130 lines
4.3 KiB
C++
130 lines
4.3 KiB
C++
/* Copyright 2015 OpenMarket Ltd
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "olm/base64.hh"
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namespace {
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static const std::uint8_t ENCODE_BASE64[64] = {
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0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
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0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50,
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0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
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0x59, 0x5A, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66,
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0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E,
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0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76,
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0x77, 0x78, 0x79, 0x7A, 0x30, 0x31, 0x32, 0x33,
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0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x2B, 0x2F,
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};
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static const std::uint8_t E = -1;
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static const std::uint8_t DECODE_BASE64[128] = {
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/* 0x0 0x1 0x2 0x3 0x4 0x5 0x6 0x7 0x8 0x9 0xA 0xB 0xC 0xD 0xE 0xF */
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E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E,
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E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E,
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E, E, E, E, E, E, E, E, E, E, E, 62, E, E, E, 63,
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52, 53, 54, 55, 56, 57, 58, 59, 60, 61, E, E, E, E, E, E,
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E, 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, E, E, E, E, E,
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E, 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, E, E, E, E, E,
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};
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} // namespace
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std::uint8_t * olm::encode_base64(
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t * output
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) {
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std::uint8_t const * end = input + (input_length / 3) * 3;
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std::uint8_t const * pos = input;
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while (pos != end) {
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unsigned value = pos[0];
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value <<= 8; value |= pos[1];
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value <<= 8; value |= pos[2];
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pos += 3;
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output[3] = ENCODE_BASE64[value & 0x3F];
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value >>= 6; output[2] = ENCODE_BASE64[value & 0x3F];
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value >>= 6; output[1] = ENCODE_BASE64[value & 0x3F];
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value >>= 6; output[0] = ENCODE_BASE64[value];
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output += 4;
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}
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unsigned remainder = input + input_length - pos;
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std::uint8_t * result = output;
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if (remainder) {
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unsigned value = pos[0];
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if (remainder == 2) {
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value <<= 8; value |= pos[1];
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value <<= 2;
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output[2] = ENCODE_BASE64[value & 0x3F];
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value >>= 6;
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result += 3;
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} else {
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value <<= 4;
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result += 2;
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}
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output[1] = ENCODE_BASE64[value & 0x3F];
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value >>= 6;
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output[0] = ENCODE_BASE64[value];
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}
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return result;
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}
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std::size_t olm::decode_base64_length(
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std::size_t input_length
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) {
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if (input_length % 4 == 1) {
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return std::size_t(-1);
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} else {
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return 3 * ((input_length + 2) / 4) + (input_length + 2) % 4 - 2;
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}
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}
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std::uint8_t const * olm::decode_base64(
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t * output
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) {
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std::uint8_t const * end = input + (input_length / 4) * 4;
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std::uint8_t const * pos = input;
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while (pos != end) {
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unsigned value = DECODE_BASE64[pos[0] & 0x7F];
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value <<= 6; value |= DECODE_BASE64[pos[1] & 0x7F];
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value <<= 6; value |= DECODE_BASE64[pos[2] & 0x7F];
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value <<= 6; value |= DECODE_BASE64[pos[3] & 0x7F];
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pos += 4;
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output[2] = value;
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value >>= 8; output[1] = value;
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value >>= 8; output[0] = value;
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output += 3;
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}
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unsigned remainder = input + input_length - pos;
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if (remainder) {
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unsigned value = DECODE_BASE64[pos[0] & 0x7F];
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value <<= 6; value |= DECODE_BASE64[pos[1] & 0x7F];
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if (remainder == 3) {
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value <<= 6; value |= DECODE_BASE64[pos[2] & 0x7F];
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value >>= 2;
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output[1] = value;
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value >>= 8;
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} else {
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value >>= 4;
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}
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output[0] = value;
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}
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return input + input_length;
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}
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