--- /dev/null
+// 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.
+
+// Regular expression library.
+
+package regexp
+
+import os "os"
+
+export var ErrUnimplemented = os.NewError("unimplemented");
+export var ErrInternal = os.NewError("internal error");
+export var ErrUnmatchedLpar = os.NewError("unmatched '('");
+export var ErrUnmatchedRpar = os.NewError("unmatched ')'");
+export var ErrExtraneousBackslash = os.NewError("extraneous backslash");
+export var ErrEmpty = os.NewError("empty subexpression or alternation");
+export var ErrBadClosure = os.NewError("repeated closure (**, ++, etc.)");
+export var ErrBareClosure = os.NewError("closure applies to nothing");
+export var ErrBadBackslash = os.NewError("illegal backslash escape");
+
+// An instruction executed by the NFA
+type Inst interface {
+ Type() int; // the type of this instruction: CHAR, ANY, etc.
+ This() int; // the index of this instruction
+ Next() int; // the index of the instruction to execute after this one
+ SetThis(i int);
+ SetNext(i int);
+ Print(ind string);
+}
+
+type RE struct {
+ expr string; // the original expression
+ ch *chan<- *RE; // reply channel when we're done
+ error *os.Error; // compile- or run-time error; nil if OK
+ ninst int;
+ inst *[]Inst;
+ start Inst;
+}
+
+const (
+ START // beginning of program: marker to start
+ = iota;
+ END; // end of program: success
+ BOT; // '^' beginning of text
+ EOT; // '$' end of text
+ CHAR; // 'a' regular character
+ ANY; // '.' any character
+ BRA; // '(' parenthesized expression
+ EBRA; // ')'; end of '(' parenthesized expression
+ ALT; // '|' alternation
+ NOP; // do nothing; makes it easy to link without patching
+)
+
+// --- START start of program
+type Start struct {
+ this int;
+ next int;
+}
+
+func (start *Start) Type() int { return START }
+func (start *Start) This() int { return start.this }
+func (start *Start) Next() int { return start.next }
+func (start *Start) SetThis(i int) { start.this = i }
+func (start *Start) SetNext(i int) { start.next = i }
+func (start *Start) Print(ind string) { print(ind, "start") }
+
+// --- END end of program
+type End struct {
+ this int;
+ next int;
+}
+
+func (end *End) Type() int { return END }
+func (end *End) This() int { return end.this }
+func (end *End) Next() int { return end.next }
+func (end *End) SetThis(i int) { end.this = i }
+func (end *End) SetNext(i int) { end.next = i }
+func (end *End) Print(ind string) { print(ind, "end") }
+
+// --- BOT beginning of text
+type Bot struct {
+ this int;
+ next int;
+}
+
+func (bot *Bot) Type() int { return BOT }
+func (bot *Bot) This() int { return bot.this }
+func (bot *Bot) Next() int { return bot.next }
+func (bot *Bot) SetThis(i int) { bot.this = i }
+func (bot *Bot) SetNext(i int) { bot.next = i }
+func (bot *Bot) Print(ind string) { print(ind, "bot") }
+
+// --- EOT end of text
+type Eot struct {
+ this int;
+ next int;
+}
+
+func (eot *Eot) Type() int { return EOT }
+func (eot *Eot) This() int { return eot.this }
+func (eot *Eot) Next() int { return eot.next }
+func (eot *Eot) SetThis(i int) { eot.this = i }
+func (eot *Eot) SetNext(i int) { eot.next = i }
+func (eot *Eot) Print(ind string) { print(ind, "eot") }
+
+// --- CHAR a regular character
+type Char struct {
+ this int;
+ next int;
+ char int;
+ set bool;
+}
+
+func (char *Char) Type() int { return CHAR }
+func (char *Char) This() int { return char.this }
+func (char *Char) Next() int { return char.next }
+func (char *Char) SetThis(i int) { char.this = i }
+func (char *Char) SetNext(i int) { char.next = i }
+func (char *Char) Print(ind string) { print(ind, "char ", string(char.char)) }
+
+func NewChar(char int) *Char {
+ c := new(Char);
+ c.char = char;
+ return c;
+}
+
+// --- ANY any character
+type Any struct {
+ this int;
+ next int;
+}
+
+func (any *Any) Type() int { return ANY }
+func (any *Any) This() int { return any.this }
