如何在將其寫入iOS中的NSOutputStream時讀取NSInputStream？

Question

我正在將一個Android應用程序移植到iPhone（更像是改進基於Android版本的iPhone應用程序），我需要分割和組合大型未壓縮的音頻文件。

目前，我將所有文件加載到內存中並將它們拆分並將它們組合在不同的函數中。 它崩潰了100MB +文件。

這是執行此操作所需的新流程：

我有兩個錄音（file1和file2）和一個拆分位置，我希望file2插入file1。

- 創建file1和file2的輸入流以及outputfile的輸出流。

-rawrite新的CAF標頭

- 讀取inputStream1中的數據，直到達到分割點，然后將所有數據寫入輸出文件。 並將其寫入輸出流。

-read inputStream2中的所有數據並將其寫入輸出文件。

- 從inputStream1讀取剩余數據並將其寫入輸出文件。

這是我的Android代碼：

    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();

這是我的writeBytesToLimit函數：

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中執行此操作？ 對兩個NSInputStreams和一個NSOutputStream使用相同的委托看起來會變得非常混亂。 有沒有人看過如何做到這一點的例子（干凈）？

Answer 1

我最終使用了NSFileHandle。 例如，這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;