mirror of
https://github.com/golang/go
synced 2024-11-12 08:20:22 -07:00
beginnings of regular expression library.
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
parent
583dac04e3
commit
8f5b277cac
20
usr/r/regexp/Makefile
Normal file
20
usr/r/regexp/Makefile
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# Copyright 2009 The Go Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style
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# license that can be found in the LICENSE file.
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A=6
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G=$(A)g
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L=$(A)l
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all: main
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main: main.6
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$L -o main main.6
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main.6: regexp.6
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clean:
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rm -f *.6 main
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%.6: %.go
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$G $<
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22
usr/r/regexp/main.go
Normal file
22
usr/r/regexp/main.go
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@ -0,0 +1,22 @@
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"os";
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"regexp";
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)
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func main() {
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str := "a*b*c*";
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if sys.argc() > 1 {
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str = sys.argv(1);
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}
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re, err := regexp.Compile(str);
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if err != nil {
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print("error: ", err.String(), "\n");
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sys.exit(1);
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}
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}
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489
usr/r/regexp/regexp.go
Normal file
489
usr/r/regexp/regexp.go
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@ -0,0 +1,489 @@
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Regular expression library.
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package regexp
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import os "os"
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export var ErrUnimplemented = os.NewError("unimplemented");
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export var ErrInternal = os.NewError("internal error");
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export var ErrUnmatchedLpar = os.NewError("unmatched '('");
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export var ErrUnmatchedRpar = os.NewError("unmatched ')'");
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export var ErrExtraneousBackslash = os.NewError("extraneous backslash");
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export var ErrEmpty = os.NewError("empty subexpression or alternation");
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export var ErrBadClosure = os.NewError("repeated closure (**, ++, etc.)");
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export var ErrBareClosure = os.NewError("closure applies to nothing");
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export var ErrBadBackslash = os.NewError("illegal backslash escape");
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// An instruction executed by the NFA
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type Inst interface {
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Type() int; // the type of this instruction: CHAR, ANY, etc.
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This() int; // the index of this instruction
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Next() int; // the index of the instruction to execute after this one
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SetThis(i int);
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SetNext(i int);
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Print(ind string);
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}
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type RE struct {
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expr string; // the original expression
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ch *chan<- *RE; // reply channel when we're done
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error *os.Error; // compile- or run-time error; nil if OK
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ninst int;
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inst *[]Inst;
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start Inst;
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}
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const (
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START // beginning of program: marker to start
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= iota;
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END; // end of program: success
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BOT; // '^' beginning of text
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EOT; // '$' end of text
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CHAR; // 'a' regular character
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ANY; // '.' any character
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BRA; // '(' parenthesized expression
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EBRA; // ')'; end of '(' parenthesized expression
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ALT; // '|' alternation
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NOP; // do nothing; makes it easy to link without patching
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)
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// --- START start of program
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type Start struct {
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this int;
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next int;
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}
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func (start *Start) Type() int { return START }
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func (start *Start) This() int { return start.this }
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func (start *Start) Next() int { return start.next }
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func (start *Start) SetThis(i int) { start.this = i }
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func (start *Start) SetNext(i int) { start.next = i }
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func (start *Start) Print(ind string) { print(ind, "start") }
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// --- END end of program
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type End struct {
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this int;
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next int;
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}
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func (end *End) Type() int { return END }
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func (end *End) This() int { return end.this }
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func (end *End) Next() int { return end.next }
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func (end *End) SetThis(i int) { end.this = i }
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func (end *End) SetNext(i int) { end.next = i }
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func (end *End) Print(ind string) { print(ind, "end") }
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// --- BOT beginning of text
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type Bot struct {
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this int;
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next int;
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}
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func (bot *Bot) Type() int { return BOT }
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func (bot *Bot) This() int { return bot.this }
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func (bot *Bot) Next() int { return bot.next }
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func (bot *Bot) SetThis(i int) { bot.this = i }
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func (bot *Bot) SetNext(i int) { bot.next = i }
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func (bot *Bot) Print(ind string) { print(ind, "bot") }
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// --- EOT end of text
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type Eot struct {
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this int;
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next int;
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}
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func (eot *Eot) Type() int { return EOT }
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func (eot *Eot) This() int { return eot.this }
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func (eot *Eot) Next() int { return eot.next }
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func (eot *Eot) SetThis(i int) { eot.this = i }
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func (eot *Eot) SetNext(i int) { eot.next = i }
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func (eot *Eot) Print(ind string) { print(ind, "eot") }
