gemini-browser

iter.go (11280B)

---

 // 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 {
 		p0 := i.p
 		i.setDone()
 		return i.rb.src.bytes[p0: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)
 }