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Merge pull request #6727 from n8sh/strip-ascii

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Add ASCII fast path to stripLeft & avoid unnecessary decoding
This commit is contained in:
Steven Schveighoffer 2018-10-18 10:49:13 -04:00 • committed by GitHub
commit 4e6f70a134
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1 changed files with 80 additions and 12 deletions
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92
std/string.d
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@ -2937,26 +2937,90 @@ if (isForwardRange!Range && isSomeChar!(ElementEncodingType!Range) &&
{
static import std.ascii;
static import std.uni;
import std.utf : decodeFront;
while (!input.empty)
static if (is(Unqual!(ElementEncodingType!Range) == dchar)
|| is(Unqual!(ElementEncodingType!Range) == wchar))
{
auto c = input.front;
if (std.ascii.isASCII(c))
// Decoding is never needed for dchar. It happens not to be needed
// here for wchar because no whitepace is outside the basic
// multilingual plane meaning every whitespace character is encoded
// with a single wchar and due to the design of UTF-16 those wchars
// will not occur as part of the encoding of multi-wchar codepoints.
static if (isDynamicArray!Range)
{
if (!std.ascii.isWhite(c))
break;
input.popFront();
foreach (i; 0 .. input.length)
{
if (!std.uni.isWhite(input[i]))
return input[i .. $];
}
return input[$ .. $];
}
else
{
auto save = input.save;
auto dc = decodeFront(input);
if (!std.uni.isWhite(dc))
return save;
while (!input.empty)
{
if (!std.uni.isWhite(input.front))
break;
input.popFront();
}
return input;
}
}
else
{
static if (isDynamicArray!Range)
{
// ASCII optimization for dynamic arrays.
size_t i = 0;
for (const size_t end = input.length; i < end; ++i)
{
auto c = input[i];
if (c >= 0x80) goto NonAsciiPath;
if (!std.ascii.isWhite(c)) break;
}
input = input[i .. $];
return input;
NonAsciiPath:
input = input[i .. $];
// Fall through to standard case.
}
static if (ElementType!Range.sizeof > ElementEncodingType!Range.sizeof)
{
// Type performs its own decoding.
while (!input.empty)
{
if (!std.uni.isWhite(input.front))
break;
input.popFront();
}
return input;
}
else
{
// Type doesn't perform its own decoding.
import std.utf : decodeFront, UseReplacementDchar;
while (!input.empty)
{
auto c = input.front;
if (std.ascii.isASCII(c))
{
if (!std.ascii.isWhite(c))
break;
input.popFront();
}
else
{
auto save = input.save;
auto dc = decodeFront!(UseReplacementDchar.yes)(input);
if (!std.uni.isWhite(dc))
return save;
}
}
return input;
}
}
return input;
}
///
@ -2967,6 +3031,8 @@ if (isForwardRange!Range && isSomeChar!(ElementEncodingType!Range) &&
"hello world ");
assert(stripLeft("\n\t\v\rhello world\n\t\v\r") ==
"hello world\n\t\v\r");
assert(stripLeft(" \u2028hello world") ==
"hello world");
assert(stripLeft("hello world") ==
"hello world");
assert(stripLeft([lineSep] ~ "hello world" ~ lineSep) ==
@ -2978,6 +3044,8 @@ if (isForwardRange!Range && isSomeChar!(ElementEncodingType!Range) &&
import std.utf : byChar;
assert(stripLeft(" hello world "w.byChar).array ==
"hello world ");
assert(stripLeft(" \u2022hello world ".byChar).array ==
"\u2022hello world ");
}
auto stripLeft(Range)(auto ref Range str)