src/pkg/exp/datafmt/parser.go - go - Git at Google

 // 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 datafmt

 import (
 	"container/vector"
 	"go/scanner"
 	"go/token"
 	"os"
 	"strconv"
 	"strings"
 )

 // ----------------------------------------------------------------------------
 // Parsing

 type parser struct {
 	scanner.ErrorVector
 	scanner scanner.Scanner
 	file    *token.File
 	pos     token.Pos   // token position
 	tok     token.Token // one token look-ahead
 	lit     string      // token literal

 	packs map[string]string // PackageName -> ImportPath
 	rules map[string]expr   // RuleName -> Expression
 }

 func (p *parser) next() {
 	p.pos, p.tok, p.lit = p.scanner.Scan()
 	switch p.tok {
 	case token.CHAN, token.FUNC, token.INTERFACE, token.MAP, token.STRUCT:
 		// Go keywords for composite types are type names
 		// returned by reflect. Accept them as identifiers.
 		p.tok = token.IDENT // p.lit is already set correctly
 	}
 }

 func (p *parser) init(fset *token.FileSet, filename string, src []byte) {
 	p.ErrorVector.Reset()
 	p.file = fset.AddFile(filename, fset.Base(), len(src))
 	p.scanner.Init(p.file, src, p, scanner.AllowIllegalChars) // return '@' as token.ILLEGAL w/o error message
 	p.next()                                                  // initializes pos, tok, lit
 	p.packs = make(map[string]string)
 	p.rules = make(map[string]expr)
 }

 func (p *parser) error(pos token.Pos, msg string) {
 	p.Error(p.file.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 += " " + 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() string {
 	name := p.lit
 	p.expect(token.IDENT)
 	return name
 }

 func (p *parser) parseTypeName() (string, bool) {
 	pos := p.pos
 	name, isIdent := p.parseIdentifier(), true
 	if p.tok == token.PERIOD {
 		// got a package name, lookup package
 		if importPath, found := p.packs[name]; found {
 			name = importPath
 		} else {
 			p.error(pos, "package not declared: "+name)
 		}
 		p.next()
 		name, isIdent = name+"."+p.parseIdentifier(), false
 	}
 	return name, isIdent
 }

 // Parses a rule name and returns it. If the rule name is
 // a package-qualified type name, the package name is resolved.
 // The 2nd result value is true iff the rule name consists of a
 // single identifier only (and thus could be a package name).
 //
 func (p *parser) parseRuleName() (string, bool) {
 	name, isIdent := "", false
 	switch p.tok {
 	case token.IDENT:
 		name, isIdent = p.parseTypeName()
 	case token.DEFAULT:
 		name = "default"
 		p.next()
 	case token.QUO:
 		name = "/"
 		p.next()
 	default:
 		p.errorExpected(p.pos, "rule name")
 		p.next() // make progress in any case
 	}
 	return name, isIdent
 }

 func (p *parser) parseString() string {
 	s := ""
 	if p.tok == token.STRING {
 		s, _ = strconv.Unquote(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()
 		return s
 	} else {
 		p.expect(token.STRING)
 	}
 	return s
 }

 func (p *parser) parseLiteral() literal {
 	s := []byte(p.parseString())

 	// A string literal may contain %-format specifiers. To simplify
 	// and speed up printing of the literal, split it into segments
 	// that start with "%" possibly followed by a last segment that
 	// starts with some other character.
 	var list vector.Vector
 	i0 := 0
 	for i := 0; i < len(s); i++ {
 		if s[i] == '%' && i+1 < len(s) {
 			// the next segment starts with a % format
 			if i0 < i {
 				// the current segment is not empty, split it off
 				list.Push(s[i0:i])
 				i0 = i
 			}
 			i++ // skip %; let loop skip over char after %
 		}
 	}
 	// the final segment may start with any character
 	// (it is empty iff the string is empty)
 	list.Push(s[i0:])

