1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "byte_buffer.h" 18 19 #include <stdatomic.h> 20 #include <string.h> 21 22 typedef _Atomic int32_t writer_pos_t; 23 24 ssize_t byteBuffer_write(byte_buffer_t byteBuffer, size_t byteBufferSize, 25 const char *srcBuffer, size_t frameCount, int channels) { 26 // bytebufferSize is in bytes 27 const size_t dataSectionSize = byteBufferSize - sizeof(writer_pos_t); 28 writer_pos_t *rear_ptr = (writer_pos_t*)(byteBuffer + dataSectionSize); 29 writer_pos_t rear = *rear_ptr; 30 // rear should not exceed 2^31 - 1, or else overflow will happen 31 32 size_t frameSize = channels * sizeof(short); // only one channel 33 int32_t maxLengthInShort = dataSectionSize / frameSize; 34 // mask the upper bits to get the correct position in the pipe 35 writer_pos_t tempRear = rear & (maxLengthInShort - 1); 36 size_t part1 = maxLengthInShort - tempRear; 37 38 if (part1 > frameCount) { 39 part1 = frameCount; 40 } 41 42 if (part1 > 0) { 43 memcpy(byteBuffer + (tempRear * frameSize), srcBuffer, 44 part1 * frameSize); 45 46 size_t part2 = frameCount - part1; 47 if (part2 > 0) { 48 memcpy(byteBuffer, (srcBuffer + (part1 * frameSize)), 49 part2 * frameSize); 50 } 51 } 52 53 // increase value of rear using the strongest memory ordering 54 // (since it's being read by Java we can't control the ordering 55 // used by the other side). 56 atomic_store(rear_ptr, rear + frameCount); 57 return frameCount; 58 } 59