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// --- CHAR a regular character
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type Char struct {
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this int;
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next int;
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char int;
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set bool;
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}
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func (char *Char) Type() int { return CHAR }
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func (char *Char) This() int { return char.this }
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func (char *Char) Next() int { return char.next }
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func (char *Char) SetThis(i int) { char.this = i }
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func (char *Char) SetNext(i int) { char.next = i }
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func (char *Char) Print(ind string) { print(ind, "char ", string(char.char)) }
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func NewChar(char int) *Char {
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c := new(Char);
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c.char = char;
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return c;
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}
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// --- ANY any character
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type Any struct {
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this int;
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next int;
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}
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func (any *Any) Type() int { return ANY }
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func (any *Any) This() int { return any.this }
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func (any *Any) Next() int { return any.next }
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func (any *Any) SetThis(i int) { any.this = i }
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func (any *Any) SetNext(i int) { any.next = i }
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func (any *Any) Print(ind string) { print(ind, "any") }
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// --- BRA parenthesized expression
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type Bra struct {
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this int;
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next int;
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}
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func (bra *Bra) Type() int { return BRA }
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func (bra *Bra) This() int { return bra.this }
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func (bra *Bra) Next() int { return bra.next }
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func (bra *Bra) SetThis(i int) { bra.this = i }
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func (bra *Bra) SetNext(i int) { bra.next = i }
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func (bra *Bra) Print(ind string) { print(ind , "bra"); }
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// --- EBRA end of parenthesized expression
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type Ebra struct {
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this int;
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next int;
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n int; // subexpression number
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}
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func (ebra *Ebra) Type() int { return BRA }
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func (ebra *Ebra) This() int { return ebra.this }
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func (ebra *Ebra) Next() int { return ebra.next }
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func (ebra *Ebra) SetThis(i int) { ebra.this = i }
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func (ebra *Ebra) SetNext(i int) { ebra.next = i }
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func (ebra *Ebra) Print(ind string) { print(ind , "ebra ", ebra.n); }
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// --- ALT alternation
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type Alt struct {
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this int;
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next int;
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left int; // other branch
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}
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func (alt *Alt) Type() int { return ALT }
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func (alt *Alt) This() int { return alt.this }
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func (alt *Alt) Next() int { return alt.next }
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func (alt *Alt) SetThis(i int) { alt.this = i }
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func (alt *Alt) SetNext(i int) { alt.next = i }
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func (alt *Alt) Print(ind string) { print(ind , "alt(", alt.left, ")"); }
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// --- NOP no operation
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type Nop struct {
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this int;
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next int;
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}
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func (nop *Nop) Type() int { return NOP }
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func (nop *Nop) This() int { return nop.this }
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func (nop *Nop) Next() int { return nop.next }
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func (nop *Nop) SetThis(i int) { nop.this = i }
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func (nop *Nop) SetNext(i int) { nop.next = i }
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func (nop *Nop) Print(ind string) { print(ind, "nop") }
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func (re *RE) AddInst(inst Inst) int {
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if re.ninst >= cap(re.inst) {
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panic("write the code to grow inst")
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}
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re.inst[re.ninst] = inst;
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i := re.ninst;
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inst.SetThis(re.ninst);
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re.ninst++;
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inst.SetNext(re.ninst);
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return i;
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}
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// report error and exit compiling/executing goroutine
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func (re *RE) Error(err *os.Error) {
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re.error = err;
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re.ch <- re;
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sys.goexit();
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}
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type Parser struct {
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re *RE;
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nbra int;
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pos int;
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ch int;
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}
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const EOF = -1
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func (p *Parser) c() int {
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return p.ch;
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}
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func (p *Parser) nextc() int {
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if p.pos >= len(p.re.expr) {
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p.ch = EOF
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} else {
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c, w := sys.stringtorune(p.re.expr, p.pos); // TODO: stringotorune shoudl take a string*
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p.ch = c;
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p.pos += w;
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}
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return p.ch;
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}
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func NewParser(re *RE) *Parser {
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parser := new(Parser);
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parser.re = re;
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parser.nextc(); // load p.ch
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return parser;
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}
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/*
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Grammar:
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regexp:
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concatenation { '|' concatenation }
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concatenation:
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{ closure }
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closure:
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term { '*' | '+' | '?' }
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term:
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'.'
