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Diffstat (limited to 'vendor/golang.org/x/text/unicode/bidi/core.go')
| -rw-r--r-- | vendor/golang.org/x/text/unicode/bidi/core.go | 1058 |
1 files changed, 1058 insertions, 0 deletions
diff --git a/vendor/golang.org/x/text/unicode/bidi/core.go b/vendor/golang.org/x/text/unicode/bidi/core.go new file mode 100644 index 0000000..d4c1399 --- /dev/null +++ b/vendor/golang.org/x/text/unicode/bidi/core.go @@ -0,0 +1,1058 @@ +// Copyright 2015 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 bidi + +import "log" + +// This implementation is a port based on the reference implementation found at: +// http://www.unicode.org/Public/PROGRAMS/BidiReferenceJava/ +// +// described in Unicode Bidirectional Algorithm (UAX #9). +// +// Input: +// There are two levels of input to the algorithm, since clients may prefer to +// supply some information from out-of-band sources rather than relying on the +// default behavior. +// +// - Bidi class array +// - Bidi class array, with externally supplied base line direction +// +// Output: +// Output is separated into several stages: +// +// - levels array over entire paragraph +// - reordering array over entire paragraph +// - levels array over line +// - reordering array over line +// +// Note that for conformance to the Unicode Bidirectional Algorithm, +// implementations are only required to generate correct reordering and +// character directionality (odd or even levels) over a line. Generating +// identical level arrays over a line is not required. Bidi explicit format +// codes (LRE, RLE, LRO, RLO, PDF) and BN can be assigned arbitrary levels and +// positions as long as the rest of the input is properly reordered. +// +// As the algorithm is defined to operate on a single paragraph at a time, this +// implementation is written to handle single paragraphs. Thus rule P1 is +// presumed by this implementation-- the data provided to the implementation is +// assumed to be a single paragraph, and either contains no 'B' codes, or a +// single 'B' code at the end of the input. 'B' is allowed as input to +// illustrate how the algorithm assigns it a level. +// +// Also note that rules L3 and L4 depend on the rendering engine that uses the +// result of the bidi algorithm. This implementation assumes that the rendering +// engine expects combining marks in visual order (e.g. to the left of their +// base character in RTL runs) and that it adjusts the glyphs used to render +// mirrored characters that are in RTL runs so that they render appropriately. + +// level is the embedding level of a character. Even embedding levels indicate +// left-to-right order and odd levels indicate right-to-left order. The special +// level of -1 is reserved for undefined order. +type level int8 + +const implicitLevel level = -1 + +// in returns if x is equal to any of the values in set. +func (c Class) in(set ...Class) bool { + for _, s := range set { + if c == s { + return true + } + } + return false +} + +// A paragraph contains the state of a paragraph. +type paragraph struct { + initialTypes []Class + + // Arrays of properties needed for paired bracket evaluation in N0 + pairTypes []bracketType // paired Bracket types for paragraph + pairValues []rune // rune for opening bracket or pbOpen and pbClose; 0 for pbNone + + embeddingLevel level // default: = implicitLevel; + + // at the paragraph levels + resultTypes []Class + resultLevels []level + + // Index of matching PDI for isolate initiator characters. For other + // characters, the value of matchingPDI will be set to -1. For isolate + // initiators with no matching PDI, matchingPDI will be set to the length of + // the input string. + matchingPDI []int + + // Index of matching isolate initiator for PDI characters. For other + // characters, and for PDIs with no matching isolate initiator, the value of + // matchingIsolateInitiator will be set to -1. + matchingIsolateInitiator []int +} + +// newParagraph initializes a paragraph. The user needs to supply a few arrays +// corresponding to the preprocessed text input. The types correspond to the +// Unicode BiDi classes for each rune. pairTypes indicates the bracket type for +// each rune. pairValues provides a unique bracket class identifier for each +// rune (suggested is the