src/pkg/json/parse.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.

 // JSON (JavaScript Object Notation) parser.
 // See http://www.json.org/

 // The json package implements a simple parser and
 // representation for JSON (JavaScript Object Notation),
 // as defined at http://www.json.org/.
 package json

 import (
 	"bytes";
 	"strconv";
 	"utf8";
 )

 // Strings
 //
 //   Double quoted with escapes: \" \\ \/ \b \f \n \r \t \uXXXX.
 //   No literal control characters, supposedly.
 //   Have also seen \' and embedded newlines.

 func _UnHex(p string, r, l int) (v int, ok bool) {
 	v = 0;
 	for i := r; i < l; i++ {
 		if i >= len(p) {
 			return 0, false
 		}
 		v *= 16;
 		switch {
 		case '0' <= p[i] && p[i] <= '9':
 			v += int(p[i] - '0')
 		case 'a' <= p[i] && p[i] <= 'f':
 			v += int(p[i] - 'a' + 10)
 		case 'A' <= p[i] && p[i] <= 'F':
 			v += int(p[i] - 'A' + 10)
 		default:
 			return 0, false
 		}
 	}
 	return v, true;
 }

 // Unquote unquotes the JSON-quoted string s,
 // returning a raw string t.  If s is not a valid
 // JSON-quoted string, Unquote returns with ok set to false.
 func Unquote(s string) (t string, ok bool) {
 	if len(s) < 2 || s[0] != '"' || s[len(s)-1] != '"' {
 		return
 	}
 	b := make([]byte, len(s));
 	w := 0;
 	for r := 1; r < len(s)-1; {
 		switch {
 		case s[r] == '\\':
 			r++;
 			if r >= len(s)-1 {
 				return
 			}
 			switch s[r] {
 			default:
 				return
 			case '"', '\\', '/', '\'':
 				b[w] = s[r];
 				r++;
 				w++;
 			case 'b':
 				b[w] = '\b';
 				r++;
 				w++;
 			case 'f':
 				b[w] = '\f';
 				r++;
 				w++;
 			case 'n':
 				b[w] = '\n';
 				r++;
 				w++;
 			case 'r':
 				b[w] = '\r';
 				r++;
 				w++;
 			case 't':
 				b[w] = '\t';
 				r++;
 				w++;
 			case 'u':
 				r++;
 				rune, ok := _UnHex(s, r, 4);
 				if !ok {
 					return
 				}
 				r += 4;
 				w += utf8.EncodeRune(rune, b[w:len(b)]);
 			}
 		// Control characters are invalid, but we've seen raw \n.
 		case s[r] < ' ' && s[r] != '\n':
 			if s[r] == '\n' {
 				b[w] = '\n';
 				r++;
 				w++;
 				break;
 			}
 			return;
 		// ASCII
 		case s[r] < utf8.RuneSelf:
 			b[w] = s[r];
 			r++;
 			w++;
 		// Coerce to well-formed UTF-8.
 		default:
 			rune, size := utf8.DecodeRuneInString(s[r:len(s)]);
 			r += size;
 			w += utf8.EncodeRune(rune, b[w:len(b)]);
 		}
 	}
 	return string(b[0:w]), true;
 }

 // Quote quotes the raw string s using JSON syntax,
 // so that Unquote(Quote(s)) = s, true.
 func Quote(s string) string {
 	chr := make([]byte, utf8.UTFMax);
 	chr0 := chr[0:1];
 	b := new(bytes.Buffer);
 	chr[0] = '"';
 	b.Write(chr0);
 	for i := 0; i < len(s); i++ {
 		switch {
 		case s[i] == '"' || s[i] == '\\':
 			chr[0] = '\\';
 			chr[1] = s[i];
 			b.Write(chr[0:2]);

 		case s[i] == '\b':
 			chr[0] = '\\';
 			chr[1] = 'b';
 			b.Write(chr[0:2]);

 		case s[i] == '\f':
 			chr[0] = '\\';
 			chr[1] = 'f';
 			b.Write(chr[0:2]);

 		case s[i] == '\n':
 			chr[0] = '\\';
 			chr[1] = 'n';
 			b.Write(chr[0:2]);

 		case s[i] == '\r':
 			chr[0] = '\\';
 			chr[1] = 'r';
 			b.Write(chr[0:2]);

 		case s[i] == '\t':
 			chr[0] = '\\';
 			chr[1] = 't';
 			b.Write(chr[0:2]);

 		case 0x20 <= s[i] && s[i] < utf8.RuneSelf:
 			chr[0] = s[i];
 			b.Write(chr0);
 		}
 	}
 	chr[0] = '"';
 	b.Write(chr0);
 	return b.String();
 }


