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//===- Base64.cpp ---------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#define INVALID_BASE64_BYTE 64
#include "llvm/Support/Base64.h"
static char decodeBase64Byte(uint8_t Ch) {
constexpr char Inv = INVALID_BASE64_BYTE;
static const char DecodeTable[] = {
Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........
Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........
Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........
Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........
Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........
Inv, Inv, Inv, 62, Inv, Inv, Inv, 63, // ...+.../
52, 53, 54, 55, 56, 57, 58, 59, // 01234567
60, 61, Inv, Inv, Inv, 0, Inv, Inv, // 89...=..
Inv, 0, 1, 2, 3, 4, 5, 6, // .ABCDEFG
7, 8, 9, 10, 11, 12, 13, 14, // HIJKLMNO
15, 16, 17, 18, 19, 20, 21, 22, // PQRSTUVW
23, 24, 25, Inv, Inv, Inv, Inv, Inv, // XYZ.....
Inv, 26, 27, 28, 29, 30, 31, 32, // .abcdefg
33, 34, 35, 36, 37, 38, 39, 40, // hijklmno
41, 42, 43, 44, 45, 46, 47, 48, // pqrstuvw
49, 50, 51 // xyz.....
};
if (Ch >= sizeof(DecodeTable))
return Inv;
return DecodeTable[Ch];
}
llvm::Error llvm::decodeBase64(llvm::StringRef Input,
std::vector<char> &Output) {
constexpr char Base64InvalidByte = INVALID_BASE64_BYTE;
// Invalid table value with short name to fit in the table init below. The
// invalid value is 64 since valid base64 values are 0 - 63.
Output.clear();
const uint64_t InputLength = Input.size();
if (InputLength == 0)
return Error::success();
// Make sure we have a valid input string length which must be a multiple
// of 4.
if ((InputLength % 4) != 0)
return createStringError(std::errc::illegal_byte_sequence,
"Base64 encoded strings must be a multiple of 4 "
"bytes in length");
const uint64_t FirstValidEqualIdx = InputLength - 2;
char Hex64Bytes[4];
for (uint64_t Idx = 0; Idx < InputLength; Idx += 4) {
for (uint64_t ByteOffset = 0; ByteOffset < 4; ++ByteOffset) {
const uint64_t ByteIdx = Idx + ByteOffset;
const char Byte = Input[ByteIdx];
const char DecodedByte = decodeBase64Byte(Byte);
bool Illegal = DecodedByte == Base64InvalidByte;
if (!Illegal && Byte == '=') {
if (ByteIdx < FirstValidEqualIdx) {
// We have an '=' in the middle of the string which is invalid, only
// the last two characters can be '=' characters.
Illegal = true;
} else if (ByteIdx == FirstValidEqualIdx && Input[ByteIdx + 1] != '=') {
// We have an equal second to last from the end and the last character
// is not also an equal, so the '=' character is invalid
Illegal = true;
}
}
if (Illegal)
return createStringError(
std::errc::illegal_byte_sequence,
"Invalid Base64 character %#2.2x at index %" PRIu64, Byte, ByteIdx);
Hex64Bytes[ByteOffset] = DecodedByte;
}
// Now we have 6 bits of 3 bytes in value in each of the Hex64Bytes bytes.
// Extract the right bytes into the Output buffer.
Output.push_back((Hex64Bytes[0] << 2) + ((Hex64Bytes[1] >> 4) & 0x03));
Output.push_back((Hex64Bytes[1] << 4) + ((Hex64Bytes[2] >> 2) & 0x0f));
Output.push_back((Hex64Bytes[2] << 6) + (Hex64Bytes[3] & 0x3f));
}
// If we had valid trailing '=' characters strip the right number of bytes
// from the end of the output buffer. We already know that the Input length
// it a multiple of 4 and is not zero, so direct character access is safe.
if (Input.back() == '=') {
Output.pop_back();
if (Input[InputLength - 2] == '=')
Output.pop_back();
}
return Error::success();
}
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