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/*
* Copyright (c) 2020-2021, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Stream.h>
#include <AK/Types.h>
namespace AK {
struct LEB128 {
template<typename StreamT, typename ValueType = size_t>
static bool read_unsigned(StreamT& stream, ValueType& result)
{
[[maybe_unused]] size_t backup_offset = 0;
if constexpr (requires { stream.offset(); })
backup_offset = stream.offset();
InputStream& input_stream { stream };
result = 0;
size_t num_bytes = 0;
while (true) {
if (input_stream.unreliable_eof()) {
if constexpr (requires { stream.seek(backup_offset); })
stream.seek(backup_offset);
input_stream.set_fatal_error();
return false;
}
u8 byte = 0;
input_stream >> byte;
if (input_stream.has_any_error())
return false;
result = (result) | (static_cast<ValueType>(byte & ~(1 << 7)) << (num_bytes * 7));
if (!(byte & (1 << 7)))
break;
++num_bytes;
}
return true;
}
template<typename StreamT, typename ValueType = ssize_t>
static bool read_signed(StreamT& stream, ValueType& result)
{
using UValueType = MakeUnsigned<ValueType>;
[[maybe_unused]] size_t backup_offset = 0;
if constexpr (requires { stream.offset(); })
backup_offset = stream.offset();
InputStream& input_stream { stream };
result = 0;
size_t num_bytes = 0;
u8 byte = 0;
do {
if (input_stream.unreliable_eof()) {
if constexpr (requires { stream.seek(backup_offset); })
stream.seek(backup_offset);
input_stream.set_fatal_error();
return false;
}
input_stream >> byte;
if (input_stream.has_any_error())
return false;
result = (result) | (static_cast<UValueType>(byte & ~(1 << 7)) << (num_bytes * 7));
++num_bytes;
} while (byte & (1 << 7));
if (num_bytes * 7 < sizeof(UValueType) * 4 && (byte & 0x40)) {
// sign extend
result |= ((UValueType)(-1) << (num_bytes * 7));
}
return true;
}
};
}
using AK::LEB128;
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