source: code/trunk/vendor/github.com/dlclark/regexp2/match.go@ 67

package regexp2

import (
        "bytes"
        "fmt"
)

// Match is a single regex result match that contains groups and repeated captures
//      -Groups
//    -Capture
type Match struct {
        Group //embeded group 0

        regex       *Regexp
        otherGroups []Group

        // input to the match
        textpos   int
        textstart int

        capcount   int
        caps       []int
        sparseCaps map[int]int

        // output from the match
        matches    [][]int
        matchcount []int

        // whether we've done any balancing with this match.  If we
        // have done balancing, we'll need to do extra work in Tidy().
        balancing bool
}

// Group is an explicit or implit (group 0) matched group within the pattern
type Group struct {
        Capture // the last capture of this group is embeded for ease of use

        Name     string    // group name
        Captures []Capture // captures of this group
}

// Capture is a single capture of text within the larger original string
type Capture struct {
        // the original string
        text []rune
        // the position in the original string where the first character of
        // captured substring was found.
        Index int
        // the length of the captured substring.
        Length int
}

// String returns the captured text as a String
func (c *Capture) String() string {
        return string(c.text[c.Index : c.Index+c.Length])
}

// Runes returns the captured text as a rune slice
func (c *Capture) Runes() []rune {
        return c.text[c.Index : c.Index+c.Length]
}

func newMatch(regex *Regexp, capcount int, text []rune, startpos int) *Match {
        m := Match{
                regex:      regex,
                matchcount: make([]int, capcount),
                matches:    make([][]int, capcount),
                textstart:  startpos,
                balancing:  false,
        }
        m.Name = "0"
        m.text = text
        m.matches[0] = make([]int, 2)
        return &m
}

func newMatchSparse(regex *Regexp, caps map[int]int, capcount int, text []rune, startpos int) *Match {
        m := newMatch(regex, capcount, text, startpos)
        m.sparseCaps = caps
        return m
}

func (m *Match) reset(text []rune, textstart int) {
        m.text = text
        m.textstart = textstart
        for i := 0; i < len(m.matchcount); i++ {
                m.matchcount[i] = 0
        }
        m.balancing = false
}

func (m *Match) tidy(textpos int) {

        interval := m.matches[0]
        m.Index = interval[0]
        m.Length = interval[1]
        m.textpos = textpos
        m.capcount = m.matchcount[0]
        //copy our root capture to the list
        m.Group.Captures = []Capture{m.Group.Capture}

        if m.balancing {
                // The idea here is that we want to compact all of our unbalanced captures.  To do that we
                // use j basically as a count of how many unbalanced captures we have at any given time
                // (really j is an index, but j/2 is the count).  First we skip past all of the real captures
                // until we find a balance captures.  Then we check each subsequent entry.  If it's a balance
                // capture (it's negative), we decrement j.  If it's a real capture, we increment j and copy
                // it down to the last free position.
                for cap := 0; cap < len(m.matchcount); cap++ {
                        limit := m.matchcount[cap] * 2
                        matcharray := m.matches[cap]

                        var i, j int

                        for i = 0; i < limit; i++ {
                                if matcharray[i] < 0 {
                                        break
                                }
                        }

                        for j = i; i < limit; i++ {
                                if matcharray[i] < 0 {
                                        // skip negative values
                                        j--
                                } else {
                                        // but if we find something positive (an actual capture), copy it back to the last
                                        // unbalanced position.
                                        if i != j {
                                                matcharray[j] = matcharray[i]
                                        }
                                        j++
                                }
                        }

                        m.matchcount[cap] = j / 2
                }

                m.balancing = false
        }
}

// isMatched tells if a group was matched by capnum
func (m *Match) isMatched(cap int) bool {
        return cap < len(m.matchcount) && m.matchcount[cap] > 0 && m.matches[cap][m.matchcount[cap]*2-1] != (-3+1)
}

// matchIndex returns the index of the last specified matched group by capnum
func (m *Match) matchIndex(cap int) int {
        i := m.matches[cap][m.matchcount[cap]*2-2]
        if i >= 0 {
                return i
        }

        return m.matches[cap][-3-i]
}

// matchLength returns the length of the last specified matched group by capnum
func (m *Match) matchLength(cap int) int {
        i := m.matches[cap][m.matchcount[cap]*2-1]
        if i >= 0 {
                return i
        }

        return m.matches[cap][-3-i]
}

// Nonpublic builder: add a capture to the group specified by "c"
func (m *Match) addMatch(c, start, l int) {

        if m.matches[c] == nil {
                m.matches[c] = make([]int, 2)
        }

        capcount := m.matchcount[c]

        if capcount*2+2 > len(m.matches[c]) {
                oldmatches := m.matches[c]
                newmatches := make([]int, capcount*8)
                copy(newmatches, oldmatches[:capcount*2])
                m.matches[c] = newmatches
        }

        m.matches[c][capcount*2] = start
        m.matches[c][capcount*2+1] = l
        m.matchcount[c] = capcount + 1
        //log.Printf("addMatch: c=%v, i=%v, l=%v ... matches: %v", c, start, l, m.matches)
}

