Add String.replaceRange and use it in replaceFirst{,Mapped}.

R=floitsch@google.com

Review URL: https://codereview.chromium.org//949753005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@44022 260f80e4-7a28-3924-810f-c04153c831b5

Author: lrhn

runtime/lib/string_patch.dart

@@ -572,11 +572,30 @@ class _StringBase {
                         : pattern.allMatches(this, startIndex).iterator;
     if (!iterator.moveNext()) return this;
     Match match = iterator.current;
-    return "${this.substring(0, match.start)}"
-           "$replacement"
-           "${this.substring(match.end)}";
+    return replaceRange(match.start, match.end, replacement);
   }
 
+  String replaceRange(int start, int end, String replacement) {
+    int length = this.length;
+    end = RangeError.checkValidRange(start, end, length);
+    bool replacementIsOneByte = replacement._isOneByte;
+    int replacementLength = replacement.length;
+    int totalLength = start + (length - end) + replacementLength;
+    if (replacementIsOneByte && this._isOneByte) {
+      var result = _OneByteString._allocate(totalLength);
+      int index = 0;
+      index = result._setRange(index, this, 0, start);
+      index = result._setRange(start, replacement, 0, replacementLength);
+      result._setRange(index, this, end, length);
+      return result;
+    }
+    List slices = [];
+    _addReplaceSlice(slices, 0, start);
+    if (replacement.length > 0) slices.add(replacement);
+    _addReplaceSlice(slices, end, length);
+    return _joinReplaceAllResult(this, slices, totalLength,
+                                 replacementIsOneByte);
+  }
 
   static int _addReplaceSlice(List matches, int start, int end) {
     int length = end - start;
@@ -719,23 +738,7 @@ class _StringBase {
     if (!matches.moveNext()) return this;
     var match = matches.current;
     var replacement = "${replace(match)}";
-    var slices = [];
-    int length = 0;
-    if (match.start > 0) {
-      length += _addReplaceSlice(slices, 0, match.start);
-    }
-    slices.add(replacement);
-    length += replacement.length;
-    if (match.end < this.length) {
-      length += _addReplaceSlice(slices, match.end, this.length);
-    }
-    bool replacementIsOneByte = replacement._isOneByte;
-    if (replacementIsOneByte &&
-        length < _maxJoinReplaceOneByteStringLength &&
-        this._isOneByte) {
-      return _joinReplaceAllOneByteResult(this, slices, length);
-    }
-    return _joinReplaceAllResult(this, slices, length, replacementIsOneByte);
+    return replaceRange(match.start, match.end, replacement);
   }
 
   static String _matchString(Match match) => match[0];
@@ -1216,6 +1219,23 @@ class _OneByteString extends _StringBase implements String {
   // This is internal helper method. Code point value must be a valid
   // Latin1 value (0..0xFF), index must be valid.
   void _setAt(int index, int codePoint) native "OneByteString_setAt";
+
+  // Should be optimizable to a memory move.
+  // Accepts both _OneByteString and _ExternalOneByteString as argument.
+  // Returns index after last character written.
+  int _setRange(int index, String oneByteString, int start, int end) {
+    assert(oneByteString._isOneByte);
+    assert(0 <= start);
+    assert(start <= end);
+    assert(end <= oneByteString.length);
+    assert(0 <= index);
+    assert(index + (end - start) <= length);
+    for (int i = start; i < end; i++) {
+      _setAt(index, oneByteString.codeUnitAt(i));
+      index += 1;
+    }
+    return index;
+  }
 }
 
 

sdk/lib/_internal/compiler/js_lib/interceptors.dart

@@ -31,6 +31,7 @@ import 'dart:_js_helper' show allMatchesInStringUnchecked,
                               stringReplaceAllUnchecked,
                               stringReplaceFirstUnchecked,
                               stringReplaceFirstMappedUnchecked,
+                              stringReplaceRangeUnchecked,
                               lookupAndCacheInterceptor,
                               lookupDispatchRecord,
                               StringMatch,

sdk/lib/_internal/compiler/js_lib/js_string.dart

@@ -97,6 +97,14 @@ class JSString extends Interceptor implements String, JSIndexable {
     }
   }
 
