Ticket #6775: 6775.diff

wp-includes/default-filters.php

@@ -178 +178 @@
-add_action('init', 'smilies_init', 5);
-add_action( 'plugins_loaded', 'wp_maybe_load_widgets', 0 );
-add_action( 'shutdown', 'wp_ob_end_flush_all', 1);
+add_action( 'pre_post_update', 'wp_save_revision' );
-add_action('publish_post', '_publish_post_hook', 5, 1);
-add_action('future_post', '_future_post_hook', 5, 2);
-add_action('future_page', '_future_post_hook', 5, 2);

wp-includes/post-template.php

@@ -564 +564 @@
-        return false;
-}
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wp-includes/post.php

@@ -2990 +2990 @@
-        }
-}
-
+/* Post Revisions */
+
+/**
+ * _wp_revision_fields() - determines which fields of posts are to be saved in revisions
+ *
+ * Does two things. If passed a postn *array*, it will return a post array ready to be
+ * insterted into the posts table as a post revision.
+ * Otherwise, returns an array whose keys are the post fields to be saved post revisions.
+ *
+ * @package WordPress
+ * @subpackage Post Revisions
+ * @since 2.6
+ *
+ * @param array $post optional a post array to be processed for insertion as a post revision
+ * @return array post array ready to be inserted as a post revision or array of fields that can be versioned
+ */
+function _wp_revision_fields( $post = null ) {
+        static $fields = false;
+
+        if ( !$fields ) {
+                // Allow these to be versioned
+                $fields = array(
+                        'post_title' => __( 'Title' ),
+                        'post_author' => __( 'Author' ),
+                        'post_content' => __( 'Content' ),
+                        'post_excerpt' => __( 'Excerpt' ),
+                );
+
+                // WP uses these internally either in versioning or elsewhere - they cannot be versioned
+                foreach ( array( 'ID', 'post_name', 'post_parent', 'post_date', 'post_date_gmt', 'post_status', 'post_type', 'comment_count' ) as $protect )
+                        unset( $fields[$protect] );
+        }
+
+        if ( !is_array($post) )
+                return $fields;
+
+        $return = array();
+        foreach ( array_intersect( array_keys( $post ), array_keys( $fields ) ) as $field )
+                $return[$field] = $post[$field];
+
+        $return['post_parent']   = $post['ID'];
+        $return['post_status']   = 'inherit';
+        $return['post_type']     = 'revision';
+        $return['post_name']     = "$post[ID]-revision";
+        $return['post_date']     = $post['post_modified'];
+        $return['post_date_gmt'] = $post['post_modified_gmt'];
+
+        return $return;
+}
+
+/**
+ * wp_save_revision() - Saves an already existing post as a post revision.  Typically used immediately prior to post updates.
+ *
+ * @package WordPress
+ * @subpackage Post Revisions
+ * @since 2.6
+ *
+ * @uses _wp_put_revision()
+ *
+ * @param int $post_id The ID of the post to save as a revision
+ * @return mixed null or 0 if error, new revision ID if success
+ */
+function wp_save_revision( $post_id ) {
+        // TODO: rework autosave to use special type of post revision
+        if ( @constant( 'DOING_AUTOSAVE' ) )
+                return;
+
+        if ( !$post = get_post( $post_id, ARRAY_A ) )
+                return;
+
+        // TODO: open this up for pages also
+        if ( 'post' != $post->post_type )
+                retun;
+
+        return _wp_put_revision( $post );
+}
+
+/**
+ * _wp_put_revision() - Inserts post data into the posts table as a post revision
+ *
+ * @package WordPress
+ * @subpackage Post Revisions
+ * @since 2.6
+ *
+ * @uses wp_insert_post()
+ *
+ * @param int|object|array $post post ID, post object OR post array
+ * @return mixed null or 0 if error, new revision ID if success
+ */
+function _wp_put_revision( $post = null ) {
+        if ( is_object($post) )
+                $post = get_object_vars( $post );
+        elseif ( !is_array($post) )
+                $post = get_post($post, ARRAY_A);
+
+        if ( !$post || empty($post['ID']) )
+                return;
+
+        if ( isset($post['post_type']) && 'revision' == $post_post['type'] )
