You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
 
rocksdb/thrift/lib/cpp/transport/TBufferTransports.h

973 lines
27 KiB

/*
* 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
*
* 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 THRIFT_TRANSPORT_TBUFFERTRANSPORTS_H_
#define THRIFT_TRANSPORT_TBUFFERTRANSPORTS_H_ 1
#include <cstring>
#include "boost/scoped_array.hpp"
#include "folly/Likely.h"
#include "thrift/lib/cpp/transport/TTransport.h"
#include "thrift/lib/cpp/transport/TVirtualTransport.h"
namespace apache { namespace thrift { namespace transport {
/**
* Base class for all transports that use read/write buffers for performance.
*
* TBufferBase is designed to implement the fast-path "memcpy" style
* operations that work in the common case. It does so with small and
* (eventually) nonvirtual, inlinable methods. TBufferBase is an abstract
* class. Subclasses are expected to define the "slow path" operations
* that have to be done when the buffers are full or empty.
*
*/
class TBufferBase : public TVirtualTransport<TBufferBase> {
public:
/**
* Fast-path read.
*
* When we have enough data buffered to fulfill the read, we can satisfy it
* with a single memcpy, then adjust our internal pointers. If the buffer
* is empty, we call out to our slow path, implemented by a subclass.
* This method is meant to eventually be nonvirtual and inlinable.
*/
uint32_t read(uint8_t* buf, uint32_t len) {
uint8_t* new_rBase = rBase_ + len;
if (LIKELY(new_rBase <= rBound_)) {
std::memcpy(buf, rBase_, len);
rBase_ = new_rBase;
return len;
}
return readSlow(buf, len);
}
/**
* Shortcutted version of readAll.
*/
uint32_t readAll(uint8_t* buf, uint32_t len) {
uint8_t* new_rBase = rBase_ + len;
if (LIKELY(new_rBase <= rBound_)) {
std::memcpy(buf, rBase_, len);
rBase_ = new_rBase;
return len;
}
return apache::thrift::transport::readAll(*this, buf, len);
}
/**
* Fast-path write.
*
* When we have enough empty space in our buffer to accommodate the write, we
* can satisfy it with a single memcpy, then adjust our internal pointers.
* If the buffer is full, we call out to our slow path, implemented by a
* subclass. This method is meant to eventually be nonvirtual and
* inlinable.
*/
void write(const uint8_t* buf, uint32_t len) {
uint8_t* new_wBase = wBase_ + len;
if (LIKELY(new_wBase <= wBound_)) {
std::memcpy(wBase_, buf, len);
wBase_ = new_wBase;
return;
}
writeSlow(buf, len);
}
/**
* Fast-path borrow. A lot like the fast-path read.
*/
const uint8_t* borrow(uint8_t* buf, uint32_t* len) {
if (LIKELY(static_cast<ptrdiff_t>(*len) <= rBound_ - rBase_)) {
// With strict aliasing, writing to len shouldn't force us to
// refetch rBase_ from memory. TODO(dreiss): Verify this.
*len = rBound_ - rBase_;
return rBase_;
}
return borrowSlow(buf, len);
}
/**
* Consume doesn't require a slow path.
* When the read ptr catches up with write ptr, invokes consumeEnd().
*/
void consume(uint32_t len) {
if (LIKELY(static_cast<ptrdiff_t>(len) <= rBound_ - rBase_)) {
rBase_ += len;
if (rBase_ == wBase_) {
// This is required for TMemoryBuffer.
consumeEnd();
}
} else {
throw TTransportException(TTransportException::BAD_ARGS,
"consume did not follow a borrow.");
}
}
protected:
/// Slow path read.
virtual uint32_t readSlow(uint8_t* buf, uint32_t len) = 0;
/// Slow path write.
virtual void writeSlow(const uint8_t* buf, uint32_t len) = 0;
/// consumeEnd, invoked when all data has been consumed.
virtual void consumeEnd() { }
/**
* Slow path borrow.
