mirror of
https://github.com/dart-lang/sdk
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ce4b15c0e9
- bit length - truncate to signed fixed width integer - truncate to unsigned fixed width integer This change is motivated by a program that spends 20-30% of its time here: // TODO(5828): Replace this with a bit-length method on int when available. int n_bitLength = this.n.toRadixString(2).length; See Also https://code.google.com/p/dart/issues/detail?id=5828#c3 https://code.google.com/p/dart/issues/detail?id=6486#c2 https://code.google.com/p/dart/issues/detail?id=5798#c5 https://code.google.com/p/dart/issues/detail?id=12008 R=lrn@google.com, srdjan@google.com Review URL: https://codereview.chromium.org//23645003 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@27269 260f80e4-7a28-3924-810f-c04153c831b5
176 lines
4.1 KiB
Dart
176 lines
4.1 KiB
Dart
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// Testing Bigints.
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library bit_twiddling_test;
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import "package:expect/expect.dart";
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bool haveBigints() {
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return 100000000000000000000 + 1 != 100000000000000000000;
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}
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testBitLength() {
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check(int i, width) {
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Expect.equals(width, i.bitLength, '$i.bitLength == $width');
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// (~i) written as (-i-1) to avoid issues with limited range of dart2js ops.
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Expect.equals(width, (-i-1).bitLength, '(~$i).bitLength == $width');
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}
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check(0, 0);
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check(1, 1);
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check(2, 2);
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check(3, 2);
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check(4, 3);
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check(5, 3);
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check(6, 3);
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check(7, 3);
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check(8, 4);
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check(127, 7);
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check(128, 8);
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check(129, 8);
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check(2147483646, 31);
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check(2147483647, 31);
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check(2147483648, 32);
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check(2147483649, 32);
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check(4294967295, 32);
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check(4294967296, 33);
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check(0xffffffffff, 40);
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check(0xfffffffffff, 44);
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check(0xffffffffffff, 48);
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check(0x1000000000000, 49);
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check(0x1000000000001, 49);
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check(0x1ffffffffffff, 49);
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check(0x2000000000000, 50);
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check(0x2000000000001, 50);
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if (haveBigints()) {
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check(0xffffffffffffff, 56);
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check(0xffffffffffffffff, 64);
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check(0xffffffffffffffffff, 72);
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check(0x1000000000000000000, 73);
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check(0x1000000000000000001, 73);
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check(0xfffffffffffffffffffffffffffffffffffffe, 152);
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check(0xffffffffffffffffffffffffffffffffffffff, 152);
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check(0x100000000000000000000000000000000000000, 153);
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check(0x100000000000000000000000000000000000001, 153);
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}
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}
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testToUnsigned() {
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checkU(src, width, expected) {
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Expect.equals(expected, src.toUnsigned(width));
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}
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checkU(1, 8, 1);
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checkU(0xff, 8, 0xff);
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checkU(0xffff, 8, 0xff);
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checkU(-1, 8, 0xff);
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checkU(0xffffffff, 32, 0xffffffff);
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checkU(0x7fffffff, 30, 0x3fffffff);
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checkU(0x7fffffff, 31, 0x7fffffff);
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checkU(0x7fffffff, 32, 0x7fffffff);
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checkU(0x80000000, 30, 0);
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checkU(0x80000000, 31, 0);
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checkU(0x80000000, 32, 0x80000000);
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checkU(0xffffffff, 30, 0x3fffffff);
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checkU(0xffffffff, 31, 0x7fffffff);
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checkU(0xffffffff, 32, 0xffffffff);
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checkU(0x100000000, 30, 0);
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checkU(0x100000000, 31, 0);
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checkU(0x100000000, 32, 0);
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checkU(0x1ffffffff, 30, 0x3fffffff);
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checkU(0x1ffffffff, 31, 0x7fffffff);
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checkU(0x1ffffffff, 32, 0xffffffff);
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checkU(-1, 0, 0);
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checkU( 0, 0, 0);
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checkU( 1, 0, 0);
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checkU( 2, 0, 0);
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checkU( 3, 0, 0);
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checkU(-1, 1, 1);
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checkU( 0, 1, 0);
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checkU( 1, 1, 1);
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checkU( 2, 1, 0);
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checkU( 3, 1, 1);
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checkU( 4, 1, 0);
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checkU(-1, 2, 3);
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checkU( 0, 2, 0);
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checkU( 1, 2, 1);
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checkU( 2, 2, 2);
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checkU( 3, 2, 3);
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checkU( 4, 2, 0);
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checkU(-1, 3, 7);
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checkU( 0, 3, 0);
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checkU( 1, 3, 1);
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checkU( 2, 3, 2);
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checkU( 3, 3, 3);
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checkU( 4, 3, 4);
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}
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testToSigned() {
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checkS(src, width, expected) {
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Expect.equals(expected, src.toSigned(width),
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'$src.toSigned($width) == $expected');
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}
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checkS(1, 8, 1);
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checkS(0xff, 8, -1);
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checkS(0xffff, 8, -1);
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checkS(-1, 8, -1);
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checkS(128, 8, -128);
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checkS(0xffffffff, 32, -1);
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checkS(0x7fffffff, 30, -1);
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checkS(0x7fffffff, 31, -1);
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checkS(0x7fffffff, 32, 0x7fffffff);
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checkS(0x80000000, 30, 0);
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checkS(0x80000000, 31, 0);
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checkS(0x80000000, 32, -2147483648);
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checkS(0xffffffff, 30, -1);
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checkS(0xffffffff, 31, -1);
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checkS(0xffffffff, 32, -1);
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checkS(0x100000000, 30, 0);
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checkS(0x100000000, 31, 0);
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checkS(0x100000000, 32, 0);
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checkS(0x1ffffffff, 30, -1);
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checkS(0x1ffffffff, 31, -1);
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checkS(0x1ffffffff, 32, -1);
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checkS(-1, 1, -1);
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checkS( 0, 1, 0);
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checkS( 1, 1, -1); // The only bit is the sign bit.
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checkS( 2, 1, 0);
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checkS( 3, 1, -1);
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checkS( 4, 1, 0);
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checkS(-1, 2, -1);
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checkS( 0, 2, 0);
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checkS( 1, 2, 1);
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checkS( 2, 2, -2);
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checkS( 3, 2, -1);
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checkS( 4, 2, 0);
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checkS(-1, 3, -1);
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checkS( 0, 3, 0);
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checkS( 1, 3, 1);
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checkS( 2, 3, 2);
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checkS( 3, 3, 3);
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checkS( 4, 3, -4);
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}
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main() {
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testBitLength();
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testToUnsigned();
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testToSigned();
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}
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