;
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int j = 0;
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int in_ = 0;
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unsigned char char_array_4[4], char_array_3[3];
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result.reserve(result.size() + in_len * 3 / 4 + 10);
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while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) {
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char_array_4[i++] = encoded_string[in_]; in_++;
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if (i ==4) {
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for (i = 0; i <4; i++)
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char_array_4[i] = base64_chars.find(char_array_4[i]);
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char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
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char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
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char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
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for (i = 0; (i < 3); i++)
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result += char_array_3[i];
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i = 0;
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}
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}
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if (i) {
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for (j = i; j <4; j++)
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char_array_4[j] = 0;
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for (j = 0; j <4; j++)
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char_array_4[j] = base64_chars.find(char_array_4[j]);
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char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
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char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
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char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
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for (j = 0; (j < i - 1); j++)
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result += char_array_3[j];
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}
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}
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// new code from https://stackoverflow.com/a/34571089
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// note that the encoding algorithm from this page was slower (and bugged !)
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// this code is not using std::vector::find
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// static init equivalent to:
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// decode_indexes.assign(256, -1);
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// for (int i=0; i<64; ++i)
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// decode_indexes[base64_chars[i]] = i;
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static const int decode_indexes[] = {
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
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52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
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-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
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15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
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-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
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41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
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};
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void base64_decode(std::string& result, const std::string &stringToDecode) {
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result.reserve(result.size() + stringToDecode.size() * 3 / 4 + 10);
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int val=0, valb=-8;
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for (std::string::const_iterator c = stringToDecode.begin(); c != stringToDecode.end(); ++c)
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{
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size_t index = static_cast<size_t>(*c);
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if (decode_indexes[index] == -1)
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break;
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val = (val<<6) + decode_indexes[index];
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valb += 6;
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if (valb>=0) {
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result.push_back(char((val>>valb)&0xFF));
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valb-=8;
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}
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}
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}
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