Add uncompress2() function, which returns the input size used.

uncompr.c

 /* uncompr.c -- decompress a memory buffer
- * Copyright (C) 1995-2003, 2010, 2014 Jean-loup Gailly, Mark Adler
+ * Copyright (C) 1995-2003, 2010, 2014, 2016 Jean-loup Gailly, Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -9,31 +9,34 @@
 #include "zlib.h"
 
 /* ===========================================================================
-     Decompresses the source buffer into the destination buffer.  sourceLen is
-   the byte length of the source buffer. Upon entry, destLen is the total
-   size of the destination buffer, which must be large enough to hold the
-   entire uncompressed data. (The size of the uncompressed data must have
-   been saved previously by the compressor and transmitted to the decompressor
-   by some mechanism outside the scope of this compression library.)
-   Upon exit, destLen is the actual size of the compressed buffer.
+     Decompresses the source buffer into the destination buffer.  *sourceLen is
+   the byte length of the source buffer. Upon entry, *destLen is the total size
+   of the destination buffer, which must be large enough to hold the entire
+   uncompressed data. (The size of the uncompressed data must have been saved
+   previously by the compressor and transmitted to the decompressor by some
+   mechanism outside the scope of this compression library.) Upon exit,
+   *destLen is the size of the decompressed data and *sourceLen is the number
+   of source bytes consumed. Upon return, source + *sourceLen points to the
+   first unused input byte.
 
-     uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
-   enough memory, Z_BUF_ERROR if there was not enough room in the output
-   buffer, or Z_DATA_ERROR if the input data was corrupted, including if the
-   input data is an incomplete zlib stream.
+     uncompress returns Z_OK if success, Z_MEM_ERROR if there was not enough
+   memory, Z_BUF_ERROR if there was not enough room in the output buffer, or
+   Z_DATA_ERROR if the input data was corrupted, including if the input data is
+   an incomplete zlib stream.
 */
-int ZEXPORT uncompress (dest, destLen, source, sourceLen)
+int ZEXPORT uncompress2 (dest, destLen, source, sourceLen)
     Bytef *dest;
     uLongf *destLen;
     const Bytef *source;
-    uLong sourceLen;
+    uLong *sourceLen;
 {
     z_stream stream;
     int err;
     const uInt max = (uInt)0 - 1;
-    uLong left;
+    uLong len, left;
     Byte buf[1];    /* for detection of incomplete stream when *destLen == 0 */
 
+    len = *sourceLen;
     if (*destLen) {
         left = *destLen;
         *destLen = 0;
@@ -61,12 +64,13 @@ int ZEXPORT uncompress (dest, destLen, source, sourceLen)
             left -= stream.avail_out;
         }
         if (stream.avail_in == 0) {
-            stream.avail_in = sourceLen > (uLong)max ? max : (uInt)sourceLen;
-            sourceLen -= stream.avail_in;
+            stream.avail_in = len > (uLong)max ? max : (uInt)len;
+            len -= stream.avail_in;
         }
         err = inflate(&stream, Z_NO_FLUSH);
     } while (err == Z_OK);
 
+    *sourceLen -= len + stream.avail_in;
     if (dest != buf)
         *destLen = stream.total_out;
     else if (stream.total_out && err == Z_BUF_ERROR)
@@ -78,3 +82,12 @@ int ZEXPORT uncompress (dest, destLen, source, sourceLen)
            err == Z_BUF_ERROR && left + stream.avail_out ? Z_DATA_ERROR :
            err;
 }
+
+int ZEXPORT uncompress (dest, destLen, source, sourceLen)
+    Bytef *dest;
+    uLongf *destLen;
+    const Bytef *source;
+    uLong sourceLen;
+{
+    return uncompress2(dest, destLen, source, &sourceLen);
+}

zlib.h

@@ -1246,7 +1246,7 @@ ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
    uncompressed data.  (The size of the uncompressed data must have been saved
    previously by the compressor and transmitted to the decompressor by some
    mechanism outside the scope of this compression library.) Upon exit, destLen
-   is the actual size of the uncompressed buffer.
+   is the actual size of the uncompressed data.
 
      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
    enough memory, Z_BUF_ERROR if there was not enough room in the output
@@ -1255,6 +1255,14 @@ ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
    buffer with the uncompressed data up to that point.
 */
 
+ZEXTERN int ZEXPORT uncompress2 OF((Bytef *dest,   uLongf *destLen,
+                                    const Bytef *source, uLong *sourceLen));
+/*
+     Same as uncompress, except that sourceLen is a pointer, where the
+   length of the source is *sourceLen.  On return, *sourceLen is the number of
+   source bytes consumed.
+*/
+
                         /* gzip file access functions */
 
 /*