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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [exp/] [norm/] [forminfo.go] - Rev 861
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// 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.
type runeInfo struct {
pos uint8 // start position in reorderBuffer; used in composition.go
size uint8 // length of UTF-8 encoding of this rune
ccc uint8 // canonical combining class
flags qcInfo // quick check flags
}
// functions dispatchable per form
type lookupFunc func(b input, i int) runeInfo
type decompFunc func(b input, i int) []byte
// formInfo holds Form-specific functions and tables.
type formInfo struct {
form Form
composing, compatibility bool // form type
decompose decompFunc
info lookupFunc
}
var formTable []*formInfo
func init() {
formTable = make([]*formInfo, 4)
for i := range formTable {
f := &formInfo{}
formTable[i] = f
f.form = Form(i)
if Form(i) == NFKD || Form(i) == NFKC {
f.compatibility = true
f.decompose = decomposeNFKC
f.info = lookupInfoNFKC
} else {
f.decompose = decomposeNFC
f.info = lookupInfoNFC
}
if Form(i) == NFC || Form(i) == NFKC {
f.composing = true
}
}
}
// 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.
func (i runeInfo) boundaryBefore() bool {
if i.ccc == 0 && !i.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
}
func (i runeInfo) boundaryAfter() bool {
return i.isInert()
}
// We pack quick check data in 4 bits:
// 0: NFD_QC Yes (0) or No (1). No also means there is a decomposition.
// 1..2: NFC_QC Yes(00), No (10), or Maybe (11)
// 3: Combines forward (0 == false, 1 == true)
//
// When all 4 bits are zero, the character is inert, meaning it is never
// influenced by normalization.
//
// We pack the bits for both NFC/D and NFKC/D in one byte.
type qcInfo uint8
func (i runeInfo) isYesC() bool { return i.flags&0x4 == 0 }
func (i runeInfo) isYesD() bool { return i.flags&0x1 == 0 }
func (i runeInfo) combinesForward() bool { return i.flags&0x8 != 0 }
func (i runeInfo) combinesBackward() bool { return i.flags&0x2 != 0 } // == isMaybe
func (i runeInfo) hasDecomposition() bool { return i.flags&0x1 != 0 } // == isNoD
func (r runeInfo) isInert() bool {
return r.flags&0xf == 0 && r.ccc == 0
}
// Wrappers for tables.go
// The 16-bit value of the decomposition tries is an index into a byte
// array of UTF-8 decomposition sequences. The first byte is the number
// of bytes in the decomposition (excluding this length byte). The actual
// sequence starts at the offset+1.
func decomposeNFC(s input, i int) []byte {
p := s.decomposeNFC(i)
n := decomps[p]
p++
return decomps[p : p+uint16(n)]
}
func decomposeNFKC(s input, i int) []byte {
p := s.decomposeNFKC(i)
n := decomps[p]
p++
return decomps[p : p+uint16(n)]
}
// 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]
}
// The 16-bit character info has the following bit layout:
// 0..7 CCC value.
// 8..11 qcInfo for NFC/NFD
// 12..15 qcInfo for NFKC/NFKD
func lookupInfoNFC(b input, i int) runeInfo {
v, sz := b.charinfo(i)
return runeInfo{size: uint8(sz), ccc: uint8(v), flags: qcInfo(v >> 8)}
}
func lookupInfoNFKC(b input, i int) runeInfo {
v, sz := b.charinfo(i)
return runeInfo{size: uint8(sz), ccc: uint8(v), flags: qcInfo(v >> 12)}
}
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