Tentative implementation of string slices (hidden under the flag --string-slices).

test/mjsunit/string-slices.js

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[Yang, 2011/07/27 11:51:58]

Mostly a copy of test/mjsunit/substr.js, but using --string-slices flag and a
few additional tests.

+// Flags: --string-slices
+
 var s = 'abcdefghijklmn';
 assertEquals(s, s.substr());
 assertEquals(s, s.substr(0));
 assertEquals(s, s.substr('0'));
 assertEquals(s, s.substr(void 0));
 assertEquals(s, s.substr(null));
 assertEquals(s, s.substr(false));
 assertEquals(s, s.substr(0.9));
 assertEquals(s, s.substr({ valueOf: function() { return 0; } }));
 assertEquals(s, s.substr({ toString: function() { return '0'; } }));
@@ skipping 25 matching lines @@
 
 
 // Test substrings of different lengths and alignments.
 // First ASCII.
 var x = "ASCII";
 for (var i = 0; i < 25; i++) {
   x += (i >> 4).toString(16) + (i & 0x0f).toString(16);
 }
 /x/.exec(x);  // Try to force a flatten.
 for (var i = 5; i < 25; i++) {
-  for (var j = 0; j < 25; j++) {
+  for (var j = 12; j < 25; j++) {
     var z = x.substring(i, i+j);
     var w = Math.random() * 42;  // Allocate something new in new-space.
     assertEquals(j, z.length);
     for (var k = 0; k < j; k++) {
       assertEquals(x.charAt(i+k), z.charAt(k));
     }
   }
 }
-
-
 // Then two-byte strings.
 x = "UC16\u2028";  // Non-ascii char forces two-byte string.
 for (var i = 0; i < 25; i++) {
   x += (i >> 4).toString(16) + (i & 0x0f).toString(16);
 }
 /x/.exec(x);  // Try to force a flatten.
 for (var i = 5; i < 25; i++) {
   for (var j = 0; j < 25; j++) {
     var z = x.substring(i, i + j);
     var w = Math.random() * 42;  // Allocate something new in new-space.
     assertEquals(j, z.length);
     for (var k = 0; k < j; k++) {
       assertEquals(x.charAt(i+k), z.charAt(k));
     }
   }
 }
 
-
 // Keep creating strings to to force allocation failure on substring creation.
 var x = "0123456789ABCDEF";
 x += x;  // 2^5
 x += x;
 x += x;
 x += x;
 x += x;
 x += x;  // 2^10
 x += x;
 x += x;
@@ skipping 16 matching lines @@
 x += x;  // 2^10
 x += x;
 x += x;
 var xl = x.length;
 var cache = [];
 for (var i = 0; i < 10000; i++) {
   var z = x.substring(i % xl);
   assertEquals(xl - (i % xl), z.length);
   cache.push(z);
 }
+
+// Substring of substring.
+var cache = [];
+var last = x;
+var offset = 0;
+for (var i = 0; i < 64; i++) {
+  var z = last.substring(i);
+  last = z;
+  cache.push(z);
+  offset += i;
+}
+for (var i = 63; i >= 0; i--) {
+  var z = cache.pop();
+  assertTrue(/\u2028123456789ABCDEF/.test(z));
+  assertEquals(xl - offset, z.length);
+  offset -= i;
+}
+
+//Test charAt for different strings.

[antonm, 2011/07/27 12:16:39]

nit: missing space before Test.

+flat = "abcdefghijkl12345";
+cons = flat + flat.toUpperCase();
+slice = "abcdefghijklmn12345".slice(1, -1);
+for ( var i = 0; i < 50; i++) {

[antonm, 2011/07/27 12:16:39]

nit: unnecessary space after ( (here and below)

+        assertEquals(String.fromCharCode(97+i%11), flat.charAt(i%11));
+        assertEquals(String.fromCharCode(97+i%11), cons.charAt(i%11));
+        assertEquals(String.fromCharCode(98+i%11), slice.charAt(i%11));
+        assertEquals(String.fromCharCode(101), slice.charAt(3));
+}
+flat = "abcdefghijkl1\u20232345";
+cons = flat + flat.toUpperCase();
+slice = "abcdefghijklmn1\u20232345".slice(1, -1);
+for ( var i = 0; i < 50; i++) {
+        assertEquals(String.fromCharCode(97+i%11), flat.charAt(i%11));
+        assertEquals(String.fromCharCode(97+i%11), cons.charAt(i%11));
+        assertEquals(String.fromCharCode(98+i%11), slice.charAt(i%11));
+        assertEquals(String.fromCharCode(101), slice.charAt(3));
+}
+
+// Concatenate substrings.
+var ascii = 'abcdefghijklmnop';
+var utf = '\u03B1\u03B2\u03B3\u03B4\u03B5\u03B6\u03B7\u03B8\u03B9\u03BA\u03BB';
+assertEquals("klmno", ascii.substring(10,15) + ascii.substring(16));
+assertEquals("\u03B4\u03B7", utf.substring(3,4) + utf.substring(6,7));
+assertEquals("klp", ascii.substring(10,12) + ascii.substring(15,16));
+assertEquals("\u03B1\u03B4\u03B5", utf.substring(0,1) + utf.substring(5,3));
+assertEquals("", ascii.substring(16) + utf.substring(16));
+assertEquals("bcdef\u03B4\u03B5\u03B6\u03B7\u03B8\u03B9",
+        ascii.substring(1,6) + utf.substring(3,9));
+assertEquals("\u03B4\u03B5\u03B6\u03B7\u03B8\u03B9abcdefghijklmnop",
+    utf.substring(3,9) + ascii);
+assertEquals("\u03B2\u03B3\u03B4\u03B5\u03B4\u03B5\u03B6\u03B7",
+    utf.substring(5,1) + utf.substring(3,7));
+