From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- libgo/go/ebnf/parser.go | 208 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 208 insertions(+) create mode 100644 libgo/go/ebnf/parser.go (limited to 'libgo/go/ebnf/parser.go') diff --git a/libgo/go/ebnf/parser.go b/libgo/go/ebnf/parser.go new file mode 100644 index 000000000..c38530177 --- /dev/null +++ b/libgo/go/ebnf/parser.go @@ -0,0 +1,208 @@ +// 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 ebnf + +import ( + "go/scanner" + "go/token" + "os" + "strconv" +) + + +type parser struct { + fset *token.FileSet + scanner.ErrorVector + scanner scanner.Scanner + pos token.Pos // token position + tok token.Token // one token look-ahead + lit []byte // token literal +} + + +func (p *parser) next() { + p.pos, p.tok, p.lit = p.scanner.Scan() + if p.tok.IsKeyword() { + // TODO Should keyword mapping always happen outside scanner? + // Or should there be a flag to scanner to enable keyword mapping? + p.tok = token.IDENT + } +} + + +func (p *parser) error(pos token.Pos, msg string) { + p.Error(p.fset.Position(pos), msg) +} + + +func (p *parser) errorExpected(pos token.Pos, msg string) { + msg = "expected " + msg + if pos == p.pos { + // the error happened at the current position; + // make the error message more specific + msg += ", found '" + p.tok.String() + "'" + if p.tok.IsLiteral() { + msg += " " + string(p.lit) + } + } + p.error(pos, msg) +} + + +func (p *parser) expect(tok token.Token) token.Pos { + pos := p.pos + if p.tok != tok { + p.errorExpected(pos, "'"+tok.String()+"'") + } + p.next() // make progress in any case + return pos +} + + +func (p *parser) parseIdentifier() *Name { + pos := p.pos + name := string(p.lit) + p.expect(token.IDENT) + return &Name{pos, name} +} + + +func (p *parser) parseToken() *Token { + pos := p.pos + value := "" + if p.tok == token.STRING { + value, _ = strconv.Unquote(string(p.lit)) + // Unquote may fail with an error, but only if the scanner found + // an illegal string in the first place. In this case the error + // has already been reported. + p.next() + } else { + p.expect(token.STRING) + } + return &Token{pos, value} +} + + +func (p *parser) parseTerm() (x Expression) { + pos := p.pos + + switch p.tok { + case token.IDENT: + x = p.parseIdentifier() + + case token.STRING: + tok := p.parseToken() + x = tok + if p.tok == token.ELLIPSIS { + p.next() + x = &Range{tok, p.parseToken()} + } + + case token.LPAREN: + p.next() + x = &Group{pos, p.parseExpression()} + p.expect(token.RPAREN) + + case token.LBRACK: + p.next() + x = &Option{pos, p.parseExpression()} + p.expect(token.RBRACK) + + case token.LBRACE: + p.next() + x = &Repetition{pos, p.parseExpression()} + p.expect(token.RBRACE) + } + + return x +} + + +func (p *parser) parseSequence() Expression { + var list Sequence + + for x := p.parseTerm(); x != nil; x = p.parseTerm() { + list = append(list, x) + } + + // no need for a sequence if list.Len() < 2 + switch len(list) { + case 0: + return nil + case 1: + return list[0] + } + + return list +} + + +func (p *parser) parseExpression() Expression { + var list Alternative + + for { + if x := p.parseSequence(); x != nil { + list = append(list, x) + } + if p.tok != token.OR { + break + } + p.next() + } + + // no need for an Alternative node if list.Len() < 2 + switch len(list) { + case 0: + return nil + case 1: + return list[0] + } + + return list +} + + +func (p *parser) parseProduction() *Production { + name := p.parseIdentifier() + p.expect(token.ASSIGN) + expr := p.parseExpression() + p.expect(token.PERIOD) + return &Production{name, expr} +} + + +func (p *parser) parse(fset *token.FileSet, filename string, src []byte) Grammar { + // initialize parser + p.fset = fset + p.ErrorVector.Reset() + p.scanner.Init(fset.AddFile(filename, fset.Base(), len(src)), src, p, 0) + p.next() // initializes pos, tok, lit + + grammar := make(Grammar) + for p.tok != token.EOF { + prod := p.parseProduction() + name := prod.Name.String + if _, found := grammar[name]; !found { + grammar[name] = prod + } else { + p.error(prod.Pos(), name+" declared already") + } + } + + return grammar +} + + +// Parse parses a set of EBNF productions from source src. +// It returns a set of productions. Errors are reported +// for incorrect syntax and if a production is declared +// more than once. Position information is recorded relative +// to the file set fset. +// +func Parse(fset *token.FileSet, filename string, src []byte) (Grammar, os.Error) { + var p parser + grammar := p.parse(fset, filename, src) + return grammar, p.GetError(scanner.Sorted) +} -- cgit v1.2.3