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beginnings of regular expression library.

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will move elsewhere when more complete.
parses, does not execute.
no character classes yet.

R=rsc
DELTA=522  (522 added, 0 deleted, 0 changed)
OCL=16863
CL=16874
This commit is contained in:
Rob Pike 2008-10-09 19:40:53 -07:00
parent 583dac04e3
commit 8f5b277cac
3 changed files with 531 additions and 0 deletions
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20
usr/r/regexp/Makefile Normal file
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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.
A=6
G=$(A)g
L=$(A)l
all: main
main: main.6
$L -o main main.6
main.6: regexp.6
clean:
rm -f *.6 main
%.6: %.go
$G $<

22
usr/r/regexp/main.go Normal file
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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 main
import (
"os";
"regexp";
)
func main() {
str := "a*b*c*";
if sys.argc() > 1 {
str = sys.argv(1);
}
re, err := regexp.Compile(str);
if err != nil {
print("error: ", err.String(), "\n");
sys.exit(1);
}
}

489
usr/r/regexp/regexp.go Normal file
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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.
// 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
}