1 /**
2 * Copyright (C) ARM Limited 2010-2014. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
9 #include "Fifo.h"
11 #include <stdlib.h>
12 #ifdef WIN32
13 #define valloc malloc
14 #endif
16 #include "Logging.h"
18 // bufferSize is the amount of data to be filled
19 // singleBufferSize is the maximum size that may be filled during a single write
20 // (bufferSize + singleBufferSize) will be allocated
21 Fifo::Fifo(int singleBufferSize, int bufferSize, sem_t* readerSem) {
22 mWrite = mRead = mReadCommit = mRaggedEnd = 0;
23 mWrapThreshold = bufferSize;
24 mSingleBufferSize = singleBufferSize;
25 mReaderSem = readerSem;
26 mBuffer = (char*)valloc(bufferSize + singleBufferSize);
27 mEnd = false;
29 if (mBuffer == NULL) {
30 logg->logError(__FILE__, __LINE__, "failed to allocate %d bytes", bufferSize + singleBufferSize);
31 handleException();
32 }
34 if (sem_init(&mWaitForSpaceSem, 0, 0)) {
35 logg->logError(__FILE__, __LINE__, "sem_init() failed");
36 handleException();
37 }
38 }
40 Fifo::~Fifo() {
41 free(mBuffer);
42 sem_destroy(&mWaitForSpaceSem);
43 }
45 int Fifo::numBytesFilled() const {
46 return mWrite - mRead + mRaggedEnd;
47 }
49 char* Fifo::start() const {
50 return mBuffer;
51 }
53 bool Fifo::isEmpty() const {
54 return mRead == mWrite && mRaggedEnd == 0;
55 }
57 bool Fifo::isFull() const {
58 return willFill(0);
59 }
61 // Determines if the buffer will fill assuming 'additional' bytes will be added to the buffer
62 // 'full' means there is less than singleBufferSize bytes available contiguously; it does not mean there are zero bytes available
63 bool Fifo::willFill(int additional) const {
64 if (mWrite > mRead) {
65 if (numBytesFilled() + additional < mWrapThreshold) {
66 return false;
67 }
68 } else {
69 if (numBytesFilled() + additional < mWrapThreshold - mSingleBufferSize) {
70 return false;
71 }
72 }
73 return true;
74 }
76 // This function will stall until contiguous singleBufferSize bytes are available
77 char* Fifo::write(int length) {
78 if (length <= 0) {
79 length = 0;
80 mEnd = true;
81 }
83 // update the write pointer
84 mWrite += length;
86 // handle the wrap-around
87 if (mWrite >= mWrapThreshold) {
88 mRaggedEnd = mWrite;
89 mWrite = 0;
90 }
92 // send a notification that data is ready
93 sem_post(mReaderSem);
95 // wait for space
96 while (isFull()) {
97 sem_wait(&mWaitForSpaceSem);
98 }
100 return &mBuffer[mWrite];
101 }
103 void Fifo::release() {
104 // update the read pointer now that the data has been handled
105 mRead = mReadCommit;
107 // handle the wrap-around
108 if (mRead >= mWrapThreshold) {
109 mRaggedEnd = mRead = mReadCommit = 0;
110 }
112 // send a notification that data is free (space is available)
113 sem_post(&mWaitForSpaceSem);
114 }
116 // This function will return null if no data is available
117 char* Fifo::read(int *const length) {
118 // wait for data
119 if (isEmpty() && !mEnd) {
120 return NULL;
121 }
123 // obtain the length
124 do {
125 mReadCommit = mRaggedEnd ? mRaggedEnd : mWrite;
126 *length = mReadCommit - mRead;
127 } while (*length < 0); // plugs race condition without using semaphores
129 return &mBuffer[mRead];
130 }