*
* POSTCONDITION: return == NULL || rBound_ - rBase_ >= *len
*/
virtual const uint8_t* borrowSlow(uint8_t* buf, uint32_t* len) = 0;
/**
* Trivial constructor.
*
* Initialize pointers safely. Constructing is not a very
* performance-sensitive operation, so it is okay to just leave it to
* the concrete class to set up pointers correctly.
*/
TBufferBase()
: rBase_(NULL)
, rBound_(NULL)
, wBase_(NULL)
, wBound_(NULL)
{}
/// Convenience mutator for setting the read buffer.
void setReadBuffer(uint8_t* buf, uint32_t len) {
rBase_ = buf;
rBound_ = buf+len;
}
/// Convenience mutator for setting the write buffer.
void setWriteBuffer(uint8_t* buf, uint32_t len) {
wBase_ = buf;
wBound_ = buf+len;
}
virtual ~TBufferBase() {}
/// Reads begin here.
uint8_t* rBase_;
/// Reads may extend to just before here.
uint8_t* rBound_;
/// Writes begin here.
uint8_t* wBase_;
/// Writes may extend to just before here.
uint8_t* wBound_;
};
/**
* Buffered transport. For reads it will read more data than is requested
* and will serve future data out of a local buffer. For writes, data is
* stored to an in memory buffer before being written out.
*
*/
class TBufferedTransport
: public TVirtualTransport<TBufferedTransport, TBufferBase> {
public:
static const int DEFAULT_BUFFER_SIZE = 512;
/// Use default buffer sizes.
explicit TBufferedTransport(boost::shared_ptr<TTransport> transport)
: transport_(transport)
, rBufSize_(DEFAULT_BUFFER_SIZE)
, wBufSize_(DEFAULT_BUFFER_SIZE)
, wBufResetSize_(0)
, wBufResetEveryN_(0)
, wBufResetCount_(0)
, rBuf_(new uint8_t[rBufSize_])
, wBuf_(new uint8_t[wBufSize_])
{
initPointers();
}
/// Use specified buffer sizes.
TBufferedTransport(boost::shared_ptr<TTransport> transport, uint32_t sz)
: transport_(transport)
, rBufSize_(sz)
, wBufSize_(sz)
, wBufResetSize_(0)
, wBufResetEveryN_(0)
, wBufResetCount_(0)
, rBuf_(new uint8_t[rBufSize_])
, wBuf_(new uint8_t[wBufSize_])
{
initPointers();
}
/**
* Ctor with initial read and write buffer sizes and write buffer reset
* behaviour settings.
*
* @param transport Underlying transport.
* @param sz Initial buffer size.
* @param reset_sz Buffer size after a reset. See also reset_every_n.
* @param reset_every_n Reset the buffer after every N calls to flush().
* If set to zero (default), no reset is done.
*/
TBufferedTransport(boost::shared_ptr<TTransport> transport, uint32_t rsz,
uint32_t wsz, uint32_t reset_sz = 0,
uint32_t reset_every_n = 0)
: transport_(transport)
, rBufSize_(rsz)
, wBufSize_(wsz)
, wBufResetSize_(reset_sz)
, wBufResetEveryN_(reset_every_n)
, wBufResetCount_(0)
, rBuf_(new uint8_t[rBufSize_])
, wBuf_(new uint8_t[wBufSize_])
{
initPointers();
}
// Tries to put some data back in the beginning of the read buffer.
void putBack(uint8_t* buf, uint32_t len);
void open() {
transport_->open();
}
bool isOpen() {
return transport_->isOpen();
}
bool peek() {
if (rBase_ == rBound_) {
setReadBuffer(rBuf_.get(), transport_->read(rBuf_.get(), rBufSize_));
}
return (rBound_ > rBase_);
}
void close() {
flush();
transport_->close();
}
virtual uint32_t readSlow(uint8_t* buf, uint32_t len);
virtual void writeSlow(const uint8_t* buf, uint32_t len);
void flush();
/**
* The following behavior is currently implemented by TBufferedTransport,
* but that may change in a future version:
* 1/ If len is at most rBufSize_, borrow will never return NULL.
