java - How to I find out the size of a GZIP section embedded in firmware? -

i analyzing firmware images contain many different sections, 1 of gzip section.

i able know location of start of gzip section using magic number , gzipinputstream in java.

however, need know compressed size of gzip section. gzipinputstream return me uncompressed file size.

is there has idea?

you can count number of byte read using custom inputstream. need force stream read 1 byte @ time ensure don't read more need.

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you can wrap current inputstream in this

class countinginputstream extends inputstream {     final inputstream is;     int counter = 0;      public countinginputstream(inputstream is) {         this.is = is;     }      public int read() throws ioexception {         int read = is.read();         if (read >= 0) counter++;         return read;     } } 

and wrap in gzipinputstream. field counter hold number of bytes read.

to use bufferedinputstream can do

 inputstream = new bufferedinputstream(new fileinputstream(filename));  // read data or skip want start.   countinginputstream cis = new countinginputstream(is);  gzipinputstream gzis = new gzipinputstream(cis);  // read compressed data  dis.read(...);   int dataread = cis.counter;