+                return new WP_Error( 'post_type', __( 'Cannot create a revision of a revision' ) );
+
+        $post = _wp_revision_fields( $post );
+
+        if ( $revision_id = wp_insert_post( $post ) )
+                do_action( '_wp_put_revision', $revision_id );
+
+        return $revision_id;
+}
+
+/**
+ * wp_get_revision() - Gets a post revision
+ *
+ * @package WordPress
+ * @subpackage Post Revisions
+ * @since 2.6
+ *
+ * @uses get_post()
+ *
+ * @param int|object $post post ID or post object
+ * @param $output optional OBJECT, ARRAY_A, or ARRAY_N
+ * @param string $filter optional sanitation filter.  @see sanitize_post()
+ * @return mixed null if error or post object if success
+ */
+function &wp_get_revision(&$post, $output = OBJECT, $filter = 'raw') {
+        $null = null;
+        if ( !$revision = get_post( $post, OBJECT, $filter ) )
+                return $revision;
+        if ( 'revision' !== $revision->post_type )
+                return $null;
+
+        if ( $output == OBJECT ) {
+                return $revision;
+        } elseif ( $output == ARRAY_A ) {
+                $_revision = get_object_vars($revision);
+                return $_revision;
+        } elseif ( $output == ARRAY_N ) {
+                $_revision = array_values(get_object_vars($revision));
+                return $_revision;
+        }
+
+        return $revision;
+}
+
+/**
+ * wp_restore_revision() - Restores a post to the specified revision
+ *
+ * Can restore a past using all fields of the post revision, or only selected fields.
+ *
+ * @package WordPress
+ * @subpackage Post Revisions
+ * @since 2.6
+ *
+ * @uses wp_get_revision()
+ * @uses wp_update_post()
+ *
+ * @param int|object $revision_id revision ID or revision object
+ * @param array $fields optional What fields to restore from.  Defaults to all.
+ * @return mixed null if error, false if no fields to restore, (int) post ID if success
+ */
+function wp_restore_revision( $revision_id, $fields = null ) {
+        if ( !$revision = wp_get_revision( $revision_id, ARRAY_A ) )
+                return $revision;
+
+        if ( !is_array( $fields ) )
+                $fields = array_keys( _wp_revision_fields() );
+
+        $update = array();
+        foreach( array_intersect( array_keys( $revision ), $fields ) as $field )
+                $update[$field] = $revision[$field];
+
+        if ( !$update )
+                return false;
+
+        $update['ID'] = $revision['post_parent'];
+
+        if ( $post_id = wp_update_post( $update ) )
+                do_action( 'wp_restore_revision', $post_id, $revision['ID'] );
+
+        return $post_id;
+}
+
+/**
+ * wp_delete_revision() - Deletes a revision.
+ *
+ * Deletes the row from the posts table corresponding to the specified revision
+ *
+ * @package WordPress
+ * @subpackage Post Revisions
+ * @since 2.6
+ *
+ * @uses wp_get_revision()
+ * @uses wp_delete_post()
+ *
+ * @param int|object $revision_id revision ID or revision object
+ * @param array $fields optional What fields to restore from.  Defaults to all.
+ * @return mixed null if error, false if no fields to restore, (int) post ID if success
+ */
+function wp_delete_revision( $revision_id ) {
+        if ( !$revision = wp_get_revision( $revision_id ) )
+                return $revision;
+
+        if ( $delete = wp_delete_post( $revision->ID ) )
+                do_action( 'wp_delete_revision', $revision->ID, $revision );
+
+        return $delete;
+}
+
+/**
+ * wp_get_post_revisions() - Returns all revisions of specified post
+ *
+ * @package WordPress
+ * @subpackage Post Revisions
+ * @since 2.6
+ *
+ * @uses get_children()
+ *
+ * @param int|object $post_id post ID or post object
+ * @return array empty if no revisions
+ */
+function wp_get_post_revisions( $post_id = 0 ) {
+        if ( ( !$post = get_post( $post_id ) ) || empty( $post->ID ) )
+                return array();
+
+        if ( !$revisions = get_children( array( 'post_parent' => $post->ID, 'post_type' => 'revision' ) ) )
+                return array();
+        return $revisions;
+}
+
-?>