* Depending on the underlying transport, it could throw an exception
* or hang forever.
* 2/ Some borrow requests may copy bytes internally. However,
* if len is at most rBufSize_/2, none of the copied bytes
* will ever have to be copied again. For optimal performance,
* stay under this limit.
*/
virtual const uint8_t* borrowSlow(uint8_t* buf, uint32_t* len);
boost::shared_ptr<TTransport> getUnderlyingTransport() {
return transport_;
}
/*
* TVirtualTransport provides a default implementation of readAll().
* We want to use the TBufferBase version instead.
*/
using TBufferBase::readAll;
protected:
void initPointers() {
setReadBuffer(rBuf_.get(), 0);
setWriteBuffer(wBuf_.get(), wBufSize_);
// Write size never changes.
}
boost::shared_ptr<TTransport> transport_;
uint32_t rBufSize_;
uint32_t wBufSize_;
uint32_t wBufResetSize_;
uint32_t wBufResetEveryN_;
uint32_t wBufResetCount_;
boost::scoped_array<uint8_t> rBuf_;
boost::scoped_array<uint8_t> wBuf_;
};
/**
* Wraps a transport into a buffered one.
*
*/
class TBufferedTransportFactory : public TTransportFactory {
public:
TBufferedTransportFactory() {}
virtual ~TBufferedTransportFactory() {}
/**
* Wraps the transport into a buffered one.
*/
virtual boost::shared_ptr<TTransport> getTransport(boost::shared_ptr<TTransport> trans) {
return boost::shared_ptr<TTransport>(new TBufferedTransport(trans));
}
};
/**
* Framed transport. All writes go into an in-memory buffer until flush is
* called, at which point the transport writes the length of the entire
* binary chunk followed by the data payload. This allows the receiver on the
* other end to always do fixed-length reads.
*
*/
class TFramedTransport
: public TVirtualTransport<TFramedTransport, TBufferBase> {
public:
static const int DEFAULT_BUFFER_SIZE = 512;
/// Use default buffer sizes.
explicit TFramedTransport(boost::shared_ptr<TTransport> transport)
: transport_(transport)
, rBufSize_(0)
, wBufSize_(DEFAULT_BUFFER_SIZE)
, wBufResetSize_(0)
, wBufResetEveryN_(0)
, wBufResetCount_(0)
, rBuf_()
, wBuf_(new uint8_t[wBufSize_])
{
initPointers();
}
/**
* Ctor with initial buffer size and write buffer reset behaviour settings.
*
* @param transport Underlying transport.
* @param sz Initial buffer size.
* @param reset_sz Buffer size after a reset. See also reset_every_n.
* @param reset_every_n Reset the buffer after every N calls to flush().
* If set to zero (default), no reset is done.
*/
TFramedTransport(boost::shared_ptr<TTransport> transport, uint32_t sz,
uint32_t reset_sz = 0, uint32_t reset_every_n = 0)
: transport_(transport)
, rBufSize_(0)
, wBufSize_(sz)
, wBufResetSize_(reset_sz)
, wBufResetEveryN_(reset_every_n)
, wBufResetCount_(0)
, rBuf_()
, wBuf_(new uint8_t[wBufSize_])
{
assert(wBufResetSize_ == 0 || wBufSize_ <= wBufResetSize_);
initPointers();
}
void open() {
transport_->open();
}
bool isOpen() {
return transport_->isOpen();
}
bool peek() {
return (rBase_ < rBound_) || transport_->peek();
}
void close() {
flush();
transport_->close();
}
virtual uint32_t readSlow(uint8_t* buf, uint32_t len);
virtual void writeSlow(const uint8_t* buf, uint32_t len);
virtual void flush();
uint32_t readEnd();
uint32_t writeEnd();
const uint8_t* borrowSlow(uint8_t* buf, uint32_t* len);
boost::shared_ptr<TTransport> getUnderlyingTransport() {
return transport_;
}
/*
* TVirtualTransport provides a default implementation of readAll().
