From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 22 Sep 2017 19:03:33 +0000 (+0200)
Subject: fileio: try to read one byte too much in read_full_stream()
X-Git-Tag: v235.1~85
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=acd34fa3f200bd4c4caccc7973425d434fb1ec97;p=elogind.git

fileio: try to read one byte too much in read_full_stream()

Let's read one byte more than the file size we read from stat() on the
first fread() invocation. That way, the first read() will already be
short and indicate eof to fread().

This is a minor optimization, and replaces #3908.
---

diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index d5751a3b5..5dc303bb4 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -270,11 +270,11 @@ int read_full_stream(FILE *f, char **contents, size_t *size) {
                 if (st.st_size > READ_FULL_BYTES_MAX)
                         return -E2BIG;
 
-                /* Start with the right file size, but be prepared for
-                 * files from /proc which generally report a file size
-                 * of 0 */
+                /* Start with the right file size, but be prepared for files from /proc which generally report a file
+                 * size of 0. Note that we increase the size to read here by one, so that the first read attempt
+                 * already makes us notice the EOF. */
                 if (st.st_size > 0)
-                        n = st.st_size;
+                        n = st.st_size + 1;
         }
 
         l = 0;