DeflatorInputStream和DeflatorOutputStream不重建原始数据

Question

我想压缩一些数据,所以我遇到了DeflatorInputStream和DeflatorOutputStream类.但是,以下示例显示在使用这些类时,我似乎无法重建原始数据.

当我切换到ZipInputStream和ZipOutputStream它确实有效,但由于我本身不需要zip文件,我认为通用压缩会更好.主要是我有兴趣理解为什么这个例子不起作用.

//Create some "random" data
int bytesLength = 1024;
byte[] bytes = new byte[bytesLength];
for(int i = 0; i < bytesLength; i++) {
     bytes[i] = (byte) (i % 10);
}

//Compress the data, and write it to somewhere (a byte array for this example)
ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
DeflaterOutputStream outputStream = new DeflaterOutputStream(arrayOutputStream);
outputStream.write(bytes);

//Read and decompress the data
byte[] readBuffer = new byte[5000];
ByteArrayInputStream arrayInputStream = new ByteArrayInputStream(arrayOutputStream.toByteArray());
DeflaterInputStream inputStream = new DeflaterInputStream(arrayInputStream);
int read = inputStream.read(readBuffer);

//Should hold the original (reconstructed) data
byte[] actuallyRead = Arrays.copyOf(readBuffer, read);

//Results differ - will print false
System.out.println(Arrays.equals(bytes, actuallyRead));

Answer 1

责备历史先例.在Unix上,该函数用于扭转deflate叫inflate.因此,与许多其他Java IO类不同,输入和输出流对(显然)没有匹配的名称.

DeflaterOutputStream实际上不允许您反转通货紧缩,而是在将字节从接收器传递给源时缩小字节.DeflaterInputStream 也会缩小,但它会在数据从源流向接收器时执行其操作.

为了以未压缩(膨胀)格式读取数据,您需要使用InflaterInputStream:

InflaterInputStream inputStream = new InflaterInputStream(arrayInputStream);

此外,由于可能无法在一次read调用中从流中获取所有压缩数据,因此需要使用循环.像这样的东西:

int read;
byte[] finalBuf = new byte[0], swapBuf;
byte[] readBuffer = new byte[5012];

ByteArrayInputStream arrayInputStream = new ByteArrayInputStream(
        compressed);
InflaterInputStream inputStream = new InflaterInputStream(
        arrayInputStream);
while ((read = inputStream.read(readBuffer)) != -1) {
    System.out.println("Intermediate read: " + read);
    swapBuf = finalBuf;
    finalBuf = new byte[swapBuf.length + read];
    System.arraycopy(swapBuf, 0, finalBuf, 0, swapBuf.length);
    System.arraycopy(readBuffer, 0, finalBuf, swapBuf.length, read);
}

最后,确保在检索压缩字节之前刷新deflater输出流(或者关闭流).