 // _Lexer

 type _Lexer struct {
 	s	string;
 	i	int;
 	kind	int;
 	token	string;
 }

 func punct(c byte) bool {
 	return c == '"' || c == '[' || c == ']' || c == ':' || c == '{' || c == '}' || c == ','
 }

 func white(c byte) bool	{ return c == ' ' || c == '\t' || c == '\n' || c == '\v' }

 func skipwhite(p string, i int) int {
 	for i < len(p) && white(p[i]) {
 		i++
 	}
 	return i;
 }

 func skiptoken(p string, i int) int {
 	for i < len(p) && !punct(p[i]) && !white(p[i]) {
 		i++
 	}
 	return i;
 }

 func skipstring(p string, i int) int {
 	for i++; i < len(p) && p[i] != '"'; i++ {
 		if p[i] == '\\' {
 			i++
 		}
 	}
 	if i >= len(p) {
 		return i
 	}
 	return i + 1;
 }

 func (t *_Lexer) Next() {
 	i, s := t.i, t.s;
 	i = skipwhite(s, i);
 	if i >= len(s) {
 		t.kind = 0;
 		t.token = "";
 		t.i = len(s);
 		return;
 	}

 	c := s[i];
 	switch {
 	case c == '-' || '0' <= c && c <= '9':
 		j := skiptoken(s, i);
 		t.kind = '1';
 		t.token = s[i:j];
 		i = j;

 	case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
 		j := skiptoken(s, i);
 		t.kind = 'a';
 		t.token = s[i:j];
 		i = j;

 	case c == '"':
 		j := skipstring(s, i);
 		t.kind = '"';
 		t.token = s[i:j];
 		i = j;

 	case c == '[', c == ']', c == ':', c == '{', c == '}', c == ',':
 		t.kind = int(c);
 		t.token = s[i : i+1];
 		i++;

 	default:
 		t.kind = '?';
 		t.token = s[i : i+1];
 	}

 	t.i = i;
 }


 // Parser
 //
 // Implements parsing but not the actions.  Those are
 // carried out by the implementation of the Builder interface.
 // A Builder represents the object being created.
 // Calling a method like Int64(i) sets that object to i.
 // Calling a method like Elem(i) or Key(s) creates a
 // new builder for a subpiece of the object (logically,
 // an array element or a map key).
 //
 // There are two Builders, in other files.
 // The JsonBuilder builds a generic Json structure
 // in which maps are maps.
 // The StructBuilder copies data into a possibly
 // nested data structure, using the "map keys"
 // as struct field names.

 type _Value interface{}

 // BUG(rsc): The json Builder interface needs to be
 // reconciled with the xml Builder interface.

 // A Builder is an interface implemented by clients and passed
 // to the JSON parser.  It gives clients full control over the
 // eventual representation returned by the parser.
 type Builder interface {
 	// Set value
 	Int64(i int64);
 	Uint64(i uint64);
 	Float64(f float64);
 	String(s string);
 	Bool(b bool);
 	Null();
 	Array();
 	Map();

 	// Create sub-Builders
 	Elem(i int) Builder;
 	Key(s string) Builder;

