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Bug 1247359 - micro-optimize the common case of String{Begins,End}With; r=erahm

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StringBeginsWith (resp. StringEndsWith) takes a defaulted
nsStringComparator object for doing comparisons.  The flexibility this
affords is great, but the cost is not: nsStringComparator has virtual
methods, so initializing that defaulted object (at every callsite)
requires a temporary object whose vtable must be initialized.

Since the overwhemingly common case is to use the default comparator
anyway, we should not use defaulted arguments and instead provide the
default comparator/user-provided comparator cases as separate overloads.
This change eliminates the virtual call for the majority of callsites
and reduces codesize as well.
This commit is contained in:
Nathan Froyd
2016-02-10 14:31:06 -05:00
parent b0c5f158c3
commit c3cd9afb6f
2 changed files with 52 additions and 8 deletions
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44
xpcom/string/nsReadableUtils.cpp
View File

@@ -1026,6 +1026,17 @@ CountCharInReadable(const nsACString& aStr, char aChar)
return count;
}
bool
StringBeginsWith(const nsAString& aSource, const nsAString& aSubstring)
{
nsAString::size_type src_len = aSource.Length(),
sub_len = aSubstring.Length();
if (sub_len > src_len) {
return false;
}
return Substring(aSource, 0, sub_len).Equals(aSubstring);
}
bool
StringBeginsWith(const nsAString& aSource, const nsAString& aSubstring,
const nsStringComparator& aComparator)
@@ -1038,6 +1049,17 @@ StringBeginsWith(const nsAString& aSource, const nsAString& aSubstring,
return Substring(aSource, 0, sub_len).Equals(aSubstring, aComparator);
}
bool
StringBeginsWith(const nsACString& aSource, const nsACString& aSubstring)
{
nsACString::size_type src_len = aSource.Length(),
sub_len = aSubstring.Length();
if (sub_len > src_len) {
return false;
}
return Substring(aSource, 0, sub_len).Equals(aSubstring);
}
bool
StringBeginsWith(const nsACString& aSource, const nsACString& aSubstring,
const nsCStringComparator& aComparator)
@@ -1050,6 +1072,17 @@ StringBeginsWith(const nsACString& aSource, const nsACString& aSubstring,
return Substring(aSource, 0, sub_len).Equals(aSubstring, aComparator);
}
bool
StringEndsWith(const nsAString& aSource, const nsAString& aSubstring)
{
nsAString::size_type src_len = aSource.Length(),
sub_len = aSubstring.Length();
if (sub_len > src_len) {
return false;
}
return Substring(aSource, src_len - sub_len, sub_len).Equals(aSubstring);
}
bool
StringEndsWith(const nsAString& aSource, const nsAString& aSubstring,
const nsStringComparator& aComparator)
@@ -1063,6 +1096,17 @@ StringEndsWith(const nsAString& aSource, const nsAString& aSubstring,
aComparator);
}
bool
StringEndsWith(const nsACString& aSource, const nsACString& aSubstring)
{
nsACString::size_type src_len = aSource.Length(),
sub_len = aSubstring.Length();
if (sub_len > src_len) {
return false;
}
return Substring(aSource, src_len - sub_len, sub_len).Equals(aSubstring);
}
bool
StringEndsWith(const nsACString& aSource, const nsACString& aSubstring,
const nsCStringComparator& aComparator)