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// Copyright 2009 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 regexp implements regular expression search.
//
// The syntax of the regular expressions accepted is the same
// general syntax used by Perl, Python, and other languages.
// More precisely, it is the syntax accepted by RE2 and described at
// http://code.google.com/p/re2/wiki/Syntax, except for \C.
//
// All characters are UTF-8-encoded code points.
//
// There are 16 methods of Regexp that match a regular expression and identify
// the matched text.  Their names are matched by this regular expression:
//
//      Find(All)?(String)?(Submatch)?(Index)?
//
// If 'All' is present, the routine matches successive non-overlapping
// matches of the entire expression.  Empty matches abutting a preceding
// match are ignored.  The return value is a slice containing the successive
// return values of the corresponding non-'All' routine.  These routines take
// an extra integer argument, n; if n >= 0, the function returns at most n
// matches/submatches.
//
// If 'String' is present, the argument is a string; otherwise it is a slice
// of bytes; return values are adjusted as appropriate.
//
// If 'Submatch' is present, the return value is a slice identifying the
// successive submatches of the expression.  Submatches are matches of
// parenthesized subexpressions within the regular expression, numbered from
// left to right in order of opening parenthesis.  Submatch 0 is the match of
// the entire expression, submatch 1 the match of the first parenthesized
// subexpression, and so on.
//
// If 'Index' is present, matches and submatches are identified by byte index
// pairs within the input string: result[2*n:2*n+1] identifies the indexes of
// the nth submatch.  The pair for n==0 identifies the match of the entire
// expression.  If 'Index' is not present, the match is identified by the
// text of the match/submatch.  If an index is negative, it means that
// subexpression did not match any string in the input.
//
// There is also a subset of the methods that can be applied to text read
// from a RuneReader:
//
//      MatchReader, FindReaderIndex, FindReaderSubmatchIndex
//
// This set may grow.  Note that regular expression matches may need to
// examine text beyond the text returned by a match, so the methods that
// match text from a RuneReader may read arbitrarily far into the input
// before returning.
//
// (There are a few other methods that do not match this pattern.)
//
package regexp

import (
        "bytes"
        "io"
        "regexp/syntax"
        "strconv"
        "strings"
        "sync"
        "unicode/utf8"
)

var debug = false

// Regexp is the representation of a compiled regular expression.
// The public interface is entirely through methods.
// A Regexp is safe for concurrent use by multiple goroutines.
type Regexp struct {
        // read-only after Compile
        expr           string         // as passed to Compile
        prog           *syntax.Prog   // compiled program
        prefix         string         // required prefix in unanchored matches
        prefixBytes    []byte         // prefix, as a []byte
        prefixComplete bool           // prefix is the entire regexp
        prefixRune     rune           // first rune in prefix
        cond           syntax.EmptyOp // empty-width conditions required at start of match
        numSubexp      int
        subexpNames    []string
        longest        bool

        // cache of machines for running regexp
        mu      sync.Mutex
        machine []*machine
}

// String returns the source text used to compile the regular expression.
func (re *Regexp) String() string {
        return re.expr
}

// Compile parses a regular expression and returns, if successful,
// a Regexp object that can be used to match against text.
//
// When matching against text, the regexp returns a match that
// begins as early as possible in the input (leftmost), and among those
// it chooses the one that a backtracking search would have found first.
// This so-called leftmost-first matching is the same semantics
// that Perl, Python, and other implementations use, although this
// package implements it without the expense of backtracking.
// For POSIX leftmost-longest matching, see CompilePOSIX.
func Compile(expr string) (*Regexp, error) {
        return compile(expr, syntax.Perl, false)
}

