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mostly doc changes per review feedback.
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There were also a couple of minor code changes (variable renames and such)
but no algorithmic changes.
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@dangoor
dangoor committed Jan 16, 2013
1 parent 705b097 commit 112b206
Showing 1 changed file with 47 additions and 17 deletions.
64 changes: 47 additions & 17 deletions src/utils/StringMatch.js
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Original file line number Diff line number Diff line change
Expand Up @@ -102,8 +102,8 @@ define(function (require, exports, module) {
}

// states used during the scanning of the string
var SPECIALS_COMPARE = 0;
var CONSECUTIVE_COMPARE = 1;
var SPECIALS_MATCH = 0;
var ANY_MATCH = 1;

// Scores can be hard to make sense of. The DEBUG_SCORES flag
// provides a way to peek into the parts that made up a score.
Expand Down Expand Up @@ -145,6 +145,35 @@ define(function (require, exports, module) {
* search will backtrack and try to find matches for the whole query earlier in the
* string.
*
* A contrived example will help illustrate how the searching and backtracking works. It's a bit long,
* but it illustrates different pieces of the algorithm which can be tricky. Let's say that we're
* searching the string "AzzBzzCzdzezzDgxgEF" for "abcdex".
*
* To start with, it will match "abcde" from the query to "A B C D E" in the string (the spaces
* represent gaps in the matched part of the string), because those are all "special characters".
* However, the "x" in the query doesn't match the "F" which is the only character left in the
* string.
*
* Backtracking kicks in. The "E" is pulled off of the match list. backtrackTo is set to the "g"
* before the "E" (which means that the next time we backtrack, we'll need to at least that far back.
* deadBranches[4] is set to the "g" before the "E" as well. This means that for the 5th
* query character (the "e") we know that we don't have a match beyond that point in the string.
*
* To resume searching, the backtrack function looks at the previous match (the "D") and starts
* searching in character-by-character (ANY_MATCH) mode right after that. It fails to find an
* "e" before it gets to deadBranches[4], so it has to backtrack again.
*
* This time, the "D" is pulled off the match list. backtrackTo goes back to the "z" before the "D".
* deadBranches[3] is set to the "z" before the "D", because we know that for the "dex" part of the
* query, we can't make it work past the "D". We'll resume searching with the "z" after the "C".
*
* Doing an ANY_MATCH search, we find the "d". We then start searching specials for "e", but we
* stop before we get to "E" because deadBranches[4] tells us that's a dead end. So, we switch
* to ANY_MATCH and find the "e".
*
* Finally, we search for the "x". We don't find a special that matches, so we start an ANY_MATCH
* search. Then we find the "x", and we have a successful match.
*
* @param {string} query the search string (generally lower cased)
* @param {string} str the string to compare with (generally lower cased)
* @param {Array} specials list of special indexes in str (from findSpecialCharacters)
Expand Down Expand Up @@ -177,7 +206,7 @@ define(function (require, exports, module) {

queryCounter = 0;

var state = SPECIALS_COMPARE;
var state = SPECIALS_MATCH;

// Compares the current character from the query string against the
// special characters in str. Returns true if a match was found,
Expand Down Expand Up @@ -231,7 +260,9 @@ define(function (require, exports, module) {
}

// we pulled off a match, which means that we need to put a character
// back into our query
// back into our query. strCounter is going to be set once we've pulled
// off the right special character and know where we're going to restart
// searching from.
queryCounter--;

if (item instanceof SpecialMatch) {
Expand All @@ -250,7 +281,7 @@ define(function (require, exports, module) {

// since we failed with the specials along this track, we're
// going to reset to looking for matches consecutively.
state = CONSECUTIVE_COMPARE;
state = ANY_MATCH;

// we figure out where to start looking based on the new
// last item in the list. If there isn't anything else
Expand All @@ -274,19 +305,19 @@ define(function (require, exports, module) {

// keep looping until we've either exhausted the query or the string
while (queryCounter < query.length && strCounter < str.length && strCounter <= deadBranches[queryCounter]) {
if (state === SPECIALS_COMPARE) {
if (state === SPECIALS_MATCH) {
if (!findMatchingSpecial()) {
state = CONSECUTIVE_COMPARE;
state = ANY_MATCH;
}
}

if (state === CONSECUTIVE_COMPARE) {
if (state === ANY_MATCH) {
// we look character by character for matches
if (query[queryCounter] === str[strCounter]) {
// got a match! record it, and switch back to searching specials
queryCounter++;
result.push(new NormalMatch(strCounter++));
state = SPECIALS_COMPARE;
state = SPECIALS_MATCH;
} else {
// no match, keep looking
strCounter++;
Expand All @@ -296,7 +327,7 @@ define(function (require, exports, module) {

// if we've finished the query, or we haven't finished the query but we have no
// more backtracking we can do, then we're all done searching.
if ((queryCounter < query.length && !backtrack()) || queryCounter >= query.length) {
if (queryCounter >= query.length || (queryCounter < query.length && !backtrack())) {
break;
}
}
Expand All @@ -321,20 +352,19 @@ define(function (require, exports, module) {
* at the beginning of the query which did not match in the last segment.
*
* @param {string} query the search string (generally lower cased)
* @param {string} str the original string to search
* @param {string} compareStr the string to compare with (generally lower cased)
* @param {string} str the string to compare with (generally lower cased)
* @param {Array} specials list of special indexes in str (from findSpecialCharacters)
* @param {int} startingSpecial index into specials array to start scanning with
* @param {boolean} lastSegmentStart which character does the last segment start at
* @return {{ranges:Array.<{text:string, matched:boolean, includesLastSegment:boolean}>, remainder:string, matchGoodness:int, scoreDebug: Object}} matched ranges and score
* @return {{remainder:int, matchList:Array.<SpecialMatch|NormalMatch>}} matched indexes or null if no matches possible
*/
function _lastSegmentSearch(query, compareStr, specials, startingSpecial, lastSegmentStart) {
function _lastSegmentSearch(query, str, specials, startingSpecial, lastSegmentStart) {
var queryCounter, matchList;

// It's possible that the query is longer than the last segment.
// If so, we can chop off the bit that we know couldn't possibly be there.
var remainder = "";
var extraCharacters = specials[startingSpecial] + query.length - compareStr.length;
var extraCharacters = specials[startingSpecial] + query.length - str.length;

if (extraCharacters > 0) {
remainder = query.substring(0, extraCharacters);
Expand All @@ -343,7 +373,7 @@ define(function (require, exports, module) {

for (queryCounter = 0; queryCounter < query.length; queryCounter++) {
matchList = _generateMatchList(query.substring(queryCounter),
compareStr, specials, startingSpecial);
str, specials, startingSpecial);

// if we've got a match *or* there are no segments in this string, we're done
if (matchList || startingSpecial === 0) {
Expand Down Expand Up @@ -371,7 +401,7 @@ define(function (require, exports, module) {
* @param {string} str the original string to search
* @param {Array} specials list of special indexes in str (from findSpecialCharacters)
* @param {int} lastSegmentSpecialsIndex index into specials array to start scanning with
* @return {{ranges:Array.<{text:string, matched:boolean, includesLastSegment:boolean}>, matchGoodness:int, scoreDebug: Object}} matched ranges and score
* @return {Array.<SpecialMatch|NormalMatch>} matched indexes or null if no matches possible
*/
function _wholeStringSearch(query, str, specials, lastSegmentSpecialsIndex) {
// set up query as all lower case and make a lower case string to use for comparisons
Expand Down

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