--- /dev/null
+// 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
+
+// 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 decompostion).
+// 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]
+}
+
+// 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.
+func combine(a, b rune) rune {
+ key := uint32(uint16(a))<<16 + uint32(uint16(b))
+ 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
+}
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