// CompilePOSIX is like Compile but restricts the regular expression
// to POSIX ERE (egrep) syntax and changes the match semantics to
// leftmost-longest.
//
// That is, when matching against text, the regexp returns a match that
// begins as early as possible in the input (leftmost), and among those
// it chooses a match that is as long as possible.
// This so-called leftmost-longest matching is the same semantics
// that early regular expression implementations used and that POSIX
// specifies.
//
// However, there can be multiple leftmost-longest matches, with different
// submatch choices, and here this package diverges from POSIX.
// Among the possible leftmost-longest matches, this package chooses
// the one that a backtracking search would have found first, while POSIX
// specifies that the match be chosen to maximize the length of the first
// subexpression, then the second, and so on from left to right.
// The POSIX rule is computationally prohibitive and not even well-defined.
// See http://swtch.com/~rsc/regexp/regexp2.html#posix for details.
func CompilePOSIX(expr string) (*Regexp, error) {
        return compile(expr, syntax.POSIX, true)
}

func compile(expr string, mode syntax.Flags, longest bool) (*Regexp, error) {
        re, err := syntax.Parse(expr, mode)
        if err != nil {
                return nil, err
        }
        maxCap := re.MaxCap()
        capNames := re.CapNames()

        re = re.Simplify()
        prog, err := syntax.Compile(re)
        if err != nil {
                return nil, err
        }
        regexp := &Regexp{
                expr:        expr,
                prog:        prog,
                numSubexp:   maxCap,
                subexpNames: capNames,
                cond:        prog.StartCond(),
                longest:     longest,
        }
        regexp.prefix, regexp.prefixComplete = prog.Prefix()
        if regexp.prefix != "" {
                // TODO(rsc): Remove this allocation by adding
                // IndexString to package bytes.
                regexp.prefixBytes = []byte(regexp.prefix)
                regexp.prefixRune, _ = utf8.DecodeRuneInString(regexp.prefix)
        }
        return regexp, nil
}

// get returns a machine to use for matching re.
// It uses the re's machine cache if possible, to avoid
// unnecessary allocation.
func (re *Regexp) get() *machine {
        re.mu.Lock()
        if n := len(re.machine); n > 0 {
                z := re.machine[n-1]
                re.machine = re.machine[:n-1]
                re.mu.Unlock()
                return z
        }
        re.mu.Unlock()
        z := progMachine(re.prog)
        z.re = re
        return z
}

// put returns a machine to the re's machine cache.
// There is no attempt to limit the size of the cache, so it will
// grow to the maximum number of simultaneous matches
// run using re.  (The cache empties when re gets garbage collected.)
func (re *Regexp) put(z *machine) {
        re.mu.Lock()
        re.machine = append(re.machine, z)
        re.mu.Unlock()
}

// MustCompile is like Compile but panics if the expression cannot be parsed.
// It simplifies safe initialization of global variables holding compiled regular
// expressions.
func MustCompile(str string) *Regexp {
        regexp, error := Compile(str)
        if error != nil {
                panic(`regexp: Compile(` + quote(str) + `): ` + error.Error())
        }
        return regexp
}

// MustCompilePOSIX is like CompilePOSIX but panics if the expression cannot be parsed.
// It simplifies safe initialization of global variables holding compiled regular
// expressions.
func MustCompilePOSIX(str string) *Regexp {
        regexp, error := CompilePOSIX(str)
        if error != nil {
                panic(`regexp: CompilePOSIX(` + quote(str) + `): ` + error.Error())
        }
        return regexp
}

func quote(s string) string {
        if strconv.CanBackquote(s) {
                return "`" + s + "`"
        }
        return strconv.Quote(s)
}

// NumSubexp returns the number of parenthesized subexpressions in this Regexp.
func (re *Regexp) NumSubexp() int {
        return re.numSubexp
}

// SubexpNames returns the names of the parenthesized subexpressions
// in this Regexp.  The name for the first sub-expression is names[1],
// so that if m is a match slice, the name for m[i] is SubexpNames()[i].
// Since the Regexp as a whole cannot be named, names[0] is always
// the empty string.  The slice should not be modified.
func (re *Regexp) SubexpNames() []string {
        return re.subexpNames
}

const endOfText rune = -1

// input abstracts different representations of the input text. It provides
// one-character lookahead.
type input interface {
        step(pos int) (r rune, width int) // advance one rune
        canCheckPrefix() bool             // can we look ahead without losing info?
        hasPrefix(re *Regexp) bool
        index(re *Regexp, pos int) int
        context(pos int) syntax.EmptyOp
}

