// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package norm
import "encoding/binary"
// This file contains Form-specific logic and wrappers for data in tables.go.
// Rune info is stored in a separate trie per composing form. A composing form
// and its corresponding decomposing form share the same trie. Each trie maps
// a rune to a uint16. The values take two forms. For v >= 0x8000:
// bits
// 15: 1 (inverse of NFD_QC bit of qcInfo)
// 13..7: qcInfo (see below). isYesD is always true (no decomposition).
// 6..0: ccc (compressed CCC value).
// For v < 0x8000, the respective rune has a decomposition and v is an index
// into a byte array of UTF-8 decomposition sequences and additional info and
// has the form:
// <header> <decomp_byte>* [<tccc> [<lccc>]]
// The header contains the number of bytes in the decomposition (excluding this
// length byte). The two most significant bits of this length byte correspond
// to bit 5 and 4 of qcInfo (see below). The byte sequence itself starts at v+1.
// The byte sequence is followed by a trailing and leading CCC if the values
// for these are not zero. The value of v determines which ccc are appended
// to the sequences. For v < firstCCC, there are none, for v >= firstCCC,
// the sequence is followed by a trailing ccc, and for v >= firstLeadingCC
// there is an additional leading ccc. The value of tccc itself is the
// trailing CCC shifted left 2 bits. The two least-significant bits of tccc
// are the number of trailing non-starters.
const (
qcInfoMask = 0x3F // to clear all but the relevant bits in a qcInfo
headerLenMask = 0x3F // extract the length value from the header byte
headerFlagsMask = 0xC0 // extract the qcInfo bits from the header byte
)
// Properties provides access to normalization properties of a rune.
type Properties struct {
pos uint8 // start position in reorderBuffer; used in composition.go
size uint8 // length of UTF-8 encoding of this rune
ccc uint8 // leading canonical combining class (ccc if not decomposition)
tccc uint8 // trailing canonical combining class (ccc if not decomposition)
nLead uint8 // number of leading non-starters.
flags qcInfo // quick check flags
index uint16
}
// functions dispatchable per form
type lookupFunc func(b input, i int) Properties
// formInfo holds Form-specific functions and tables.
type formInfo struct {
form Form
composing, compatibility bool // form type
info lookupFunc
nextMain iterFunc
}
var formTable = []*formInfo{{
form: NFC,
composing: true,
compatibility: false,
info: lookupInfoNFC,
nextMain: nextComposed,
}, {
form: NFD,
composing: false,
compatibility: false,
info: lookupInfoNFC,
nextMain: nextDecomposed,
}, {
form: NFKC,
composing: true,
compatibility: true,
info: lookupInfoNFKC,
nextMain: nextComposed,
}, {
form: NFKD,
composing: false,
compatibility: true,
info: lookupInfoNFKC,
nextMain: nextDecomposed,
}}
// We do not distinguish between boundaries for NFC, NFD, etc. to avoid
// unexpected behavior for the user. For example, in NFD, there is a boundary
// after 'a'. However, 'a' might combine with modifiers, so from the application's
// perspective it is not a good boundary. We will therefore always use the
// boundaries for the combining variants.
// BoundaryBefore returns true if this rune starts a new segment and
// cannot combine with any rune on the left.
func (p Properties) BoundaryBefore() bool {
if p.ccc == 0 && !p.combinesBackward() {
return true
}
// We assume that the CCC of the first character in a decomposition
// is always non-zero if different from info.ccc and that we can return
// false at this point. This is verified by maketables.
return false
}
// BoundaryAfter returns true if runes cannot combine with or otherwise
// interact with this or previous runes.
func (p Properties) BoundaryAfter() bool {
// TODO: loosen these conditions.
return p.isInert()
}
// We pack quick check data in 4 bits:
//
// 5: Combines forward (0 == false, 1 == true)
// 4..3: NFC_QC Yes(00), No (10), or Maybe (11)
// 2: NFD_QC Yes (0) or No (1). No also means there is a decomposition.
// 1..0: Number of trailing non-starters.
