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