// inputString scans a string.
type inputString struct {
        str string
}

func (i *inputString) step(pos int) (rune, int) {
        if pos < len(i.str) {
                c := i.str[pos]
                if c < utf8.RuneSelf {
                        return rune(c), 1
                }
                return utf8.DecodeRuneInString(i.str[pos:])
        }
        return endOfText, 0
}

func (i *inputString) canCheckPrefix() bool {
        return true
}

func (i *inputString) hasPrefix(re *Regexp) bool {
        return strings.HasPrefix(i.str, re.prefix)
}

func (i *inputString) index(re *Regexp, pos int) int {
        return strings.Index(i.str[pos:], re.prefix)
}

func (i *inputString) context(pos int) syntax.EmptyOp {
        r1, r2 := endOfText, endOfText
        if pos > 0 && pos <= len(i.str) {
                r1, _ = utf8.DecodeLastRuneInString(i.str[:pos])
        }
        if pos < len(i.str) {
                r2, _ = utf8.DecodeRuneInString(i.str[pos:])
        }
        return syntax.EmptyOpContext(r1, r2)
}

// inputBytes scans a byte slice.
type inputBytes struct {
        str []byte
}

func (i *inputBytes) step(pos int) (rune, int) {
        if pos < len(i.str) {
                c := i.str[pos]
                if c < utf8.RuneSelf {
                        return rune(c), 1
                }
                return utf8.DecodeRune(i.str[pos:])
        }
        return endOfText, 0
}

func (i *inputBytes) canCheckPrefix() bool {
        return true
}

func (i *inputBytes) hasPrefix(re *Regexp) bool {
        return bytes.HasPrefix(i.str, re.prefixBytes)
}

func (i *inputBytes) index(re *Regexp, pos int) int {
        return bytes.Index(i.str[pos:], re.prefixBytes)
}

func (i *inputBytes) context(pos int) syntax.EmptyOp {
        r1, r2 := endOfText, endOfText
        if pos > 0 && pos <= len(i.str) {
                r1, _ = utf8.DecodeLastRune(i.str[:pos])
        }
        if pos < len(i.str) {
                r2, _ = utf8.DecodeRune(i.str[pos:])
        }
        return syntax.EmptyOpContext(r1, r2)
}

// inputReader scans a RuneReader.
type inputReader struct {
        r     io.RuneReader
        atEOT bool
        pos   int
}

func (i *inputReader) step(pos int) (rune, int) {
        if !i.atEOT && pos != i.pos {
                return endOfText, 0

        }
        r, w, err := i.r.ReadRune()
        if err != nil {
                i.atEOT = true
                return endOfText, 0
        }
        i.pos += w
        return r, w
}

func (i *inputReader) canCheckPrefix() bool {
        return false
}

func (i *inputReader) hasPrefix(re *Regexp) bool {
        return false
}

func (i *inputReader) index(re *Regexp, pos int) int {
        return -1
}

func (i *inputReader) context(pos int) syntax.EmptyOp {
        return 0
}

// LiteralPrefix returns a literal string that must begin any match
// of the regular expression re.  It returns the boolean true if the
// literal string comprises the entire regular expression.
func (re *Regexp) LiteralPrefix() (prefix string, complete bool) {
        return re.prefix, re.prefixComplete
}

// MatchReader returns whether the Regexp matches the text read by the
// RuneReader.  The return value is a boolean: true for match, false for no
// match.
func (re *Regexp) MatchReader(r io.RuneReader) bool {
        return re.doExecute(r, nil, "", 0, 0) != nil
}

// MatchString returns whether the Regexp matches the string s.
// The return value is a boolean: true for match, false for no match.
func (re *Regexp) MatchString(s string) bool {
        return re.doExecute(nil, nil, s, 0, 0) != nil
}

// Match returns whether the Regexp matches the byte slice b.
// The return value is a boolean: true for match, false for no match.
func (re *Regexp) Match(b []byte) bool {
        return re.doExecute(nil, b, "", 0, 0) != nil
}