wp-includes/wp-diff.php

@@ +1 @@
+<?php
+
+if ( !class_exists( 'Text_Diff' ) ) {
+        require( 'Text/Diff.php' );
+        require( 'Text/Diff/Renderer.php' );
+        require( 'Text/Diff/Renderer/inline.php' );
+}
+
+
+/* Descendent of a bastard child of piece of an old MediaWiki Diff Formatter
+ *
+ * Basically all that remains is the table structure and some method names.
+ */
+
+class WP_Text_Diff_Renderer_Table extends Text_Diff_Renderer {
+        var $_leading_context_lines  = 10000;
+        var $_trailing_context_lines = 10000;
+        var $_diff_threshold = 0.6;
+
+        var $inline_diff_renderer = 'WP_Text_Diff_Renderer_inline';
+
+        function Text_Diff_Renderer_Table( $params = array() ) {
+                $parent = get_parent_class($this);
+                $this->$parent( $params );
+        }
+
+        function _startBlock( $header ) {
+                return '';
+        }
+
+        function _lines( $lines, $prefix=' ' ) {
+        }
+
+        // HTML-escape parameter before calling this
+        function addedLine( $line ) {
+                return "<td>+</td><td class='diff-addedline'>{$line}</td>";
+        }
+
+        // HTML-escape parameter before calling this
+        function deletedLine( $line ) {
+                return "<td>-</td><td class='diff-deletedline'>{$line}</td>";
+        }
+
+        // HTML-escape parameter before calling this
+        function contextLine( $line ) {
+                return "<td> </td><td class='diff-context'>{$line}</td>";
+        }
+
+        function emptyLine() {
+                return '<td colspan="2">&nbsp;</td>';
+        }
+
+        function _added( $lines, $encode = true ) {
+                $r = '';
+                foreach ($lines as $line) {
+                        if ( $encode )
+                                $line = htmlspecialchars( $line );
+                        $r .= '<tr>' . $this->emptyLine() . $this->addedLine( $line ) . "</tr>\n";
+                }
+                return $r;
+        }
+
+        function _deleted( $lines, $encode = true ) {
+                $r = '';
+                foreach ($lines as $line) {
+                        if ( $encode )
+                                $line = htmlspecialchars( $line );
+                        $r .= '<tr>' . $this->deletedLine( $line ) . $this->emptyLine() . "</tr>\n";
+                }
+                return $r;
+        }
+
+        function _context( $lines, $encode = true ) {
+                $r = '';
+                foreach ($lines as $line) {
+                        if ( $encode )
+                                $line = htmlspecialchars( $line );
+                        $r .= '<tr>' .
+                                $this->contextLine( $line ) . $this->contextLine( $line ) . "</tr>\n";
+                }
+                return $r;
+        }
+
+        // Process changed lines to do word-by-word diffs for extra highlighting (TRAC style)
+        // sometimes these lines can actually be deleted or added rows - we do additional processing
+        // to figure that out
+        function _changed( $orig, $final ) {
+                $r = '';
+
+                // Does the aforementioned additional processing
+                // *_matches tell what rows are "the same" in orig and final.  Those pairs will be diffed to get word changes
+                //      match is numeric: an index in other column
+                //      match is 'X': no match.  It is a new row
+                // *_rows are column vectors for the orig column and the final column.
+                //      row >= 0: an indix of the $orig or $final array
+                //      row  < 0: a blank row for that column
+                list($orig_matches, $final_matches, $orig_rows, $final_rows) = $this->interleave_changed_lines( $orig, $final );
+
+
+                // These will hold the word changes as determined by an inline diff
+                $orig_diffs  = array();
+                $final_diffs = array();
+
+                // Compute word diffs for each matched pair using the inline diff
+                foreach ( $orig_matches as $o => $f ) {
+                        if ( is_numeric($o) && is_numeric($f) ) {
+                                $text_diff = new Text_Diff( 'auto', array( array($orig[$o]), array($final[$f]) ) );
+                                $renderer = new $this->inline_diff_renderer;
+                                $diff = $renderer->render( $text_diff );
+
+                                // If they're too different, don't include any <ins> or <dels>
+                                if ( $diff_count = preg_match_all( '!(<ins>.*?</ins>|<del>.*?</del>)!', $diff, $diff_matches ) ) {
+                                        // length of all text between <ins> or <del>
+                                        $stripped_matches = strlen(strip_tags( join(' ', $diff_matches[0]) ));