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character
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characterclass
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'(' regexp ')'
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*/
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func (p *Parser) Regexp() (start, end int)
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const NULL = -1
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func special(c int) bool {
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s := `\.+*?()|[-]`;
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for i := 0; i < len(s); i++ {
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if c == int(s[i]) {
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return true
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}
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}
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return false
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}
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func (p *Parser) Term() (start, end int) {
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switch c := p.c(); c {
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case ')', '|', EOF:
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return NULL, NULL;
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case '*', '+', '|':
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p.re.Error(ErrBareClosure);
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case '.':
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p.nextc();
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start = p.re.AddInst(new(Any));
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return start, start;
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case '(':
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p.nextc();
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start, end = p.Regexp();
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if p.c() != ')' {
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p.re.Error(ErrUnmatchedLpar);
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}
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p.nextc();
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p.nbra++;
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bra := new(Bra);
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brai := p.re.AddInst(bra);
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ebra := new(Ebra);
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ebrai := p.re.AddInst(ebra);
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ebra.n = p.nbra;
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if start == NULL {
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if end != NULL { p.re.Error(ErrInternal) }
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start = ebrai
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} else {
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p.re.inst[end].SetNext(ebrai);
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}
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bra.SetNext(start);
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return brai, ebrai;
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case '\\':
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c = p.nextc();
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switch {
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case c == EOF:
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p.re.Error(ErrExtraneousBackslash);
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case c == 'n':
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c = '\n';
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case special(c):
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// c is as delivered
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default:
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p.re.Error(ErrBadBackslash);
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}
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fallthrough;
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default:
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p.nextc();
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start = p.re.AddInst(NewChar(c));
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return start, start
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}
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panic("unreachable");
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}
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func (p *Parser) Closure() (start, end int) {
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start, end = p.Term();
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if start == NULL {
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return start, end
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}
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switch p.c() {
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case '*':
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// (start,end)*:
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alt := new(Alt);
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alti := p.re.AddInst(alt);
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p.re.inst[end].SetNext(alti); // after end, do alt
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alt.left = start; // alternate brach: return to start
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start = alti; // alt becomes new (start, end)
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end = alti;
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case '+':
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// (start,end)+:
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alt := new(Alt);
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alti := p.re.AddInst(alt);
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p.re.inst[end].SetNext(alti); // after end, do alt
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alt.left = start; // alternate brach: return to start
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end = alti; // start is unchanged; end is alt
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case '?':
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// (start,end)?:
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alt := new(Alt);
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alti := p.re.AddInst(alt);
|
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nop := new(Nop);
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nopi := p.re.AddInst(nop);
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alt.left = start; // alternate branch is start
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alt.next = nopi; // follow on to nop
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p.re.inst[end].SetNext(nopi); // after end, go to nop
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start = alti; // start is now alt
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end = nopi; // end is nop pointed to by both branches
|
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default:
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||||
return start, end;
|
||||
}
|
||||
switch p.nextc() {
|
||||
case '*', '+', '?':
|
||||
p.re.Error(ErrBadClosure);
|
||||
}
|
||||
return start, end;
|
||||
}
|
||||
|
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func (p *Parser) Concatenation() (start, end int) {
|
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start, end = NULL, NULL;
|
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for {
|
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nstart, nend := p.Closure();
|
||||
switch {
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||||
case nstart == NULL: // end of this concatenation
|
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return start, end;
|
||||
case start == NULL: // this is first element of concatenation
|
||||
start, end = nstart, nend;
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||||
default:
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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));
|
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nstart, nend = nopi, nopi;
|
||||
}
|
||||
alt := new(Alt);
|
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alti := p.re.AddInst(alt);
|
||||
alt.left = start;
|
||||
alt.next = nstart;
|
||||
nop := new(Nop);
|
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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() {
|
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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
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user