Refactor code to make it simpler.

The changes should also:
- fix unlikely edge case when replacement line is the same as the
  old line (would have resulted in timeout)
- reduce memory footprint
- avoid applying string search beyond maxlines replacement limit

_test/tests/inc/io_replaceinfile.test.php

@@ -2,6 +2,8 @@
 
 class io_replaceinfile_test extends DokuWikiTest {
 
+    protected $contents = "The\012Delete\012Delete\012Delete01\012Delete02\012Delete\012DeleteX\012Test\012";
+
     /*
      * dependency for tests needing zlib extension to pass
      */
@@ -21,8 +23,8 @@ public function test_ext_bz2() {
     }
 
     function _write($file){
-        $contents = "The\012Delete\012Delete\012Delete01\012Delete02\012Delete\012DeleteX\012Test\012";
-        io_saveFile($file, $contents);
+
+        io_saveFile($file, $this->contents);
         // Replace one, no regex
         $this->assertTrue(io_replaceInFile($file, "Delete\012", "Delete00\012", false, 1));
         $this->assertEquals("The\012Delete00\012Delete\012Delete01\012Delete02\012Delete\012DeleteX\012Test\012", io_readFile($file));
@@ -41,6 +43,7 @@ function test_replace(){
         $this->_write(TMP_DIR.'/test.txt');
     }
 
+
     /**
      * @depends test_ext_zlib
      */
@@ -55,4 +58,25 @@ function test_bzwrite(){
         $this->_write(TMP_DIR.'/test.txt.bz2');
     }
 
+    /**
+     *
+     */
+    function test_edgecase1()
+    {
+        $file = TMP_DIR . '/test.txt';
+        // Replace all, no regex, backreference like construct in replacement line
+        io_saveFile($file, $this->contents);
+        $this->assertTrue(io_replaceInFile($file, "Delete\012", "Delete\\00\012", false, -1));
+        $this->assertEquals("The\012Delete\\00\012Delete\\00\012Delete01\012Delete02\012Delete\\00\012DeleteX\012Test\012", io_readFile($file), "Edge case: backreference like construct in replacement line");
+    }
+    /**
+     * @small
+     */
+    function test_edgecase2() {
+        $file = TMP_DIR.'/test.txt';
+        // Replace all, no regex, replacement line == search line
+        io_saveFile($file, $this->contents);
+        $this->assertTrue(io_replaceInFile($file, "Delete\012", "Delete\012", false, -1));
+        $this->assertEquals("The\012Delete\012Delete\012Delete01\012Delete02\012Delete\012DeleteX\012Test\012", io_readFile($file), "Edge case: new line the same as old line");
+    }
 }

inc/io.php

@@ -311,28 +311,23 @@ function io_replaceInFile($file, $oldline, $newline, $regex=false, $maxlines=0)
         $lines = file($file);
     }
 
-    // remove all matching lines
-    if ($regex) {
-        if($maxlines > 0) {
-            $matches = preg_grep($oldline, $lines);
-            $count = 0;
-            foreach($matches as $ix=>$m) {
-                $lines[$ix] = preg_replace($oldline, $newline, $m);
-                if(++$count >= $maxlines) break;
-            }
-        } else {
-            $lines = ($maxlines == 0) ? preg_grep($oldline, $lines, PREG_GREP_INVERT)
-                                      : preg_replace($oldline, $newline, $lines, $maxlines);
-        }
-    } else {
+    // make non-regexes into regexes
+    $pattern = $regex ? $oldline : '/'.preg_quote($oldline,'/').'/';
+    $replace = $regex ? $newline : addcslashes($newline, '\$');
+
+    // remove matching lines
+    if ($maxlines > 0) {
         $count = 0;
-        $replaceline = $maxlines == 0 ? '' : $newline;
-        $pos = array_search($oldline,$lines); //return null or false if not found
-        while(is_int($pos)){
-            $lines[$pos] = $replaceline;
-            if($maxlines > 0 && ++$count >= $maxlines) break;
-            $pos = array_search($oldline,$lines);
+        $matched = 0;
+        while (($count < $maxlines) && (list($i,$line) = each($lines))) {
+            // $matched will be set to 0|1 depending on whether pattern is matched and line replaced
+            $lines[$i] = preg_replace($pattern, $replace, $line, -1, $matched);
+            if ($matched) $count++;
         }
+    } else {
+        $lines = ($maxlines == 0) ?
+            preg_grep($pattern, $lines, PREG_GREP_INVERT) :
+            preg_replace($pattern, $replace, $lines);
     }
 
     if($maxlines == 0 && ((string)$newline) !== '') {