README
¶
CSS 
This package is a CSS3 lexer and parser written in Go. Both follow the specification at CSS Syntax Module Level 3. The lexer takes an io.Reader and converts it into tokens until the EOF. The parser returns a parse tree of the full io.Reader input stream, but the low-level Next function can be used for stream parsing to returns grammar units until the EOF.
Installation
Run the following command
go get -u github.com/tdewolff/parse/v2/css
or add the following import and run project with go get
import "github.com/tdewolff/parse/v2/css"
Lexer
Usage
The following initializes a new Lexer with io.Reader r:
l := css.NewLexer(r)
To tokenize until EOF an error, use:
for {
tt, text := l.Next()
switch tt {
case css.ErrorToken:
// error or EOF set in l.Err()
return
// ...
}
}
All tokens (see CSS Syntax Module Level 3):
ErrorToken // non-official token, returned when errors occur
IdentToken
FunctionToken // rgb( rgba( ...
AtKeywordToken // @abc
HashToken // #abc
StringToken
BadStringToken
URLToken // url(
BadURLToken
DelimToken // any unmatched character
NumberToken // 5
PercentageToken // 5%
DimensionToken // 5em
UnicodeRangeToken
IncludeMatchToken // ~=
DashMatchToken // |=
PrefixMatchToken // ^=
SuffixMatchToken // $=
SubstringMatchToken // *=
ColumnToken // ||
WhitespaceToken
CDOToken // <!--
CDCToken // -->
ColonToken
SemicolonToken
CommaToken
BracketToken // ( ) [ ] { }, all bracket tokens use this, Data() can distinguish between the brackets
CommentToken // non-official token
Examples
package main
import (
"os"
"github.com/tdewolff/parse/v2/css"
)
// Tokenize CSS3 from stdin.
func main() {
l := css.NewLexer(os.Stdin)
for {
tt, text := l.Next()
switch tt {
case css.ErrorToken:
if l.Err() != io.EOF {
fmt.Println("Error on line", l.Line(), ":", l.Err())
}
return
case css.IdentToken:
fmt.Println("Identifier", string(text))
case css.NumberToken:
fmt.Println("Number", string(text))
// ...
}
}
}
Parser
Usage
The following creates a new Parser.
// true because this is the content of an inline style attribute
p := css.NewParser(bytes.NewBufferString("color: red;"), true)
To iterate over the stylesheet, use:
for {
gt, _, data := p.Next()
if gt == css.ErrorGrammar {
break
}
// ...
}
All grammar units returned by Next:
ErrorGrammar
AtRuleGrammar
EndAtRuleGrammar
RulesetGrammar
EndRulesetGrammar
DeclarationGrammar
TokenGrammar
Examples
package main
import (
"bytes"
"fmt"
"github.com/tdewolff/parse/v2/css"
)
func main() {
// true because this is the content of an inline style attribute
p := css.NewParser(bytes.NewBufferString("color: red;"), true)
out := ""
for {
gt, _, data := p.Next()
if gt == css.ErrorGrammar {
break
} else if gt == css.AtRuleGrammar || gt == css.BeginAtRuleGrammar || gt == css.BeginRulesetGrammar || gt == css.DeclarationGrammar {
out += string(data)
if gt == css.DeclarationGrammar {
out += ":"
}
for _, val := range p.Values() {
out += string(val.Data)
}
if gt == css.BeginAtRuleGrammar || gt == css.BeginRulesetGrammar {
out += "{"
} else if gt == css.AtRuleGrammar || gt == css.DeclarationGrammar {
out += ";"
}
} else {
out += string(data)
}
}
fmt.Println(out)
}
License
Released under the MIT license.
Documentation
¶
Overview ¶
Package css is a CSS3 lexer and parser following the specifications at http://www.w3.org/TR/css-syntax-3/.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func HSL2RGB ¶
HSL2RGB converts HSL to RGB with all of range [0,1] from http://www.w3.org/TR/css3-color/#hsl-color
func IsURLUnquoted ¶
IsURLUnquoted returns true if the bytes are a valid unquoted URL.