+  String replaceRange(int start, int end, String replacement) {
+    checkString(replacement);
+    checkInt(start);
+    end = RangeError.checkValidRange(start, end, this.length);
+    checkInt(end);
+    return stringReplaceRangeUnchecked(this, start, end, replacement);
+  }
+
   List<String> _defaultSplit(Pattern pattern) {
     List<String> result = <String>[];
     // End of most recent match. That is, start of next part to add to result.

sdk/lib/_internal/compiler/js_lib/string_helper.dart

@@ -82,7 +82,7 @@ stringReplaceFirstRE(receiver, regexp, to, startIndex) {
   if (match == null) return receiver;
   var start = match.start;
   var end = match.end;
-  return "${receiver.substring(0,start)}$to${receiver.substring(end)}";
+  return stringReplaceRangeUnchecked(receiver, start, end, to);
 }
 
 const String ESCAPE_REGEXP = r'[[\]{}()*+?.\\^$|]';
@@ -197,8 +197,8 @@ stringReplaceFirstUnchecked(receiver, from, to, int startIndex) {
   if (from is String) {
     int index = receiver.indexOf(from, startIndex);
     if (index < 0) return receiver;
-    return '${receiver.substring(0, index)}$to'
-           '${receiver.substring(index + from.length)}';
+    int end = index + from.length;
+    return stringReplaceRangeUnchecked(receiver, index, end, to);
   }
   if (from is JSSyntaxRegExp) {
     return startIndex == 0 ?
@@ -226,3 +226,10 @@ stringReplaceFirstMappedUnchecked(receiver, from, replace,
 stringJoinUnchecked(array, separator) {
   return JS('String', r'#.join(#)', array, separator);
 }
+
+String stringReplaceRangeUnchecked(String receiver,
+                                   int start, int end, String replacement) {
+  var prefix = JS('String', '#.substring(0, #)', receiver, start);
+  var suffix = JS('String', '#.substring(#)', receiver, end);
+  return "$prefix$replacement$suffix";
+}

sdk/lib/core/string.dart

@@ -476,6 +476,19 @@ abstract class String implements Comparable<String>, Pattern {
    */
   String replaceAllMapped(Pattern from, String replace(Match match));
 
+  /**
+   * Replaces the substring from [start] to [end] with [replacement].
+   *
+   * Returns a new string equivalent to:
+   *
+   *     this.substring(0, start) + replacement + this.substring(end)
+   *
+   * The [start] and [end] indices must specify a valid range of this string.
+   * That is `0 <= start <= end <= this.length`.
+   * If [end] is `null`, it defaults to [length].
+   */
+  String replaceRange(int start, int end, String replacement);
+
   /**
    * Splits the string at matches of [pattern] and returns a list of substrings.
    *

tests/corelib/string_replace_test.dart

@@ -210,6 +210,29 @@ main() {
   var n = new Naughty();
   Expect.throws(
     () => "foo-bar".replaceFirstMapped("bar", (v) { return n; }));
+
+  for (var string in ["", "x", "foo", "x\u2000z"]) {
+    for (var replacement in ["", "foo", string]) {
+      for (int start = 0; start <= string.length; start++) {
+        var expect;
+        for (int end = start; end <= string.length; end++) {
+          expect = string.substring(0, start) +
+                   replacement +
+                   string.substring(end);
+          Expect.equals(expect, string.replaceRange(start, end, replacement),
+                        '"$string"[$start:$end]="$replacement"');
+        }
+        // Reuse expect from "end == string.length" case when omitting end.
+        Expect.equals(expect, string.replaceRange(start, null, replacement),
+                      '"$string"[$start:]="$replacement"');
+      }
+    }
+    Expect.throws(() => string.replaceRange(0, 0, null));
+    Expect.throws(() => string.replaceRange(0, 0, 42));
+    Expect.throws(() => string.replaceRange(0, 0, ["x"]));
+    Expect.throws(() => string.replaceRange(-1, 0, "x"));
+    Expect.throws(() => string.replaceRange(0, string.length + 1, "x"));
+  }
 }
 
 // Fails to return a String on toString, throws if converted by "$naughty".