diff options
Diffstat (limited to 'vendor/github.com/rivo/uniseg/graphemerules.go')
| -rw-r--r-- | vendor/github.com/rivo/uniseg/graphemerules.go | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/vendor/github.com/rivo/uniseg/graphemerules.go b/vendor/github.com/rivo/uniseg/graphemerules.go new file mode 100644 index 000000000..5d399d29c --- /dev/null +++ b/vendor/github.com/rivo/uniseg/graphemerules.go @@ -0,0 +1,176 @@ +package uniseg + +// 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 +) + +// grTransitions implements the grapheme cluster parser's state transitions. +// Maps state and property to a new state, a breaking instruction, and rule +// number. The breaking instruction always refers to the boundary between the +// last and next code point. Returns negative values if no transition is found. +// +// This function is used 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 from (3) and breaking instruction +// from the transition with the lower rule number, prefer (3) if rule numbers +// are equal. Stop. +// 6. Assume grAny and grBoundary. +// +// Unicode version 15.0.0. +func grTransitions(state, prop int) (newState int, newProp int, boundary int) { + // It turns out that using a big switch statement is much faster than using + // a map. + + switch uint64(state) | uint64(prop)<<32 { + // GB5 + case grAny | prCR<<32: + return grCR, grBoundary, 50 + case grAny | prLF<<32: + return grControlLF, grBoundary, 50 + case grAny | prControl<<32: + return grControlLF, grBoundary, 50 + + // GB4 + case grCR | prAny<<32: + return grAny, grBoundary, 40 + case grControlLF | prAny<<32: + return grAny, grBoundary, 40 + + // GB3 + case grCR | prLF<<32: + return grControlLF, grNoBoundary, 30 + + // GB6 + case grAny | prL<<32: + return grL, grBoundary, 9990 + case grL | prL<<32: + return grL, grNoBoundary, 60 + case grL | prV<<32: + return grLVV, grNoBoundary, 60 + case grL | prLV<<32: + return grLVV, grNoBoundary, 60 + case grL | prLVT<<32: + return grLVTT, grNoBoundary, 60 + + // GB7 + case grAny | prLV<<32: + return grLVV, grBoundary, 9990 + case grAny | prV<<32: + return grLVV, grBoundary, 9990 + case grLVV | prV<<32: + return grLVV, grNoBoundary, 70 + case grLVV | prT<<32: + return grLVTT, grNoBoundary, 70 + + // GB8 + case grAny | prLVT<<32: + return grLVTT, grBoundary, 9990 + case grAny | prT<<32: + return grLVTT, grBoundary, 9990 + case grLVTT | prT<<32: + return grLVTT, grNoBoundary, 80 + + // GB9 + case grAny | prExtend<<32: + return grAny, grNoBoundary, 90 + case grAny | prZWJ<<32: + return grAny, grNoBoundary, 90 + + // GB9a + case grAny | prSpacingMark<<32: + return grAny, grNoBoundary, 91 + + // GB9b + case grAny | prPrepend<<32: + return grPrepend, grBoundary, 9990 + case grPrepend | prAny<<32: + return grAny, grNoBoundary, 92 + + // GB11 + case grAny | prExtendedPictographic<<32: + return grExtendedPictographic, grBoundary, 9990 + case grExtendedPictographic | prExtend<<32: + return grExtendedPictographic, grNoBoundary, 110 + case grExtendedPictographic | prZWJ<<32: + return grExtendedPictographicZWJ, grNoBoundary, 110 + case grExtendedPictographicZWJ | prExtendedPictographic<<32: + return grExtendedPictographic, grNoBoundary, 110 + + // GB12 / GB13 + case grAny | prRegionalIndicator<<32: + return grRIOdd, grBoundary, 9990 + case grRIOdd | prRegionalIndicator<<32: + return grRIEven, grNoBoundary, 120 + case grRIEven | prRegionalIndicator<<32: + return grRIOdd, grBoundary, 120 + default: + return -1, -1, -1 + } +} + +// transitionGraphemeState determines the new state of the grapheme cluster +// parser given the current state and the next code point. It also returns the +// code point's grapheme property (the value mapped by the [graphemeCodePoints] +// table) and whether a cluster boundary was detected. +func transitionGraphemeState(state int, r rune) (newState, prop int, boundary bool) { + // Determine the property of the next character. + prop = propertyGraphemes(r) + + // Find the applicable transition. + nextState, nextProp, _ := grTransitions(state, prop) + if nextState >= 0 { + // We have a specific transition. We'll use it. + return nextState, prop, nextProp == grBoundary + } + + // No specific transition found. Try the less specific ones. + anyPropState, anyPropProp, anyPropRule := grTransitions(state, prAny) + anyStateState, anyStateProp, anyStateRule := grTransitions(grAny, prop) + if anyPropState >= 0 && anyStateState >= 0 { + // Both apply. We'll use a mix (see comments for grTransitions). + newState = anyStateState + boundary = anyStateProp == grBoundary + if anyPropRule < anyStateRule { + boundary = anyPropProp == grBoundary + } + return + } + + if anyPropState >= 0 { + // We only have a specific state. + return anyPropState, prop, anyPropProp == 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. + } + + if anyStateState >= 0 { + // We only have a specific property. + return anyStateState, prop, anyStateProp == grBoundary + } + + // No known transition. GB999: Any รท Any. + return grAny, prop, true +} |