Types ¶
type GrammarType ¶
type GrammarType uint32
GrammarType determines the type of grammar.
const ( ErrorGrammar GrammarType = iota // extra token when errors occur CommentGrammar AtRuleGrammar BeginAtRuleGrammar EndAtRuleGrammar QualifiedRuleGrammar BeginRulesetGrammar EndRulesetGrammar DeclarationGrammar TokenGrammar CustomPropertyGrammar )
GrammarType values.
func (GrammarType) String ¶
func (tt GrammarType) String() string
String returns the string representation of a GrammarType.
type Hash ¶
type Hash uint32
Hash defines perfect hashes for a predefined list of strings
const ( Document Hash = 0x8 // document Font_Face Hash = 0x809 // font-face Keyframes Hash = 0x1109 // keyframes Media Hash = 0x2105 // media Page Hash = 0x2604 // page Supports Hash = 0x1908 // supports )
Unique hash definitions to be used instead of strings
type Lexer ¶
type Lexer struct {
// contains filtered or unexported fields
}
Lexer is the state for the lexer.
func NewLexer ¶
NewLexer returns a new Lexer for a given io.Reader.
Example ¶
l := NewLexer(bytes.NewBufferString("color: red;"))
out := ""
for {
tt, data := l.Next()
if tt == ErrorToken {
break
} else if tt == WhitespaceToken || tt == CommentToken {
continue
}
out += string(data)
}
fmt.Println(out)
Output: color:red;
func (*Lexer) Err ¶
Err returns the error encountered during lexing, this is often io.EOF but also other errors can be returned.
func (*Lexer) Next ¶
Next returns the next Token. It returns ErrorToken when an error was encountered. Using Err() one can retrieve the error message.
type Parser ¶
type Parser struct {
// contains filtered or unexported fields
}
Parser is the state for the parser.
func NewParser ¶
NewParser returns a new CSS parser from an io.Reader. isInline specifies whether this is an inline style attribute.
Example ¶
p := NewParser(bytes.NewBufferString("color: red;"), true) // false because this is the content of an inline style attribute
out := ""
for {
gt, _, data := p.Next()
if gt == ErrorGrammar {
break
} else if gt == AtRuleGrammar || gt == BeginAtRuleGrammar || gt == BeginRulesetGrammar || gt == DeclarationGrammar {
out += string(data)
if gt == DeclarationGrammar {
out += ":"
}
for _, val := range p.Values() {
out += string(val.Data)
}
if gt == BeginAtRuleGrammar || gt == BeginRulesetGrammar {
out += "{"
} else if gt == AtRuleGrammar || gt == DeclarationGrammar {
out += ";"
}
} else {
out += string(data)
}
}
fmt.Println(out)
Output: color:red;
func (*Parser) Err ¶
Err returns the error encountered during parsing, this is often io.EOF but also other errors can be returned.
func (*Parser) HasParseError ¶ added in v2.4.3
HasParseError returns true if there is a parse error (and not a read error).
func (*Parser) Next ¶
func (p *Parser) Next() (GrammarType, TokenType, []byte)
Next returns the next Grammar. It returns ErrorGrammar when an error was encountered. Using Err() one can retrieve the error message.
type State ¶
type State func(*Parser) GrammarType
State is the state function the parser currently is in.
type TokenType ¶
type TokenType uint32
TokenType determines the type of token, eg. a number or a semicolon.
const ( ErrorToken TokenType = iota // extra token when errors occur IdentToken FunctionToken // rgb( rgba( ... AtKeywordToken // @abc HashToken // #abc StringToken BadStringToken URLToken BadURLToken DelimToken // any unmatched character NumberToken // 5 PercentageToken // 5% DimensionToken // 5em UnicodeRangeToken // U+554A IncludeMatchToken // ~= DashMatchToken // |= PrefixMatchToken // ^= SuffixMatchToken // $= SubstringMatchToken // *= ColumnToken // || WhitespaceToken // space \t \r \n \f CDOToken // <!-- CDCToken // --> ColonToken // : SemicolonToken // ; CommaToken // , LeftBracketToken // [ RightBracketToken // ] LeftParenthesisToken // ( RightParenthesisToken // ) LeftBraceToken // { RightBraceToken // } CommentToken // extra token for comments EmptyToken CustomPropertyNameToken CustomPropertyValueToken )
TokenType values.
Source Files