v8/test/mjsunit/string-externalize.js

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// Flags: --expose-externalize-string

var size = 1024;

function test() {
  var str = "";

  // Build an ascii cons string.
  for (var i = 0; i < size; i++) {
      str += String.fromCharCode(i & 0x7f);
  }
  assertTrue(isAsciiString(str));

  var twoByteExternalWithAsciiData =
      "AA" + (function() { return "A"; })();
  externalizeString(twoByteExternalWithAsciiData, true /* force two-byte */);
  assertFalse(isAsciiString(twoByteExternalWithAsciiData));

  var realTwoByteExternalString =
      "\u1234\u1234" + (function() { return "\u1234"; })();
  externalizeString(realTwoByteExternalString);
  assertFalse(isAsciiString(realTwoByteExternalString));

  assertTrue(isAsciiString(["a", twoByteExternalWithAsciiData].join("")));

  // Appending a two-byte string that contains only ascii chars should
  // still produce an ascii cons.
  var str1 = str + twoByteExternalWithAsciiData;
  assertTrue(isAsciiString(str1));

  // Force flattening of the string.
  var old_length = str1.length - twoByteExternalWithAsciiData.length;
  for (var i = 0; i < old_length; i++) {
    assertEquals(String.fromCharCode(i & 0x7f), str1[i]);
  }
  for (var i = old_length; i < str1.length; i++) {
    assertEquals("A", str1[i]);
  }

  // Flattened string should still be ascii.
  assertTrue(isAsciiString(str1));

  // Lower-casing an ascii string should produce ascii.
  assertTrue(isAsciiString(str1.toLowerCase()));

  assertFalse(isAsciiString(["a", realTwoByteExternalString].join("")));

  // Appending a real two-byte string should produce a two-byte cons.
  var str2 = str + realTwoByteExternalString;
  assertFalse(isAsciiString(str2));

  // Force flattening of the string.
  old_length = str2.length - realTwoByteExternalString.length;
  for (var i = 0; i < old_length; i++) {
    assertEquals(String.fromCharCode(i & 0x7f), str2[i]);
  }
  for (var i = old_length; i < str.length; i++) {
    assertEquals("\u1234", str2[i]);
  }

  // Flattened string should still be two-byte.
  assertFalse(isAsciiString(str2));
}

// Run the test many times to ensure IC-s don't break things.
for (var i = 0; i < 10; i++) {
  test();
}