Holger Hildebrandt | fa07499 | 2020-03-27 15:42:06 +0000 | [diff] [blame] | 1 | // Copyright 2011 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package norm |
| 6 | |
| 7 | type valueRange struct { |
| 8 | value uint16 // header: value:stride |
| 9 | lo, hi byte // header: lo:n |
| 10 | } |
| 11 | |
| 12 | type sparseBlocks struct { |
| 13 | values []valueRange |
| 14 | offset []uint16 |
| 15 | } |
| 16 | |
| 17 | var nfcSparse = sparseBlocks{ |
| 18 | values: nfcSparseValues[:], |
| 19 | offset: nfcSparseOffset[:], |
| 20 | } |
| 21 | |
| 22 | var nfkcSparse = sparseBlocks{ |
| 23 | values: nfkcSparseValues[:], |
| 24 | offset: nfkcSparseOffset[:], |
| 25 | } |
| 26 | |
| 27 | var ( |
| 28 | nfcData = newNfcTrie(0) |
| 29 | nfkcData = newNfkcTrie(0) |
| 30 | ) |
| 31 | |
| 32 | // lookupValue determines the type of block n and looks up the value for b. |
| 33 | // For n < t.cutoff, the block is a simple lookup table. Otherwise, the block |
| 34 | // is a list of ranges with an accompanying value. Given a matching range r, |
| 35 | // the value for b is by r.value + (b - r.lo) * stride. |
| 36 | func (t *sparseBlocks) lookup(n uint32, b byte) uint16 { |
| 37 | offset := t.offset[n] |
| 38 | header := t.values[offset] |
| 39 | lo := offset + 1 |
| 40 | hi := lo + uint16(header.lo) |
| 41 | for lo < hi { |
| 42 | m := lo + (hi-lo)/2 |
| 43 | r := t.values[m] |
| 44 | if r.lo <= b && b <= r.hi { |
| 45 | return r.value + uint16(b-r.lo)*header.value |
| 46 | } |
| 47 | if b < r.lo { |
| 48 | hi = m |
| 49 | } else { |
| 50 | lo = m + 1 |
| 51 | } |
| 52 | } |
| 53 | return 0 |
| 54 | } |