 	// convert list into a literal
 	lit := make(literal, list.Len())
 	for i := 0; i < list.Len(); i++ {
 		lit[i] = list.At(i).([]byte)
 	}

 	return lit
 }

 func (p *parser) parseField() expr {
 	var fname string
 	switch p.tok {
 	case token.ILLEGAL:
 		if p.lit != "@" {
 			return nil
 		}
 		fname = "@"
 		p.next()
 	case token.MUL:
 		fname = "*"
 		p.next()
 	case token.IDENT:
 		fname = p.parseIdentifier()
 	default:
 		return nil
 	}

 	var ruleName string
 	if p.tok == token.COLON {
 		p.next()
 		ruleName, _ = p.parseRuleName()
 	}

 	return &field{fname, ruleName}
 }

 func (p *parser) parseOperand() (x expr) {
 	switch p.tok {
 	case token.STRING:
 		x = p.parseLiteral()

 	case token.LPAREN:
 		p.next()
 		x = p.parseExpression()
 		if p.tok == token.SHR {
 			p.next()
 			x = &group{x, p.parseExpression()}
 		}
 		p.expect(token.RPAREN)

 	case token.LBRACK:
 		p.next()
 		x = &option{p.parseExpression()}
 		p.expect(token.RBRACK)

 	case token.LBRACE:
 		p.next()
 		x = p.parseExpression()
 		var div expr
 		if p.tok == token.QUO {
 			p.next()
 			div = p.parseExpression()
 		}
 		x = &repetition{x, div}
 		p.expect(token.RBRACE)

 	default:
 		x = p.parseField() // may be nil
 	}

 	return x
 }

 func (p *parser) parseSequence() expr {
 	var list vector.Vector

 	for x := p.parseOperand(); x != nil; x = p.parseOperand() {
 		list.Push(x)
 	}

 	// no need for a sequence if list.Len() < 2
 	switch list.Len() {
 	case 0:
 		return nil
 	case 1:
 		return list.At(0).(expr)
 	}

 	// convert list into a sequence
 	seq := make(sequence, list.Len())
 	for i := 0; i < list.Len(); i++ {
 		seq[i] = list.At(i).(expr)
 	}
 	return seq
 }

 func (p *parser) parseExpression() expr {
 	var list vector.Vector

 	for {
 		x := p.parseSequence()
 		if x != nil {
 			list.Push(x)
 		}
 		if p.tok != token.OR {
 			break
 		}
 		p.next()
 	}

 	// no need for an alternatives if list.Len() < 2
 	switch list.Len() {
 	case 0:
 		return nil
 	case 1:
 		return list.At(0).(expr)
 	}

 	// convert list into a alternatives
 	alt := make(alternatives, list.Len())
 	for i := 0; i < list.Len(); i++ {
 		alt[i] = list.At(i).(expr)
 	}
 	return alt
 }

 func (p *parser) parseFormat() {
 	for p.tok != token.EOF {
 		pos := p.pos

 		name, isIdent := p.parseRuleName()
 		switch p.tok {
 		case token.STRING:
 			// package declaration
 			importPath := p.parseString()

 			// add package declaration
 			if !isIdent {
 				p.error(pos, "illegal package name: "+name)
 			} else if _, found := p.packs[name]; !found {
 				p.packs[name] = importPath
 			} else {
 				p.error(pos, "package already declared: "+name)
 			}

 		case token.ASSIGN:
 			// format rule
 			p.next()
 			x := p.parseExpression()

 			// add rule
 			if _, found := p.rules[name]; !found {
 				p.rules[name] = x
 			} else {
 				p.error(pos, "format rule already declared: "+name)
 			}

 		default:
 			p.errorExpected(p.pos, "package declaration or format rule")
 			p.next() // make progress in any case
 		}

 		if p.tok == token.SEMICOLON {
 			p.next()
 		} else {
 			break
 		}
 	}
 	p.expect(token.EOF)
 }

 func remap(p *parser, name string) string {
 	i := strings.Index(name, ".")
 	if i >= 0 {
 		packageName, suffix := name[0:i], name[i:]
 		// lookup package
 		if importPath, found := p.packs[packageName]; found {
 			name = importPath + suffix
 		} else {
 			var invalidPos token.Position
 			p.Error(invalidPos, "package not declared: "+packageName)
 		}
 	}
 	return name
 }

 // Parse parses a set of format productions from source src. Custom
 // formatters may be provided via a map of formatter functions. If
 // there are no errors, the result is a Format and the error is nil.
 // Otherwise the format is nil and a non-empty ErrorList is returned.
 //
 func Parse(fset *token.FileSet, filename string, src []byte, fmap FormatterMap) (Format, os.Error) {
 	// parse source
 	var p parser
 	p.init(fset, filename, src)
 	p.parseFormat()

