Justin Marshall
80 lines
3.1 KiB
C++
80 lines
3.1 KiB
C++
#include "base64.h"
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namespace {
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int DecodeCharacter(const unsigned char character) {
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if (character >= 'A' && character <= 'Z') return character - 'A';
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if (character >= 'a' && character <= 'z') return character - 'a' + 26;
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if (character >= '0' && character <= '9') return character - '0' + 52;
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if (character == '+') return 62;
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if (character == '/') return 63;
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return -1;
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}
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} // namespace
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void idBase64::Encode(const unsigned char* source, const int size) {
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static const unsigned char alphabet[] =
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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if (source == nullptr || size <= 0) {
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if (EnsureAlloced(1)) data[0] = 0;
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len = 0;
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return;
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}
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const int outputLength = ((size + 2) / 3) * 4;
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if (!EnsureAlloced(outputLength + 1)) return;
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len = 0;
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int input = 0;
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while (input + 2 < size) {
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const unsigned int value = (static_cast<unsigned int>(source[input]) << 16)
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| (static_cast<unsigned int>(source[input + 1]) << 8)
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| source[input + 2];
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data[len++] = alphabet[(value >> 18) & 63];
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data[len++] = alphabet[(value >> 12) & 63];
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data[len++] = alphabet[(value >> 6) & 63];
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data[len++] = alphabet[value & 63];
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input += 3;
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}
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if (size - input == 1) {
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const unsigned int value = static_cast<unsigned int>(source[input]) << 16;
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data[len++] = alphabet[(value >> 18) & 63];
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data[len++] = alphabet[(value >> 12) & 63];
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data[len++] = '=';
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data[len++] = '=';
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} else if (size - input == 2) {
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const unsigned int value = (static_cast<unsigned int>(source[input]) << 16)
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| (static_cast<unsigned int>(source[input + 1]) << 8);
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data[len++] = alphabet[(value >> 18) & 63];
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data[len++] = alphabet[(value >> 12) & 63];
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data[len++] = alphabet[(value >> 6) & 63];
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data[len++] = '=';
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}
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data[len] = 0;
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}
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int idBase64::Decode(unsigned char* destination) const {
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if (destination == nullptr || data == nullptr || len == 0
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|| (len & 3) != 0) return 0;
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int output = 0;
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for (int input = 0; input < len; input += 4) {
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const bool lastGroup = input + 4 == len;
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const bool pad2 = data[input + 2] == '=';
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const bool pad3 = data[input + 3] == '=';
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if ((!lastGroup && (pad2 || pad3)) || (pad2 && !pad3)) return 0;
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const int a = DecodeCharacter(data[input]);
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const int b = DecodeCharacter(data[input + 1]);
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const int c = pad2 ? 0 : DecodeCharacter(data[input + 2]);
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const int d = pad3 ? 0 : DecodeCharacter(data[input + 3]);
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if (a < 0 || b < 0 || c < 0 || d < 0) return 0;
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const unsigned int value = (static_cast<unsigned int>(a) << 18)
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| (static_cast<unsigned int>(b) << 12)
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| (static_cast<unsigned int>(c) << 6)
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| static_cast<unsigned int>(d);
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destination[output++] = static_cast<unsigned char>(value >> 16);
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if (!pad2) destination[output++] = static_cast<unsigned char>(value >> 8);
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if (!pad3) destination[output++] = static_cast<unsigned char>(value);
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}
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destination[output] = 0;
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return output;
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}
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