go core 源码
golang core 代码
文件路径：/src/vendor/golang.org/x/text/unicode/bidi/core.go
// 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 (
"fmt"
"log"
)
// This implementation is a port based on the reference implementation found at:
// https://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.
func newParagraph(types []Class, pairTypes []bracketType, pairValues []rune, levels level) (*paragraph, error) {
var err error
if err = validateTypes(types); err != nil {
return nil, err
}
if err = validatePbTypes(pairTypes); err != nil {
return nil, err
}
if err = validatePbValues(pairValues, pairTypes); err != nil {
return nil, err
}
if err = validateParagraphEmbeddingLevel(levels); err != nil {
return nil, err
}
p := ¶graph{
initialTypes: append([]Class(nil), types...),
embeddingLevel: levels,
pairTypes: pairTypes,
pairValues: pairValues,
resultTypes: append([]Class(nil), types...),
}
p.run()
return p, nil
}
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.
precedingCharacterType := s.sos
for i, t := range s.types {
if t == NSM {
s.types[i] = precedingCharacterType
} else {
// if t.in(LRI, RLI, FSI, PDI) {
// precedingCharacterType = ON
// }
precedingCharacterType = 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
}
func validateTypes(types []Class) error {
if len(types) == 0 {
return fmt.Errorf("types is null")
}
for i, t := range types[:len(types)-1] {
if t == B {
return fmt.Errorf("B type before end of paragraph at index: %d", i)
}
}
return nil
}
func validateParagraphEmbeddingLevel(embeddingLevel level) error {
if embeddingLevel != implicitLevel &&
embeddingLevel != 0 &&
embeddingLevel != 1 {
return fmt.Errorf("illegal paragraph embedding level: %d", embeddingLevel)
}
return nil
}
func validateLineBreaks(linebreaks []int, textLength int) error {
prev := 0
for i, next := range linebreaks {
if next <= prev {
return fmt.Errorf("bad linebreak: %d at index: %d", next, i)
}
prev = next
}
if prev != textLength {
return fmt.Errorf("last linebreak was %d, want %d", prev, textLength)
}
return nil
}
func validatePbTypes(pairTypes []bracketType) error {
if len(pairTypes) == 0 {
return fmt.Errorf("pairTypes is null")
}
for i, pt := range pairTypes {
switch pt {
case bpNone, bpOpen, bpClose:
default:
return fmt.Errorf("illegal pairType value at %d: %v", i, pairTypes[i])
}
}
return nil
}
func validatePbValues(pairValues []rune, pairTypes []bracketType) error {
if pairValues == nil {
return fmt.Errorf("pairValues is null")
}
if len(pairTypes) != len(pairValues) {
return fmt.Errorf("pairTypes is different length from pairValues")
}
return nil
}
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