Faster ascii string case conversion.

test/mjsunit/string-case.js

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+// Flags: --random-seed=17
+
 assertEquals("ΚΟΣΜΟΣ ΚΟΣΜΟΣ".toLowerCase(), "κοσμος κοσμος");
+
+var A_CODE = "A".charCodeAt(0);
+var Z_CODE = "Z".charCodeAt(0);
+var a_CODE = "a".charCodeAt(0);
+var z_CODE = "z".charCodeAt(0);
+
+function charCodeToLower(charCode) {
+  if (A_CODE <= charCode && charCode <= Z_CODE) {
+    return charCode + a_CODE - A_CODE;
+  }
+  return charCode;
+}
+
+function charCodeToUpper(charCode) {
+  if (a_CODE <= charCode && charCode <= z_CODE) {
+    return charCode - (a_CODE - A_CODE);
+  }
+  return charCode;
+}
+
+function generator(i, j) {
+  return Math.min(0x7f, i + j);
+}
+
+function randomGenerator(i, j) {

[antonm, 2010/10/26 17:17:33]

I don't think you have to declare unused arguments here (at least JS allows
that).  I find them somewhat misleading, but up to you.

[Vitaly Repeshko, 2010/10/26 18:14:48]

Obsolete.

+  return Math.round(0x7f * Math.random());
+}
+
+function test(generator, length) {
+  for (var i = 0; i < 0x7f; i++) {
+    var str = "";
+    var strLower = "";
+    var strUpper = "";
+    for (var j = 0; j < length; j++) {
+      var c = generator(i, j);
+      str += String.fromCharCode(c);
+      strLower += String.fromCharCode(charCodeToLower(c));
+      strUpper += String.fromCharCode(charCodeToUpper(c));
+    }
+    assertEquals(strLower, str.toLowerCase());
+    assertEquals(strUpper, str.toUpperCase());
+  }
+}
+
+for (var i = 1; i <= 1024; i <<= 1); {
+  for (var j = 0; j < 10; j++) {
+    test(generator, i + j);

[antonm, 2010/10/26 17:17:33]

I am slightly concerned that string pattern for this case is too regular, for
example, you only cases when string starts with lower case chars (0 or more)
than has a region of upper case chars and again lower case.  Maybe I'd only
leave pseudo-random generator, but up to you.

[Vitaly Repeshko, 2010/10/26 18:14:48]

You're right. I dropped the half-baked deterministic part of the test and
increased the number of passes to exercise more inputs using the random number
generator. A nice side effect of this is that the test no longer timeouts on
ARM.

+    test(randomGenerator, i + j);
+  }
+}