vendor/golang.org/x/net/idna/trieval.go

   1 // Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
   2
   3 package idna
   4
   5 // This file contains definitions for interpreting the trie value of the idna
   6 // trie generated by "go run gen*.go". It is shared by both the generator
   7 // program and the resultant package. Sharing is achieved by the generator
   8 // copying gen_trieval.go to trieval.go and changing what's above this comment.
   9
  10 // info holds information from the IDNA mapping table for a single rune. It is
  11 // the value returned by a trie lookup. In most cases, all information fits in
  12 // a 16-bit value. For mappings, this value may contain an index into a slice
  13 // with the mapped string. Such mappings can consist of the actual mapped value
  14 // or an XOR pattern to be applied to the bytes of the UTF8 encoding of the
  15 // input rune. This technique is used by the cases packages and reduces the
  16 // table size significantly.
  17 //
  18 // The per-rune values have the following format:
  19 //
  20 //   if mapped {
  21 //     if inlinedXOR {
  22 //       15..13 inline XOR marker
  23 //       12..11 unused
  24 //       10..3  inline XOR mask
  25 //     } else {
  26 //       15..3  index into xor or mapping table
  27 //     }
  28 //   } else {
  29 //       15..14 unused
  30 //       13     mayNeedNorm
  31 //       12..11 attributes
  32 //       10..8  joining type
  33 //        7..3  category type
  34 //   }
  35 //      2  use xor pattern
  36 //   1..0  mapped category
  37 //
  38 // See the definitions below for a more detailed description of the various
  39 // bits.
  40 type info uint16
  41
  42 const (
  43         catSmallMask = 0x3
  44         catBigMask   = 0xF8
  45         indexShift   = 3
  46         xorBit       = 0x4    // interpret the index as an xor pattern
  47         inlineXOR    = 0xE000 // These bits are set if the XOR pattern is inlined.
  48
  49         joinShift = 8
  50         joinMask  = 0x07
  51
  52         // Attributes
  53         attributesMask = 0x1800
  54         viramaModifier = 0x1800
  55         modifier       = 0x1000
  56         rtl            = 0x0800
  57
  58         mayNeedNorm = 0x2000
  59 )
  60
  61 // A category corresponds to a category defined in the IDNA mapping table.
  62 type category uint16
  63
  64 const (
  65         unknown              category = 0 // not currently defined in unicode.
  66         mapped               category = 1
  67         disallowedSTD3Mapped category = 2
  68         deviation            category = 3
  69 )
  70
  71 const (
  72         valid               category = 0x08
  73         validNV8            category = 0x18
  74         validXV8            category = 0x28
  75         disallowed          category = 0x40
  76         disallowedSTD3Valid category = 0x80
  77         ignored             category = 0xC0
  78 )
  79
  80 // join types and additional rune information
  81 const (
  82         joiningL = (iota + 1)
  83         joiningD
  84         joiningT
  85         joiningR
  86
  87         //the following types are derived during processing
  88         joinZWJ
  89         joinZWNJ
  90         joinVirama
  91         numJoinTypes
  92 )
  93
  94 func (c info) isMapped() bool {
  95         return c&0x3 != 0
  96 }
  97
  98 func (c info) category() category {
  99         small := c & catSmallMask
 100         if small != 0 {
 101                 return category(small)
 102         }
 103         return category(c & catBigMask)
 104 }
 105
 106 func (c info) joinType() info {
 107         if c.isMapped() {
 108                 return 0
 109         }
 110         return (c >> joinShift) & joinMask
 111 }
 112
 113 func (c info) isModifier() bool {
 114         return c&(modifier|catSmallMask) == modifier
 115 }
 116
 117 func (c info) isViramaModifier() bool {
 118         return c&(attributesMask|catSmallMask) == viramaModifier
 119 }