// MatchReader checks whether a textual regular expression matches the text
// read by the RuneReader.  More complicated queries need to use Compile and
// the full Regexp interface.
func MatchReader(pattern string, r io.RuneReader) (matched bool, error error) {
        re, err := Compile(pattern)
        if err != nil {
                return false, err
        }
        return re.MatchReader(r), nil
}

// MatchString checks whether a textual regular expression
// matches a string.  More complicated queries need
// to use Compile and the full Regexp interface.
func MatchString(pattern string, s string) (matched bool, error error) {
        re, err := Compile(pattern)
        if err != nil {
                return false, err
        }
        return re.MatchString(s), nil
}

// Match checks whether a textual regular expression
// matches a byte slice.  More complicated queries need
// to use Compile and the full Regexp interface.
func Match(pattern string, b []byte) (matched bool, error error) {
        re, err := Compile(pattern)
        if err != nil {
                return false, err
        }
        return re.Match(b), nil
}

// ReplaceAllString returns a copy of src in which all matches for the Regexp
// have been replaced by repl.  No support is provided for expressions
// (e.g. \1 or $1) in the replacement string.
func (re *Regexp) ReplaceAllString(src, repl string) string {
        return re.ReplaceAllStringFunc(src, func(string) string { return repl })
}

// ReplaceAllStringFunc returns a copy of src in which all matches for the
// Regexp have been replaced by the return value of of function repl (whose
// first argument is the matched string).  No support is provided for
// expressions (e.g. \1 or $1) in the replacement string.
func (re *Regexp) ReplaceAllStringFunc(src string, repl func(string) string) string {
        lastMatchEnd := 0 // end position of the most recent match
        searchPos := 0    // position where we next look for a match
        buf := new(bytes.Buffer)
        for searchPos <= len(src) {
                a := re.doExecute(nil, nil, src, searchPos, 2)
                if len(a) == 0 {
                        break // no more matches
                }

                // Copy the unmatched characters before this match.
                io.WriteString(buf, src[lastMatchEnd:a[0]])

                // Now insert a copy of the replacement string, but not for a
                // match of the empty string immediately after another match.
                // (Otherwise, we get double replacement for patterns that
                // match both empty and nonempty strings.)
                if a[1] > lastMatchEnd || a[0] == 0 {
                        io.WriteString(buf, repl(src[a[0]:a[1]]))
                }
                lastMatchEnd = a[1]

                // Advance past this match; always advance at least one character.
                _, width := utf8.DecodeRuneInString(src[searchPos:])
                if searchPos+width > a[1] {
                        searchPos += width
                } else if searchPos+1 > a[1] {
                        // This clause is only needed at the end of the input
                        // string.  In that case, DecodeRuneInString returns width=0.
                        searchPos++
                } else {
                        searchPos = a[1]
                }
        }

        // Copy the unmatched characters after the last match.
        io.WriteString(buf, src[lastMatchEnd:])

        return buf.String()
}

// ReplaceAll returns a copy of src in which all matches for the Regexp
// have been replaced by repl.  No support is provided for expressions
// (e.g. \1 or $1) in the replacement text.
func (re *Regexp) ReplaceAll(src, repl []byte) []byte {
        return re.ReplaceAllFunc(src, func([]byte) []byte { return repl })
}

// ReplaceAllFunc returns a copy of src in which all matches for the
// Regexp have been replaced by the return value of of function repl (whose
// first argument is the matched []byte).  No support is provided for
// expressions (e.g. \1 or $1) in the replacement string.
func (re *Regexp) ReplaceAllFunc(src []byte, repl func([]byte) []byte) []byte {
        lastMatchEnd := 0 // end position of the most recent match
        searchPos := 0    // position where we next look for a match
        buf := new(bytes.Buffer)
        for searchPos <= len(src) {
                a := re.doExecute(nil, src, "", searchPos, 2)
                if len(a) == 0 {
                        break // no more matches
                }