+func (any *Any) Next() int { return any.next }
+func (any *Any) SetThis(i int) { any.this = i }
+func (any *Any) SetNext(i int) { any.next = i }
+func (any *Any) Print(ind string) { print(ind, "any") }
+
+// --- BRA parenthesized expression
+type Bra struct {
+ this int;
+ next int;
+}
+
+func (bra *Bra) Type() int { return BRA }
+func (bra *Bra) This() int { return bra.this }
+func (bra *Bra) Next() int { return bra.next }
+func (bra *Bra) SetThis(i int) { bra.this = i }
+func (bra *Bra) SetNext(i int) { bra.next = i }
+func (bra *Bra) Print(ind string) { print(ind , "bra"); }
+
+// --- EBRA end of parenthesized expression
+type Ebra struct {
+ this int;
+ next int;
+ n int; // subexpression number
+}
+
+func (ebra *Ebra) Type() int { return BRA }
+func (ebra *Ebra) This() int { return ebra.this }
+func (ebra *Ebra) Next() int { return ebra.next }
+func (ebra *Ebra) SetThis(i int) { ebra.this = i }
+func (ebra *Ebra) SetNext(i int) { ebra.next = i }
+func (ebra *Ebra) Print(ind string) { print(ind , "ebra ", ebra.n); }
+
+// --- ALT alternation
+type Alt struct {
+ this int;
+ next int;
+ left int; // other branch
+}
+
+func (alt *Alt) Type() int { return ALT }
+func (alt *Alt) This() int { return alt.this }
+func (alt *Alt) Next() int { return alt.next }
+func (alt *Alt) SetThis(i int) { alt.this = i }
+func (alt *Alt) SetNext(i int) { alt.next = i }
+func (alt *Alt) Print(ind string) { print(ind , "alt(", alt.left, ")"); }
+
+// --- NOP no operation
+type Nop struct {
+ this int;
+ next int;
+}
+
+func (nop *Nop) Type() int { return NOP }
+func (nop *Nop) This() int { return nop.this }
+func (nop *Nop) Next() int { return nop.next }
+func (nop *Nop) SetThis(i int) { nop.this = i }
+func (nop *Nop) SetNext(i int) { nop.next = i }
+func (nop *Nop) Print(ind string) { print(ind, "nop") }
+
+
+func (re *RE) AddInst(inst Inst) int {
+ if re.ninst >= cap(re.inst) {
+ panic("write the code to grow inst")
+ }
+ re.inst[re.ninst] = inst;
+ i := re.ninst;
+ inst.SetThis(re.ninst);
+ re.ninst++;
+ inst.SetNext(re.ninst);
+ return i;
+}
+
+// report error and exit compiling/executing goroutine
+func (re *RE) Error(err *os.Error) {
+ re.error = err;
+ re.ch <- re;
+ sys.goexit();
+}
+
+type Parser struct {
+ re *RE;
+ nbra int;
+ pos int;
+ ch int;
+}
+
+const EOF = -1
+
+func (p *Parser) c() int {
+ return p.ch;
+}
+
+func (p *Parser) nextc() int {
+ if p.pos >= len(p.re.expr) {
+ p.ch = EOF
+ } else {
+ c, w := sys.stringtorune(p.re.expr, p.pos); // TODO: stringotorune shoudl take a string*
+ p.ch = c;
+ p.pos += w;
+ }
+ return p.ch;
+}
+
+func NewParser(re *RE) *Parser {
+ parser := new(Parser);
+ parser.re = re;
+ parser.nextc(); // load p.ch
+ return parser;
+}
+
+/*
+
+Grammar:
+ regexp:
+ concatenation { '|' concatenation }
+ concatenation:
+ { closure }
+ closure:
+ term { '*' | '+' | '?' }
+ term:
+ '.'
+ character
+ characterclass
+ '(' regexp ')'
+
+*/
+
+func (p *Parser) Regexp() (start, end int)
+
+const NULL = -1
+
+func special(c int) bool {
+ s := `\.+*?()|[-]`;
+ for i := 0; i < len(s); i++ {
+ if c == int(s[i]) {
+ return true
+ }
+ }
+ return false
+}
+
+func (p *Parser) Term() (start, end int) {
+ switch c := p.c(); c {
+ case ')', '|', EOF:
+ return NULL, NULL;
+ case '*', '+', '|':
+ p.re.Error(ErrBareClosure);
+ case '.':
+ p.nextc();
+ start = p.re.AddInst(new(Any));
+ return start, start;
+ case '(':
+ p.nextc();
+ start, end = p.Regexp();
+ if p.c() != ')' {
+ p.re.Error(ErrUnmatchedLpar);
+ }
+ p.nextc();
+ p.nbra++;
+ bra := new(Bra);
+ brai := p.re.AddInst(bra);
+ ebra := new(Ebra);
+ ebrai := p.re.AddInst(ebra);
+ ebra.n = p.nbra;
+ if start == NULL {
+ if end != NULL { p.re.Error(ErrInternal) }
+ start = ebrai
+ } else {
+ p.re.inst[end].SetNext(ebrai);
+ }
+ bra.SetNext(start);
+ return brai, ebrai;
+ case '\\':
+ c = p.nextc();
+ switch {
+ case c == EOF:
+ p.re.Error(ErrExtraneousBackslash);
