From: Mark Adler <madler@alumni.caltech.edu>
Date: Thu, 24 Apr 2014 23:45:36 +0000 (-0400)
Subject: Assure that gzoffset() is correct when appending.
X-Git-Tag: 1.9.9-b1~793^2~12
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=51bf318c94b6f15a2fafd09f5c3867f4f1d5d0c2;p=thirdparty%2Fzlib-ng.git

Assure that gzoffset() is correct when appending.

An open() with O_APPEND followed by an lseek() to determine the
position will return zero for a non-empty file, even though the
next write will start at the end of the file.  This commit works
around that by doing an lseek() to the end when appending.
---

diff --git a/gzlib.c b/gzlib.c
index 28732020e..8b23ecd98 100644
--- a/gzlib.c
+++ b/gzlib.c
@@ -189,8 +189,10 @@ local gzFile gz_open(const void *path, int fd, const char *mode) {
         free(state);
         return NULL;
     }
-    if (state->mode == GZ_APPEND)
+    if (state->mode == GZ_APPEND) {
+        LSEEK(state->fd, 0, SEEK_END);  /* so gzoffset() is correct */
         state->mode = GZ_WRITE;         /* simplify later checks */
+    }
 
     /* save the current position for rewinding (only if reading) */
     if (state->mode == GZ_READ) {