* We want to use the TBufferBase version instead.
*/
using TBufferBase::readAll;
protected:
/// Constructor for subclassing.
TFramedTransport()
: rBufSize_(0)
, wBufSize_(DEFAULT_BUFFER_SIZE)
, wBufResetSize_(0)
, wBufResetEveryN_(0)
, wBufResetCount_(0)
, rBuf_()
, wBuf_(new uint8_t[wBufSize_])
{
initPointers();
}
/**
* Reads a frame of input from the underlying stream.
*
* Returns true if a frame was read successfully, or false on EOF.
* (Raises a TTransportException if EOF occurs after a partial frame.)
*
* @param req_sz The size of the requested data. readFrame may read more
* than this amount, but should not read less.
*/
virtual bool readFrame(uint32_t min_frame_sz);
void initPointers() {
setReadBuffer(NULL, 0);
setWriteBuffer(wBuf_.get(), wBufSize_);
// Pad the buffer so we can insert the size later.
int32_t pad = 0;
this->write((uint8_t*)&pad, sizeof(pad));
}
boost::shared_ptr<TTransport> transport_;
uint32_t rBufSize_;
uint32_t wBufSize_;
uint32_t wBufResetSize_;
uint32_t wBufResetEveryN_;
uint32_t wBufResetCount_;
boost::scoped_array<uint8_t> rBuf_;
boost::scoped_array<uint8_t> wBuf_;
};
/**
* Wraps a transport into a framed one.
*
*/
class TFramedTransportFactory : public TTransportFactory {
public:
TFramedTransportFactory() {}
virtual ~TFramedTransportFactory() {}
/**
* Wraps the transport into a framed one.
*/
virtual boost::shared_ptr<TTransport> getTransport(boost::shared_ptr<TTransport> trans) {
return boost::shared_ptr<TTransport>(new TFramedTransport(trans));
}
};
/**
* A memory buffer is a transport that simply reads from and writes to an
* in memory buffer. Anytime you call write on it, the data is simply placed
* into a buffer, and anytime you call read, data is read from that buffer.
*
* The buffers are allocated using C constructs malloc,realloc, and the size
* doubles as necessary. We've considered using scoped
*
*/
class TMemoryBuffer : public TVirtualTransport<TMemoryBuffer, TBufferBase> {
private:
TMemoryBuffer(const TMemoryBuffer&);
TMemoryBuffer &operator=(const TMemoryBuffer&);
// Common initialization done by all constructors.
void initCommon(uint8_t* buf, uint32_t size, bool owner, uint32_t wPos) {
if (buf == NULL && size != 0) {
assert(owner);
buf = (uint8_t*)std::malloc(size);
if (buf == NULL) {
throw std::bad_alloc();
}
}
buffer_ = buf;
bufferSize_ = size;
rBase_ = buffer_;
rBound_ = buffer_ + wPos;
// TODO(dreiss): Investigate NULL-ing this if !owner.
wBase_ = buffer_ + wPos;
wBound_ = buffer_ + bufferSize_;
owner_ = owner;
linkedBuffer_ = NULL;
observerCount_ = 0;
// rBound_ is really an artifact. In principle, it should always be
// equal to wBase_. We update it in a few places (computeRead, etc.).
}
public:
static const uint32_t defaultSize = 1024;
/**
* This enum specifies how a TMemoryBuffer should treat
* memory passed to it via constructors or resetBuffer.
*
* OBSERVE:
* TMemoryBuffer will simply store a pointer to the memory.
* It is the callers responsibility to ensure that the pointer
* remains valid for the lifetime of the TMemoryBuffer,
* and that it is properly cleaned up.
* Note that no data can be written to observed buffers.
*
* COPY:
* TMemoryBuffer will make an internal copy of the buffer.
* The caller has no responsibilities.
*
* TAKE_OWNERSHIP:
* TMemoryBuffer will become the "owner" of the buffer,
* and will be responsible for freeing it.
* The memory must have been allocated with malloc.
