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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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
*
* https://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 avro_BufferReader_hh__
#define avro_BufferReader_hh__
#include "Buffer.hh"
#include <type_traits>
#ifdef min
#undef min
#endif
/**
* \file BufferReader.hh
*
* \brief Helper class for reading bytes from buffer in a streaming manner,
* without the overhead of istreams.
*
**/
namespace avro {
/**
* Helper class for reading bytes from buffer without worrying about
* chunk boundaries. May read from an InputBuffer or OutputBuffer.
*
**/
class AVRO_DECL BufferReader : private boost::noncopyable {
public:
typedef detail::data_type data_type;
typedef detail::size_type size_type;
private:
size_type chunkRemaining() const {
return iter_->dataSize() - chunkPos_;
}
void incrementChunk(size_type howMuch) {
bytesRemaining_ -= howMuch;
chunkPos_ += howMuch;
if (chunkPos_ == iter_->dataSize()) {
chunkPos_ = 0;
++iter_;
}
}
void rewind() {
iter_ = bufferImpl_->beginRead();
bytesRemaining_ = bytes_;
chunkPos_ = 0;
}
const data_type *addr() const {
return iter_->tellReadPos() + chunkPos_;
}
public:
explicit BufferReader(const InputBuffer &buf) : bufferImpl_(buf.pimpl_),
iter_(bufferImpl_->beginRead()),
bytes_(bufferImpl_->size()),
bytesRemaining_(bytes_),
chunkPos_(0) {}
explicit BufferReader(const OutputBuffer &buf) : bufferImpl_(buf.pimpl_),
iter_(bufferImpl_->beginRead()),
bytes_(bufferImpl_->size()),
bytesRemaining_(bytes_),
chunkPos_(0) {}
/**
* How many bytes are still not read from this buffer.
**/
size_type bytesRemaining() const {
return bytesRemaining_;
}
/**
* Read a block of data from the front of the buffer.
**/
size_type bytesRead() const {
return bytes_ - bytesRemaining_;
}
/**
* Read a block of data from the buffer.
**/
size_type read(data_type *data, size_type size) {
if (size > bytesRemaining_) {
size = bytesRemaining_;
}
size_type sizeToRead = size;
while (sizeToRead) {
const size_type toRead = std::min(sizeToRead, chunkRemaining());
memcpy(data, addr(), toRead);
sizeToRead -= toRead;
data += toRead;
incrementChunk(toRead);
}
return size;
}
/**
* Read a block of data from the buffer.
**/
bool read(std::string &str, size_type size) {
if (size > bytesRemaining_) {
return false;
}
if (size <= chunkRemaining()) {
fastStringRead(str, size);
} else {
slowStringRead(str, size);
}
return true;
}
/**
* Read a single value from the buffer. The value must be a "fundamental"
* type, e.g. int, float, etc. (otherwise use the other writeTo tests).
*
**/
template<typename T>
bool read(T &val) {
return read(val, std::is_fundamental<T>());
}
/**
* Skips a block of data from the buffer.
**/
bool skip(size_type bytes) {
bool skipped = false;
if (bytes <= bytesRemaining_) {
doSkip(bytes);
skipped = true;
}
return skipped;
}
/**
* Seek to a position in the buffer.
**/
bool seek(size_type pos) {
if (pos > bytes_) {
return false;
}
size_type toSkip = pos;
size_type curPos = bytesRead();
// if the seek position is ahead, we can use skip to get there
if (pos >= curPos) {
toSkip -= curPos;
}
// if the seek position is ahead of the start of the chunk we can back up to
// start of the chunk
else if (pos >= (curPos - chunkPos_)) {
curPos -= chunkPos_;
bytesRemaining_ += chunkPos_;
chunkPos_ = 0;
toSkip -= curPos;
} else {
rewind();
}
doSkip(toSkip);
return true;
}
bool peek(char &val) {
bool ret = (bytesRemaining_ > 0);
if (ret) {
val = *(addr());
}
return ret;
}
InputBuffer copyData(size_type bytes) {
if (bytes > bytesRemaining_) {
// force no copy
bytes = 0;
}
detail::BufferImpl::SharedPtr newImpl(new detail::BufferImpl);
if (bytes) {
bufferImpl_->copyData(*newImpl, iter_, chunkPos_, bytes);
doSkip(bytes);
}
return InputBuffer(newImpl);
}
private:
void doSkip(size_type sizeToSkip) {
while (sizeToSkip) {
const size_type toSkip = std::min(sizeToSkip, chunkRemaining());
sizeToSkip -= toSkip;
incrementChunk(toSkip);
}
}
template<typename T>
bool read(T &val, const std::true_type &) {
if (sizeof(T) > bytesRemaining_) {
return false;
}
if (sizeof(T) <= chunkRemaining()) {
val = *(reinterpret_cast<const T *>(addr()));
incrementChunk(sizeof(T));
} else {
read(reinterpret_cast<data_type *>(&val), sizeof(T));
}
return true;
}
/// An uninstantiable function, that is if boost::is_fundamental check fails
template<typename T>
bool read(T &val, const std::false_type &) {
static_assert(sizeof(T) == 0, "Not a valid type to read");
return false;
}
void fastStringRead(std::string &str, size_type sizeToCopy) {
str.assign(addr(), sizeToCopy);
incrementChunk(sizeToCopy);
}
void slowStringRead(std::string &str, size_type sizeToCopy) {
str.clear();
str.reserve(sizeToCopy);
while (sizeToCopy) {
const size_type toCopy = std::min(sizeToCopy, chunkRemaining());
str.append(addr(), toCopy);
sizeToCopy -= toCopy;
incrementChunk(toCopy);
}
}
detail::BufferImpl::ConstSharedPtr bufferImpl_;
detail::BufferImpl::ChunkList::const_iterator iter_;
size_type bytes_;
size_type bytesRemaining_;
size_type chunkPos_;
};
} // namespace avro
#endif
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