//
// When all 4 bits are zero, the character is inert, meaning it is never
// influenced by normalization.
type qcInfo uint8
func (p Properties) isYesC() bool { return p.flags&0x10 == 0 }
func (p Properties) isYesD() bool { return p.flags&0x4 == 0 }
func (p Properties) combinesForward() bool { return p.flags&0x20 != 0 }
func (p Properties) combinesBackward() bool { return p.flags&0x8 != 0 } // == isMaybe
func (p Properties) hasDecomposition() bool { return p.flags&0x4 != 0 } // == isNoD
func (p Properties) isInert() bool {
return p.flags&qcInfoMask == 0 && p.ccc == 0
}
func (p Properties) multiSegment() bool {
return p.index >= firstMulti && p.index < endMulti
}
func (p Properties) nLeadingNonStarters() uint8 {
return p.nLead
}
func (p Properties) nTrailingNonStarters() uint8 {
return uint8(p.flags & 0x03)
}
// Decomposition returns the decomposition for the underlying rune
// or nil if there is none.
func (p Properties) Decomposition() []byte {
// TODO: create the decomposition for Hangul?
if p.index == 0 {
return nil
}
i := p.index
n := decomps[i] & headerLenMask
i++
return decomps[i : i+uint16(n)]
}
// Size returns the length of UTF-8 encoding of the rune.
func (p Properties) Size() int {
return int(p.size)
}
// CCC returns the canonical combining class of the underlying rune.
func (p Properties) CCC() uint8 {
if p.index >= firstCCCZeroExcept {
return 0
}
return ccc[p.ccc]
}
// LeadCCC returns the CCC of the first rune in the decomposition.
// If there is no decomposition, LeadCCC equals CCC.
func (p Properties) LeadCCC() uint8 {
return ccc[p.ccc]
}
// TrailCCC returns the CCC of the last rune in the decomposition.
// If there is no decomposition, TrailCCC equals CCC.
func (p Properties) TrailCCC() uint8 {
return ccc[p.tccc]
}
func buildRecompMap() {
recompMap = make(map[uint32]rune, len(recompMapPacked)/8)
var buf [8]byte
for i := 0; i < len(recompMapPacked); i += 8 {
copy(buf[:], recompMapPacked[i:i+8])
key := binary.BigEndian.Uint32(buf[:4])
val := binary.BigEndian.Uint32(buf[4:])
recompMap[key] = rune(val)
}
}
// Recomposition
// We use 32-bit keys instead of 64-bit for the two codepoint keys.
// This clips off the bits of three entries, but we know this will not
// result in a collision. In the unlikely event that changes to
// UnicodeData.txt introduce collisions, the compiler will catch it.
// Note that the recomposition map for NFC and NFKC are identical.
// combine returns the combined rune or 0 if it doesn't exist.
//
// The caller is responsible for calling
// recompMapOnce.Do(buildRecompMap) sometime before this is called.
func combine(a, b rune) rune {
key := uint32(uint16(a))<<16 + uint32(uint16(b))
if recompMap == nil {
panic("caller error") // see func comment
}
return recompMap[key]
}
func lookupInfoNFC(b input, i int) Properties {
v, sz := b.charinfoNFC(i)
return compInfo(v, sz)
}
func lookupInfoNFKC(b input, i int) Properties {
v, sz := b.charinfoNFKC(i)
return compInfo(v, sz)
}
// Properties returns properties for the first rune in s.
func (f Form) Properties(s []byte) Properties {
if f == NFC || f == NFD {
return compInfo(nfcData.lookup(s))
}
return compInfo(nfkcData.lookup(s))
}
// PropertiesString returns properties for the first rune in s.
func (f Form) PropertiesString(s string) Properties {
if f == NFC || f == NFD {
return compInfo(nfcData.lookupString(s))
}
return compInfo(nfkcData.lookupString(s))
}
// compInfo converts the information contained in v and sz
// to a Properties. See the comment at the top of the file
// for more information on the format.
func compInfo(v uint16, sz int) Properties {
if v == 0 {
return Properties{size: uint8(sz)}
} else if v >= 0x8000 {
p := Properties{
size: uint8(sz),
ccc: uint8(v),
tccc: uint8(v),
flags: qcInfo(v >> 8),
}
if p.ccc > 0 || p.combinesBackward() {
p.nLead = uint8(p.flags & 0x3)
}
return p
}
// has decomposition
h := decomps[v]
f := (qcInfo(h&headerFlagsMask) >> 2) | 0x4
p := Properties{size: uint8(sz), flags: f, index: v}
if v >= firstCCC {
v += uint16(h&headerLenMask) + 1
c := decomps[v]
p.tccc = c >> 2
p.flags |= qcInfo(c & 0x3)
if v >= firstLeadingCCC {
p.nLead = c & 0x3
if v >= firstStarterWithNLead {
// We were tricked. Remove the decomposition.
p.flags &= 0x03
p.index = 0
return p
}
p.ccc = decomps[v+1]
}
}
return p
}
