java - 河豚代码应等效，但不应等效

我们有一个包装BouncyCastle（实际上是Android的SpongyCastle）Blowfish的类，以加密要流式传输的数据：

public class BlowfishOutputStream extends OutputStream
{
    private final OutputStream os;
    private final PaddedBufferedBlockCipher bufferedCipher;

我们的原始代码在一次操作中将整个字节数组加密后再写入输出流

public void write(byte[] raw, int offset, int length) throws IOException
{
    byte[] out = new byte[bufferedCipher.getOutputSize(length)];
    int result = this.bufferedCipher.processBytes(raw, 0, length, out, 0);
    if (result > 0)
    {
        this.os.write(out, 0, result);
    }
}

发送图像（即一次发送大量数据）时，会导致两个副本立即保留在内存中。

以下代码是等效的，但不是等效的，我也不知道为什么。我可以验证是否正在发送数据（c2的总和等于length），但是当我们在服务器上收到数据时，经过一个中间过程会丢弃该图像，然后再查看到达的内容。在此阶段，我所知道的是，当使用初始代码时，可以接收到响应，并且可以提取出包含的图像，当使用替换代码时，可以接收到（并接受）响应，但是图像似乎没有被提取。

public void write(byte[] raw, int offset, int length) throws IOException
{
    // write to the output stream as we encrypt, not all at once.
    final byte[] inBuffer = new byte[Constants.ByteBufferSize];
    final byte[] outBuffer = new byte[Constants.ByteBufferSize];
    ByteArrayInputStream bis = new ByteArrayInputStream(raw);
    // read into inBuffer, encrypt into outBuffer and write to output stream
    for (int len; (len = bis.read(inBuffer)) != -1;)
    {
        int c2 = this.bufferedCipher.processBytes(inBuffer, 0, len, outBuffer, 0);
        this.os.write(outBuffer, 0, c2);
    }
}

请注意，此问题不是由于缺少对doFinal的调用而引起的，因为在关闭流时会调用该调用。

public void close() throws IOException
{
    byte[] out = new byte[bufferedCipher.getOutputSize(0)];
    int result = this.bufferedCipher.doFinal(out, 0);
    if (result > 0)
    {
        this.os.write(out, 0, result);
    }
    *nb try/catch omitted*
}

最佳答案

证实了，尽管具有讽刺意味的是，问题不在于图像，而在于先前的数据中，但该数据正在写入完整的raw字节数组，而不仅仅是写入指定的范围。快速加密字节数组的等效代码为：

@Override
public void write(byte[] raw, int offset, int length) throws IOException
{
    // write to the stream as we encrypt, not all at once.
    final byte[] inBuffer = new byte[Constants.ByteBufferSize];
    final byte[] outBuffer = new byte[Constants.ByteBufferSize];
    int readStart = offset;
    // read into inBuffer, encrypt into outBuffer and write to output stream
    while(readStart<length)
    {
        int readAmount = Math.min(length-readStart, inBuffer.length);
        System.arraycopy(raw, readStart, inBuffer, 0, readAmount);
        readStart+=readAmount;
        int c2 = this.bufferedCipher.processBytes(inBuffer, 0, readAmount, outBuffer, 0);
        this.os.write(outBuffer, 0, c2);
    }
}

关于java - 河豚代码应等效，但不应等效，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/10220574/