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-rw-r--r--tools/gator/daemon/Fifo.cpp130
1 files changed, 130 insertions, 0 deletions
diff --git a/tools/gator/daemon/Fifo.cpp b/tools/gator/daemon/Fifo.cpp
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+++ b/tools/gator/daemon/Fifo.cpp
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+/**
+ * Copyright (C) ARM Limited 2010-2013. 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>
+#ifdef WIN32
+#define valloc malloc
+#endif
+
+#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*)valloc(bufferSize + singleBufferSize);
+ mEnd = false;
+
+ if (mBuffer == NULL) {
+ logg->logError(__FILE__, __LINE__, "failed to allocate %d bytes", bufferSize + singleBufferSize);
+ handleException();
+ }
+
+ if (sem_init(&mWaitForSpaceSem, 0, 0)) {
+ logg->logError(__FILE__, __LINE__, "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];
+}