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filter.go
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filter.go
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package filter
import "strconv"
import "regexp"
import "bytes"
import "bufio"
import "io"
var replacer = regexp.MustCompile(`\$\d+`)
type Config map[string]interface{}
type regexps map[*regexp.Regexp]interface{}
// Filter metrics from reader to the given writer.
func Filter(r io.Reader, w io.Writer, conf Config) error {
s := bufio.NewScanner(r)
filters := compile(conf)
for s.Scan() {
metric := s.Bytes()
parts := bytes.SplitN(metric, []byte("|"), 2)
name := parts[0]
if len(name) == 0 {
continue
}
tail := parts[1]
for regexp, v := range filters {
matches := regexp.FindAllSubmatch(name, -1)
if matches == nil {
continue
}
switch v.(type) {
case string:
w.Write(replace([]byte(v.(string)), matches))
w.Write([]byte("|"))
w.Write(tail)
w.Write([]byte("\n"))
case bool:
w.Write(metric)
w.Write([]byte("\n"))
}
}
}
return s.Err()
}
// Replace placeholders in `b` with the respective match.
func replace(b []byte, matches [][][]byte) []byte {
return replacer.ReplaceAllFunc(b, func(b []byte) []byte {
i, err := strconv.Atoi(string(b[1:]))
if err != nil {
panic(err)
}
return matches[0][i]
})
}
// Compile map of regexps:substitution.
func compile(conf Config) regexps {
r := make(regexps)
for k, v := range conf {
r[regexp.MustCompile(k)] = v
}
return r
}