如何在将其写入iOS中的NSOutputStream时读取NSInputStream？

Question

我正在将一个Android应用程序移植到iPhone（更像是改进基于Android版本的iPhone应用程序），我需要分割和组合大型未压缩的音频文件。

目前，我将所有文件加载到内存中并将它们拆分并将它们组合在不同的函数中。 它崩溃了100MB +文件。

这是执行此操作所需的新流程：

我有两个录音（file1和file2）和一个拆分位置，我希望file2插入file1。

- 创建file1和file2的输入流以及outputfile的输出流。

-rawrite新的CAF标头

- 读取inputStream1中的数据，直到达到分割点，然后将所有数据写入输出文件。 并将其写入输出流。

-read inputStream2中的所有数据并将其写入输出文件。

- 从inputStream1读取剩余数据并将其写入输出文件。

这是我的Android代码：

    File file1File = new File(file1);
    File file2File = new File(file2);

    long file1Length = file1File.length();
    long file2Length = file2File.length();

    FileInputStream file1ByteStream = new FileInputStream(file1);
    FileInputStream file2ByteStream = new FileInputStream(file2);
    FileOutputStream outputFileByteStream = new FileOutputStream(outputFile);


    // time = fileLength / (Sample Rate * Channels * Bits per sample / 8)
    // convert position to number of bytes for this function
    long sampleRate = eRecorder.RECORDER_SAMPLERATE;
    int channels = 1;
    long bitsPerSample = eRecorder.RECORDER_BPP;
    long bytePositionLength = (position * (sampleRate * channels * bitsPerSample / 8)) / 1000;



    //calculate total data size
            int dataSize = 0;
            dataSize = (int)(file1Length + file2Length);

            WriteWaveFileHeaderForMerge(outputFileByteStream, dataSize,
                    dataSize + 36,
                    eRecorder.RECORDER_SAMPLERATE, 1,
                    2 * eRecorder.RECORDER_SAMPLERATE);




    long bytesWritten = 0;

    int length = 0;

    //set limit for bytes read, and write file1 bytes to outputfile until split position reached
    int limit = (int)bytePositionLength;


    //read bytes to limit
    writeBytesToLimit(file1ByteStream, outputFileByteStream, limit);    
    file1ByteStream.close();


    file2ByteStream.skip(44);//skip wav file header
    writeBytesToLimit(file2ByteStream, outputFileByteStream, (int)file2Length);
    file2ByteStream.close();

    //calculate length of remaining file1 bytes to be written
    long file1offset = bytePositionLength;

    //reinitialize file1 input stream
    file1ByteStream = new FileInputStream(file1);

    file1ByteStream.skip(file1offset);
    writeBytesToLimit(file1ByteStream, outputFileByteStream, (int)file1Length);

    file1ByteStream.close();
    outputFileByteStream.close();

这是我的writeBytesToLimit函数：

private void writeBytesToLimit(FileInputStream inputStream, FileOutputStream outputStream, int byteLimit) throws IOException
{
    int bytesRead = 0;
    int chunkSize = 65536;
    int length = 0;
    byte[] buffer = new byte[chunkSize];
    while((length = inputStream.read(buffer)) != -1)
    {
        bytesRead += length;
        if(bytesRead >= byteLimit)
        {
            int leftoverBytes = byteLimit % chunkSize;              
            byte[] smallBuffer = new byte[leftoverBytes];
            System.arraycopy(buffer, 0, smallBuffer, 0, leftoverBytes);
            outputStream.write(smallBuffer);
            break;
        }

        if(length == chunkSize)
            outputStream.write(buffer);
        else
        {
            byte[] smallBuffer = new byte[length];
            System.arraycopy(buffer, 0, smallBuffer, 0, length);
            outputStream.write(smallBuffer);
        }

    }

}

我如何在iOS中执行此操作？ 对两个NSInputStreams和一个NSOutputStream使用相同的委托看起来会变得非常混乱。 有没有人看过如何做到这一点的例子（干净）？

Answer 1

我最终使用了NSFileHandle。 例如，这是我正在做的第一部分。

NSData *readData = [[NSData alloc] init];
NSFileHandle *reader1 = [NSFileHandle fileHandleForReadingAtPath:file1Path];
NSFileHandle *writer = [NSFileHandle fileHandleForWritingAtPath:outputFilePath];

//start reading data from file1 to split point and writing it to file
long bytesRead = 0;
while(bytesRead < splitPointInBytes)
{

    //read a chunk of data
    readData = [reader1 readDataOfLength:chunkSize];
    if(readData.length == 0)break;
    //trim data if too much was read
    if(bytesRead + readData.length > splitPointInBytes)
    {
        //get difference of read bytes and byte limit
        long difference = bytesRead + readData.length - splitPointInBytes;

        //trim data
        NSMutableData *readDataMutable = [NSMutableData dataWithData:readData];
        [readDataMutable setLength:readDataMutable.length - difference];
        readData = [NSData dataWithData:readDataMutable];

        NSLog(@"Too much data read, trimming");
    }

    //write data to output file
    [writer writeData:readData];

    //update byte counter
    bytesRead += readData.length;
}
long file1BytesWritten = bytesRead;