--- /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
+
+import (
+ "fmt"
+ "unicode/utf8"
+)
+
+// MaxSegmentSize is the maximum size of a byte buffer needed to consider any
+// sequence of starter and non-starter runes for the purpose of normalization.
+const MaxSegmentSize = maxByteBufferSize
+
+// An Iter iterates over a string or byte slice, while normalizing it
+// to a given Form.
+type Iter struct {
+ rb reorderBuffer
+ buf [maxByteBufferSize]byte
+ info Properties // first character saved from previous iteration
+ next iterFunc // implementation of next depends on form
+ asciiF iterFunc
+
+ p int // current position in input source
+ multiSeg []byte // remainder of multi-segment decomposition
+}
+
+type iterFunc func(*Iter) []byte
+
+// Init initializes i to iterate over src after normalizing it to Form f.
+func (i *Iter) Init(f Form, src []byte) {
+ i.p = 0
+ if len(src) == 0 {
+ i.setDone()
+ i.rb.nsrc = 0
+ return
+ }
+ i.multiSeg = nil
+ i.rb.init(f, src)
+ i.next = i.rb.f.nextMain
+ i.asciiF = nextASCIIBytes
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ i.rb.ss.first(i.info)
+}
+
+// InitString initializes i to iterate over src after normalizing it to Form f.
+func (i *Iter) InitString(f Form, src string) {
+ i.p = 0
+ if len(src) == 0 {
+ i.setDone()
+ i.rb.nsrc = 0
+ return
+ }
+ i.multiSeg = nil
+ i.rb.initString(f, src)
+ i.next = i.rb.f.nextMain
+ i.asciiF = nextASCIIString
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ i.rb.ss.first(i.info)
+}
+
+// Seek sets the segment to be returned by the next call to Next to start
+// at position p. It is the responsibility of the caller to set p to the
+// start of a segment.
+func (i *Iter) Seek(offset int64, whence int) (int64, error) {
+ var abs int64
+ switch whence {
+ case 0:
+ abs = offset
+ case 1:
+ abs = int64(i.p) + offset
+ case 2:
+ abs = int64(i.rb.nsrc) + offset
+ default:
+ return 0, fmt.Errorf("norm: invalid whence")
+ }
+ if abs < 0 {
+ return 0, fmt.Errorf("norm: negative position")
+ }
+ if int(abs) >= i.rb.nsrc {
+ i.setDone()
+ return int64(i.p), nil
+ }
+ i.p = int(abs)
+ i.multiSeg = nil
+ i.next = i.rb.f.nextMain
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ i.rb.ss.first(i.info)
+ return abs, nil
+}
+
+// returnSlice returns a slice of the underlying input type as a byte slice.
+// If the underlying is of type []byte, it will simply return a slice.
+// If the underlying is of type string, it will copy the slice to the buffer
+// and return that.
+func (i *Iter) returnSlice(a, b int) []byte {
+ if i.rb.src.bytes == nil {
+ return i.buf[:copy(i.buf[:], i.rb.src.str[a:b])]
+ }
+ return i.rb.src.bytes[a:b]
+}
+
+// Pos returns the byte position at which the next call to Next will commence processing.
+func (i *Iter) Pos() int {
+ return i.p
+}
+
+func (i *Iter) setDone() {
+ i.next = nextDone
+ i.p = i.rb.nsrc
+}
+
+// Done returns true if there is no more input to process.
+func (i *Iter) Done() bool {
+ return i.p >= i.rb.nsrc
+}
+
+// Next returns f(i.input[i.Pos():n]), where n is a boundary of i.input.
+// For any input a and b for which f(a) == f(b), subsequent calls
+// to Next will return the same segments.
+// Modifying runes are grouped together with the preceding starter, if such a starter exists.
+// Although not guaranteed, n will typically be the smallest possible n.
+func (i *Iter) Next() []byte {
+ return i.next(i)
+}
+
+func nextASCIIBytes(i *Iter) []byte {
+ p := i.p + 1
+ if p >= i.rb.nsrc {
+ i.setDone()
+ return i.rb.src.bytes[i.p:p]
+ }
+ if i.rb.src.bytes[p] < utf8.RuneSelf {
+ p0 := i.p
+ i.p = p
+ return i.rb.src.bytes[p0:p]
+ }
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ i.next = i.rb.f.nextMain
+ return i.next(i)
+}
+
+func nextASCIIString(i *Iter) []byte {
+ p := i.p + 1
+ if p >= i.rb.nsrc {
+ i.buf[0] = i.rb.src.str[i.p]
+ i.setDone()
+ return i.buf[:1]
+ }
+ if i.rb.src.str[p] < utf8.RuneSelf {
+ i.buf[0] = i.rb.src.str[i.p]
+ i.p = p
+ return i.buf[:1]
+ }
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ i.next = i.rb.f.nextMain
+ return i.next(i)
+}
+
+func nextHangul(i *Iter) []byte {
+ p := i.p
+ next := p + hangulUTF8Size
+ if next >= i.rb.nsrc {
+ i.setDone()
+ } else if i.rb.src.hangul(next) == 0 {
+ i.rb.ss.next(i.info)
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ i.next = i.rb.f.nextMain
+ return i.next(i)
+ }
+ i.p = next
+ return i.buf[:decomposeHangul(i.buf[:], i.rb.src.hangul(p))]
+}
+
+func nextDone(i *Iter) []byte {
+ return nil
+}
+
+// nextMulti is used for iterating over multi-segment decompositions
+// for decomposing normal forms.