+                                        // since we count lengith of text between <ins> or <del> (instead of picking just one),
+                                        //      we double the length of chars not in those tags.
+                                        $stripped_diff = strlen(strip_tags( $diff )) * 2 - $stripped_matches;
+                                        $diff_ratio = $stripped_matches / $stripped_diff;
+                                        if ( $diff_ratio > $this->_diff_threshold )
+                                                continue; // Too different.  Don't save diffs.
+                                }
+
+                                // Un-inline the diffs by removing del or ins
+                                $orig_diffs[$o]  = preg_replace( '|<ins>.*?</ins>|', '', $diff );
+                                $final_diffs[$f] = preg_replace( '|<del>.*?</del>|', '', $diff );
+                        }
+                }
+
+                foreach ( array_keys($orig_rows) as $row ) {
+                        // Both columns have blanks.  Ignore them.
+                        if ( $orig_rows[$row] < 0 && $final_rows[$row] < 0 )
+                                continue;
+
+                        // If we have a word based diff, use it.  Otherwise, use the normal line.
+                        $orig_line  = isset($orig_diffs[$orig_rows[$row]])
+                                ? $orig_diffs[$orig_rows[$row]]
+                                : htmlspecialchars($orig[$orig_rows[$row]]);
+                        $final_line = isset($final_diffs[$final_rows[$row]])
+                                ? $final_diffs[$final_rows[$row]]
+                                : htmlspecialchars($final[$final_rows[$row]]);
+
+                        if ( $orig_rows[$row] < 0 ) { // Orig is blank.  This is really an added row.
+                                $r .= $this->_added( array($final_line), false );
+                        } elseif ( $final_rows[$row] < 0 ) { // Final is blank.  This is really a deleted row.
+                                $r .= $this->_deleted( array($orig_line), false );
+                        } else { // A true changed row.
+                                $r .= '<tr>' . $this->deletedLine( $orig_line ) . $this->addedLine( $final_line ) . "</tr>\n";
+                        }
+                }
+
+                return $r;
+        }
+
+        // Takes changed blocks and matches which rows in orig turned into which rows in final.
+        // Returns
+        //      *_matches ( which rows match with which )
+        //      *_rows ( order of rows in each column interleaved with blank rows as necessary )
+        function interleave_changed_lines( $orig, $final ) {
+
+                // Contains all pairwise string comparisons.  Keys are such that this need only be a one dimensional array.
+                $matches = array();
+                foreach ( array_keys($orig) as $o ) {
+                        foreach ( array_keys($final) as $f ) {
+                                $matches["$o,$f"] = $this->compute_string_distance( $orig[$o], $final[$f] );
+                        }
+                }
+                asort($matches); // Order by string distance.
+
+                $orig_matches  = array();
+                $final_matches = array();
+
+                foreach ( $matches as $keys => $difference ) {
+                        list($o, $f) = explode(',', $keys);
+                        $o = (int) $o;
+                        $f = (int) $f;
+
+                        // Already have better matches for these guys
+                        if ( isset($orig_matches[$o]) && isset($final_matches[$f]) )
+                                continue;
+
+                        // First match for these guys.  Must be best match
+                        if ( !isset($orig_matches[$o]) && !isset($final_matches[$f]) ) {
+                                $orig_matches[$o] = $f;
+                                $final_matches[$f] = $o;
+                                continue;
+                        }
+
+                        // Best match of this final is already taken?  Must mean this final is a new row.
+                        if ( isset($orig_matches[$o]) )
+                                $final_matches[$f] = 'x';
+
+                        // Best match of this orig is already taken?  Must mean this orig is a deleted row.
+                        elseif ( isset($final_matches[$f]) )
+                                $orig_matches[$o] = 'x';
+                }
+
+                // We read the text in this order
+                ksort($orig_matches);
+                ksort($final_matches);
+
+
+                // Stores rows and blanks for each column.
+                $orig_rows = $orig_rows_copy = array_keys($orig_matches);