 	// Flush changes to parent Builder if necessary.
 	Flush();
 }

 func parse(lex *_Lexer, build Builder) bool {
 	ok := false;
 Switch:
 	switch lex.kind {
 	case 0:
 		break
 	case '1':
 		// If the number is exactly an integer, use that.
 		if i, err := strconv.Atoi64(lex.token); err == nil {
 			build.Int64(i);
 			ok = true;
 		} else if i, err := strconv.Atoui64(lex.token); err == nil {
 			build.Uint64(i);
 			ok = true;
 		} else
 		// Fall back to floating point.
 		if f, err := strconv.Atof64(lex.token); err == nil {
 			build.Float64(f);
 			ok = true;
 		}

 	case 'a':
 		switch lex.token {
 		case "true":
 			build.Bool(true);
 			ok = true;
 		case "false":
 			build.Bool(false);
 			ok = true;
 		case "null":
 			build.Null();
 			ok = true;
 		}

 	case '"':
 		if str, ok1 := Unquote(lex.token); ok1 {
 			build.String(str);
 			ok = true;
 		}

 	case '[':
 		// array
 		build.Array();
 		lex.Next();
 		n := 0;
 		for lex.kind != ']' {
 			if n > 0 {
 				if lex.kind != ',' {
 					break Switch
 				}
 				lex.Next();
 			}
 			if !parse(lex, build.Elem(n)) {
 				break Switch
 			}
 			n++;
 		}
 		ok = true;

 	case '{':
 		// map
 		lex.Next();
 		build.Map();
 		n := 0;
 		for lex.kind != '}' {
 			if n > 0 {
 				if lex.kind != ',' {
 					break Switch
 				}
 				lex.Next();
 			}
 			if lex.kind != '"' {
 				break Switch
 			}
 			key, ok := Unquote(lex.token);
 			if !ok {
 				break Switch
 			}
 			lex.Next();
 			if lex.kind != ':' {
 				break Switch
 			}
 			lex.Next();
 			if !parse(lex, build.Key(key)) {
 				break Switch
 			}
 			n++;
 		}
 		ok = true;
 	}

 	if ok {
 		lex.Next()
 	}
 	build.Flush();
 	return ok;
 }

 // Parse parses the JSON syntax string s and makes calls to
 // the builder to construct a parsed representation.
 // On success, it returns with ok set to true.
 // On error, it returns with ok set to false, errindx set
 // to the byte index in s where a syntax error occurred,
 // and errtok set to the offending token.
 func Parse(s string, builder Builder) (ok bool, errindx int, errtok string) {
 	lex := new(_Lexer);
 	lex.s = s;
 	lex.Next();
 	if parse(lex, builder) {
 		if lex.kind == 0 {	// EOF
 			return true, 0, ""
 		}
 	}
 	return false, lex.i, lex.token;
 }
	// 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.

	// JSON (JavaScript Object Notation) parser.
	// See http://www.json.org/

	// The json package implements a simple parser and
	// representation for JSON (JavaScript Object Notation),
	// as defined at http://www.json.org/.
	package json

	import (
	"bytes";
	"strconv";
	"utf8";
	)

	// Strings
	//
	// Double quoted with escapes: \" \\ \/ \b \f \n \r \t \uXXXX.
	// No literal control characters, supposedly.
	// Have also seen \' and embedded newlines.

	func _UnHex(p string, r, l int) (v int, ok bool) {
	v = 0;
	for i := r; i < l; i++ {
	if i >= len(p) {
	return 0, false
	}
	v *= 16;
	switch {
	case '0' <= p[i] && p[i] <= '9':
	v += int(p[i] - '0')
	case 'a' <= p[i] && p[i] <= 'f':
	v += int(p[i] - 'a' + 10)
	case 'A' <= p[i] && p[i] <= 'F':
	v += int(p[i] - 'A' + 10)
	default:
	return 0, false
	}
	}
	return v, true;
	}