*/
enum MemoryPolicy
{ OBSERVE = 1
, COPY = 2
, TAKE_OWNERSHIP = 3
};
/**
* Construct a TMemoryBuffer with a default-sized buffer,
* owned by the TMemoryBuffer object.
*/
TMemoryBuffer() {
initCommon(NULL, defaultSize, true, 0);
}
/**
* Construct a TMemoryBuffer with a buffer of a specified size,
* owned by the TMemoryBuffer object.
*
* @param sz The initial size of the buffer.
*/
explicit TMemoryBuffer(uint32_t sz) {
initCommon(NULL, sz, true, 0);
}
/**
* Construct a TMemoryBuffer with buf as its initial contents.
*
* @param buf The initial contents of the buffer.
* Note that, while buf is a non-const pointer,
* TMemoryBuffer will not write to it if policy == OBSERVE,
* so it is safe to const_cast<uint8_t*>(whatever).
* @param sz The size of @c buf.
* @param policy See @link MemoryPolicy @endlink .
*/
TMemoryBuffer(uint8_t* buf, uint32_t sz, MemoryPolicy policy = OBSERVE) {
if (buf == NULL && sz != 0) {
throw TTransportException(TTransportException::BAD_ARGS,
"TMemoryBuffer given null buffer with non-zero size.");
}
switch (policy) {
case OBSERVE:
case TAKE_OWNERSHIP:
initCommon(buf, sz, policy == TAKE_OWNERSHIP, sz);
break;
case COPY:
initCommon(NULL, sz, true, 0);
this->write(buf, sz);
break;
default:
throw TTransportException(TTransportException::BAD_ARGS,
"Invalid MemoryPolicy for TMemoryBuffer");
}
}
explicit TMemoryBuffer(TMemoryBuffer *buffer) {
initCommon(buffer->rBase_, buffer->available_read(), false,
buffer->available_read());
// Have to set buffer_ appropriately so this buffer can take ownership
// later if necessary. initCommon sets all other state correctly.
buffer_ = buffer->buffer_;
linkedBuffer_ = buffer;
linkedBuffer_->observe(this);
}
~TMemoryBuffer() {
cleanup();
}
// Set this buffer to observe the next length bytes of buffer.
void link(TMemoryBuffer *buffer, uint32_t length) {
assert(length <= buffer->available_read());
cleanup();
initCommon(buffer->rBase_, length, false, length);
buffer_ = buffer->buffer_;
linkedBuffer_ = buffer;
linkedBuffer_->observe(this);
}
bool isOpen() {
return true;
}
bool peek() {
return (rBase_ < wBase_);
}
void open() {}
void close() {}
uint32_t getBufferSize() const { return bufferSize_; }
// TODO(dreiss): Make bufPtr const.
void getBuffer(uint8_t** bufPtr, uint32_t* sz) {
*bufPtr = rBase_;
*sz = wBase_ - rBase_;
}
std::string getBufferAsString() {
if (buffer_ == NULL) {
return "";
}
uint8_t* buf;
uint32_t sz;
getBuffer(&buf, &sz);
return std::string((char*)buf, (std::string::size_type)sz);
}
void appendBufferToString(std::string& str) {
if (buffer_ == NULL) {
return;
}
uint8_t* buf;
uint32_t sz;
getBuffer(&buf, &sz);
str.append((char*)buf, sz);
}
void resetBuffer() {
rBase_ = buffer_;
rBound_ = buffer_;
wBase_ = buffer_;
// It isn't safe to write into a buffer we don't own.
if (!owner_) {
wBound_ = wBase_;
bufferSize_ = 0;
}
}
// Register an observer of the memory in this buffer.
//
// A TMemoryBuffer with one or more observers has special handling
// for operations that would invalidate the data being observed. If
// an operation would invalidate the buffer pointer (eg: realloc, free),
// ownership of that buffer is first transferred to one of the observing
// TMemoryBuffers.