                // Copy the unmatched characters before this match.
                buf.Write(src[lastMatchEnd:a[0]])

                // Now insert a copy of the replacement string, but not for a
                // match of the empty string immediately after another match.
                // (Otherwise, we get double replacement for patterns that
                // match both empty and nonempty strings.)
                if a[1] > lastMatchEnd || a[0] == 0 {
                        buf.Write(repl(src[a[0]:a[1]]))
                }
                lastMatchEnd = a[1]

                // Advance past this match; always advance at least one character.
                _, width := utf8.DecodeRune(src[searchPos:])
                if searchPos+width > a[1] {
                        searchPos += width
                } else if searchPos+1 > a[1] {
                        // This clause is only needed at the end of the input
                        // string.  In that case, DecodeRuneInString returns width=0.
                        searchPos++
                } else {
                        searchPos = a[1]
                }
        }

        // Copy the unmatched characters after the last match.
        buf.Write(src[lastMatchEnd:])

        return buf.Bytes()
}

var specialBytes = []byte(`\.+*?()|[]{}^$`)

func special(b byte) bool {
        return bytes.IndexByte(specialBytes, b) >= 0
}

// QuoteMeta returns a string that quotes all regular expression metacharacters
// inside the argument text; the returned string is a regular expression matching
// the literal text.  For example, QuoteMeta(`[foo]`) returns `\[foo\]`.
func QuoteMeta(s string) string {
        b := make([]byte, 2*len(s))

        // A byte loop is correct because all metacharacters are ASCII.
        j := 0
        for i := 0; i < len(s); i++ {
                if special(s[i]) {
                        b[j] = '\\'
                        j++
                }
                b[j] = s[i]
                j++
        }
        return string(b[0:j])
}

// The number of capture values in the program may correspond
// to fewer capturing expressions than are in the regexp.
// For example, "(a){0}" turns into an empty program, so the
// maximum capture in the program is 0 but we need to return
// an expression for \1.  Pad appends -1s to the slice a as needed.
func (re *Regexp) pad(a []int) []int {
        if a == nil {
                // No match.
                return nil
        }
        n := (1 + re.numSubexp) * 2
        for len(a) < n {
                a = append(a, -1)
        }
        return a
}

// Find matches in slice b if b is non-nil, otherwise find matches in string s.
func (re *Regexp) allMatches(s string, b []byte, n int, deliver func([]int)) {
        var end int
        if b == nil {
                end = len(s)
        } else {
                end = len(b)
        }

        for pos, i, prevMatchEnd := 0, 0, -1; i < n && pos <= end; {
                matches := re.doExecute(nil, b, s, pos, re.prog.NumCap)
                if len(matches) == 0 {
                        break
                }

                accept := true
                if matches[1] == pos {
                        // We've found an empty match.
                        if matches[0] == prevMatchEnd {
                                // We don't allow an empty match right
                                // after a previous match, so ignore it.
                                accept = false
                        }
                        var width int
                        // TODO: use step()
                        if b == nil {
                                _, width = utf8.DecodeRuneInString(s[pos:end])
                        } else {
                                _, width = utf8.DecodeRune(b[pos:end])
                        }
                        if width > 0 {
                                pos += width
                        } else {
                                pos = end + 1
                        }
                } else {
                        pos = matches[1]
                }
                prevMatchEnd = matches[1]

                if accept {
                        deliver(re.pad(matches))
                        i++
                }
        }
}

// Find returns a slice holding the text of the leftmost match in b of the regular expression.
// A return value of nil indicates no match.
func (re *Regexp) Find(b []byte) []byte {
        a := re.doExecute(nil, b, "", 0, 2)
        if a == nil {
                return nil
        }
        return b[a[0]:a[1]]
}

// FindIndex returns a two-element slice of integers defining the location of
// the leftmost match in b of the regular expression.  The match itself is at
// b[loc[0]:loc[1]].
// A return value of nil indicates no match.
func (re *Regexp) FindIndex(b []byte) (loc []int) {
        a := re.doExecute(nil, b, "", 0, 2)
        if a == nil {
                return nil
        }
        return a[0:2]
}

