GZipInputStream .read()将零插入缓冲区

Question

我有一个奇怪的程序,GzipInputStream零填充缓冲区的一部分.我有幸知道流中的字节应该是什么样的,我可以看到缓冲区正在填充8个正确的字节和12个零(不应该为零)

BYTES应该看起来像这样----> 0 20 82 22 -91 27 -96 65 66 65 88 32 32 32 32 81 32 0 0 0 100 78

BYTES实际上看起来像这样---> 0 20 82 22 -91 27 -96 65 66 65 0 0 0 0 0 0 0 0 0 0 0 0

前两个字节表示一个整数,用于确定前两个字节之后的可变长度(以字节为单位)的大小.所以在这个例子中,第一个字节是0 20,而在BIG_ENDIAN中,这给我们后续的有效载荷大小为20个字节.

这是我的阅读代码

gzipInputStream = new GZIPInputStream(url.openStream());        

byte[] payload = new byte[2];
gzipInputStream.read(payload);
for(int i=0;i<payload.length;i++){
    System.out.println(payload[i]);
}
int payloadSize = ((payload[0] & 0xFF) << 8) | ((payload[1]) & 0xFF);
//read the next payloadSize bytes
byte[] messageBytes = new byte[payloadSize];

gzipInputStream.read(messageBytes);

所以前两个字节是有效载荷数组中的字节,后两个字节是messageBytes中的字节.无法弄清楚

修改代码归功于NPE

            byte[] payloadSizeBytes = new byte[2];
            int payloadSizeBytesRead = 0;
            while(payloadSizeBytesRead < 2){
                int r = gzipInputStream.read(buffer);
                if(r>0){
                    payloadSizeBytes[payloadSizeBytesRead] = buffer[0];
                    payloadSizeBytesRead++;
                }
            }
            int payloadSize = ((payloadSizeBytes[0] & 0xFF) << 8) | ((payloadSizeBytes[1]) & 0xFF);
            //read the next payloadSize bytes
            byte[] messageBytes = new byte[payloadSize];
            int messageBytesRead = 0;
            while(messageBytesRead < payloadSize){
                int r = gzipInputStream.read(buffer);
                if(r>0){
                    messageBytes[messageBytesRead] = buffer[0];
                    messageBytesRead++;
                }
            }
            for(int i=0;i<messageBytes.length;i++){
                System.out.println(messageBytes[i]);
            }

Answer 1

合同read(byte[])是它读取一些数据,并返回已读取的字节数.事实上,你忽略了返回值.相反,您应该检查返回值read()并继续调用,read()直到您读取payloadSize字节为止.

一个简单的方法是read(b, off, len)在循环中使用:

int payloadSize = ((payload[0] & 0xFF) << 8) | ((payload[1]) & 0xFF);
byte[] messageBytes = new byte[payloadSize];

int bytesRead = 0;
while (bytesRead < payloadSize) {
   bytesRead += gzipInputStream.read(messageBytes, bytesRead, payloadSize - bytesRead);
}