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parsing.go
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parsing.go
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package config
import (
"bytes"
"io/ioutil"
"os"
"golang.org/x/text/transform"
)
func expandVariables(data []byte) ([]byte, error) {
return ioutil.ReadAll(transform.NewReader(bytes.NewBuffer(data), newExpandTransformer()))
}
// expandTransformer implements transform.Transformer
type expandTransformer struct {
transform.NopResetter
}
func newExpandTransformer() *expandTransformer {
return &expandTransformer{}
}
// Transform -
func (t *expandTransformer) Transform(dst, src []byte, atEOF bool) (int, int, error) {
var buf bytes.Buffer
var index int
startIndex := bytes.Index(src, []byte{'$', '{'})
for startIndex != -1 {
if _, err := buf.Write(src[index : startIndex+index]); err != nil {
return 0, 0, err
}
var name, def string
endIndex := bytes.Index(src[startIndex+index:], []byte{'}'})
separatorIndex := bytes.Index(src[startIndex+index:startIndex+index+endIndex], []byte{':', '-'})
if separatorIndex == -1 {
name = string(src[startIndex+index+2 : startIndex+index+endIndex])
} else {
name = string(src[startIndex+index+2 : startIndex+index+separatorIndex])
def = string(src[startIndex+index+separatorIndex+2 : startIndex+index+endIndex])
}
if envVal, ok := os.LookupEnv(name); ok {
def = envVal
}
if def == "" {
def = `""`
}
if _, err := buf.Write([]byte(def)); err != nil {
return 0, 0, err
}
index += startIndex + endIndex + 1
startIndex = bytes.Index(src[index:], []byte{'$', '{'})
}
if _, err := buf.Write(src[index:]); err != nil {
return 0, 0, err
}
return copy(dst, buf.Bytes()), len(src), nil
}