Source file src/pkg/vendor/golang.org/x/text/unicode/norm/trie.go

     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	}
    55	

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