rune of the open bracket for opening and matching +// close brackets, after normalization). The embedding levels are optional, but +// may be supplied to encode embedding levels of styled text. +// +// TODO: return an error. +func newParagraph(types []Class, pairTypes []bracketType, pairValues []rune, levels level) *paragraph { + validateTypes(types) + validatePbTypes(pairTypes) + validatePbValues(pairValues, pairTypes) + validateParagraphEmbeddingLevel(levels) + + p := ¶graph{ + initialTypes: append([]Class(nil), types...), + embeddingLevel: levels, + + pairTypes: pairTypes, + pairValues: pairValues, + + resultTypes: append([]Class(nil), types...), + } + p.run() + return p +} + +func (p *paragraph) Len() int { return len(p.initialTypes) } + +// The algorithm. Does not include line-based processing (Rules L1, L2). +// These are applied later in the line-based phase of the algorithm. +func (p *paragraph) run() { + p.determineMatchingIsolates() + + // 1) determining the paragraph level + // Rule P1 is the requirement for entering this algorithm. + // Rules P2, P3. + // If no externally supplied paragraph embedding level, use default. + if p.embeddingLevel == implicitLevel { + p.embeddingLevel = p.determineParagraphEmbeddingLevel(0, p.Len()) + } + + // Initialize result levels to paragraph embedding level. + p.resultLevels = make([]level, p.Len()) + setLevels(p.resultLevels, p.embeddingLevel) + + // 2) Explicit levels and directions + // Rules X1-X8. + p.determineExplicitEmbeddingLevels() + + // Rule X9. + // We do not remove the embeddings, the overrides, the PDFs, and the BNs + // from the string explicitly. But they are not copied into isolating run + // sequences when they are created, so they are removed for all + // practical purposes. + + // Rule X10. + // Run remainder of algorithm one isolating run sequence at a time + for _, seq := range p.determineIsolatingRunSequences() { + // 3) resolving weak types + // Rules W1-W7. + seq.resolveWeakTypes() + + // 4a) resolving paired brackets + // Rule N0 + resolvePairedBrackets(seq) + + // 4b) resolving neutral types + // Rules N1-N3. + seq.resolveNeutralTypes() + + // 5) resolving implicit embedding levels + // Rules I1, I2. + seq.resolveImplicitLevels() + + // Apply the computed levels and types + seq.applyLevelsAndTypes() + } + + // Assign appropriate levels to 'hide' LREs, RLEs, LROs, RLOs, PDFs, and + // BNs. This is for convenience, so the resulting level array will have + // a value for every character. + p.assignLevelsToCharactersRemovedByX9() +} + +// determineMatchingIsolates determines the matching PDI for each isolate +// initiator and vice versa. +// +// Definition BD9. +// +// At the end of this function: +// +// - The member variable matchingPDI is set to point to the index of the +// matching PDI character for each isolate initiator character. If there is +// no matching PDI, it is set to the length of the input text. For other +// characters, it is set to -1. +// - The member variable matchingIsolateInitiator is set to point to the +// index of the matching isolate initiator character for each PDI character. +// If there is no matching isolate initiator, or the character is not a PDI, +// it is set to -1. +func (p *paragraph) determineMatchingIsolates() { + p.matchingPDI = make([]int, p.Len()) + p.matchingIsolateInitiator = make([]int, p.Len()) + + for i := range p.matchingIsolateInitiator { + p.matchingIsolateInitiator[i] = -1 + } + + for i := range p.matchingPDI { + p.matchingPDI[i] = -1 + + if t := p.resultTypes[i]; t.in(LRI, RLI, FSI) { + depthCounter := 1 + for j := i + 1; j < p.Len(); j++ { + if u := p.resultTypes[j]; u.in(LRI, RLI, FSI) { + depthCounter++ + } else if u == PDI { + if depthCounter--; depthCounter == 0 { + p.matchingPDI[i] = j + p.matchingIsolateInitiator[j] = i + break + } + } + } + if p.matchingPDI[i] == -1 { + p.matchingPDI[i] = p.Len() + } + } + } +} + +// determineParagraphEmbeddingLevel reports the resolved paragraph direction of +// the substring limited by the given range [start, end). +// +// Determines the paragraph level based on rules P2, P3. This is also used +// in rule X5c to find if an FSI should resolve to LRI or RLI. +func (p *paragraph) determineParagraphEmbeddingLevel(start, end int) level { + var strongType Class = unknownClass + + // Rule P2. + for i := start; i < end; i++ { + if t := p.resultTypes[i]; t.in(L, AL, R) { + strongType = t + break + } else if t.in(FSI, LRI, RLI) { + i = p.matchingPDI[i] // skip over to the matching PDI + if i > end { + log.Panic("assert (i <= end)") + } + } + } + // Rule P3. + switch strongType { + case unknownClass: // none found + // default embedding level when no strong types found is 0. + return 0 + case L: + return 0 + default: // AL, R + return 1 + } +} + +const maxDepth = 125 + +// This stack will store the embedding levels and override and isolated +// statuses +type directionalStatusStack struct { + stackCounter int + embeddingLevelStack [maxDepth + 1]level + overrideStatusStack [maxDepth + 1]Class + isolateStatusStack [maxDepth + 1]bool +} + +func (s *directionalStatusStack) empty() { s.stackCounter = 0 } +func (s *directionalStatusStack) pop() { s.stackCounter-- } +func (s *directionalStatusStack) depth() int { return s.stackCounter } + +func (s *directionalStatusStack) push(level level, overrideStatus Class, isolateStatus bool) { + s.embeddingLevelStack[s.stackCounter] = level + s.overrideStatusStack[s.stackCounter] = overrideStatus + s.isolateStatusStack[s.stackCounter] = isolateStatus + s.stackCounter++ +} + +func (s *directionalStatusStack) lastEmbeddingLevel() level { + return s.embeddingLevelStack[s.stackCounter-1] +} + +func (s *directionalStatusStack) lastDirectionalOverrideStatus() Class { + return s.overrideStatusStack[s.stackCounter-1] +} + +func (s *directionalStatusStack) lastDirectionalIsolateStatus() bool { + return s.isolateStatusStack[s.stackCounter-1] +} + +// Determine explicit levels using rules X1 - X8 +func (p *paragraph) determineExplicitEmbeddingLevels() { + var stack directionalStatusStack + var overflowIsolateCount, overflowEmbeddingCount, validIsolateCount int + + // Rule X1. + stack.push(p.embeddingLevel, ON, false) + + for i, t := range p.resultTypes { + // Rules X2, X3, X4, X5, X5a, X5b, X5c + switch t { + case RLE, LRE, RLO, LRO, RLI, LRI, FSI: + isIsolate := t.in(RLI, LRI, FSI) + isRTL := t.in(RLE, RLO, RLI) + + // override if this is an FSI that resolves to RLI + if t == FSI { + isRTL = (p.determineParagraphEmbeddingLevel(i+1, p.matchingPDI[i]) == 1) + } + if isIsolate { + p.resultLevels[i] = stack.lastEmbeddingLevel() + if stack.lastDirectionalOverrideStatus() != ON { + p.resultTypes[i] = stack.lastDirectionalOverrideStatus() + } + } + + var newLevel level + if isRTL { + // least greater odd + newLevel = (stack.lastEmbeddingLevel() + 1) | 1 + } else { + // least greater even + newLevel = (stack.lastEmbeddingLevel() + 2) &^ 1 + } + + if newLevel <= maxDepth && overflowIsolateCount == 0 && overflowEmbeddingCount == 0 { + if isIsolate { + validIsolateCount++ + } + // Push new embedding level, override status, and isolated + // status. + // No check for valid stack counter, since the level check + // suffices. + switch t { + case LRO: + stack.push(newLevel, L, isIsolate) + case RLO: + stack.push(newLevel, R, isIsolate) + default: + stack.push(newLevel, ON, isIsolate) + } + // Not really part of the spec + if !isIsolate { + p.resultLevels[i] = newLevel + } + } else { + // This is an invalid explicit formatting character, + // so apply the "Otherwise" part of rules X2-X5b. + if isIsolate { + overflowIsolateCount++ + } else { // !isIsolate + if overflowIsolateCount == 0 { + overflowEmbeddingCount++ + } + } + } + + // Rule X6a + case PDI: + if overflowIsolateCount > 0 { + overflowIsolateCount-- + } else if validIsolateCount == 0 { + // do nothing + } else { + overflowEmbeddingCount = 0 + for !stack.lastDirectionalIsolateStatus() { + stack.pop() + } + stack.pop() + validIsolateCount-- + } + p.resultLevels[i] = stack.lastEmbeddingLevel() + + // Rule X7 + case PDF: + // Not really part of the spec + p.resultLevels[i] = stack.lastEmbeddingLevel() + + if overflowIsolateCount > 0 { + // do nothing + } else if overflowEmbeddingCount > 0 { + overflowEmbeddingCount-- + } else if !stack.lastDirectionalIsolateStatus() && stack.depth() >= 2 { + stack.pop() + } + + case B: // paragraph separator. + // Rule X8. + + // These values are reset for clarity, in this implementation B + // can only occur as the last code in the array. + stack.empty() + overflowIsolateCount = 0 + overflowEmbeddingCount = 0 + validIsolateCount = 0 + p.resultLevels[i] = p.embeddingLevel + + default: + p.resultLevels[i] = stack.lastEmbeddingLevel() + if stack.lastDirectionalOverrideStatus() != ON { + p.resultTypes[i] = stack.lastDirectionalOverrideStatus() + } + } + } +} + +type isolatingRunSequence struct { + p *paragraph + + indexes []int // indexes to the original string + + types []Class // type of each character using the index + resolvedLevels []level // resolved levels after application of rules + level level + sos, eos Class +} + +func (i *isolatingRunSequence) Len() int { return len(i.indexes) } + +func maxLevel(a, b level) level { + if a > b { + return a + } + return b +} + +// Rule X10, second bullet: Determine the start-of-sequence (sos) and end-of-sequence (eos) types, +// either L or R, for each isolating run sequence. +func (p *paragraph) isolatingRunSequence(indexes []int) *isolatingRunSequence { + length := len(indexes) + types := make([]Class, length) + for i, x := range indexes { + types[i] = p.resultTypes[x] + } + + // assign level, sos and eos + prevChar := indexes[0] - 1 + for prevChar >= 0 && isRemovedByX9(p.initialTypes[prevChar]) { + prevChar-- + } + prevLevel := p.embeddingLevel + if prevChar >= 0 { + prevLevel = p.resultLevels[prevChar] + } + + var succLevel level + lastType := types[length-1] + if lastType.in(LRI, RLI, FSI) { + succLevel = p.embeddingLevel + } else { + // the first character after the end of run sequence + limit := indexes[length-1] + 1 + for ; limit < p.Len() && isRemovedByX9(p.initialTypes[limit]); limit++ { + + } + succLevel = p.embeddingLevel + if limit < p.Len() { + succLevel = p.resultLevels[limit] + } + } + level := p.resultLevels[indexes[0]] + return &isolatingRunSequence{ + p: p, + indexes: indexes, + types: types, + level: level, + sos: typeForLevel(maxLevel(prevLevel, level)), + eos: typeForLevel(maxLevel(succLevel, level)), + } +} + +// Resolving weak types Rules W1-W7. +// +// Note that some weak types (EN, AN) remain after this processing is +// complete. +func (s *isolatingRunSequence) resolveWeakTypes() { + + // on entry, only these types remain + s.assertOnly(L, R, AL, EN, ES, ET, AN, CS, B, S, WS, ON, NSM, LRI, RLI, FSI, PDI) + + // Rule W1. + // Changes all NSMs. + preceedingCharacterType := s.sos + for i, t := range s.types { + if t == NSM { + s.types[i] = preceedingCharacterType + } else { + if t.in(LRI, RLI, FSI, PDI) { + preceedingCharacterType = ON + } + preceedingCharacterType = t + } + } + + // Rule W2. + // EN does not change at the start of the run, because sos != AL. + for i, t := range s.types { + if t == EN { + for j := i - 1; j >= 0; j-- { + if t := s.types[j]; t.in(L, R, AL) { + if t == AL { + s.types[i] = AN + } + break + } + } + } + } + + // Rule W3. + for i, t := range s.types { + if t == AL { + s.types[i] = R + } + } + + // Rule W4. + // Since there must be values on both sides for this rule to have an + // effect, the scan skips the first and last value. + // + // Although the scan proceeds left to right, and changes the type + // values in a way that would appear to affect the computations + // later in the scan, there is actually no problem. A change in the + // current value can only affect the value to its immediate right, + // and only affect it if it is ES or CS. But the current value can + // only change if the value to its right is not ES or CS. Thus + // either the current value will not change, or its change will have + // no effect on the remainder of the analysis. + + for i := 1; i < s.Len()-1; i++ { + t := s.types[i] + if t == ES || t == CS { + prevSepType := s.types[i-1] + succSepType := s.types[i+1] + if prevSepType == EN && succSepType == EN { + s.types[i] = EN + } else if s.types[i] == CS && prevSepType == AN && succSepType == AN { + s.types[i] = AN + } + } + } + + // Rule W5. + for i, t := range s.types { + if t == ET { + // locate end of sequence + runStart := i + runEnd := s.findRunLimit(runStart, ET) + + // check values at ends of sequence + t := s.sos + if runStart > 0 { + t = s.types[runStart-1] + } + if t != EN { + t = s.eos + if runEnd < len(s.types) { + t = s.types[runEnd] + } + } + if t == EN { + setTypes(s.types[runStart:runEnd], EN) + } + // continue at end of sequence + i = runEnd + } + } + + // Rule W6. + for i, t := range s.types { + if t.in(ES, ET, CS) { + s.types[i] = ON + } + } + + // Rule W7. + for i, t := range s.types { + if t == EN { + // set default if we reach start of run + prevStrongType := s.sos + for j := i - 1; j >= 0; j-- { + t = s.types[j] + if t == L || t == R { // AL's have been changed to R + prevStrongType = t + break + } + } + if prevStrongType == L { + s.types[i] = L + } + } + } +} + +// 6) resolving neutral types Rules N1-N2. +func (s *isolatingRunSequence) resolveNeutralTypes() { + + // on entry, only these types can be in resultTypes + s.assertOnly(L, R, EN, AN, B, S, WS, ON, RLI, LRI, FSI, PDI) + + for i, t := range s.types { + switch t { + case WS, ON, B, S, RLI, LRI, FSI, PDI: + // find bounds of run of neutrals + runStart := i + runEnd := s.findRunLimit(runStart, B, S, WS, ON, RLI, LRI, FSI, PDI) + + // determine effective types at ends of run + var leadType, trailType Class + + // Note that the character found can only be L, R, AN, or + // EN. + if runStart == 0 { + leadType = s.sos + } else { + leadType = s.types[runStart-1] + if leadType.in(AN, EN) { + leadType = R + } + } + if runEnd == len(s.types) { + trailType = s.eos + } else { + trailType = s.types[runEnd] + if trailType.in(AN, EN) { + trailType = R + } + } + + var resolvedType Class + if leadType == trailType { + // Rule N1. + resolvedType = leadType + } else { + // Rule N2. + // Notice the embedding level of the run is used, not + // the paragraph embedding level. + resolvedType = typeForLevel(s.level) + } + + setTypes(s.types[runStart:runEnd], resolvedType) + + // skip over run of (former) neutrals + i = runEnd + } + } +} + +func setLevels(levels []level, newLevel level) { + for i := range levels { + levels[i] = newLevel + } +} + +func setTypes(types []Class, newType Class) { + for i := range types { + types[i] = newType + } +} + +// 7) resolving implicit embedding levels Rules I1, I2. +func (s *isolatingRunSequence) resolveImplicitLevels() { + + // on entry, only these types can be in resultTypes + s.assertOnly(L, R, EN, AN) + + s.resolvedLevels = make([]level, len(s.types)) + setLevels(s.resolvedLevels, s.level) + + if (s.level & 1) == 0 { // even level + for i, t := range s.types { + // Rule I1. + if t == L { + // no change + } else if t == R { + s.resolvedLevels[i] += 1 + } else { // t == AN || t == EN + s.resolvedLevels[i] += 2 + } + } + } else { // odd level + for i, t := range s.types { + // Rule I2. + if t == R { + // no change + } else { // t == L || t == AN || t == EN + s.resolvedLevels[i] += 1 + } + } + } +} + +// Applies the levels and types resolved in rules W1-I2 to the +// resultLevels array. +func (s *isolatingRunSequence) applyLevelsAndTypes() { + for i, x := range s.indexes { + s.p.resultTypes[x] = s.types[i] + s.p.resultLevels[x] = s.resolvedLevels[i] + } +} + +// Return the limit of the run consisting only of the types in validSet +// starting at index. This checks the value at index, and will return +// index if that value is not in validSet. +func (s *isolatingRunSequence) findRunLimit(index int, validSet ...Class) int { +loop: + for ; index < len(s.types); index++ { + t := s.types[index] + for _, valid := range validSet { + if t == valid { + continue loop + } + } + return index // didn't find a match in validSet + } + return len(s.types) +} + +// Algorithm validation. Assert that all values in types are in the +// provided set. +func (s *isolatingRunSequence) assertOnly(codes ...Class) { +loop: + for i, t := range s.types { + for _, c := range codes { + if t == c { + continue loop + } + } + log.Panicf("invalid bidi code %v present in assertOnly at position %d", t, s.indexes[i]) + } +} + +// determineLevelRuns returns an array of level runs. Each level run is +// described as an array of indexes into the input string. +// +// Determines the level runs. Rule X9 will be applied in determining the +// runs, in the way that makes sure the characters that are supposed to be +// removed are not included in the runs. +func (p *paragraph) determineLevelRuns() [][]int { + run := []int{} + allRuns := [][]int{} + currentLevel := implicitLevel + + for i := range p.initialTypes { + if !isRemovedByX9(p.initialTypes[i]) { + if p.resultLevels[i] != currentLevel { + // we just encountered a new run; wrap up last run + if currentLevel >= 0 { // only wrap it up if there was a run + allRuns = append(allRuns, run) + run = nil + } + // Start new run + currentLevel = p.resultLevels[i] + } + run = append(run, i) + } + } + // Wrap up the final run, if any + if len(run) > 0 { + allRuns = append(allRuns, run) + } + return allRuns +} + +// Definition BD13. Determine isolating run sequences. +func (p *paragraph) determineIsolatingRunSequences() []*isolatingRunSequence { + levelRuns := p.determineLevelRuns() + + // Compute the run that each character belongs to + runForCharacter := make([]int, p.Len()) + for i, run := range levelRuns { + for _, index := range run { + runForCharacter[index] = i + } + } + + sequences := []*isolatingRunSequence{} + + var currentRunSequence []int + + for _, run := range levelRuns { + first := run[0] + if p.initialTypes[first] != PDI || p.matchingIsolateInitiator[first] == -1 { + currentRunSequence = nil + // int run = i; + for { + // Copy this level run into currentRunSequence + currentRunSequence = append(currentRunSequence, run...) + + last := currentRunSequence[len(currentRunSequence)-1] + lastT := p.initialTypes[last] + if lastT.in(LRI, RLI, FSI) && p.matchingPDI[last] != p.Len() { + run = levelRuns[runForCharacter[p.matchingPDI[last]]] + } else { + break + } + } + sequences = append(sequences, p.isolatingRunSequence(currentRunSequence)) + } + } + return sequences +} + +// Assign level information to characters removed by rule X9. This is for +// ease of relating the level information to the original input data. Note +// that the levels assigned to these codes are arbitrary, they're chosen so +// as to avoid breaking level runs. +func (p *paragraph) assignLevelsToCharactersRemovedByX9() { + for i, t := range p.initialTypes { + if t.in(LRE, RLE, LRO, RLO, PDF, BN) { + p.resultTypes[i] = t + p.resultLevels[i] = -1 + } + } + // now propagate forward the levels information (could have + // propagated backward, the main thing is not to introduce a level + // break where one doesn't already exist). + + if p.resultLevels[0] == -1 { + p.resultLevels[0] = p.embeddingLevel + } + for i := 1; i < len(p.initialTypes); i++ { + if p.resultLevels[i] == -1 { + p.resultLevels[i] = p.resultLevels[i-1] + } + } + // Embedding information is for informational purposes only so need not be + // adjusted. +} + +// +// Output +// + +// getLevels computes levels array breaking lines at offsets in linebreaks. +// Rule L1. +// +// The linebreaks array must include at least one value. The values must be +// in strictly increasing order (no duplicates) between 1 and the length of +// the text, inclusive. The last value must be the length of the text. +func (p *paragraph) getLevels(linebreaks []int) []level { + // Note that since the previous processing has removed all + // P, S, and WS values from resultTypes, the values referred to + // in these rules are the initial types, before any processing + // has been applied (including processing of overrides). + // + // This example implementation has reinserted explicit format codes + // and BN, in order that the levels array correspond to the + // initial text. Their final placement is not normative. + // These codes are treated like WS in this implementation, + // so they don't interrupt sequences of WS. + + validateLineBreaks(linebreaks, p.Len()) + + result := append([]level(nil), p.resultLevels...) + + // don't worry about linebreaks since if there is a break within + // a series of WS values preceding S, the linebreak itself + // causes the reset. + for i, t := range p.initialTypes { + if t.in(B, S) { + // Rule L1, clauses one and two. + result[i] = p.embeddingLevel + + // Rule L1, clause three. + for j := i - 1; j >= 0; j-- { + if isWhitespace(p.initialTypes[j]) { // including format codes + result[j] = p.embeddingLevel + } else { + break + } + } + } + } + + // Rule L1, clause four. + start := 0 + for _, limit := range linebreaks { + for j := limit - 1; j >= start; j-- { + if isWhitespace(p.initialTypes[j]) { // including format codes + result[j] = p.embeddingLevel + } else { + break + } + } + start = limit + } + + return result +} + +// getReordering returns the reordering of lines from a visual index to a +// logical index for line breaks at the given offsets. +// +// Lines are concatenated from left to right. So for example, the fifth +// character from the left on the third line is +// +// getReordering(linebreaks)[linebreaks[1] + 4] +// +// (linebreaks[1] is the position after the last character of the second +// line, which is also the index of the first character on the third line, +// and adding four gets the fifth character from the left). +// +// The linebreaks array must include at least one value. The values must be +// in strictly increasing order (no duplicates) between 1 and the length of +// the text, inclusive. The last value must be the length of the text. +func (p *paragraph) getReordering(linebreaks []int) []int { + validateLineBreaks(linebreaks, p.Len()) + + return computeMultilineReordering(p.getLevels(linebreaks), linebreaks) +} + +// Return multiline reordering array for a given level array. Reordering +// does not occur across a line break. +func computeMultilineReordering(levels []level, linebreaks []int) []int { + result := make([]int, len(levels)) + + start := 0 + for _, limit := range linebreaks { + tempLevels := make([]level, limit-start) + copy(tempLevels, levels[start:]) + + for j, order := range computeReordering(tempLevels) { + result[start+j] = order + start + } + start = limit + } + return result +} + +// Return reordering array for a given level array. This reorders a single +// line. The reordering is a visual to logical map. For example, the +// leftmost char is string.charAt(order[0]). Rule L2. +func computeReordering(levels []level) []int { + result := make([]int, len(levels)) + // initialize order + for i := range result { + result[i] = i + } + + // locate highest level found on line. + // Note the rules say text, but no reordering across line bounds is + // performed, so this is sufficient. + highestLevel := level(0) + lowestOddLevel := level(maxDepth + 2) + for _, level := range levels { + if level > highestLevel { + highestLevel = level + } + if level&1 != 0 && level < lowestOddLevel { + lowestOddLevel = level + } + } + + for level := highestLevel; level >= lowestOddLevel; level-- { + for i := 0; i < len(levels); i++ { + if levels[i] >= level { + // find range of text at or above this level + start := i + limit := i + 1 + for limit < len(levels) && levels[limit] >= level { + limit++ + } + + for j, k := start, limit-1; j < k; j, k = j+1, k-1 { + result[j], result[k] = result[k], result[j] + } + // skip to end of level run + i = limit + } + } + } + + return result +} + +// isWhitespace reports whether the type is considered a whitespace type for the +// line break rules. +func isWhitespace(c Class) bool { + switch c { + case LRE, RLE, LRO, RLO, PDF, LRI, RLI, FSI, PDI, BN, WS: + return true + } + return false +} + +// isRemovedByX9 reports whether the type is one of the types removed in X9. +func isRemovedByX9(c Class) bool { + switch c { + case LRE, RLE, LRO, RLO, PDF, BN: + return true + } + return false +} + +// typeForLevel reports the strong type (L or R) corresponding to the level. +func typeForLevel(level level) Class { + if (level & 0x1) == 0 { + return L + } + return R +} + +// TODO: change validation to not panic + +func validateTypes(types []Class) { + if len(types) == 0 { + log.Panic("types is null") + } + for i, t := range types[:len(types)-1] { + if t == B { + log.Panicf("B type before end of paragraph at index: %d", i) + } + } +} + +func validateParagraphEmbeddingLevel(embeddingLevel level) { + if embeddingLevel != implicitLevel && + embeddingLevel != 0 && + embeddingLevel != 1 { + log.Panicf("illegal paragraph embedding level: %d", embeddingLevel) + } +} + +func validateLineBreaks(linebreaks []int, textLength int) { + prev := 0 + for i, next := range linebreaks { + if next <= prev { + log.Panicf("bad linebreak: %d at index: %d", next, i) + } + prev = next + } + if prev != textLength { + log.Panicf("last linebreak was %d, want %d", prev, textLength) + } +} + +func validatePbTypes(pairTypes []bracketType) { + if len(pairTypes) == 0 { + log.Panic("pairTypes is null") + } + for i, pt := range pairTypes { + switch pt { + case bpNone, bpOpen, bpClose: + default: + log.Panicf("illegal pairType value at %d: %v", i, pairTypes[i]) + } + } +} + +func validatePbValues(pairValues []rune, pairTypes []bracketType) { + if pairValues == nil { + log.Panic("pairValues is null") + } + if len(pairTypes) != len(pairValues) { + log.Panic("pairTypes is different length from pairValues") + } +} |