// FindString returns a string holding the text of the leftmost match in s of the regular
// expression.  If there is no match, the return value is an empty string,
// but it will also be empty if the regular expression successfully matches
// an empty string.  Use FindStringIndex or FindStringSubmatch if it is
// necessary to distinguish these cases.
func (re *Regexp) FindString(s string) string {
        a := re.doExecute(nil, nil, s, 0, 2)
        if a == nil {
                return ""
        }
        return s[a[0]:a[1]]
}

// FindStringIndex returns a two-element slice of integers defining the
// location of the leftmost match in s of the regular expression.  The match
// itself is at s[loc[0]:loc[1]].
// A return value of nil indicates no match.
func (re *Regexp) FindStringIndex(s string) []int {
        a := re.doExecute(nil, nil, s, 0, 2)
        if a == nil {
                return nil
        }
        return a[0:2]
}

// FindReaderIndex returns a two-element slice of integers defining the
// location of the leftmost match of the regular expression in text read from
// the RuneReader.  The match itself is at s[loc[0]:loc[1]].  A return
// value of nil indicates no match.
func (re *Regexp) FindReaderIndex(r io.RuneReader) []int {
        a := re.doExecute(r, nil, "", 0, 2)
        if a == nil {
                return nil
        }
        return a[0:2]
}

// FindSubmatch returns a slice of slices holding the text of the leftmost
// match of the regular expression in b and the matches, if any, of its
// subexpressions, as defined by the 'Submatch' descriptions in the package
// comment.
// A return value of nil indicates no match.
func (re *Regexp) FindSubmatch(b []byte) [][]byte {
        a := re.doExecute(nil, b, "", 0, re.prog.NumCap)
        if a == nil {
                return nil
        }
        ret := make([][]byte, 1+re.numSubexp)
        for i := range ret {
                if 2*i < len(a) && a[2*i] >= 0 {
                        ret[i] = b[a[2*i]:a[2*i+1]]
                }
        }
        return ret
}

// FindSubmatchIndex returns a slice holding the index pairs identifying the
// leftmost match of the regular expression in b and the matches, if any, of
// its subexpressions, as defined by the 'Submatch' and 'Index' descriptions
// in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindSubmatchIndex(b []byte) []int {
        return re.pad(re.doExecute(nil, b, "", 0, re.prog.NumCap))
}

// FindStringSubmatch returns a slice of strings holding the text of the
// leftmost match of the regular expression in s and the matches, if any, of
// its subexpressions, as defined by the 'Submatch' description in the
// package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindStringSubmatch(s string) []string {
        a := re.doExecute(nil, nil, s, 0, re.prog.NumCap)
        if a == nil {
                return nil
        }
        ret := make([]string, 1+re.numSubexp)
        for i := range ret {
                if 2*i < len(a) && a[2*i] >= 0 {
                        ret[i] = s[a[2*i]:a[2*i+1]]
                }
        }
        return ret
}

// FindStringSubmatchIndex returns a slice holding the index pairs
// identifying the leftmost match of the regular expression in s and the
// matches, if any, of its subexpressions, as defined by the 'Submatch' and
// 'Index' descriptions in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindStringSubmatchIndex(s string) []int {
        return re.pad(re.doExecute(nil, nil, s, 0, re.prog.NumCap))
}

// FindReaderSubmatchIndex returns a slice holding the index pairs
// identifying the leftmost match of the regular expression of text read by
// the RuneReader, and the matches, if any, of its subexpressions, as defined
// by the 'Submatch' and 'Index' descriptions in the package comment.  A
// return value of nil indicates no match.
func (re *Regexp) FindReaderSubmatchIndex(r io.RuneReader) []int {
        return re.pad(re.doExecute(r, nil, "", 0, re.prog.NumCap))
}

const startSize = 10 // The size at which to start a slice in the 'All' routines.

