forked from mirror/brotli
44 lines
1.2 KiB
Go
44 lines
1.2 KiB
Go
|
package brotli
|
||
|
|
|
||
|
|
/* Copyright 2013 Google Inc. All Rights Reserved.
|
||
|
|
|
||
|
|
Distributed under MIT license.
|
||
|
|
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* Block split point selection utilities. */
|
||
|
|
/* Copyright 2013 Google Inc. All Rights Reserved.
|
||
|
|
|
||
|
|
Distributed under MIT license.
|
||
|
|
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* Functions for clustering similar histograms together. */
|
||
|
|
type HistogramPair struct {
|
||
|
|
idx1 uint32
|
||
|
|
idx2 uint32
|
||
|
|
cost_combo float64
|
||
|
|
cost_diff float64
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Copyright 2013 Google Inc. All Rights Reserved.
|
||
|
|
|
||
|
|
Distributed under MIT license.
|
||
|
|
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* Functions for clustering similar histograms together. */
|
||
|
|
func HistogramPairIsLess(p1 *HistogramPair, p2 *HistogramPair) bool {
|
||
|
|
if p1.cost_diff != p2.cost_diff {
|
||
|
|
return p1.cost_diff > p2.cost_diff
|
||
|
|
}
|
||
|
|
|
||
|
|
return (p1.idx2 - p1.idx1) > (p2.idx2 - p2.idx1)
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Returns entropy reduction of the context map when we combine two clusters. */
|
||
|
|
func ClusterCostDiff(size_a uint, size_b uint) float64 {
|
||
|
|
var size_c uint = size_a + size_b
|
||
|
|
return float64(size_a)*FastLog2(size_a) + float64(size_b)*FastLog2(size_b) - float64(size_c)*FastLog2(size_c)
|
||
|
|
}
|