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Improve Appender growth scheme.

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monarch dodra 2013-07-12 18:10:39 +02:00 • committed by monarchdodra
parent 395b72204e
commit 0b8302b68d
1 changed files with 10 additions and 5 deletions
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15
std/array.d
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@ -2234,14 +2234,19 @@ struct Appender(A : T[], T)
// ensure we can add nelems elements, resizing as necessary // ensure we can add nelems elements, resizing as necessary
private void ensureAddable(size_t nelems) @safe pure nothrow private void ensureAddable(size_t nelems) @safe pure nothrow
{ {
static size_t newCapacity(size_t newlength) @safe pure nothrow //Calculates an efficient growth scheme based on the old capacity
//of data, and the minimum requested capacity.
//arg curLen: The current length
//arg reqLen: The length as requested by the user
//ret sugLen: A suggested growth.
static size_t newCapacity(size_t curLen, size_t reqLen) @safe pure nothrow
{ {
long mult = 100 + (1000L) / (bsr(newlength * T.sizeof) + 1); long mult = 100 + (1000L) / (bsr(curLen * T.sizeof) + 1);
// limit to doubling the length, we don't want to grow too much // limit to doubling the length, we don't want to grow too much
if(mult > 200) if(mult > 200)
mult = 200; mult = 200;
auto newext = cast(size_t)((newlength * mult + 99) / 100); auto sugLen = cast(size_t)((curLen * mult + 99) / 100);
return newext > newlength ? newext : newlength; return max(reqLen, sugLen);
} }
if (!_data) if (!_data)
@ -2274,7 +2279,7 @@ struct Appender(A : T[], T)
// Time to reallocate. // Time to reallocate.
// We need to almost duplicate what's in druntime, except we // We need to almost duplicate what's in druntime, except we
// have better access to the capacity field. // have better access to the capacity field.
auto newlen = newCapacity(reqlen); auto newlen = newCapacity(_data.capacity, reqlen);
// first, try extending the current block // first, try extending the current block
auto u = ()@trusted{ return auto u = ()@trusted{ return
GC.extend(_data.arr.ptr, nelems * T.sizeof, (newlen - len) * T.sizeof); GC.extend(_data.arr.ptr, nelems * T.sizeof, (newlen - len) * T.sizeof);