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/**
* Copyright (C) ARM Limited 2010-2015. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include "Fifo.h"
#include <stdlib.h>
#include "Logging.h"
// bufferSize is the amount of data to be filled
// singleBufferSize is the maximum size that may be filled during a single write
// (bufferSize + singleBufferSize) will be allocated
Fifo::Fifo(int singleBufferSize, int bufferSize, sem_t* readerSem) {
mWrite = mRead = mReadCommit = mRaggedEnd = 0;
mWrapThreshold = bufferSize;
mSingleBufferSize = singleBufferSize;
mReaderSem = readerSem;
mBuffer = (char*)malloc(bufferSize + singleBufferSize);
mEnd = false;
if (mBuffer == NULL) {
logg.logError("failed to allocate %d bytes", bufferSize + singleBufferSize);
handleException();
}
if (sem_init(&mWaitForSpaceSem, 0, 0)) {
logg.logError("sem_init() failed");
handleException();
}
}
Fifo::~Fifo() {
free(mBuffer);
sem_destroy(&mWaitForSpaceSem);
}
int Fifo::numBytesFilled() const {
return mWrite - mRead + mRaggedEnd;
}
char* Fifo::start() const {
return mBuffer;
}
bool Fifo::isEmpty() const {
return mRead == mWrite && mRaggedEnd == 0;
}
bool Fifo::isFull() const {
return willFill(0);
}
// Determines if the buffer will fill assuming 'additional' bytes will be added to the buffer
// 'full' means there is less than singleBufferSize bytes available contiguously; it does not mean there are zero bytes available
bool Fifo::willFill(int additional) const {
if (mWrite > mRead) {
if (numBytesFilled() + additional < mWrapThreshold) {
return false;
}
} else {
if (numBytesFilled() + additional < mWrapThreshold - mSingleBufferSize) {
return false;
}
}
return true;
}
// This function will stall until contiguous singleBufferSize bytes are available
char* Fifo::write(int length) {
if (length <= 0) {
length = 0;
mEnd = true;
}
// update the write pointer
mWrite += length;
// handle the wrap-around
if (mWrite >= mWrapThreshold) {
mRaggedEnd = mWrite;
mWrite = 0;
}
// send a notification that data is ready
sem_post(mReaderSem);
// wait for space
while (isFull()) {
sem_wait(&mWaitForSpaceSem);
}
return &mBuffer[mWrite];
}
void Fifo::release() {
// update the read pointer now that the data has been handled
mRead = mReadCommit;
// handle the wrap-around
if (mRead >= mWrapThreshold) {
mRaggedEnd = mRead = mReadCommit = 0;
}
// send a notification that data is free (space is available)
sem_post(&mWaitForSpaceSem);
}
// This function will return null if no data is available
char* Fifo::read(int *const length) {
// wait for data
if (isEmpty() && !mEnd) {
return NULL;
}
// obtain the length
do {
mReadCommit = mRaggedEnd ? mRaggedEnd : mWrite;
*length = mReadCommit - mRead;
} while (*length < 0); // plugs race condition without using semaphores
return &mBuffer[mRead];
}
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