source: code/trunk/vendor/golang.org/x/net/idna/trieval.go@ 145

// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.

package idna

// This file contains definitions for interpreting the trie value of the idna
// trie generated by "go run gen*.go". It is shared by both the generator
// program and the resultant package. Sharing is achieved by the generator
// copying gen_trieval.go to trieval.go and changing what's above this comment.

// info holds information from the IDNA mapping table for a single rune. It is
// the value returned by a trie lookup. In most cases, all information fits in
// a 16-bit value. For mappings, this value may contain an index into a slice
// with the mapped string. Such mappings can consist of the actual mapped value
// or an XOR pattern to be applied to the bytes of the UTF8 encoding of the
// input rune. This technique is used by the cases packages and reduces the
// table size significantly.
//
// The per-rune values have the following format:
//
//      if mapped {
//        if inlinedXOR {
//          15..13 inline XOR marker
//          12..11 unused
//          10..3  inline XOR mask
//        } else {
//          15..3  index into xor or mapping table
//        }
//      } else {
//          15..14 unused
//          13     mayNeedNorm
//          12..11 attributes
//          10..8  joining type
//           7..3  category type
//      }
//         2  use xor pattern
//      1..0  mapped category
//
// See the definitions below for a more detailed description of the various
// bits.
type info uint16

const (
        catSmallMask = 0x3
        catBigMask   = 0xF8
        indexShift   = 3
        xorBit       = 0x4    // interpret the index as an xor pattern
        inlineXOR    = 0xE000 // These bits are set if the XOR pattern is inlined.

        joinShift = 8
        joinMask  = 0x07

        // Attributes
        attributesMask = 0x1800
        viramaModifier = 0x1800
        modifier       = 0x1000
        rtl            = 0x0800

        mayNeedNorm = 0x2000
)

// A category corresponds to a category defined in the IDNA mapping table.
type category uint16

const (
        unknown              category = 0 // not currently defined in unicode.
        mapped               category = 1
        disallowedSTD3Mapped category = 2
        deviation            category = 3
)

const (
        valid               category = 0x08
        validNV8            category = 0x18
        validXV8            category = 0x28
        disallowed          category = 0x40
        disallowedSTD3Valid category = 0x80
        ignored             category = 0xC0
)

// join types and additional rune information
const (
        joiningL = (iota + 1)
        joiningD
        joiningT
        joiningR

        //the following types are derived during processing
        joinZWJ
        joinZWNJ
        joinVirama
        numJoinTypes
)

func (c info) isMapped() bool {
        return c&0x3 != 0
}

func (c info) category() category {
        small := c & catSmallMask
        if small != 0 {
                return category(small)
        }
        return category(c & catBigMask)
}

func (c info) joinType() info {
        if c.isMapped() {
                return 0
        }
        return (c >> joinShift) & joinMask
}

func (c info) isModifier() bool {
        return c&(modifier|catSmallMask) == modifier
}

func (c info) isViramaModifier() bool {
        return c&(attributesMask|catSmallMask) == viramaModifier
}