trie.go

     1  // Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
     2  
     3  // Copyright 2016 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  package idna
     8  
     9  // Sparse block handling code.
    10  
    11  type valueRange struct {
    12  	value  uint16 // header: value:stride
    13  	lo, hi byte   // header: lo:n
    14  }
    15  
    16  type sparseBlocks struct {
    17  	values []valueRange
    18  	offset []uint16
    19  }
    20  
    21  var idnaSparse = sparseBlocks{
    22  	values: idnaSparseValues[:],
    23  	offset: idnaSparseOffset[:],
    24  }
    25  
    26  // Don't use newIdnaTrie to avoid unconditional linking in of the table.
    27  var trie = &idnaTrie{}
    28  
    29  // lookup determines the type of block n and looks up the value for b.
    30  // For n < t.cutoff, the block is a simple lookup table. Otherwise, the block
    31  // is a list of ranges with an accompanying value. Given a matching range r,
    32  // the value for b is by r.value + (b - r.lo) * stride.
    33  func (t *sparseBlocks) lookup(n uint32, b byte) uint16 {
    34  	offset := t.offset[n]
    35  	header := t.values[offset]
    36  	lo := offset + 1
    37  	hi := lo + uint16(header.lo)
    38  	for lo < hi {
    39  		m := lo + (hi-lo)/2
    40  		r := t.values[m]
    41  		if r.lo <= b && b <= r.hi {
    42  			return r.value + uint16(b-r.lo)*header.value
    43  		}
    44  		if b < r.lo {
    45  			hi = m
    46  		} else {
    47  			lo = m + 1
    48  		}
    49  	}
    50  	return 0
    51  }
    52
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