// FindAll is the 'All' version of Find; it returns a slice of all successive
// matches of the expression, as defined by the 'All' description in the
// package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAll(b []byte, n int) [][]byte {
        if n < 0 {
                n = len(b) + 1
        }
        result := make([][]byte, 0, startSize)
        re.allMatches("", b, n, func(match []int) {
                result = append(result, b[match[0]:match[1]])
        })
        if len(result) == 0 {
                return nil
        }
        return result
}

// FindAllIndex is the 'All' version of FindIndex; it returns a slice of all
// successive matches of the expression, as defined by the 'All' description
// in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAllIndex(b []byte, n int) [][]int {
        if n < 0 {
                n = len(b) + 1
        }
        result := make([][]int, 0, startSize)
        re.allMatches("", b, n, func(match []int) {
                result = append(result, match[0:2])
        })
        if len(result) == 0 {
                return nil
        }
        return result
}

// FindAllString is the 'All' version of FindString; it returns a slice of all
// successive matches of the expression, as defined by the 'All' description
// in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAllString(s string, n int) []string {
        if n < 0 {
                n = len(s) + 1
        }
        result := make([]string, 0, startSize)
        re.allMatches(s, nil, n, func(match []int) {
                result = append(result, s[match[0]:match[1]])
        })
        if len(result) == 0 {
                return nil
        }
        return result
}

// FindAllStringIndex is the 'All' version of FindStringIndex; it returns a
// slice of all successive matches of the expression, as defined by the 'All'
// description in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAllStringIndex(s string, n int) [][]int {
        if n < 0 {
                n = len(s) + 1
        }
        result := make([][]int, 0, startSize)
        re.allMatches(s, nil, n, func(match []int) {
                result = append(result, match[0:2])
        })
        if len(result) == 0 {
                return nil
        }
        return result
}

// FindAllSubmatch is the 'All' version of FindSubmatch; it returns a slice
// of all successive matches of the expression, as defined by the 'All'
// description in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAllSubmatch(b []byte, n int) [][][]byte {
        if n < 0 {
                n = len(b) + 1
        }
        result := make([][][]byte, 0, startSize)
        re.allMatches("", b, n, func(match []int) {
                slice := make([][]byte, len(match)/2)
                for j := range slice {
                        if match[2*j] >= 0 {
                                slice[j] = b[match[2*j]:match[2*j+1]]
                        }
                }
                result = append(result, slice)
        })
        if len(result) == 0 {
                return nil
        }
        return result
}

// FindAllSubmatchIndex is the 'All' version of FindSubmatchIndex; it returns
// a slice of all successive matches of the expression, as defined by the
// 'All' description in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAllSubmatchIndex(b []byte, n int) [][]int {
        if n < 0 {
                n = len(b) + 1
        }
        result := make([][]int, 0, startSize)
        re.allMatches("", b, n, func(match []int) {
                result = append(result, match)
        })
        if len(result) == 0 {
                return nil
        }
        return result
}

// FindAllStringSubmatch is the 'All' version of FindStringSubmatch; it
// returns a slice of all successive matches of the expression, as defined by
// the 'All' description in the package comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAllStringSubmatch(s string, n int) [][]string {
        if n < 0 {
                n = len(s) + 1
        }
        result := make([][]string, 0, startSize)
        re.allMatches(s, nil, n, func(match []int) {
                slice := make([]string, len(match)/2)
                for j := range slice {
                        if match[2*j] >= 0 {
                                slice[j] = s[match[2*j]:match[2*j+1]]
                        }
                }
                result = append(result, slice)
        })
        if len(result) == 0 {
                return nil
        }
        return result
}

// FindAllStringSubmatchIndex is the 'All' version of
// FindStringSubmatchIndex; it returns a slice of all successive matches of
// the expression, as defined by the 'All' description in the package
// comment.
// A return value of nil indicates no match.
func (re *Regexp) FindAllStringSubmatchIndex(s string, n int) [][]int {
        if n < 0 {
                n = len(s) + 1
        }
        result := make([][]int, 0, startSize)
        re.allMatches(s, nil, n, func(match []int) {
                result = append(result, match)
        })
        if len(result) == 0 {
                return nil
        }
        return result
}