nagai/fune
3
0
Fork 0
forked from mirrors/gecko-dev
Code Pull requests Activity

Bug 1641827 - Simplify implementations of RemoveLastElement and TruncateLength. r=froydnj

Browse source 
Differential Revision: https://phabricator.services.mozilla.com/D77760
This commit is contained in:
Simon Giesecke 2020-06-03 08:09:17 +00:00
parent 7c486e2ce0
commit 70ed1b7b2a
1 changed files with 40 additions and 10 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

50
xpcom/ds/nsTArray.h
View file

@ -1788,12 +1788,27 @@ class nsTArray_Impl
void RemoveElementAt(index_type aIndex) { RemoveElementsAt(aIndex, 1); }
// A variation on the RemoveElementAt that removes the last element.
void RemoveLastElement() { RemoveElementAt(Length() - 1); }
void RemoveLastElement() {
// This assertion is redundant, but produces a better error message than the
// release assertion within TruncateLength.
MOZ_ASSERT(!base_type::IsEmpty());
TruncateLength(Length() - 1);
}
// Removes the last element of the array and returns a copy of it.
[[nodiscard]] elem_type PopLastElement() {
elem_type elem = std::move(LastElement());
RemoveLastElement();
// This function intentionally does not call ElementsAt and calls
// TruncateLengthUnsafe directly to avoid multiple release checks for
// non-emptiness.
// This debug assertion is redundant, but produces a better error message
// than the release assertion below.
MOZ_ASSERT(!base_type::IsEmpty());
const size_type oldLen = Length();
if (MOZ_UNLIKELY(0 == oldLen)) {
InvalidArrayIndex_CRASH(1, 0);
}
elem_type elem = std::move(Elements()[oldLen - 1]);
TruncateLengthUnsafe(oldLen - 1);
return elem;
}
@ -2132,19 +2147,19 @@ class nsTArray_Impl
// removes elements from the array (see also RemoveElementsAt).
// @param aNewLen The desired length of this array.
// @return True if the operation succeeded; false otherwise.
// See also TruncateLength if the new length is guaranteed to be smaller than
// the old.
// See also TruncateLength for a more efficient variant if the new length is
// guaranteed to be smaller than the old.
protected:
template <typename ActualAlloc = Alloc>
typename ActualAlloc::ResultType SetLength(size_type aNewLen) {
size_type oldLen = Length();
const size_type oldLen = Length();
if (aNewLen > oldLen) {
return ActualAlloc::ConvertBoolToResultType(
InsertElementsAtInternal<ActualAlloc>(oldLen, aNewLen - oldLen) !=
nullptr);
}
TruncateLength(aNewLen);
TruncateLengthUnsafe(aNewLen);
return ActualAlloc::ConvertBoolToResultType(true);
}
@ -2160,9 +2175,24 @@ class nsTArray_Impl
// RemoveElementsAt).
// @param aNewLen The desired length of this array.
void TruncateLength(size_type aNewLen) {
size_type oldLen = Length();
MOZ_ASSERT(aNewLen <= oldLen, "caller should use SetLength instead");
RemoveElementsAt(aNewLen, oldLen - aNewLen);
// This assertion is redundant, but produces a better error message than the
// release assertion below.
MOZ_ASSERT(aNewLen <= Length(), "caller should use SetLength instead");
if (MOZ_UNLIKELY(aNewLen > Length())) {
InvalidArrayIndex_CRASH(aNewLen, Length());
}
TruncateLengthUnsafe(aNewLen);
}
private:
void TruncateLengthUnsafe(size_type aNewLen) {
const size_type oldLen = Length();
if (oldLen) {
DestructRange(aNewLen, oldLen - aNewLen);
base_type::mHdr->mLength = aNewLen;
}
}
// This method ensures that the array has length at least the given