	// Unquote unquotes the JSON-quoted string s,
	// returning a raw string t. If s is not a valid
	// JSON-quoted string, Unquote returns with ok set to false.
	func Unquote(s string) (t string, ok bool) {
	if len(s) < 2 \|\| s[0] != '"' \|\| s[len(s)-1] != '"' {
	return
	}
	b := make([]byte, len(s));
	w := 0;
	for r := 1; r < len(s)-1; {
	switch {
	case s[r] == '\\':
	r++;
	if r >= len(s)-1 {
	return
	}
	switch s[r] {
	default:
	return
	case '"', '\\', '/', '\'':
	b[w] = s[r];
	r++;
	w++;
	case 'b':
	b[w] = '\b';
	r++;
	w++;
	case 'f':
	b[w] = '\f';
	r++;
	w++;
	case 'n':
	b[w] = '\n';
	r++;
	w++;
	case 'r':
	b[w] = '\r';
	r++;
	w++;
	case 't':
	b[w] = '\t';
	r++;
	w++;
	case 'u':
	r++;
	rune, ok := _UnHex(s, r, 4);
	if !ok {
	return
	}
	r += 4;
	w += utf8.EncodeRune(rune, b[w:len(b)]);
	}
	// Control characters are invalid, but we've seen raw \n.
	case s[r] < ' ' && s[r] != '\n':
	if s[r] == '\n' {
	b[w] = '\n';
	r++;
	w++;
	break;
	}
	return;
	// ASCII
	case s[r] < utf8.RuneSelf:
	b[w] = s[r];
	r++;
	w++;
	// Coerce to well-formed UTF-8.
	default:
	rune, size := utf8.DecodeRuneInString(s[r:len(s)]);
	r += size;
	w += utf8.EncodeRune(rune, b[w:len(b)]);
	}
	}
	return string(b[0:w]), true;
	}

	// Quote quotes the raw string s using JSON syntax,
	// so that Unquote(Quote(s)) = s, true.
	func Quote(s string) string {
	chr := make([]byte, utf8.UTFMax);
	chr0 := chr[0:1];
	b := new(bytes.Buffer);
	chr[0] = '"';
	b.Write(chr0);
	for i := 0; i < len(s); i++ {
	switch {
	case s[i] == '"' \|\| s[i] == '\\':
	chr[0] = '\\';
	chr[1] = s[i];
	b.Write(chr[0:2]);

	case s[i] == '\b':
	chr[0] = '\\';
	chr[1] = 'b';
	b.Write(chr[0:2]);

	case s[i] == '\f':
	chr[0] = '\\';
	chr[1] = 'f';
	b.Write(chr[0:2]);

	case s[i] == '\n':
	chr[0] = '\\';
	chr[1] = 'n';
	b.Write(chr[0:2]);

	case s[i] == '\r':
	chr[0] = '\\';
	chr[1] = 'r';
	b.Write(chr[0:2]);

	case s[i] == '\t':
	chr[0] = '\\';
	chr[1] = 't';
	b.Write(chr[0:2]);

	case 0x20 <= s[i] && s[i] < utf8.RuneSelf:
	chr[0] = s[i];
	b.Write(chr0);
	}
	}
	chr[0] = '"';
	b.Write(chr0);
	return b.String();
	}


	// _Lexer

	type _Lexer struct {
	s string;
	i int;
	kind int;
	token string;
	}

	func punct(c byte) bool {
	return c == '"' \|\| c == '[' \|\| c == ']' \|\| c == ':' \|\| c == '{' \|\| c == '}' \|\| c == ','
	}

	func white(c byte) bool { return c == ' ' \|\| c == '\t' \|\| c == '\n' \|\| c == '\v' }

	func skipwhite(p string, i int) int {
	for i < len(p) && white(p[i]) {
	i++
	}
	return i;
	}

	func skiptoken(p string, i int) int {
	for i < len(p) && !punct(p[i]) && !white(p[i]) {
	i++
	}
	return i;
	}

	func skipstring(p string, i int) int {
	for i++; i < len(p) && p[i] != '"'; i++ {
	if p[i] == '\\' {
	i++
	}
	}
	if i >= len(p) {
	return i
	}
	return i + 1;
	}

	func (t *_Lexer) Next() {
	i, s := t.i, t.s;
	i = skipwhite(s, i);
	if i >= len(s) {
	t.kind = 0;
	t.token = "";
	t.i = len(s);
	return;
	}

	c := s[i];
	switch {
	case c == '-' \|\| '0' <= c && c <= '9':
	j := skiptoken(s, i);
	t.kind = '1';
	t.token = s[i:j];
	i = j;

	case 'a' <= c && c <= 'z' \|\| 'A' <= c && c <= 'Z':
	j := skiptoken(s, i);
	t.kind = 'a';
	t.token = s[i:j];
	i = j;

