mirror of
https://github.com/Luzifer/mondash.git
synced 2024-12-23 20:41:17 +00:00
59 lines
2 KiB
Go
59 lines
2 KiB
Go
|
// Copyright 2014 The Go Authors. All rights reserved.
|
||
|
|
// Use of this source code is governed by a BSD-style
|
||
|
|
// license that can be found in the LICENSE file.
|
||
|
|
|
||
|
|
package triegen
|
||
|
|
|
||
|
|
// This file defines Compacter and its implementations.
|
||
|
|
|
||
|
|
import "io"
|
||
|
|
|
||
|
|
// A Compacter generates an alternative, more space-efficient way to store a
|
||
|
|
// trie value block. A trie value block holds all possible values for the last
|
||
|
|
// byte of a UTF-8 encoded rune. Excluding ASCII characters, a trie value block
|
||
|
|
// always has 64 values, as a UTF-8 encoding ends with a byte in [0x80, 0xC0).
|
||
|
|
type Compacter interface {
|
||
|
|
// Size returns whether the Compacter could encode the given block as well
|
||
|
|
// as its size in case it can. len(v) is always 64.
|
||
|
|
Size(v []uint64) (sz int, ok bool)
|
||
|
|
|
||
|
|
// Store stores the block using the Compacter's compression method.
|
||
|
|
// It returns a handle with which the block can be retrieved.
|
||
|
|
// len(v) is always 64.
|
||
|
|
Store(v []uint64) uint32
|
||
|
|
|
||
|
|
// Print writes the data structures associated to the given store to w.
|
||
|
|
Print(w io.Writer) error
|
||
|
|
|
||
|
|
// Handler returns the name of a function that gets called during trie
|
||
|
|
// lookup for blocks generated by the Compacter. The function should be of
|
||
|
|
// the form func (n uint32, b byte) uint64, where n is the index returned by
|
||
|
|
// the Compacter's Store method and b is the last byte of the UTF-8
|
||
|
|
// encoding, where 0x80 <= b < 0xC0, for which to do the lookup in the
|
||
|
|
// block.
|
||
|
|
Handler() string
|
||
|
|
}
|
||
|
|
|
||
|
|
// simpleCompacter is the default Compacter used by builder. It implements a
|
||
|
|
// normal trie block.
|
||
|
|
type simpleCompacter builder
|
||
|
|
|
||
|
|
func (b *simpleCompacter) Size([]uint64) (sz int, ok bool) {
|
||
|
|
return blockSize * b.ValueSize, true
|
||
|
|
}
|
||
|
|
|
||
|
|
func (b *simpleCompacter) Store(v []uint64) uint32 {
|
||
|
|
h := uint32(len(b.ValueBlocks) - blockOffset)
|
||
|
|
b.ValueBlocks = append(b.ValueBlocks, v)
|
||
|
|
return h
|
||
|
|
}
|
||
|
|
|
||
|
|
func (b *simpleCompacter) Print(io.Writer) error {
|
||
|
|
// Structures are printed in print.go.
|
||
|
|
return nil
|
||
|
|
}
|
||
|
|
|
||
|
|
func (b *simpleCompacter) Handler() string {
|
||
|
|
panic("Handler should be special-cased for this Compacter")
|
||
|
|
}
|