//
// Calls that reset an apparently empty buffer are delayed until all
// observers are detached.
void observe(TMemoryBuffer *observer) {
if (observer != NULL) {
observers_.push_back(observer);
}
observerCount_++;
}
// Remove an observer of the memory in this buffer. If there is a pending
// consumeEnd call, process it
void unobserve(TMemoryBuffer *observer) {
if (UNLIKELY(observerCount_ == 0)) {
throw TTransportException("Tried to unobserve a buffer with no "
"observers");
}
bool found = false;
if (observer != NULL) {
for(TMemoryBufferContainer::iterator it = observers_.begin();
it != observers_.end(); ++it) {
if (*it == observer) {
observers_.erase(it);
found = true;
break;
}
}
}
if (!found) {
throw TTransportException("Tried to remove an observer that was not "
"observing the buffer");
}
observerCount_--;
if (observerCount_ == 0 && rBase_ == wBase_) {
consumeEnd();
}
}
// Remove link to an observed memory buffer. If the buffer is not linked
// this is a no-op.
void unlink() {
if (linkedBuffer_ != NULL) {
linkedBuffer_->unobserve(this);
linkedBuffer_ = NULL;
}
}
/// See constructor documentation.
void resetBuffer(uint8_t* buf, uint32_t sz, MemoryPolicy policy = OBSERVE) {
// Use a variant of the copy-and-swap trick for assignment operators.
// This is sub-optimal in terms of performance for two reasons:
// 1/ The constructing and swapping of the (small) values
// in the temporary object takes some time, and is not necessary.
// 2/ If policy == COPY, we allocate the new buffer before
// freeing the old one, precluding the possibility of
// reusing that memory.
// I doubt that either of these problems could be optimized away,
// but the second is probably no a common case, and the first is minor.
// I don't expect resetBuffer to be a common operation, so I'm willing to
// bite the performance bullet to make the method this simple.
// Construct the new buffer.
TMemoryBuffer new_buffer(buf, sz, policy);
// Move it into ourself.
this->swap(new_buffer);
// Our old self gets destroyed.
}
/// See constructor documentation.
void resetBuffer(uint32_t sz) {
// Construct the new buffer.
TMemoryBuffer new_buffer(sz);
// Move it into ourself.
this->swap(new_buffer);
// Our old self gets destroyed.
}
std::string readAsString(uint32_t len) {
std::string str;
(void)readAppendToString(str, len);
return str;
}
uint32_t readAppendToString(std::string& str, uint32_t len);
// return number of bytes read
uint32_t readEnd() {
uint32_t bytes = rBase_ - buffer_;
if (rBase_ == wBase_) {
resetBuffer();
}
return bytes;
}
// Return number of bytes written
uint32_t writeEnd() {
return wBase_ - buffer_;
}
uint32_t available_read() const {
// Remember, wBase_ is the real rBound_.
return wBase_ - rBase_;
}
uint32_t available_write() const {
return wBound_ - wBase_;
}
// Returns a pointer to where the client can write data to append to
// the TMemoryBuffer, and ensures the buffer is big enough to accommodate a
// write of the provided length. The returned pointer is very convenient for
// passing to read(), recv(), or similar. You must call wroteBytes() as soon
// as data is written or the buffer will not be aware that data has changed.
uint8_t* getWritePtr(uint32_t len) {
ensureCanWrite(len);
return wBase_;
}
// Informs the buffer that the client has written 'len' bytes into storage
// that had been provided by getWritePtr().
void wroteBytes(uint32_t len);
/*
* TVirtualTransport provides a default implementation of readAll().
* We want to use the TBufferBase version instead.
*/
using TBufferBase::readAll;
/**
* Extract the read buffer from the TMemoryBuffer, or make a copy if this
* buffer does not own it. It's not safe to assume that a buffer created
* with TAKE_OWNERSHIP or COPY is still the owner of it's underlying buffer,
* because some TMemoryBuffer APIs (resetBuffer, link) change the ownership.
* Because of that, it's more consistent to make a copy rather than throw.
*
* The TMemoryBuffer's internal buffer is returned, and the caller is
* given ownership of the buffer. The caller is responsible for eventually
* freeing the buffer using free().