	case c == '"':
	j := skipstring(s, i);
	t.kind = '"';
	t.token = s[i:j];
	i = j;

	case c == '[', c == ']', c == ':', c == '{', c == '}', c == ',':
	t.kind = int(c);
	t.token = s[i : i+1];
	i++;

	default:
	t.kind = '?';
	t.token = s[i : i+1];
	}

	t.i = i;
	}


	// Parser
	//
	// Implements parsing but not the actions. Those are
	// carried out by the implementation of the Builder interface.
	// A Builder represents the object being created.
	// Calling a method like Int64(i) sets that object to i.
	// Calling a method like Elem(i) or Key(s) creates a
	// new builder for a subpiece of the object (logically,
	// an array element or a map key).
	//
	// There are two Builders, in other files.
	// The JsonBuilder builds a generic Json structure
	// in which maps are maps.
	// The StructBuilder copies data into a possibly
	// nested data structure, using the "map keys"
	// as struct field names.

	type _Value interface{}

	// BUG(rsc): The json Builder interface needs to be
	// reconciled with the xml Builder interface.

	// A Builder is an interface implemented by clients and passed
	// to the JSON parser. It gives clients full control over the
	// eventual representation returned by the parser.
	type Builder interface {
	// Set value
	Int64(i int64);
	Uint64(i uint64);
	Float64(f float64);
	String(s string);
	Bool(b bool);
	Null();
	Array();
	Map();

	// Create sub-Builders
	Elem(i int) Builder;
	Key(s string) Builder;

	// Flush changes to parent Builder if necessary.
	Flush();
	}

	func parse(lex *_Lexer, build Builder) bool {
	ok := false;
	Switch:
	switch lex.kind {
	case 0:
	break
	case '1':
	// If the number is exactly an integer, use that.
	if i, err := strconv.Atoi64(lex.token); err == nil {
	build.Int64(i);
	ok = true;
	} else if i, err := strconv.Atoui64(lex.token); err == nil {
	build.Uint64(i);
	ok = true;
	} else
	// Fall back to floating point.
	if f, err := strconv.Atof64(lex.token); err == nil {
	build.Float64(f);
	ok = true;
	}

	case 'a':
	switch lex.token {
	case "true":
	build.Bool(true);
	ok = true;
	case "false":
	build.Bool(false);
	ok = true;
	case "null":
	build.Null();
	ok = true;
	}

	case '"':
	if str, ok1 := Unquote(lex.token); ok1 {
	build.String(str);
	ok = true;
	}

	case '[':
	// array
	build.Array();
	lex.Next();
	n := 0;
	for lex.kind != ']' {
	if n > 0 {
	if lex.kind != ',' {
	break Switch
	}
	lex.Next();
	}
	if !parse(lex, build.Elem(n)) {
	break Switch
	}
	n++;
	}
	ok = true;

	case '{':
	// map
	lex.Next();
	build.Map();
	n := 0;
	for lex.kind != '}' {
	if n > 0 {
	if lex.kind != ',' {
	break Switch
	}
	lex.Next();
	}
	if lex.kind != '"' {
	break Switch
	}
	key, ok := Unquote(lex.token);
	if !ok {
	break Switch
	}
	lex.Next();
	if lex.kind != ':' {
	break Switch
	}
	lex.Next();
	if !parse(lex, build.Key(key)) {
	break Switch
	}
	n++;
	}
	ok = true;
	}

	if ok {
	lex.Next()
	}
	build.Flush();
	return ok;
	}

	// Parse parses the JSON syntax string s and makes calls to
	// the builder to construct a parsed representation.
	// On success, it returns with ok set to true.
	// On error, it returns with ok set to false, errindx set
	// to the byte index in s where a syntax error occurred,
	// and errtok set to the offending token.
	func Parse(s string, builder Builder) (ok bool, errindx int, errtok string) {
	lex := new(_Lexer);
	lex.s = s;
	lex.Next();
	if parse(lex, builder) {
	if lex.kind == 0 { // EOF
	return true, 0, ""
	}
	}
	return false, lex.i, lex.token;
	}