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/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "perfetto/ext/base/base64.h"
namespace perfetto {
namespace base {
namespace {
constexpr char kPadding = '=';
constexpr char kEncTable[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static_assert(sizeof(kEncTable) == (1u << 6) + sizeof('\0'), "Bad table size");
// Maps an ASCII character to its 6-bit value. It only contains translations
// from '+' to 'z'. Supports the standard (+/) and URL-safe (-_) alphabets.
constexpr uint8_t kX = 0xff; // Value used for invalid characters
constexpr uint8_t kDecTable[] = {
62, kX, 62, kX, 63, 52, 53, 54, 55, 56, // 00 - 09
57, 58, 59, 60, 61, kX, kX, kX, 0, kX, // 10 - 19
kX, kX, 0, 1, 2, 3, 4, 5, 6, 7, // 20 - 29
8, 9, 10, 11, 12, 13, 14, 15, 16, 17, // 30 - 39
18, 19, 20, 21, 22, 23, 24, 25, kX, kX, // 40 - 49
kX, kX, 63, kX, 26, 27, 28, 29, 30, 31, // 50 - 59
32, 33, 34, 35, 36, 37, 38, 39, 40, 41, // 60 - 69
42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // 70 - 79
};
constexpr char kMinDecChar = '+';
constexpr char kMaxDecChar = 'z';
static_assert(kMaxDecChar - kMinDecChar <= sizeof(kDecTable), "Bad table size");
inline uint8_t DecodeChar(char c) {
if (c < kMinDecChar || c > kMaxDecChar)
return kX;
return kDecTable[c - kMinDecChar];
}
} // namespace
ssize_t Base64Encode(const void* src,
size_t src_size,
char* dst,
size_t dst_size) {
const size_t padded_dst_size = Base64EncSize(src_size);
if (dst_size < padded_dst_size)
return -1; // Not enough space in output.
const uint8_t* rd = static_cast<const uint8_t*>(src);
const uint8_t* const end = rd + src_size;
size_t wr_size = 0;
while (rd < end) {
uint8_t s[3]{};
s[0] = *(rd++);
dst[wr_size++] = kEncTable[s[0] >> 2];
uint8_t carry0 = static_cast<uint8_t>((s[0] & 0x03) << 4);
if (PERFETTO_LIKELY(rd < end)) {
s[1] = *(rd++);
dst[wr_size++] = kEncTable[carry0 | (s[1] >> 4)];
} else {
dst[wr_size++] = kEncTable[carry0];
dst[wr_size++] = kPadding;
dst[wr_size++] = kPadding;
break;
}
uint8_t carry1 = static_cast<uint8_t>((s[1] & 0x0f) << 2);
if (PERFETTO_LIKELY(rd < end)) {
s[2] = *(rd++);
dst[wr_size++] = kEncTable[carry1 | (s[2] >> 6)];
} else {
dst[wr_size++] = kEncTable[carry1];
dst[wr_size++] = kPadding;
break;
}
dst[wr_size++] = kEncTable[s[2] & 0x3f];
}
PERFETTO_DCHECK(wr_size == padded_dst_size);
return static_cast<ssize_t>(padded_dst_size);
}
std::string Base64Encode(const void* src, size_t src_size) {
std::string dst;
dst.resize(Base64EncSize(src_size));
auto res = Base64Encode(src, src_size, &dst[0], dst.size());
PERFETTO_CHECK(res == static_cast<ssize_t>(dst.size()));
return dst;
}
ssize_t Base64Decode(const char* src,
size_t src_size,
uint8_t* dst,
size_t dst_size) {
const size_t min_dst_size = Base64DecSize(src_size);
if (dst_size < min_dst_size)
return -1;
const char* rd = src;
const char* const end = src + src_size;
size_t wr_size = 0;
char s[4]{};
while (rd < end) {
uint8_t d[4];
for (uint32_t j = 0; j < 4; j++) {
// Padding is only feasible for the last 2 chars of each group of 4.
s[j] = rd < end ? *(rd++) : (j < 2 ? '\0' : kPadding);
d[j] = DecodeChar(s[j]);
if (d[j] == kX)
return -1; // Invalid input char.
}
dst[wr_size] = static_cast<uint8_t>((d[0] << 2) | (d[1] >> 4));
dst[wr_size + 1] = static_cast<uint8_t>((d[1] << 4) | (d[2] >> 2));
dst[wr_size + 2] = static_cast<uint8_t>((d[2] << 6) | (d[3]));
wr_size += 3;
}
PERFETTO_CHECK(wr_size <= dst_size);
wr_size -= (s[3] == kPadding ? 1 : 0) + (s[2] == kPadding ? 1 : 0);
return static_cast<ssize_t>(wr_size);
}
Optional<std::string> Base64Decode(const char* src, size_t src_size) {
std::string dst;
dst.resize(Base64DecSize(src_size));
auto res = Base64Decode(src, src_size, reinterpret_cast<uint8_t*>(&dst[0]),
dst.size());
if (res < 0)
return nullopt; // Decoding error.
PERFETTO_CHECK(res <= static_cast<ssize_t>(dst.size()));
dst.resize(static_cast<size_t>(res));
return base::make_optional(dst);
}
} // namespace base
} // namespace perfetto