如何分割文件成块，同时还写了进去？ [英] How to split file into chunks while still writing into it?

问题描述

我试图得到控制而这个过程仍在使用文件进行写入从文件创建字节数组块。其实我的视频存储到文件，我想从同一个文件同时记录创建块。

I tried to create byte array blocks from file whil the process was still using the file for writing. Actually I am storing video into file and I would like to create chunks from the same file while recording.

下面的方法是应该从文件读取的字节块：

The following method was supposed to read blocks of bytes from file:

private byte[] getBytesFromFile(File file) throws IOException{
    InputStream is = new FileInputStream(file);
    long length = file.length();

    int numRead = 0;

    byte[] bytes = new byte[(int)length - mReadOffset];
    numRead = is.read(bytes, mReadOffset, bytes.length - mReadOffset);
    if(numRead != (bytes.length - mReadOffset)){
        throw new IOException("Could not completely read file " + file.getName());
    }

    mReadOffset += numRead;
    is.close();
    return bytes;
}

但问题是，所有的数组元素设置为0，我想这是因为在写作过程中锁定该文件。

But the problem is that all array elements are set to 0 and I guess it is because the writing process locks the file.

我会bevery感激，如果你们任何人都可以显示任何其他方式在写入到文件创建的文件块。

I would bevery thankful if anyone of you could show any other way to create file chunks while writing into file.

推荐答案

问题解决了：

private void getBytesFromFile(File file) throws IOException {
    FileInputStream is = new FileInputStream(file); //videorecorder stores video to file

    java.nio.channels.FileChannel fc = is.getChannel();
    java.nio.ByteBuffer bb = java.nio.ByteBuffer.allocate(10000);

    int chunkCount = 0;

    byte[] bytes;

    while(fc.read(bb) >= 0){
        bb.flip();
        //save the part of the file into a chunk
        bytes = bb.array();
        storeByteArrayToFile(bytes, mRecordingFile + "." + chunkCount);//mRecordingFile is the (String)path to file
        chunkCount++;
        bb.clear();
    }
}

private void storeByteArrayToFile(byte[] bytesToSave, String path) throws IOException {
    FileOutputStream fOut = new FileOutputStream(path);
    try {
        fOut.write(bytesToSave);
    }
    catch (Exception ex) {
        Log.e("ERROR", ex.getMessage());
    }
    finally {
        fOut.close();
    }
}

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