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Merge pull request #1231 from slingamn/buffer.2

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more memory-efficient implementation of line reading
This commit is contained in:
Shivaram Lingamneni 2020-11-30 02:34:25 -08:00 • committed by GitHub
commit db100f1f91
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7 changed files with 231 additions and 45 deletions
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14
irc/history/history.go
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@ -322,18 +322,6 @@ func (list *Buffer) next(index int) int {
}
}
// return n such that v <= n and n == 2**i for some i
func roundUpToPowerOfTwo(v int) int {
// http://graphics.stanford.edu/~seander/bithacks.html
v -= 1
v |= v >> 1
v |= v >> 2
v |= v >> 4
v |= v >> 8
v |= v >> 16
return v + 1
}
func (list *Buffer) maybeExpand() {
if list.window == 0 {
return // autoresize is disabled
@ -353,7 +341,7 @@ func (list *Buffer) maybeExpand() {
return // oldest element is old enough to overwrite
}
newSize := roundUpToPowerOfTwo(length + 1)
newSize := utils.RoundUpToPowerOfTwo(length + 1)
if list.maximumSize < newSize {
newSize = list.maximumSize
}

11
irc/history/history_test.go
View file

@ -241,17 +241,6 @@ func TestDisabledByResize(t *testing.T) {
assertEqual(len(items), 0, t)
}
func TestRoundUp(t *testing.T) {
assertEqual(roundUpToPowerOfTwo(2), 2, t)
assertEqual(roundUpToPowerOfTwo(3), 4, t)
assertEqual(roundUpToPowerOfTwo(64), 64, t)
assertEqual(roundUpToPowerOfTwo(65), 128, t)
assertEqual(roundUpToPowerOfTwo(100), 128, t)
assertEqual(roundUpToPowerOfTwo(1000), 1024, t)
assertEqual(roundUpToPowerOfTwo(1025), 2048, t)
assertEqual(roundUpToPowerOfTwo(269435457), 536870912, t)
}
func BenchmarkInsert(b *testing.B) {
buf := NewHistoryBuffer(1024, 0)
b.ResetTimer()