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Fix Issue 21559 - Speed up walkLength for narrow strings

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This commit is contained in:
Nathan Sashihara 2021-01-19 10:30:00 -05:00
parent 54f224a03d
commit 3733c9d202
2 changed files with 30 additions and 1 deletions
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28
std/range/primitives.d
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@ -1750,6 +1750,20 @@ if (isInputRange!Range && !isInfinite!Range)
else else
{ {
size_t result; size_t result;
static if (autodecodeStrings && isNarrowString!Range)
{
import std.utf : codeUnitLimit;
result = range.length;
foreach (const i, const c; range)
{
if (c >= codeUnitLimit!Range)
{
result = i;
break;
}
}
range = range[result .. $];
}
for ( ; !range.empty ; range.popFront() ) for ( ; !range.empty ; range.popFront() )
++result; ++result;
return result; return result;
@ -1766,6 +1780,20 @@ if (isInputRange!Range)
else else
{ {
size_t result; size_t result;
static if (autodecodeStrings && isNarrowString!Range)
{
import std.utf : codeUnitLimit;
result = upTo > range.length ? range.length : upTo;
foreach (const i, const c; range[0 .. result])
{
if (c >= codeUnitLimit!Range)
{
result = i;
break;
}
}
range = range[result .. $];
}
for ( ; result < upTo && !range.empty ; range.popFront() ) for ( ; result < upTo && !range.empty ; range.popFront() )
++result; ++result;
return result; return result;

3
std/utf.d
View file

@ -1410,7 +1410,8 @@ do
assert(str.decodeBack(i) == 'å' && i == 2 && str.empty); assert(str.decodeBack(i) == 'å' && i == 2 && str.empty);
} }
// Gives the maximum value that a code unit for the given range type can hold. // For the given range, code unit values less than this
// are guaranteed to be valid single-codepoint encodings.
package template codeUnitLimit(S) package template codeUnitLimit(S)
if (isSomeChar!(ElementEncodingType!S)) if (isSomeChar!(ElementEncodingType!S))
{ {