From: Ralph Corderoy <ralph@inputplus.co.uk>
Date: Sun, 16 Oct 2016 07:23:51 +0000 (+0100)
Subject: Stop one lseek(2) per header fetched by m_getfld.c in common case.
X-Git-Url: https://diplodocus.org/git/nmh/commitdiff_plain/f2ecc1fd04d5b842b8373e589395e0118cbe62d0?hp=bd057d60eba167871169c243a64dbf9d7d9f4cde

Stop one lseek(2) per header fetched by m_getfld.c in common case.
Only call ftello(3) in enter_getfld() when track_filepos has been
requested;  not often.
---

diff --git a/sbr/m_getfld.c b/sbr/m_getfld.c
index 4da2f3ee..531381d8 100644
--- a/sbr/m_getfld.c
+++ b/sbr/m_getfld.c
@@ -347,7 +347,7 @@ void m_getfld_state_destroy (m_getfld_state_t *gstate) {
 static void
 enter_getfld (m_getfld_state_t *gstate, FILE *iob) {
     m_getfld_state_t s;
-    off_t pos = ftello (iob);
+    off_t pos;
 
     if (! *gstate) {
 	m_getfld_state_init (gstate, iob);
@@ -363,7 +363,11 @@ enter_getfld (m_getfld_state_t *gstate, FILE *iob) {
        readpos shift code being currently unused. */
     s->iob = iob;
 
-    if (s->track_filepos  &&  (pos != 0  ||  s->last_internal_pos != 0)) {
+    if (!s->track_filepos)
+        return;
+
+    pos = ftello(iob);
+    if (pos != 0  ||  s->last_internal_pos != 0) {
 	if (s->last_internal_pos == 0) {
 	    s->total_bytes_read = pos;
 	} else {