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/*
* Copyright (C) 2016 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.
*/
#ifndef MEMORY_READER_H_
#define MEMORY_READER_H_
#include <cstdint>
#include <tuple>
#include "wifilogd/local_utils.h"
namespace android {
namespace wifilogd {
// A non-owning adapter, which helps with reading protocol messages out
// of a buffer. This is, essentially, the inverse of ByteBuffer.
//
// The user is responsible for ensuring that a MemoryReader does not
// outlive the underlying buffer.
class MemoryReader {
public:
MemoryReader(const void* buf, size_t buflen)
: head_(static_cast<const uint8_t*>(buf)), n_bytes_avail_(buflen) {}
explicit MemoryReader(std::tuple<const uint8_t*, size_t> buf)
: head_(std::get<0>(buf)), n_bytes_avail_(std::get<1>(buf)) {}
// Copies a |T| out of our referenced memory, aborting if sizeof(T) exceeds
// the number of bytes available. On success, updates the read position, and
// the number of bytes available.
template <typename T>
T CopyOutOrDie() {
CHECK(head_);
const T out{local_utils::CopyFromBufferOrDie<T>(head_, n_bytes_avail_)};
head_ += sizeof(T);
n_bytes_avail_ -= sizeof(T);
return out;
}
// Returns a pointer to the next bytes available for reading. Aborts if
// the number of available bytes is less than |n_bytes|. On success, updates
// the read position, and the number of bytes available.
RETURNS_NONNULL const uint8_t* GetBytesOrDie(size_t n_bytes);
// Returns true if the referenced memory is non-NULL, and has at least
// one byte available for reading.
explicit operator bool() const { return head_ && n_bytes_avail_; }
// Returns the number of bytes available for reading.
size_t size() const { return (head_ ? n_bytes_avail_ : 0); }
private:
const uint8_t* head_; // non-owned
size_t n_bytes_avail_;
};
} // namespace wifilogd
} // namespace android
#endif // MEMORY_READER_H_
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