+                $final_rows = array_keys($final_matches);
+
+                // Interleaves rows with blanks to keep matches aligned.
+                // We may end up with some extraneous blank rows, but we'll just ignore them later.
+                foreach ( $orig_rows_copy as $orig_row ) {
+                        $final_pos = array_search($orig_matches[$orig_row], $final_rows, true);
+                        $orig_pos = (int) array_search($orig_row, $orig_rows, true);
+
+                        if ( false === $final_pos ) { // This orig is paired with a blank final.
+                                array_splice( $final_rows, $orig_pos, 0, -1 );
+                        } elseif ( $final_pos < $orig_pos ) { // This orig's match is up a ways.  Pad final with blank rows.
+                                $diff_pos = $final_pos - $orig_pos;
+                                while ( $diff_pos < 0 )
+                                        array_splice( $final_rows, $orig_pos, 0, $diff_pos++ );
+                        } elseif ( $final_pos > $orig_pos ) { // This orig's match is down a ways.  Pad orig with blank rows.
+                                $diff_pos = $orig_pos - $final_pos;
+                                while ( $diff_pos < 0 )
+                                        array_splice( $orig_rows, $orig_pos, 0, $diff_pos++ );
+                        }
+                }
+
+
+                // Pad the ends with blank rows if the columns aren't the same length
+                $diff_count = count($orig_rows) - count($final_rows);
+                if ( $diff_count < 0 ) {
+                        while ( $diff_count < 0 )
+                                array_push($orig_rows, $diff_count++);
+                } elseif ( $diff_count > 0 ) {
+                        $diff_count = -1 * $diff_count;
+                        while ( $diff_count < 0 )
+                                array_push($final_rows, $diff_count++);
+                }
+
+                return array($orig_matches, $final_matches, $orig_rows, $final_rows);
+
+/*
+                // Debug
+                echo "\n\n\n\n\n";
+
+                echo "-- DEBUG Matches: Orig -> Final --";
+
+                foreach ( $orig_matches as $o => $f ) {
+                        echo "\n\n\n\n\n";
+                        echo "ORIG: $o, FINAL: $f\n";
+                        var_dump($orig[$o],$final[$f]);
+                }
+                echo "\n\n\n\n\n";
+
+                echo "-- DEBUG Matches: Final -> Orig --";
+
+                foreach ( $final_matches as $f => $o ) {
+                        echo "\n\n\n\n\n";
+                        echo "FINAL: $f, ORIG: $o\n";
+                        var_dump($final[$f],$orig[$o]);
+                }
+                echo "\n\n\n\n\n";
+
+                echo "-- DEBUG Rows: Orig -- Final --";
+
+                echo "\n\n\n\n\n";
+                foreach ( $orig_rows as $row => $o ) {
+                        if ( $o < 0 )
+                                $o = 'X';
+                        $f = $final_rows[$row];
+                        if ( $f < 0 )
+                                $f = 'X';
+                        echo "$o -- $f\n";
+                }
+                echo "\n\n\n\n\n";
+
+                echo "-- END DEBUG --";
+
+                echo "\n\n\n\n\n";
+
+                return array($orig_matches, $final_matches, $orig_rows, $final_rows);
+*/
+        }
+
+
+        // Computes a number that is intended to reflect the "distance" between two strings.
+        function compute_string_distance( $string1, $string2 ) {
+                // Vectors containing character frequency for all chars in each string
+                $chars1 = count_chars($string1);
+                $chars2 = count_chars($string2);
+
+                // L1-norm of difference vector.
+                $difference = array_sum( array_map( array(&$this, 'difference'), $chars1, $chars2 ) );
+
+                // $string1 has zero length? Odd.  Give huge penalty by not dividing.
+                if ( !$string1 )
+                        return $difference;
+
+                // Return distance per charcter (of string1)
+                return $difference / strlen($string1);
+        }
+
+        function difference( $a, $b ) {
+                return abs( $a - $b );
+        }
+
+}
+
+// Better word splitting than the PEAR package provides
+class WP_Text_Diff_Renderer_inline extends Text_Diff_Renderer_inline {
+
+        function _splitOnWords($string, $newlineEscape = "\n") {
+                $string = str_replace("\0", '', $string);
+                $words  = preg_split( '/([^\w])/', $string, -1, PREG_SPLIT_DELIM_CAPTURE );
+                $words  = str_replace( "\n", $newlineEscape, $words );
+                return $words;
+        }
+
+}
+
+?>