+ case c == 'n':
+ c = '\n';
+ case special(c):
+ // c is as delivered
+ default:
+ p.re.Error(ErrBadBackslash);
+ }
+ fallthrough;
+ default:
+ p.nextc();
+ start = p.re.AddInst(NewChar(c));
+ return start, start
+ }
+ panic("unreachable");
+}
+
+func (p *Parser) Closure() (start, end int) {
+ start, end = p.Term();
+ if start == NULL {
+ return start, end
+ }
+ switch p.c() {
+ case '*':
+ // (start,end)*:
+ alt := new(Alt);
+ alti := p.re.AddInst(alt);
+ p.re.inst[end].SetNext(alti); // after end, do alt
+ alt.left = start; // alternate brach: return to start
+ start = alti; // alt becomes new (start, end)
+ end = alti;
+ case '+':
+ // (start,end)+:
+ alt := new(Alt);
+ alti := p.re.AddInst(alt);
+ p.re.inst[end].SetNext(alti); // after end, do alt
+ alt.left = start; // alternate brach: return to start
+ end = alti; // start is unchanged; end is alt
+ case '?':
+ // (start,end)?:
+ alt := new(Alt);
+ alti := p.re.AddInst(alt);
+ nop := new(Nop);
+ nopi := p.re.AddInst(nop);
+ alt.left = start; // alternate branch is start
+ alt.next = nopi; // follow on to nop
+ p.re.inst[end].SetNext(nopi); // after end, go to nop
+ start = alti; // start is now alt
+ end = nopi; // end is nop pointed to by both branches
+ default:
+ return start, end;
+ }
+ switch p.nextc() {
+ case '*', '+', '?':
+ p.re.Error(ErrBadClosure);
+ }
+ return start, end;
+}
+
+func (p *Parser) Concatenation() (start, end int) {
+ start, end = NULL, NULL;
+ for {
+ nstart, nend := p.Closure();
+ switch {
+ case nstart == NULL: // end of this concatenation
+ return start, end;
+ case start == NULL: // this is first element of concatenation
+ start, end = nstart, nend;
+ default:
+ p.re.inst[end].SetNext(nstart);
+ end = nend;
+ }
+ }
+ panic("unreachable");
+}
+
+func (p *Parser) Regexp() (start, end int) {
+ start, end = p.Concatenation();
+ if start == NULL {
+ return NULL, NULL
+ }
+ for {
+ switch p.c() {
+ default:
+ return start, end;
+ case '|':
+ p.nextc();
+ nstart, nend := p.Concatenation();
+ // xyz|(nothing) is xyz or nop
+ if nstart == NULL {
+ nopi := p.re.AddInst(new(Nop));
+ nstart, nend = nopi, nopi;
+ }
+ alt := new(Alt);
+ alti := p.re.AddInst(alt);
+ alt.left = start;
+ alt.next = nstart;
+ nop := new(Nop);
+ nopi := p.re.AddInst(nop);
+ p.re.inst[end].SetNext(nopi);
+ p.re.inst[nend].SetNext(nopi);
+ start, end = alti, nopi;
+ }
+ }
+ panic("unreachable");
+}
+
+func (re *RE) UnNop(i int) int {
+ for re.inst[i].Type() == NOP {
+ i = re.inst[i].Next()
+ }
+ return i
+}
+
+func (re *RE) EliminateNops() {
+ for i := 0; i < re.ninst - 1; i++ { // last one is END
+ inst := re.inst[i];
+ inst.SetNext(re.UnNop(inst.Next()));
+ if inst.Type() == ALT {
+ alt := inst.(*Alt);
+ alt.left = re.UnNop(alt.left)
+ }
+ }
+}
+
+func (re *RE) DoParse() {
+ parser := NewParser(re);
+ start := new(Start);
+ starti := re.AddInst(start);
+ s, e := parser.Regexp();
+ if s == NULL {
+ if e != NULL { re.Error(ErrInternal) }
+ e = starti;
+ }
+ start.next = s;
+ re.inst[e].SetNext(re.AddInst(new(End)));
+
+ for i := 0; i < re.ninst; i++ {
+ inst := re.inst[i];
+ print(i, ":\t");
+ inst.Print("\t");
+ print(" -> ", inst.Next(), "\n");
+ }
+ println();
+
+ re.EliminateNops();
+
+ for i := 0; i < re.ninst; i++ {
+ inst := re.inst[i];
+ print(i, ":\t");
+ inst.Print("\t");
+ print(" -> ", inst.Next(), "\n");
+ }
+ println();
+
+ re.Error(ErrUnimplemented);
+}
+
+func Compiler(str string, ch *chan *RE) {
+ re := new(RE);
+ re.inst = new([]Inst, 100);
+ re.expr = str;
+ re.ch = ch;
+ re.DoParse();
+ ch <- re;
+}
+
+// Public interface has only execute functionality (not yet implemented)
+export type Regexp interface {
+ // Execute() bool
+}
+
+// compile in separate goroutine; wait for result
+export func Compile(str string) (regexp Regexp, error *os.Error) {
+ ch := new(chan *RE);
+ go Compiler(str, ch);
+ re := <-ch;
+ return re, re.error
+}