 	// add custom formatters, if any
 	for name, form := range fmap {
 		name = remap(&p, name)
 		if _, found := p.rules[name]; !found {
 			p.rules[name] = &custom{name, form}
 		} else {
 			var invalidPos token.Position
 			p.Error(invalidPos, "formatter already declared: "+name)
 		}
 	}

 	return p.rules, p.GetError(scanner.NoMultiples)
 }
	// 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 datafmt

	import (
	"container/vector"
	"go/scanner"
	"go/token"
	"os"
	"strconv"
	"strings"
	)

	// ----------------------------------------------------------------------------
	// Parsing

	type parser struct {
	scanner.ErrorVector
	scanner scanner.Scanner
	file *token.File
	pos token.Pos // token position
	tok token.Token // one token look-ahead
	lit string // token literal

	packs map[string]string // PackageName -> ImportPath
	rules map[string]expr // RuleName -> Expression
	}

	func (p *parser) next() {
	p.pos, p.tok, p.lit = p.scanner.Scan()
	switch p.tok {
	case token.CHAN, token.FUNC, token.INTERFACE, token.MAP, token.STRUCT:
	// Go keywords for composite types are type names
	// returned by reflect. Accept them as identifiers.
	p.tok = token.IDENT // p.lit is already set correctly
	}
	}

	func (p parser) init(fset token.FileSet, filename string, src []byte) {
	p.ErrorVector.Reset()
	p.file = fset.AddFile(filename, fset.Base(), len(src))
	p.scanner.Init(p.file, src, p, scanner.AllowIllegalChars) // return '@' as token.ILLEGAL w/o error message
	p.next() // initializes pos, tok, lit
	p.packs = make(map[string]string)
	p.rules = make(map[string]expr)
	}

	func (p *parser) error(pos token.Pos, msg string) {
	p.Error(p.file.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 += " " + 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() string {
	name := p.lit
	p.expect(token.IDENT)
	return name
	}

	func (p *parser) parseTypeName() (string, bool) {
	pos := p.pos
	name, isIdent := p.parseIdentifier(), true
	if p.tok == token.PERIOD {
	// got a package name, lookup package
	if importPath, found := p.packs[name]; found {
	name = importPath
	} else {
	p.error(pos, "package not declared: "+name)
	}
	p.next()
	name, isIdent = name+"."+p.parseIdentifier(), false
	}
	return name, isIdent
	}

	// Parses a rule name and returns it. If the rule name is
	// a package-qualified type name, the package name is resolved.
	// The 2nd result value is true iff the rule name consists of a
	// single identifier only (and thus could be a package name).
	//
	func (p *parser) parseRuleName() (string, bool) {
	name, isIdent := "", false
	switch p.tok {
	case token.IDENT:
	name, isIdent = p.parseTypeName()
	case token.DEFAULT:
	name = "default"
	p.next()
	case token.QUO:
	name = "/"
	p.next()
	default:
	p.errorExpected(p.pos, "rule name")
	p.next() // make progress in any case
	}
	return name, isIdent
	}

	func (p *parser) parseString() string {
	s := ""
	if p.tok == token.STRING {
	s, _ = strconv.Unquote(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()
	return s
	} else {
	p.expect(token.STRING)
	}
	return s
	}

	func (p *parser) parseLiteral() literal {
	s := []byte(p.parseString())

	// A string literal may contain %-format specifiers. To simplify
	// and speed up printing of the literal, split it into segments
	// that start with "%" possibly followed by a last segment that
	// starts with some other character.
	var list vector.Vector
	i0 := 0
	for i := 0; i < len(s); i++ {
	if s[i] == '%' && i+1 < len(s) {
	// the next segment starts with a % format
	if i0 < i {
	// the current segment is not empty, split it off
	list.Push(s[i0:i])
	i0 = i
	}
	i++ // skip %; let loop skip over char after %
	}
	}
	// the final segment may start with any character
	// (it is empty iff the string is empty)
	list.Push(s[i0:])

