[FFmpeg-cvslog] avcodec/xbmenc: Pre-compute variables once for parse_str_int()

[Jose Da Silva]

ffmpeg | branch: master | Jose Da Silva <digital at joescat.com> | Sun Jan 31 19:50:57 2021 -0800| [42c636c9722f64fe6290ea8eee13658d25f5fbe3] | committer: Paul B Mahol

avcodec/xbmenc: Pre-compute variables once for parse_str_int()

Some compilers are very intuitive, and others are not so much, so let's
pre-compute the variables e and keylen outside the for loop. Ensuring a
minor speed increase regardless of if compiler is smart enough to solve
this improvement for itself, or not.

Signed-off-by: Joe Da Silva <digital at joescat.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=42c636c9722f64fe6290ea8eee13658d25f5fbe3
---

 libavcodec/xbmdec.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/libavcodec/xbmdec.c b/libavcodec/xbmdec.c
index 2ce70204cf..b783d5abe5 100644
--- a/libavcodec/xbmdec.c
+++ b/libavcodec/xbmdec.c
@@ -39,11 +39,14 @@ static int convert(uint8_t x)
 
 static int parse_str_int(const uint8_t *p, const uint8_t *end, const uint8_t *key)
 {
-    for(; p<end - strlen(key); p++) {
-        if (!memcmp(p, key, strlen(key)))
+    int keylen = strlen(key);
+    const uint8_t *e = end - keylen;
+
+    for(; p < e; p++) {
+        if (!memcmp(p, key, keylen))
             break;
     }
-    p += strlen(key);
+    p += keylen;
     if (p >= end)
         return INT_MIN;