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Diffstat (limited to 'vendor/github.com/rivo/uniseg/grapheme.go')
| -rw-r--r-- | vendor/github.com/rivo/uniseg/grapheme.go | 268 |
1 files changed, 268 insertions, 0 deletions
diff --git a/vendor/github.com/rivo/uniseg/grapheme.go b/vendor/github.com/rivo/uniseg/grapheme.go new file mode 100644 index 00000000..207157f5 --- /dev/null +++ b/vendor/github.com/rivo/uniseg/grapheme.go @@ -0,0 +1,268 @@ +package uniseg + +import "unicode/utf8" + +// The states of the grapheme cluster parser. +const ( + grAny = iota + grCR + grControlLF + grL + grLVV + grLVTT + grPrepend + grExtendedPictographic + grExtendedPictographicZWJ + grRIOdd + grRIEven +) + +// The grapheme cluster parser's breaking instructions. +const ( + grNoBoundary = iota + grBoundary +) + +// The grapheme cluster parser's state transitions. Maps (state, property) to +// (new state, breaking instruction, rule number). The breaking instruction +// always refers to the boundary between the last and next code point. +// +// This map is queried as follows: +// +// 1. Find specific state + specific property. Stop if found. +// 2. Find specific state + any property. +// 3. Find any state + specific property. +// 4. If only (2) or (3) (but not both) was found, stop. +// 5. If both (2) and (3) were found, use state and breaking instruction from +// the transition with the lower rule number, prefer (3) if rule numbers +// are equal. Stop. +// 6. Assume grAny and grBoundary. +var grTransitions = map[[2]int][3]int{ + // GB5 + {grAny, prCR}: {grCR, grBoundary, 50}, + {grAny, prLF}: {grControlLF, grBoundary, 50}, + {grAny, prControl}: {grControlLF, grBoundary, 50}, + + // GB4 + {grCR, prAny}: {grAny, grBoundary, 40}, + {grControlLF, prAny}: {grAny, grBoundary, 40}, + + // GB3. + {grCR, prLF}: {grAny, grNoBoundary, 30}, + + // GB6. + {grAny, prL}: {grL, grBoundary, 9990}, + {grL, prL}: {grL, grNoBoundary, 60}, + {grL, prV}: {grLVV, grNoBoundary, 60}, + {grL, prLV}: {grLVV, grNoBoundary, 60}, + {grL, prLVT}: {grLVTT, grNoBoundary, 60}, + + // GB7. + {grAny, prLV}: {grLVV, grBoundary, 9990}, + {grAny, prV}: {grLVV, grBoundary, 9990}, + {grLVV, prV}: {grLVV, grNoBoundary, 70}, + {grLVV, prT}: {grLVTT, grNoBoundary, 70}, + + // GB8. + {grAny, prLVT}: {grLVTT, grBoundary, 9990}, + {grAny, prT}: {grLVTT, grBoundary, 9990}, + {grLVTT, prT}: {grLVTT, grNoBoundary, 80}, + + // GB9. + {grAny, prExtend}: {grAny, grNoBoundary, 90}, + {grAny, prZWJ}: {grAny, grNoBoundary, 90}, + + // GB9a. + {grAny, prSpacingMark}: {grAny, grNoBoundary, 91}, + + // GB9b. + {grAny, prPreprend}: {grPrepend, grBoundary, 9990}, + {grPrepend, prAny}: {grAny, grNoBoundary, 92}, + + // GB11. + {grAny, prExtendedPictographic}: {grExtendedPictographic, grBoundary, 9990}, + {grExtendedPictographic, prExtend}: {grExtendedPictographic, grNoBoundary, 110}, + {grExtendedPictographic, prZWJ}: {grExtendedPictographicZWJ, grNoBoundary, 110}, + {grExtendedPictographicZWJ, prExtendedPictographic}: {grExtendedPictographic, grNoBoundary, 110}, + + // GB12 / GB13. + {grAny, prRegionalIndicator}: {grRIOdd, grBoundary, 9990}, + {grRIOdd, prRegionalIndicator}: {grRIEven, grNoBoundary, 120}, + {grRIEven, prRegionalIndicator}: {grRIOdd, grBoundary, 120}, +} + +// Graphemes implements an iterator over Unicode extended grapheme clusters, +// specified in the Unicode Standard Annex #29. Grapheme clusters correspond to +// "user-perceived characters". These characters often consist of multiple +// code points (e.g. the "woman kissing woman" emoji consists of 8 code points: +// woman + ZWJ + heavy black heart (2 code points) + ZWJ + kiss mark + ZWJ + +// woman) and the rules described in Annex #29 must be applied to group those +// code points into clusters perceived by the user as one character. +type Graphemes struct { + // The code points over which this class iterates. + codePoints []rune + + // The (byte-based) indices of the code points into the original string plus + // len(original string). Thus, len(indices) = len(codePoints) + 1. + indices []int + + // The current grapheme cluster to be returned. These are indices into + // codePoints/indices. If start == end, we either haven't started iterating + // yet (0) or the iteration has already completed (1). + start, end int + + // The index of the next code point to be parsed. + pos int + + // The current state of the code point parser. + state int +} + +// NewGraphemes returns a new grapheme cluster iterator. +func NewGraphemes(s string) *Graphemes { + l := utf8.RuneCountInString(s) + codePoints := make([]rune, l) + indices := make([]int, l+1) + i := 0 + for pos, r := range s { + codePoints[i] = r + indices[i] = pos + i++ + } + indices[l] = len(s) + g := &Graphemes{ + codePoints: codePoints, + indices: indices, + } + g.Next() // Parse ahead. + return g +} + +// Next advances the iterator by one grapheme cluster and returns false if no +// clusters are left. This function must be called before the first cluster is +// accessed. +func (g *Graphemes) Next() bool { + g.start = g.end + + // The state transition gives us a boundary instruction BEFORE the next code + // point so we always need to stay ahead by one code point. + + // Parse the next code point. + for g.pos <= len(g.codePoints) { + // GB2. + if g.pos == len(g.codePoints) { + g.end = g.pos + g.pos++ + break + } + + // Determine the property of the next character. + nextProperty := property(g.codePoints[g.pos]) + g.pos++ + + // Find the applicable transition. + var boundary bool + transition, ok := grTransitions[[2]int{g.state, nextProperty}] + if ok { + // We have a specific transition. We'll use it. + g.state = transition[0] + boundary = transition[1] == grBoundary + } else { + // No specific transition found. Try the less specific ones. + transAnyProp, okAnyProp := grTransitions[[2]int{g.state, prAny}] + transAnyState, okAnyState := grTransitions[[2]int{grAny, nextProperty}] + if okAnyProp && okAnyState { + // Both apply. We'll use a mix (see comments for grTransitions). + g.state = transAnyState[0] + boundary = transAnyState[1] == grBoundary + if transAnyProp[2] < transAnyState[2] { + g.state = transAnyProp[0] + boundary = transAnyProp[1] == grBoundary + } + } else if okAnyProp { + // We only have a specific state. + g.state = transAnyProp[0] + boundary = transAnyProp[1] == grBoundary + // This branch will probably never be reached because okAnyState will + // always be true given the current transition map. But we keep it here + // for future modifications to the transition map where this may not be + // true anymore. + } else if okAnyState { + // We only have a specific property. + g.state = transAnyState[0] + boundary = transAnyState[1] == grBoundary + } else { + // No known transition. GB999: Any x Any. + g.state = grAny + boundary = true + } + } + + // If we found a cluster boundary, let's stop here. The current cluster will + // be the one that just ended. + if g.pos-1 == 0 /* GB1 */ || boundary { + g.end = g.pos - 1 + break + } + } + + return g.start != g.end +} + +// Runes returns a slice of runes (code points) which corresponds to the current +// grapheme cluster. If the iterator is already past the end or Next() has not +// yet been called, nil is returned. +func (g *Graphemes) Runes() []rune { + if g.start == g.end { + return nil + } + return g.codePoints[g.start:g.end] +} + +// Str returns a substring of the original string which corresponds to the +// current grapheme cluster. If the iterator is already past the end or Next() +// has not yet been called, an empty string is returned. +func (g *Graphemes) Str() string { + if g.start == g.end { + return "" + } + return string(g.codePoints[g.start:g.end]) +} + +// Bytes returns a byte slice which corresponds to the current grapheme cluster. +// If the iterator is already past the end or Next() has not yet been called, +// nil is returned. +func (g *Graphemes) Bytes() []byte { + if g.start == g.end { + return nil + } + return []byte(string(g.codePoints[g.start:g.end])) +} + +// Positions returns the interval of the current grapheme cluster as byte +// positions into the original string. The first returned value "from" indexes +// the first byte and the second returned value "to" indexes the first byte that +// is not included anymore, i.e. str[from:to] is the current grapheme cluster of +// the original string "str". If Next() has not yet been called, both values are +// 0. If the iterator is already past the end, both values are 1. +func (g *Graphemes) Positions() (int, int) { + return g.indices[g.start], g.indices[g.end] +} + +// Reset puts the iterator into its initial state such that the next call to +// Next() sets it to the first grapheme cluster again. +func (g *Graphemes) Reset() { + g.start, g.end, g.pos, g.state = 0, 0, 0, grAny + g.Next() // Parse ahead again. +} + +// GraphemeClusterCount returns the number of user-perceived characters +// (grapheme clusters) for the given string. To calculate this number, it +// iterates through the string using the Graphemes iterator. +func GraphemeClusterCount(s string) (n int) { + g := NewGraphemes(s) + for g.Next() { + n++ + } + return +} |