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3edc601325
Correctness improvements: * UTF errors are handled safely per spec instead of dangerously truncating strings. * There are fewer converter implementations. Performance improvements: * The old code did exact buffer length math, which meant doing UTF math twice on each input string (once for length calculation and another time for conversion). Exact length math is more complicated when handling errors properly, which the old code didn't do. The new code does UTF math on the string content only once (when converting) but risks allocating more than once. There are heuristics in place to lower the probability of reallocation in cases where the double math avoidance isn't enough of a saving to absorb an allocation and memcpy. * Previously, in UTF-16 <-> UTF-8 conversions, an ASCII prefix was optimized but a single non-ASCII code point pessimized the rest of the string. The new code tries to get back on the fast ASCII path. * UTF-16 to Latin1 conversion guarantees less about handling of out-of-range input to eliminate an operation from the inner loop on x86/x86_64. * When assigning to a pre-existing string, the new code tries to reuse the old buffer instead of first releasing the old buffer and then allocating a new one. * When reallocating from the new code, the memcpy covers only the data that is part of the logical length of the old string instead of memcpying the whole capacity. (For old callers old excess memcpy behavior is preserved due to bogus callers. See bug 1472113.) * UTF-8 strings in XPConnect that are in the Latin1 range are passed to SpiderMonkey as Latin1. New features: * Conversion between UTF-8 and Latin1 is added in order to enable faster future interop between Rust code (or otherwise UTF-8-using code) and text node and SpiderMonkey code that uses Latin1. MozReview-Commit-ID: JaJuExfILM9
63 lines
1.6 KiB
C++
63 lines
1.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsAlgorithm_h___
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#define nsAlgorithm_h___
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#include "nsCharTraits.h" // for |nsCharSourceTraits|, |nsCharSinkTraits|
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template <class T>
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inline T
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NS_ROUNDUP(const T& aA, const T& aB)
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{
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return ((aA + (aB - 1)) / aB) * aB;
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}
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// We use these instead of std::min/max because we can't include the algorithm
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// header in all of XPCOM because the stl wrappers will error out when included
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// in parts of XPCOM. These functions should never be used outside of XPCOM.
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template <class T>
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inline const T&
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XPCOM_MIN(const T& aA, const T& aB)
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{
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return aB < aA ? aB : aA;
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}
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// Must return b when a == b in case a is -0
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template <class T>
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inline const T&
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XPCOM_MAX(const T& aA, const T& aB)
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{
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return aA > aB ? aA : aB;
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}
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namespace mozilla {
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template <class T>
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inline const T&
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clamped(const T& aA, const T& aMin, const T& aMax)
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{
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MOZ_ASSERT(aMax >= aMin,
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"clamped(): aMax must be greater than or equal to aMin");
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return XPCOM_MIN(XPCOM_MAX(aA, aMin), aMax);
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}
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} // namespace mozilla
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template <class InputIterator, class T>
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inline uint32_t
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NS_COUNT(InputIterator& aFirst, const InputIterator& aLast, const T& aValue)
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{
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uint32_t result = 0;
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for (; aFirst != aLast; ++aFirst)
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if (*aFirst == aValue) {
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++result;
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}
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return result;
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}
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#endif // !defined(nsAlgorithm_h___)
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