	// convert list into a literal
	lit := make(literal, list.Len())
	for i := 0; i < list.Len(); i++ {
	lit[i] = list.At(i).([]byte)
	}

	return lit
	}

	func (p *parser) parseField() expr {
	var fname string
	switch p.tok {
	case token.ILLEGAL:
	if p.lit != "@" {
	return nil
	}
	fname = "@"
	p.next()
	case token.MUL:
	fname = "*"
	p.next()
	case token.IDENT:
	fname = p.parseIdentifier()
	default:
	return nil
	}

	var ruleName string
	if p.tok == token.COLON {
	p.next()
	ruleName, _ = p.parseRuleName()
	}

	return &field{fname, ruleName}
	}

	func (p *parser) parseOperand() (x expr) {
	switch p.tok {
	case token.STRING:
	x = p.parseLiteral()

	case token.LPAREN:
	p.next()
	x = p.parseExpression()
	if p.tok == token.SHR {
	p.next()
	x = &group{x, p.parseExpression()}
	}
	p.expect(token.RPAREN)

	case token.LBRACK:
	p.next()
	x = &option{p.parseExpression()}
	p.expect(token.RBRACK)

	case token.LBRACE:
	p.next()
	x = p.parseExpression()
	var div expr
	if p.tok == token.QUO {
	p.next()
	div = p.parseExpression()
	}
	x = &repetition{x, div}
	p.expect(token.RBRACE)

	default:
	x = p.parseField() // may be nil
	}

	return x
	}

	func (p *parser) parseSequence() expr {
	var list vector.Vector

	for x := p.parseOperand(); x != nil; x = p.parseOperand() {
	list.Push(x)
	}

	// no need for a sequence if list.Len() < 2
	switch list.Len() {
	case 0:
	return nil
	case 1:
	return list.At(0).(expr)
	}

	// convert list into a sequence
	seq := make(sequence, list.Len())
	for i := 0; i < list.Len(); i++ {
	seq[i] = list.At(i).(expr)
	}
	return seq
	}

	func (p *parser) parseExpression() expr {
	var list vector.Vector

	for {
	x := p.parseSequence()
	if x != nil {
	list.Push(x)
	}
	if p.tok != token.OR {
	break
	}
	p.next()
	}

	// no need for an alternatives if list.Len() < 2
	switch list.Len() {
	case 0:
	return nil
	case 1:
	return list.At(0).(expr)
	}

	// convert list into a alternatives
	alt := make(alternatives, list.Len())
	for i := 0; i < list.Len(); i++ {
	alt[i] = list.At(i).(expr)
	}
	return alt
	}

	func (p *parser) parseFormat() {
	for p.tok != token.EOF {
	pos := p.pos

	name, isIdent := p.parseRuleName()
	switch p.tok {
	case token.STRING:
	// package declaration
	importPath := p.parseString()

	// add package declaration
	if !isIdent {
	p.error(pos, "illegal package name: "+name)
	} else if _, found := p.packs[name]; !found {
	p.packs[name] = importPath
	} else {
	p.error(pos, "package already declared: "+name)
	}

	case token.ASSIGN:
	// format rule
	p.next()
	x := p.parseExpression()

	// add rule
	if _, found := p.rules[name]; !found {
	p.rules[name] = x
	} else {
	p.error(pos, "format rule already declared: "+name)
	}

	default:
	p.errorExpected(p.pos, "package declaration or format rule")
	p.next() // make progress in any case
	}

	if p.tok == token.SEMICOLON {
	p.next()
	} else {
	break
	}
	}
	p.expect(token.EOF)
	}

	func remap(p *parser, name string) string {
	i := strings.Index(name, ".")
	if i >= 0 {
	packageName, suffix := name[0:i], name[i:]
	// lookup package
	if importPath, found := p.packs[packageName]; found {
	name = importPath + suffix
	} else {
	var invalidPos token.Position
	p.Error(invalidPos, "package not declared: "+packageName)
	}
	}
	return name
	}

	// Parse parses a set of format productions from source src. Custom
	// formatters may be provided via a map of formatter functions. If
	// there are no errors, the result is a Format and the error is nil.
	// Otherwise the format is nil and a non-empty ErrorList is returned.
	//
	func Parse(fset *token.FileSet, filename string, src []byte, fmap FormatterMap) (Format, os.Error) {
	// parse source
	var p parser
	p.init(fset, filename, src)
	p.parseFormat()

	// add custom formatters, if any
	for name, form := range fmap {
	name = remap(&p, name)
	if _, found := p.rules[name]; !found {
	p.rules[name] = &custom{name, form}
	} else {
	var invalidPos token.Position
	p.Error(invalidPos, "formatter already declared: "+name)
	}
	}

	return p.rules, p.GetError(scanner.NoMultiples)
	}