Initial QSfera import

Server/vendor/github.com/clipperhouse/uax29/v2/graphemes/splitfunc.go

@@ -0,0 +1,205 @@
+package graphemes
+
+import (
+	"bufio"
+)
+
+// is determines if lookup intersects propert(ies)
+func (lookup property) is(properties property) bool {
+	return (lookup & properties) != 0
+}
+
+const _Ignore = _Extend
+
+// incbState tracks state for GB9c rule (Indic conjunct clusters)
+// Pattern: Consonant (Extend|Linker)* Linker (Extend|Linker)* × Consonant
+type incbState int
+
+const (
+	incbNone      incbState = iota // initial/reset
+	incbConsonant                  // seen Consonant, awaiting Linker
+	incbLinker                     // seen Consonant and Linker (conjunct ready)
+)
+
+// SplitFunc is a bufio.SplitFunc implementation of Unicode grapheme cluster segmentation, for use with bufio.Scanner.
+//
+// See https://unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries.
+var SplitFunc bufio.SplitFunc = splitFunc[[]byte]
+
+func splitFunc[T ~string | ~[]byte](data T, atEOF bool) (advance int, token T, err error) {
+	var empty T
+	if len(data) == 0 {
+		return 0, empty, nil
+	}
+
+	// These vars are stateful across loop iterations
+	var pos int
+	var lastExIgnore property = 0     // "last excluding ignored categories"
+	var lastLastExIgnore property = 0 // "last one before that"
+	var regionalIndicatorCount int
+
+	// GB9c state: tracking Indic conjunct clusters
+	var incb incbState
+
+	// Rules are usually of the form Cat1 × Cat2; "current" refers to the first property
+	// to the right of the ×, from which we look back or forward
+
+	current, w := lookup(data[pos:])
+	if w == 0 {
+		if !atEOF {
+			// Rune extends past current data, request more
+			return 0, empty, nil
+		}
+		pos = len(data)
+		return pos, data[:pos], nil
+	}
+
+	// https://unicode.org/reports/tr29/#GB1
+	// Start of text always advances
+	pos += w
+
+	for {
+		eot := pos == len(data) // "end of text"
+
+		if eot {
+			if !atEOF {
+				// Token extends past current data, request more
+				return 0, empty, nil
+			}
+
+			// https://unicode.org/reports/tr29/#GB2
+			break
+		}
+
+		/*
+			We've switched the evaluation order of GB1↓ and GB2↑. It's ok:
+			because we've checked for len(data) at the top of this function,
+			sot and eot are mutually exclusive, order doesn't matter.
+		*/
+
+		// Rules are usually of the form Cat1 × Cat2; "current" refers to the first property
+		// to the right of the ×, from which we look back or forward
+
+		// Remember previous properties to avoid lookups/lookbacks
+		last := current
+		if !last.is(_Ignore) {
+			lastLastExIgnore = lastExIgnore
+			lastExIgnore = last
+		}
+
+		// Update GB9c state based on what we just advanced past
+		if last.is(_InCBConsonant | _InCBLinker | _InCBExtend) {
+			switch {
+			case last.is(_InCBConsonant):
+				if incb != incbLinker {
+					incb = incbConsonant
+				}
+			case last.is(_InCBLinker):
+				if incb >= incbConsonant {
+					incb = incbLinker
+				}
+				// case last.is(_InCBExtend): stay in current state
+			}
+		} else {
+			incb = incbNone
+		}
+
+		current, w = lookup(data[pos:])
+		if w == 0 {
+			if atEOF {
+				// Just return the bytes, we can't do anything with them
+				pos = len(data)
+				break
+			}
+			// Rune extends past current data, request more
+			return 0, empty, nil
+		}
+
+		// Optimization: no rule can possibly apply
+		if current|last == 0 { // i.e. both are zero
+			break
+		}
+
+		// https://unicode.org/reports/tr29/#GB3
+		if current.is(_LF) && last.is(_CR) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB4
+		// https://unicode.org/reports/tr29/#GB5
+		if (current | last).is(_Control | _CR | _LF) {
+			break
+		}
+
+		// https://unicode.org/reports/tr29/#GB6
+		if current.is(_L|_V|_LV|_LVT) && last.is(_L) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB7
+		if current.is(_V|_T) && last.is(_LV|_V) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB8
+		if current.is(_T) && last.is(_LVT|_T) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB9
+		if current.is(_Extend | _ZWJ) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB9a
+		if current.is(_SpacingMark) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB9b
+		if last.is(_Prepend) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB9c
+		// Do not break within certain combinations with Indic_Conjunct_Break (InCB)=Linker.
+		if incb == incbLinker && current.is(_InCBConsonant) {
+			// After matching the pattern, reset state to start tracking a new pattern
+			// The current Consonant becomes the start of the new pattern
+			incb = incbConsonant
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB11
+		if current.is(_ExtendedPictographic) && last.is(_ZWJ) && lastLastExIgnore.is(_ExtendedPictographic) {
+			pos += w
+			continue
+		}
+
+		// https://unicode.org/reports/tr29/#GB12
+		// https://unicode.org/reports/tr29/#GB13
+		if (current & last).is(_RegionalIndicator) {
+			regionalIndicatorCount++
+
+			odd := regionalIndicatorCount%2 == 1
+			if odd {
+				pos += w
+				continue
+			}
+		}
+
+		// If we fall through all the above rules, it's a grapheme cluster break
+		break
+	}
+
+	// Return token
+	return pos, data[:pos], nil
+}