+func nextMulti(i *Iter) []byte {
+ j := 0
+ d := i.multiSeg
+ // skip first rune
+ for j = 1; j < len(d) && !utf8.RuneStart(d[j]); j++ {
+ }
+ for j < len(d) {
+ info := i.rb.f.info(input{bytes: d}, j)
+ if info.BoundaryBefore() {
+ i.multiSeg = d[j:]
+ return d[:j]
+ }
+ j += int(info.size)
+ }
+ // treat last segment as normal decomposition
+ i.next = i.rb.f.nextMain
+ return i.next(i)
+}
+
+// nextMultiNorm is used for iterating over multi-segment decompositions
+// for composing normal forms.
+func nextMultiNorm(i *Iter) []byte {
+ j := 0
+ d := i.multiSeg
+ for j < len(d) {
+ info := i.rb.f.info(input{bytes: d}, j)
+ if info.BoundaryBefore() {
+ i.rb.compose()
+ seg := i.buf[:i.rb.flushCopy(i.buf[:])]
+ i.rb.insertUnsafe(input{bytes: d}, j, info)
+ i.multiSeg = d[j+int(info.size):]
+ return seg
+ }
+ i.rb.insertUnsafe(input{bytes: d}, j, info)
+ j += int(info.size)
+ }
+ i.multiSeg = nil
+ i.next = nextComposed
+ return doNormComposed(i)
+}
+
+// nextDecomposed is the implementation of Next for forms NFD and NFKD.
+func nextDecomposed(i *Iter) (next []byte) {
+ outp := 0
+ inCopyStart, outCopyStart := i.p, 0
+ for {
+ if sz := int(i.info.size); sz <= 1 {
+ i.rb.ss = 0
+ p := i.p
+ i.p++ // ASCII or illegal byte. Either way, advance by 1.
+ if i.p >= i.rb.nsrc {
+ i.setDone()
+ return i.returnSlice(p, i.p)
+ } else if i.rb.src._byte(i.p) < utf8.RuneSelf {
+ i.next = i.asciiF
+ return i.returnSlice(p, i.p)
+ }
+ outp++
+ } else if d := i.info.Decomposition(); d != nil {
+ // Note: If leading CCC != 0, then len(d) == 2 and last is also non-zero.
+ // Case 1: there is a leftover to copy. In this case the decomposition
+ // must begin with a modifier and should always be appended.
+ // Case 2: no leftover. Simply return d if followed by a ccc == 0 value.
+ p := outp + len(d)
+ if outp > 0 {
+ i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
+ // TODO: this condition should not be possible, but we leave it
+ // in for defensive purposes.
+ if p > len(i.buf) {
+ return i.buf[:outp]
+ }
+ } else if i.info.multiSegment() {
+ // outp must be 0 as multi-segment decompositions always
+ // start a new segment.
+ if i.multiSeg == nil {
+ i.multiSeg = d
+ i.next = nextMulti
+ return nextMulti(i)
+ }
+ // We are in the last segment. Treat as normal decomposition.
+ d = i.multiSeg
+ i.multiSeg = nil
+ p = len(d)
+ }
+ prevCC := i.info.tccc
+ if i.p += sz; i.p >= i.rb.nsrc {
+ i.setDone()
+ i.info = Properties{} // Force BoundaryBefore to succeed.