// Nonpublic builder: Add a capture to balance the specified group.  This is used by the
//                     balanced match construct. (?<foo-foo2>...)
//
// If there were no such thing as backtracking, this would be as simple as calling RemoveMatch(c).
// However, since we have backtracking, we need to keep track of everything.
func (m *Match) balanceMatch(c int) {
        m.balancing = true

        // we'll look at the last capture first
        capcount := m.matchcount[c]
        target := capcount*2 - 2

        // first see if it is negative, and therefore is a reference to the next available
        // capture group for balancing.  If it is, we'll reset target to point to that capture.
        if m.matches[c][target] < 0 {
                target = -3 - m.matches[c][target]
        }

        // move back to the previous capture
        target -= 2

        // if the previous capture is a reference, just copy that reference to the end.  Otherwise, point to it.
        if target >= 0 && m.matches[c][target] < 0 {
                m.addMatch(c, m.matches[c][target], m.matches[c][target+1])
        } else {
                m.addMatch(c, -3-target, -4-target /* == -3 - (target + 1) */)
        }
}

// Nonpublic builder: removes a group match by capnum
func (m *Match) removeMatch(c int) {
        m.matchcount[c]--
}

// GroupCount returns the number of groups this match has matched
func (m *Match) GroupCount() int {
        return len(m.matchcount)
}

// GroupByName returns a group based on the name of the group, or nil if the group name does not exist
func (m *Match) GroupByName(name string) *Group {
        num := m.regex.GroupNumberFromName(name)
        if num < 0 {
                return nil
        }
        return m.GroupByNumber(num)
}

// GroupByNumber returns a group based on the number of the group, or nil if the group number does not exist
func (m *Match) GroupByNumber(num int) *Group {
        // check our sparse map
        if m.sparseCaps != nil {
                if newNum, ok := m.sparseCaps[num]; ok {
                        num = newNum
                }
        }
        if num >= len(m.matchcount) || num < 0 {
                return nil
        }

        if num == 0 {
                return &m.Group
        }

        m.populateOtherGroups()

        return &m.otherGroups[num-1]
}

// Groups returns all the capture groups, starting with group 0 (the full match)
func (m *Match) Groups() []Group {
        m.populateOtherGroups()
        g := make([]Group, len(m.otherGroups)+1)
        g[0] = m.Group
        copy(g[1:], m.otherGroups)
        return g
}

func (m *Match) populateOtherGroups() {
        // Construct all the Group objects first time called
        if m.otherGroups == nil {
                m.otherGroups = make([]Group, len(m.matchcount)-1)
                for i := 0; i < len(m.otherGroups); i++ {
                        m.otherGroups[i] = newGroup(m.regex.GroupNameFromNumber(i+1), m.text, m.matches[i+1], m.matchcount[i+1])
                }
        }
}

func (m *Match) groupValueAppendToBuf(groupnum int, buf *bytes.Buffer) {
        c := m.matchcount[groupnum]
        if c == 0 {
                return
        }

        matches := m.matches[groupnum]

        index := matches[(c-1)*2]
        last := index + matches[(c*2)-1]

        for ; index < last; index++ {
                buf.WriteRune(m.text[index])
        }
}

func newGroup(name string, text []rune, caps []int, capcount int) Group {
        g := Group{}
        g.text = text
        if capcount > 0 {
                g.Index = caps[(capcount-1)*2]
                g.Length = caps[(capcount*2)-1]
        }
        g.Name = name
        g.Captures = make([]Capture, capcount)
        for i := 0; i < capcount; i++ {
                g.Captures[i] = Capture{
                        text:   text,
                        Index:  caps[i*2],
                        Length: caps[i*2+1],
                }
        }
        //log.Printf("newGroup! capcount %v, %+v", capcount, g)

        return g
}

func (m *Match) dump() string {
        buf := &bytes.Buffer{}
        buf.WriteRune('\n')
        if len(m.sparseCaps) > 0 {
                for k, v := range m.sparseCaps {
                        fmt.Fprintf(buf, "Slot %v -> %v\n", k, v)
                }
        }

        for i, g := range m.Groups() {
                fmt.Fprintf(buf, "Group %v (%v), %v caps:\n", i, g.Name, len(g.Captures))

                for _, c := range g.Captures {
                        fmt.Fprintf(buf, "  (%v, %v) %v\n", c.Index, c.Length, c.String())
                }
        }
        /*
                for i := 0; i < len(m.matchcount); i++ {
                        fmt.Fprintf(buf, "\nGroup %v (%v):\n", i, m.regex.GroupNameFromNumber(i))

                        for j := 0; j < m.matchcount[i]; j++ {
                                text := ""

                                if m.matches[i][j*2] >= 0 {
                                        start := m.matches[i][j*2]
                                        text = m.text[start : start+m.matches[i][j*2+1]]
                                }

                                fmt.Fprintf(buf, "  (%v, %v) %v\n", m.matches[i][j*2], m.matches[i][j*2+1], text)
                        }
                }
        */
        return buf.String()
}