Improve contrib/blast to return unused bytes. Fix the test code

to report the count of unused bytes at the end correctly.  Add the
ability to provide initial input to blast().

contrib/blast/blast.c

 /* blast.c
- * Copyright (C) 2003, 2012 Mark Adler
+ * Copyright (C) 2003, 2012, 2013 Mark Adler
  * For conditions of distribution and use, see copyright notice in blast.h
- * version 1.2, 24 Oct 2012
+ * version 1.3, 24 Aug 2013
  *
  * blast.c decompresses data compressed by the PKWare Compression Library.
  * This function provides functionality similar to the explode() function of
@@ -24,8 +24,12 @@
  * 1.1  16 Feb 2003     - Fixed distance check for > 4 GB uncompressed data
  * 1.2  24 Oct 2012     - Add note about using binary mode in stdio
  *                      - Fix comparisons of differently signed integers
+ * 1.3  24 Aug 2013     - Return unused input from blast()
+ *                      - Fix test code to correctly report unused input
+ *                      - Enable the provision of initial input to blast()
  */
 
+#include <stddef.h>             /* for NULL */
 #include <setjmp.h>             /* for setjmp(), longjmp(), and jmp_buf */
 #include "blast.h"              /* prototype for blast() */
 
@@ -376,7 +380,8 @@ local int decomp(struct state *s)
 }
 
 /* See comments in blast.h */
-int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow)
+int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow,
+          unsigned *left, unsigned char **in)
 {
     struct state s;             /* input/output state */
     int err;                    /* return value */
@@ -384,7 +389,12 @@ int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow)
     /* initialize input state */
     s.infun = infun;
     s.inhow = inhow;
-    s.left = 0;
+    if (left != NULL && *left) {
+        s.left = *left;
+        s.in = *in;
+    }
+    else
+        s.left = 0;
     s.bitbuf = 0;
     s.bitcnt = 0;
 
@@ -400,6 +410,12 @@ int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow)
     else
         err = decomp(&s);               /* decompress */
 
+    /* return unused input */
+    if (left != NULL)
+        *left = s.left;
+    if (in != NULL)
+        *in = s.left ? s.in : NULL;
+
     /* write any leftover output and update the error code if needed */
     if (err != 1 && s.next && s.outfun(s.outhow, s.out, s.next) && err == 0)
         err = 1;
@@ -429,16 +445,20 @@ local int outf(void *how, unsigned char *buf, unsigned len)
 /* Decompress a PKWare Compression Library stream from stdin to stdout */
 int main(void)
 {
-    int ret, n;
+    int ret;
+    unsigned left;
 
     /* decompress to stdout */
-    ret = blast(inf, stdin, outf, stdout);
-    if (ret != 0) fprintf(stderr, "blast error: %d\n", ret);
-
-    /* see if there are any leftover bytes */
-    n = 0;
-    while (getchar() != EOF) n++;
-    if (n) fprintf(stderr, "blast warning: %d unused bytes of input\n", n);
+    left = 0;
+    ret = blast(inf, stdin, outf, stdout, &left, NULL);
+    if (ret != 0)
+        fprintf(stderr, "blast error: %d\n", ret);
+
+    /* count any leftover bytes */
+    while (getchar() != EOF)
+        left++;
+    if (left)
+        fprintf(stderr, "blast warning: %u unused bytes of input\n", left);
 
     /* return blast() error code */
     return ret;

contrib/blast/blast.h

 /* blast.h -- interface for blast.c
-  Copyright (C) 2003, 2012 Mark Adler
-  version 1.2, 24 Oct 2012
+  Copyright (C) 2003, 2012, 2013 Mark Adler
+  version 1.3, 24 Aug 2013
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the author be held liable for any damages
@@ -42,7 +42,8 @@ typedef int (*blast_out)(void *how, unsigned char *buf, unsigned len);
  */
 
 
-int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow);
+int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow,
+          unsigned *left, unsigned char **in);
 /* Decompress input to output using the provided infun() and outfun() calls.
  * On success, the return value of blast() is zero.  If there is an error in
  * the source data, i.e. it is not in the proper format, then a negative value
@@ -55,12 +56,19 @@ int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow);
  * an input error.  (blast() only asks for input if it needs it.)  inhow is for
  * use by the application to pass an input descriptor to infun(), if desired.
  *
+ * If left and in are not NULL and *left is not zero when blast() is called,
+ * then the *left bytes are *in are consumed for input before infun() is used.
+ *
  * The output function is invoked: err = outfun(how, buf, len), where the bytes
  * to be written are buf[0..len-1].  If err is not zero, then blast() returns
  * with an output error.  outfun() is always called with len <= 4096.  outhow
  * is for use by the application to pass an output descriptor to outfun(), if
  * desired.
  *
+ * If there is any unused input, *left is set to the number of bytes that were
+ * read and *in points to them.  Otherwise *left is set to zero and *in is set
+ * to NULL.  If left or in are NULL, then they are not set.
+ *
  * The return codes are:
  *
  *   2:  ran out of input before completing decompression