+ } else {
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ }
+ switch i.rb.ss.next(i.info) {
+ case ssOverflow:
+ i.next = nextCGJDecompose
+ fallthrough
+ case ssStarter:
+ if outp > 0 {
+ copy(i.buf[outp:], d)
+ return i.buf[:p]
+ }
+ return d
+ }
+ copy(i.buf[outp:], d)
+ outp = p
+ inCopyStart, outCopyStart = i.p, outp
+ if i.info.ccc < prevCC {
+ goto doNorm
+ }
+ continue
+ } else if r := i.rb.src.hangul(i.p); r != 0 {
+ outp = decomposeHangul(i.buf[:], r)
+ i.p += hangulUTF8Size
+ inCopyStart, outCopyStart = i.p, outp
+ if i.p >= i.rb.nsrc {
+ i.setDone()
+ break
+ } else if i.rb.src.hangul(i.p) != 0 {
+ i.next = nextHangul
+ return i.buf[:outp]
+ }
+ } else {
+ p := outp + sz
+ if p > len(i.buf) {
+ break
+ }
+ outp = p
+ i.p += sz
+ }
+ if i.p >= i.rb.nsrc {
+ i.setDone()
+ break
+ }
+ prevCC := i.info.tccc
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ if v := i.rb.ss.next(i.info); v == ssStarter {
+ break
+ } else if v == ssOverflow {
+ i.next = nextCGJDecompose
+ break
+ }
+ if i.info.ccc < prevCC {
+ goto doNorm
+ }
+ }
+ if outCopyStart == 0 {
+ return i.returnSlice(inCopyStart, i.p)
+ } else if inCopyStart < i.p {
+ i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
+ }
+ return i.buf[:outp]
+doNorm:
+ // Insert what we have decomposed so far in the reorderBuffer.
+ // As we will only reorder, there will always be enough room.
+ i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
+ i.rb.insertDecomposed(i.buf[0:outp])
+ return doNormDecomposed(i)
+}
+
+func doNormDecomposed(i *Iter) []byte {
+ for {
+ i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+ if i.p += int(i.info.size); i.p >= i.rb.nsrc {
+ i.setDone()
+ break
+ }
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ if i.info.ccc == 0 {
+ break
+ }
+ if s := i.rb.ss.next(i.info); s == ssOverflow {
+ i.next = nextCGJDecompose
+ break
+ }
+ }
+ // new segment or too many combining characters: exit normalization
+ return i.buf[:i.rb.flushCopy(i.buf[:])]
+}
+
+func nextCGJDecompose(i *Iter) []byte {
+ i.rb.ss = 0
+ i.rb.insertCGJ()
+ i.next = nextDecomposed
+ i.rb.ss.first(i.info)
+ buf := doNormDecomposed(i)
+ return buf
+}
+
+// nextComposed is the implementation of Next for forms NFC and NFKC.
+func nextComposed(i *Iter) []byte {
+ outp, startp := 0, i.p
+ var prevCC uint8
+ for {
+ if !i.info.isYesC() {
+ goto doNorm
+ }
+ prevCC = i.info.tccc
+ sz := int(i.info.size)
+ if sz == 0 {
+ sz = 1 // illegal rune: copy byte-by-byte
+ }
+ p := outp + sz
+ if p > len(i.buf) {
+ break
+ }
+ outp = p
+ i.p += sz
+ if i.p >= i.rb.nsrc {
+ i.setDone()
+ break
+ } else if i.rb.src._byte(i.p) < utf8.RuneSelf {
+ i.rb.ss = 0
+ i.next = i.asciiF
+ break
+ }
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ if v := i.rb.ss.next(i.info); v == ssStarter {
+ break
+ } else if v == ssOverflow {
+ i.next = nextCGJCompose
+ break
+ }
+ if i.info.ccc < prevCC {
+ goto doNorm
+ }
+ }
+ return i.returnSlice(startp, i.p)
+doNorm:
+ // reset to start position
+ i.p = startp
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ i.rb.ss.first(i.info)
+ if i.info.multiSegment() {
+ d := i.info.Decomposition()
+ info := i.rb.f.info(input{bytes: d}, 0)
+ i.rb.insertUnsafe(input{bytes: d}, 0, info)
+ i.multiSeg = d[int(info.size):]
+ i.next = nextMultiNorm
+ return nextMultiNorm(i)
+ }
+ i.rb.ss.first(i.info)
+ i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+ return doNormComposed(i)
+}
+
+func doNormComposed(i *Iter) []byte {
+ // First rune should already be inserted.
+ for {
+ if i.p += int(i.info.size); i.p >= i.rb.nsrc {
+ i.setDone()
+ break
+ }
+ i.info = i.rb.f.info(i.rb.src, i.p)
+ if s := i.rb.ss.next(i.info); s == ssStarter {
+ break
+ } else if s == ssOverflow {
+ i.next = nextCGJCompose
+ break
+ }
+ i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+ }
+ i.rb.compose()
+ seg := i.buf[:i.rb.flushCopy(i.buf[:])]
+ return seg
+}
+
+func nextCGJCompose(i *Iter) []byte {
+ i.rb.ss = 0 // instead of first
+ i.rb.insertCGJ()
+ i.next = nextComposed
+ // Note that we treat any rune with nLeadingNonStarters > 0 as a non-starter,
+ // even if they are not. This is particularly dubious for U+FF9E and UFF9A.
+ // If we ever change that, insert a check here.
+ i.rb.ss.first(i.info)
+ i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+ return doNormComposed(i)
+}
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