35ae65d5d0
Do multiply (mul) and add while tracking that the calculation does not overflow, which can be checked with ok(). The new unit test shows a couple examples. Author: Herb Derby <herb@google.com> Change-Id: I7e67671d2488d67f21d47d9618736a6bae8f23c3 Reviewed-on: https://skia-review.googlesource.com/33721 Reviewed-by: Mike Klein <mtklein@chromium.org> Commit-Queue: Herb Derby <herb@google.com>
52 lines
1.4 KiB
C++
52 lines
1.4 KiB
C++
/*
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* Copyright 2017 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "Test.h"
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#include "SkSafeMath.h"
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DEF_TEST(SafeMath, r) {
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size_t max = std::numeric_limits<size_t>::max();
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{
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size_t halfMax = max >> 1;
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size_t halfMaxPlus1 = halfMax + 1;
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SkSafeMath safe;
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REPORTER_ASSERT(r, safe.add(halfMax, halfMax) == 2 * halfMax);
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REPORTER_ASSERT(r, safe);
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REPORTER_ASSERT(r, safe.add(halfMax, halfMaxPlus1) == max);
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REPORTER_ASSERT(r, safe);
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REPORTER_ASSERT(r, safe.add(max, 1) == 0);
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REPORTER_ASSERT(r, !safe);
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}
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{
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SkSafeMath safe;
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(void) safe.add(max, max);
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REPORTER_ASSERT(r, !safe);
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}
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{
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size_t bits = (sizeof(size_t) * 8);
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size_t halfBits = bits / 2;
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size_t sqrtMax = max >> halfBits;
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size_t sqrtMaxPlus1 = sqrtMax + 1;
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SkSafeMath safe;
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REPORTER_ASSERT(r, safe.mul(sqrtMax, sqrtMax) == sqrtMax * sqrtMax);
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REPORTER_ASSERT(r, safe);
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REPORTER_ASSERT(r, safe.mul(sqrtMax, sqrtMaxPlus1) == sqrtMax << halfBits);
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REPORTER_ASSERT(r, safe);
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REPORTER_ASSERT(r, safe.mul(sqrtMaxPlus1, sqrtMaxPlus1) == 0);
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REPORTER_ASSERT(r, !safe);
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}
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{
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SkSafeMath safe;
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(void) safe.mul(max, max);
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REPORTER_ASSERT(r, !safe);
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}
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}
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