mirror of
https://github.com/Luzifer/mondash.git
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117 lines
2.7 KiB
Go
117 lines
2.7 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build ignore
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// Trie table generator.
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// Used by make*tables tools to generate a go file with trie data structures
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// for mapping UTF-8 to a 16-bit value. All but the last byte in a UTF-8 byte
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// sequence are used to lookup offsets in the index table to be used for the
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// next byte. The last byte is used to index into a table with 16-bit values.
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package main
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import (
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"fmt"
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"io"
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)
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const maxSparseEntries = 16
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type normCompacter struct {
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sparseBlocks [][]uint64
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sparseOffset []uint16
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sparseCount int
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name string
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}
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func mostFrequentStride(a []uint64) int {
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counts := make(map[int]int)
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var v int
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for _, x := range a {
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if stride := int(x) - v; v != 0 && stride >= 0 {
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counts[stride]++
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}
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v = int(x)
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}
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var maxs, maxc int
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for stride, cnt := range counts {
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if cnt > maxc || (cnt == maxc && stride < maxs) {
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maxs, maxc = stride, cnt
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}
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}
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return maxs
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}
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func countSparseEntries(a []uint64) int {
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stride := mostFrequentStride(a)
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var v, count int
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for _, tv := range a {
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if int(tv)-v != stride {
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if tv != 0 {
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count++
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}
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}
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v = int(tv)
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}
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return count
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}
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func (c *normCompacter) Size(v []uint64) (sz int, ok bool) {
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if n := countSparseEntries(v); n <= maxSparseEntries {
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return (n+1)*4 + 2, true
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}
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return 0, false
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}
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func (c *normCompacter) Store(v []uint64) uint32 {
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h := uint32(len(c.sparseOffset))
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c.sparseBlocks = append(c.sparseBlocks, v)
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c.sparseOffset = append(c.sparseOffset, uint16(c.sparseCount))
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c.sparseCount += countSparseEntries(v) + 1
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return h
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}
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func (c *normCompacter) Handler() string {
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return c.name + "Sparse.lookup"
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}
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func (c *normCompacter) Print(w io.Writer) (retErr error) {
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p := func(f string, x ...interface{}) {
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if _, err := fmt.Fprintf(w, f, x...); retErr == nil && err != nil {
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retErr = err
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}
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}
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ls := len(c.sparseBlocks)
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p("// %sSparseOffset: %d entries, %d bytes\n", c.name, ls, ls*2)
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p("var %sSparseOffset = %#v\n\n", c.name, c.sparseOffset)
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ns := c.sparseCount
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p("// %sSparseValues: %d entries, %d bytes\n", c.name, ns, ns*4)
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p("var %sSparseValues = [%d]valueRange {", c.name, ns)
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for i, b := range c.sparseBlocks {
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p("\n// Block %#x, offset %#x", i, c.sparseOffset[i])
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var v int
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stride := mostFrequentStride(b)
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n := countSparseEntries(b)
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p("\n{value:%#04x,lo:%#02x},", stride, uint8(n))
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for i, nv := range b {
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if int(nv)-v != stride {
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if v != 0 {
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p(",hi:%#02x},", 0x80+i-1)
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}
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if nv != 0 {
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p("\n{value:%#04x,lo:%#02x", nv, 0x80+i)
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}
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}
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v = int(nv)
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}
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if v != 0 {
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p(",hi:%#02x},", 0x80+len(b)-1)
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}
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}
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p("\n}\n\n")
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return
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}
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