From 6a40e12124b2d441a1085a4e486d685ed12665d0 Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Sat, 4 May 2019 19:32:52 -0500
Subject: Optimize regexec0() for long lines.

Don't strlen() to find NUL to skip to until after we've confirmed first
section hasn't got a match (by calling regexec() on it).
---
 lib/lib.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

(limited to 'lib/lib.c')

diff --git a/lib/lib.c b/lib/lib.c
index 7b7d84d6..6df9566c 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -1327,16 +1327,9 @@ int regexec0(regex_t *preg, char *string, long len, int nmatch,
   char *s = string;
 
   for (;;) {
-    long ll = 0;
-    int rc;
+    int rc = regexec(preg, s, nmatch, pmatch, eflags);
 
-    while (len && !*s) {
-      s++;
-      len--;
-    }
-    while (s[ll] && ll<len) ll++;
-
-    rc = regexec(preg, s, nmatch, pmatch, eflags);
+    // check for match
     if (!rc) {
       for (rc = 0; rc<nmatch && pmatch[rc].rm_so!=-1; rc++) {
         pmatch[rc].rm_so += s-string;
@@ -1345,10 +1338,17 @@ int regexec0(regex_t *preg, char *string, long len, int nmatch,
 
       return 0;
     }
-    if (ll==len) return rc;
 
-    s += ll;
-    len -= ll;
+    // advance past NUL bytes and try again
+    while (len && *s) {
+      s++;
+      len--;
+    }
+    while (len && !*s) {
+      s++;
+      len--;
+    }
+    if (!len) return REG_NOMATCH;
   }
 }
 
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