*
* The TMemoryBuffer itself will be reset and will allocate a new buffer the
* next time data is written into it.
*
* @param buf The returned buffer pointer is stored at the location
* specified by this argument.
* @param buflen This parameter is used to return the number of bytes of
* readable data available at the start of the returned buffer.
* (Note that this is the amount of available data, not the
* buffer capacity.)
*/
void extractReadBuffer(uint8_t** buf, uint32_t* buflen) {
*buflen = available_read();
if (owner_) {
if (rBase_ != buffer_) {
memmove(buffer_, rBase_, *buflen);
}
*buf = buffer_;
} else {
*buf = (uint8_t *)malloc(*buflen);
if (*buf == NULL) {
throw std::bad_alloc();
}
memcpy(*buf, rBase_, *buflen);
cleanup();
}
initCommon(NULL, 0, true, 0);
}
protected:
void swap(TMemoryBuffer& that) {
using std::swap;
swap(buffer_, that.buffer_);
swap(bufferSize_, that.bufferSize_);
swap(rBase_, that.rBase_);
swap(rBound_, that.rBound_);
swap(wBase_, that.wBase_);
swap(wBound_, that.wBound_);
swap(owner_, that.owner_);
swap(linkedBuffer_, that.linkedBuffer_);
swap(observerCount_, that.observerCount_);
observers_.swap(that.observers_);
for (auto buf: observers_) {
buf->linkedBuffer_ = this;
}
for (auto buf: that.observers_) {
buf->linkedBuffer_ = &that;
}
if (linkedBuffer_ != NULL) {
linkedBuffer_->unobserve(&that);
linkedBuffer_->observe(this);
}
if (that.linkedBuffer_ != NULL) {
that.linkedBuffer_->unobserve(this);
that.linkedBuffer_->observe(&that);
}
}
void transferOwnership() {
TMemoryBuffer *newOwner = NULL;
assert(!observers_.empty());
// The optimal case is to make the new owner the TMemoryBuffer
// with the longest life-span. Use FIFO as a hueristic and assign
// the new owner to the last registered observer.
newOwner = observers_.back();
observers_.pop_back();
newOwner->owner_ = true;
newOwner->linkedBuffer_ = NULL;
for (TMemoryBufferContainer::iterator it = observers_.begin();
it != observers_.end(); ++it) {
(*it)->linkedBuffer_ = newOwner;
// It's possible that an observer has other observers
newOwner->observers_.push_back(*it);
newOwner->observerCount_++;
}
observers_.clear();
observerCount_ = 0;
}
void cleanup() {
if (owner_) {
if (observerCount_ > 0) {
transferOwnership();
} else {
std::free(buffer_);
}
}
if (linkedBuffer_ != NULL) {
linkedBuffer_->unobserve(this);
}
}
void consumeEnd() {
if (observerCount_ == 0) {
resetBuffer();
}
}
// Make sure there's at least 'len' bytes available for writing.
void ensureCanWrite(uint32_t len);
// Compute the position and available data for reading.
void computeRead(uint32_t len, uint8_t** out_start, uint32_t* out_give);
uint32_t readSlow(uint8_t* buf, uint32_t len);
void writeSlow(const uint8_t* buf, uint32_t len);
const uint8_t* borrowSlow(uint8_t* buf, uint32_t* len);
// Data buffer
uint8_t* buffer_;
// Allocated buffer size
uint32_t bufferSize_;
// Is this object the owner of the buffer?
bool owner_;
TMemoryBuffer *linkedBuffer_;
uint32_t observerCount_;
// The container is a vector (rather than a list) for performance
// reasons despite the O(N) penalty in unobserve. The vec keeps the
// overhead lower in the common case, which is a single observer.
typedef std::vector<TMemoryBuffer *> TMemoryBufferContainer;
TMemoryBufferContainer observers_;
// Don't forget to update constrctors, initCommon, and swap if
// you add new members.
};
}}} // apache::thrift::transport
#endif // #ifndef THRIFT_TRANSPORT_TBUFFERTRANSPORTS_H_