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# CSS [](https://pkg.go.dev/github.com/tdewolff/parse/v2/css?tab=doc)
This package is a CSS3 lexer and parser written in [Go][1]. Both follow the specification at [CSS Syntax Module Level 3](http://www.w3.org/TR/css-syntax-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`:
``` go
l := css.NewLexer(parse.NewInput(r))
```
To tokenize until EOF an error, use:
``` go
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](http://www.w3.org/TR/css3-syntax/)):
``` go
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
``` go
package main
import (
"os"
"github.com/tdewolff/parse/v2/css"
)
// Tokenize CSS3 from stdin.
func main() {
l := css.NewLexer(parse.NewInput(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.
``` go
// true because this is the content of an inline style attribute
p := css.NewParser(parse.NewInput(bytes.NewBufferString("color: red;")), true)
```
To iterate over the stylesheet, use:
``` go
for {
gt, _, data := p.Next()
if gt == css.ErrorGrammar {
break
}
// ...
}
```
All grammar units returned by `Next`:
``` go
ErrorGrammar
AtRuleGrammar
EndAtRuleGrammar
RulesetGrammar
EndRulesetGrammar
DeclarationGrammar
TokenGrammar
```
### Examples
``` go
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(parse.NewInput(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](https://github.com/tdewolff/parse/blob/master/LICENSE.md).
[1]: http://golang.org/ "Go Language"
|