wp-includes/link-template.php

@@ -442 +442 @@
-        return $link;
-}
-
-
+, $context = 'display'
-        if ( !$post = &get_post( $id ) )
-                return;
-
+        if ( 'display' == $context )
+                $action = 'action=edit&';
+        else
+                $action = 'action=edit&';
+
-        switch ( $post->post_type ) :
-        case 'page' :
-                if ( !current_user_can( 'edit_page', $post->ID ) )
@@ -459 +464 @@
-                $file = 'media';
-                $var  = 'attachment_id';
-                break;
+        case 'revision' :
+                if ( !current_user_can( 'edit_post', $post->ID ) )
+                        return;
+                $file = 'revision';
+                $var  = 'revision';
+                $action = '';
+                break;
-        default :
-                if ( !current_user_can( 'edit_post', $post->ID ) )
-                        return;
@@ -467 +479 @@
-                break;
-        endswitch;
-        
-action=edit&
+{$action}
-}
-
-function edit_post_link( $link = 'Edit This', $before = '', $after = '' ) {

wp-includes/Text/Diff/Engine/xdiff.php

@@ +1 @@
+<?php
+/**
+ * Class used internally by Diff to actually compute the diffs.
+ *
+ * This class uses the xdiff PECL package (http://pecl.php.net/package/xdiff)
+ * to compute the differences between the two input arrays.
+ *
+ * $Horde: framework/Text_Diff/Diff/Engine/xdiff.php,v 1.6 2008/01/04 10:07:50 jan Exp $
+ *
+ * Copyright 2004-2008 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file COPYING for license information (LGPL). If you did
+ * not receive this file, see http://opensource.org/licenses/lgpl-license.php.
+ *
+ * @author  Jon Parise <jon@horde.org>
+ * @package Text_Diff
+ */
+class Text_Diff_Engine_xdiff {
+
+    /**
+     */
+    function diff($from_lines, $to_lines)
+    {
+        array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
+        array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
+
+        /* Convert the two input arrays into strings for xdiff processing. */
+        $from_string = implode("\n", $from_lines);
+        $to_string = implode("\n", $to_lines);
+
+        /* Diff the two strings and convert the result to an array. */
+        $diff = xdiff_string_diff($from_string, $to_string, count($to_lines));
+        $diff = explode("\n", $diff);
+
+        /* Walk through the diff one line at a time.  We build the $edits
+         * array of diff operations by reading the first character of the
+         * xdiff output (which is in the "unified diff" format).
+         *
+         * Note that we don't have enough information to detect "changed"
+         * lines using this approach, so we can't add Text_Diff_Op_changed
+         * instances to the $edits array.  The result is still perfectly
+         * valid, albeit a little less descriptive and efficient. */
+        $edits = array();
+        foreach ($diff as $line) {
+            switch ($line[0]) {
+            case ' ':
+                $edits[] = &new Text_Diff_Op_copy(array(substr($line, 1)));
+                break;
+
+            case '+':
+                $edits[] = &new Text_Diff_Op_add(array(substr($line, 1)));
+                break;
+
+            case '-':
+                $edits[] = &new Text_Diff_Op_delete(array(substr($line, 1)));
+                break;
+            }
+        }
+
+        return $edits;
+    }
+
+}

