找到gzip开始和结束？ [英] Find gzip start and end?

问题描述

我有一些文件，有一些随机字节和多个gzip文件。我怎样才能找到一些文件内的gzip流的开始和结束？ gzip流之间有许多随机字节。所以，基本上我需要找到任何gzip文件，并从那里得到它。

从 RFC 1952 - GZIP ：

每个GZIP文件只是一堆数据块（称为成员），每个文件包含一个。

每个成员以下列字节开头：

• 0x1F（ID1）


• 压缩方法。对于 DEFLATE d文件， 0x08 。 0-7是保留值。


• 标志。 前三位保留，必须为零。


• （4字节）上次修改时间。可以设置为0.


• 额外的标志，由压缩方法定义。


• 操作系统，实际上是文件系统。 0 = FAT，3 = UNIX，11 = NTFS
  

$ b 成员的结尾不分隔。你必须实际上走整个成员。请注意，连接多个有效的GZIP文件会创建一个有效的GZIP文件。还要注意，超过成员可能仍然会导致成员读取成员（除非解压缩库是失败 - 急切 - 完全）。

I have some file, there's some random bytes, and multiple gzip files. How can i find start and end of gzip stream inside the some file? there's many random bytes between gzip streams. So, basically i need to find any gzip file and get it from there.

解决方案

Reading from the RFC 1952 - GZIP :

Each GZIP file is just a bunch of data chunks (called members), one for each file contained.

Each member starts with the following bytes:

• 0x1F (ID1)
• 0x8B (ID2)
• compression method. 0x08 for a DEFLATEd file. 0-7 are reserved values.
• flags. The top three bits are reserved and must be zero.
• (4 bytes) last modified time. May be set to 0.
• extra flags, defined by the compression method.
• operating system, actually the file system. 0=FAT, 3=UNIX, 11=NTFS

The end of a member is not delimited. You have to actually walk the entire member. Note that concatenating multiple valid GZIP files creates a valid GZIP file. Also note that overshooting a member may still result in a successful reading of the member (unless the decompressing library is fail-eagerly-and-completely).

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