Java InputStream读取缓冲区 [英] Java InputStream read buffer

问题描述

说我正试图从Java InputStream读取这样的内容:

Say I'm trying to read from a Java InputStream like this:

ZipInputStream zis = new ZipInputStream(new FileInputStream("C:\\temp\\sample3.zip"));
zis.getNextEntry();
byte[] buffer2 = new byte[2];
int count = zis.read(buffer2));
if(count != -1) //process...
else...//something wrong, abort

我正在解析一个二进制文件，在这种情况下，我将缓冲区设置为2，因为我想读取下一个简短内容.如果要读取下一个int等等其他类型的数据，我会将缓冲区的大小设置为4.问题是，即使我知道有足够的未读数据来填充缓冲区，有时zis.read(buffer)也不会填充缓冲区.我可以简单地将整个文件内容转储到数组中并进行解析，但是随后我最终实现了自己的流读取器来执行此操作，这似乎是在重新发明轮子.我还可以实现一个read()函数来检查读取计数，如果小于buffersize，则请求更多数据来填充缓冲区，但这效率低下且难看.有更好的方法吗?

I'm parsing a binary file and I set my buffer to 2 in this case because I want to read the next short. I would set my buffer to size 4 if I want to read the next int and so on for other types. The problem is that sometimes zis.read(buffer) won't fill the buffer even when I know that there is enough unread data to fill the buffer. I could simply dump the entire file contents into an array and parse that, but then I end up implementing my own stream reader to do that which seems like re-inventing the wheel. I could also implement a read() function that checks the read count and if less than buffersize, request more data to fill the buffer, but that's inefficient and ugly. Is there a better way to do this?

这是此处发布的问题的后续问题:

This is a follow-up question to a question posted here:

Java ZipInputStream提取错误

推荐答案

有更好的方法吗?

Is there a better way to do this?

好吧... ZipInputStream最终继承自InputStream，因此您应该能够先用BufferedInputStream然后用DataInputStream包装它，并使用readShort，readInt等读取数据.

Well ... a ZipInputStream ultimately inherits from InputStream so you should be able to wrap it with a BufferedInputStream and then a DataInputStream and read data using readShort, readInt and so on.

类似这样的东西:

while (zis.getNextEntry() != null) {
  DataInputStream dis = new DataInputStream(new BufferedInputStream(zis));
  boolean done = false;
  do {
    short s = dis.readShort();
    int i = dis.readInt();
    ...
  } while (!done);
}

注意:您不应该关闭dis流，因为那样会导致zis被关闭. (显然，zis需要在外部关闭，以避免资源泄漏.)

NB: you shouldn't close the dis stream as that would cause the zis to be closed. (Obviously, the zis needs to be closed at an outer level to avoid a resource leak.)

堆栈中的BufferedInputStream确保您不会在基础流上进行很多小读取工作……这很糟糕.

The BufferedInputStream in the stack ensures that you don't do lots of small reads on the underlying stream ... which would be bad.

唯一可能的陷阱是它的方法对二进制数据的表示方式有特殊的想法；例如数字是bigendian.如果这是一个问题，请考虑将整个zip条目读取到一个字节数组中，并将其包装在ByteBuffer中.

The only possible gotcha is that its methods have particular ideas about how the binary data is represented; e.g. numbers are bigendian. If that is an issue, consider reading the entire zip entry into a byte array, and wrapping it in a ByteBuffer.

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