wp-includes/Text/Diff/Engine/native.php

@@ +1 @@
+<?php
+/**
+ * $Horde: framework/Text_Diff/Diff/Engine/native.php,v 1.10 2008/01/04 10:27:53 jan Exp $
+ *
+ * Class used internally by Text_Diff to actually compute the diffs. This
+ * class is implemented using native PHP code.
+ *
+ * The algorithm used here is mostly lifted from the perl module
+ * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
+ * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
+ *
+ * More ideas are taken from: http://www.ics.uci.edu/~eppstein/161/960229.html
+ *
+ * Some ideas (and a bit of code) are taken from analyze.c, of GNU
+ * diffutils-2.7, which can be found at:
+ * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
+ *
+ * Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
+ * Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
+ * code was written by him, and is used/adapted with his permission.
+ *
+ * Copyright 2004-2008 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file COPYING for license information (LGPL). If you did
+ * not receive this file, see http://opensource.org/licenses/lgpl-license.php.
+ *
+ * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
+ * @package Text_Diff
+ */
+class Text_Diff_Engine_native {
+
+    function diff($from_lines, $to_lines)
+    {
+        array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
+        array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
+
+        $n_from = count($from_lines);
+        $n_to = count($to_lines);
+
+        $this->xchanged = $this->ychanged = array();
+        $this->xv = $this->yv = array();
+        $this->xind = $this->yind = array();
+        unset($this->seq);
+        unset($this->in_seq);
+        unset($this->lcs);
+
+        // Skip leading common lines.
+        for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
+            if ($from_lines[$skip] !== $to_lines[$skip]) {
+                break;
+            }
+            $this->xchanged[$skip] = $this->ychanged[$skip] = false;
+        }
+
+        // Skip trailing common lines.
+        $xi = $n_from; $yi = $n_to;
+        for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
+            if ($from_lines[$xi] !== $to_lines[$yi]) {
+                break;
+            }
+            $this->xchanged[$xi] = $this->ychanged[$yi] = false;
+        }
+
+        // Ignore lines which do not exist in both files.
+        for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
+            $xhash[$from_lines[$xi]] = 1;
+        }
+        for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
+            $line = $to_lines[$yi];
+            if (($this->ychanged[$yi] = empty($xhash[$line]))) {
+                continue;
+            }
+            $yhash[$line] = 1;
+            $this->yv[] = $line;
+            $this->yind[] = $yi;
+        }
+        for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
+            $line = $from_lines[$xi];
+            if (($this->xchanged[$xi] = empty($yhash[$line]))) {
+                continue;
+            }
+            $this->xv[] = $line;
+            $this->xind[] = $xi;
+        }
+
+        // Find the LCS.
+        $this->_compareseq(0, count($this->xv), 0, count($this->yv));
+
+        // Merge edits when possible.
+        $this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged);
+        $this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged);
+
+        // Compute the edit operations.
+        $edits = array();
+        $xi = $yi = 0;
+        while ($xi < $n_from || $yi < $n_to) {
+            assert($yi < $n_to || $this->xchanged[$xi]);
+            assert($xi < $n_from || $this->ychanged[$yi]);
+
+            // Skip matching "snake".
+            $copy = array();
+            while ($xi < $n_from && $yi < $n_to
+                   && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
+                $copy[] = $from_lines[$xi++];
+                ++$yi;
+            }
+            if ($copy) {
+                $edits[] = &new Text_Diff_Op_copy($copy);
+            }
+
+            // Find deletes & adds.
+            $delete = array();
+            while ($xi < $n_from && $this->xchanged[$xi]) {
+                $delete[] = $from_lines[$xi++];
+            }
+
+            $add = array();
+            while ($yi < $n_to && $this->ychanged[$yi]) {
+                $add[] = $to_lines[$yi++];
+            }
+
+            if ($delete && $add) {
+                $edits[] = &new Text_Diff_Op_change($delete, $add);
+            } elseif ($delete) {
+                $edits[] = &new Text_Diff_Op_delete($delete);
+            } elseif ($add) {
+                $edits[] = &new Text_Diff_Op_add($add);
+            }
+        }
+
+        return $edits;
+    }
+
+    /**
+     * Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
+     * XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized
+     * segments.
+     *
+     * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an array of
+     * NCHUNKS+1 (X, Y) indexes giving the diving points between sub
+     * sequences.  The first sub-sequence is contained in (X0, X1), (Y0, Y1),
+     * the second in (X1, X2), (Y1, Y2) and so on.  Note that (X0, Y0) ==
+     * (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).