From 35ae65d5d04dc3fc75a635c90c5aa9bb1eda3812 Mon Sep 17 00:00:00 2001 From: Herb Derby Date: Fri, 11 Aug 2017 14:00:50 -0400 Subject: SkSafeMath for tracking size_t overflow 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 Change-Id: I7e67671d2488d67f21d47d9618736a6bae8f23c3 Reviewed-on: https://skia-review.googlesource.com/33721 Reviewed-by: Mike Klein Commit-Queue: Herb Derby --- tests/SafeMathTest.cpp | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 tests/SafeMathTest.cpp (limited to 'tests/SafeMathTest.cpp') diff --git a/tests/SafeMathTest.cpp b/tests/SafeMathTest.cpp new file mode 100644 index 0000000000..7f597393d0 --- /dev/null +++ b/tests/SafeMathTest.cpp @@ -0,0 +1,51 @@ +/* + * Copyright 2017 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#include "Test.h" +#include "SkSafeMath.h" + +DEF_TEST(SafeMath, r) { + size_t max = std::numeric_limits::max(); + + { + size_t halfMax = max >> 1; + size_t halfMaxPlus1 = halfMax + 1; + SkSafeMath safe; + REPORTER_ASSERT(r, safe.add(halfMax, halfMax) == 2 * halfMax); + REPORTER_ASSERT(r, safe); + REPORTER_ASSERT(r, safe.add(halfMax, halfMaxPlus1) == max); + REPORTER_ASSERT(r, safe); + REPORTER_ASSERT(r, safe.add(max, 1) == 0); + REPORTER_ASSERT(r, !safe); + } + + { + SkSafeMath safe; + (void) safe.add(max, max); + REPORTER_ASSERT(r, !safe); + } + + { + size_t bits = (sizeof(size_t) * 8); + size_t halfBits = bits / 2; + size_t sqrtMax = max >> halfBits; + size_t sqrtMaxPlus1 = sqrtMax + 1; + SkSafeMath safe; + REPORTER_ASSERT(r, safe.mul(sqrtMax, sqrtMax) == sqrtMax * sqrtMax); + REPORTER_ASSERT(r, safe); + REPORTER_ASSERT(r, safe.mul(sqrtMax, sqrtMaxPlus1) == sqrtMax << halfBits); + REPORTER_ASSERT(r, safe); + REPORTER_ASSERT(r, safe.mul(sqrtMaxPlus1, sqrtMaxPlus1) == 0); + REPORTER_ASSERT(r, !safe); + } + + { + SkSafeMath safe; + (void) safe.mul(max, max); + REPORTER_ASSERT(r, !safe); + } +} -- cgit v1.2.3