generate cryptographically secure text in Sass

examples/customfunc/README.md

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+Cryptographically secure pseudorandom number generator in Sass. Well that is easy to do with this custom `crypto()` handler!
+
+Start by registering a Sass function with the name `crypto()`. Now when `crypto()` is found in Sass, the cryptotext Go function will be called.
+
+Input
+
+``` sass
+div { text: crypto(); }
+
+```
+
+
+Output
+
+``` css
+div {
+  text: 'c91db27d5e580ef4292e'; }
+```
+
+Sass function written in Go
+
+``` go
+func cryptotext(ctx context.Context, usv libsass.SassValue) (*libsass.SassValue, error) {
+
+	c := 10
+	b := make([]byte, c)
+	_, err := rand.Read(b)
+	if err != nil {
+		return nil, err
+	}
+	res, err := libsass.Marshal(fmt.Sprintf("'%x'", b))
+	return &res, err
+}
+```

examples/customfunc/main.go

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+package main
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"log"
+	"os"
+
+	"golang.org/x/net/context"
+
+	"github.com/wellington/go-libsass"
+)
+
+// cryptotext is of type libsass.SassFunc. As libsass compiles the
+// source Sass, it will look for `crypto()` then call this function.
+func cryptotext(ctx context.Context, usv libsass.SassValue) (*libsass.SassValue, error) {
+
+	c := 10
+	b := make([]byte, c)
+	_, err := rand.Read(b)
+	if err != nil {
+		return nil, err
+	}
+	res, err := libsass.Marshal(fmt.Sprintf("'%x'", b))
+	return &res, err
+}
+
+func main() {
+	// Register a custom Sass func crypto
+	libsass.RegisterSassFunc("crypto()", cryptotext)
+
+	// Input Sass source
+	input := `div { text: crypto(); }`
+
+	buf := bytes.NewBufferString(input)
+	// Starts a compiler writing to Stdout and reading from
+	// a bytes buffer of the input source
+	comp, err := libsass.New(os.Stdout, buf)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Run() kicks off the compiler and instructs libsass how
+	// to read our input, handling the output from libsass
+	if err := comp.Run(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Output:
+	// div {
+	//   text: 'c91db27d5e580ef4292e'; }
+}