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#include <stddef.h>
#include <string.h>
#include <unistd.h>
#include "ReadBuffer.H"
static const unsigned int INITIAL_BUFFER_SIZE = 512;
ReadBuffer::ReadBuffer(int fd, unsigned int maxReadSize):
fd_(fd), buffer_(new unsigned char[INITIAL_BUFFER_SIZE]), length_(0),
size_(INITIAL_BUFFER_SIZE), start_(0),
maxReadSize_(maxReadSize)
{
}
ReadBuffer::~ReadBuffer()
{
delete[]buffer_;
}
int
ReadBuffer::doRead()
{
if ((start_ != 0) && (length_ != 0))
{
// if any bytes are left over from last time (due to partial message),
// shift them to the start of the buffer
unsigned char *nextDest = buffer_;
unsigned char *nextSrc = buffer_ + start_;
for (unsigned int i = 0; i < length_; i++)
*nextDest++ = *nextSrc++;
}
else if (length_ == size_)
{
// The buffer is full; double its size so that we can read some more
unsigned char *newBuffer = new unsigned char[size_ << 1];
memcpy(newBuffer, buffer_, size_);
delete[]buffer_;
buffer_ = newBuffer;
size_ <<= 1;
}
start_ = 0;
// Read as much data as is available
unsigned int readLength = size_ - length_;
if (maxReadSize_ && (readLength > maxReadSize_))
readLength = maxReadSize_;
int bytesRead = read(fd_, buffer_ + length_, readLength);
if (bytesRead <= 0)
return 0;
length_ += bytesRead;
return 1;
}
const unsigned char *
ReadBuffer::getMessage(unsigned int &messageLength)
{
unsigned int headerLength, dataLength, trailerLength;
if (locateMessage(buffer_ + start_, buffer_ + start_ + length_,
headerLength, dataLength, trailerLength))
{
const unsigned char *result = buffer_ + start_;
messageLength = dataLength;
if (dataLength)
result += headerLength;
else
messageLength += headerLength;
start_ += (headerLength + dataLength + trailerLength);
length_ -= (headerLength + dataLength + trailerLength);
return result;
}
else
{
// No more complete messages remain in buffer
return NULL;
}
}
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