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|
// Package implements the decoding of logfmt key-value pairs.
//
// Example logfmt message:
//
// foo=bar a=14 baz="hello kitty" cool%story=bro f %^asdf
//
// Example result in JSON:
//
// { "foo": "bar", "a": 14, "baz": "hello kitty", "cool%story": "bro", "f": true, "%^asdf": true }
//
// EBNFish:
//
// ident_byte = any byte greater than ' ', excluding '=' and '"'
// string_byte = any byte excluding '"' and '\'
// garbage = !ident_byte
// ident = ident_byte, { ident byte }
// key = ident
// value = ident | '"', { string_byte | '\', '"' }, '"'
// pair = key, '=', value | key, '=' | key
// message = { garbage, pair }, garbage
package logfmt
import (
"reflect"
"strconv"
"strings"
"time"
)
// Handler is the interface implemented by objects that accept logfmt
// key-value pairs. HandleLogfmt must copy the logfmt data if it
// wishes to retain the data after returning.
type Handler interface {
HandleLogfmt(key, val []byte) error
}
// The HandlerFunc type is an adapter to allow the use of ordinary functions as
// logfmt handlers. If f is a function with the appropriate signature,
// HandlerFunc(f) is a Handler object that calls f.
type HandlerFunc func(key, val []byte) error
func (f HandlerFunc) HandleLogfmt(key, val []byte) error {
return f(key, val)
}
// Unmarshal parses the logfmt encoding data and stores the result in the value
// pointed to by v. If v is an Handler, HandleLogfmt will be called for each
// key-value pair.
//
// If v is not a Handler, it will pass v to NewStructHandler and use the
// returned StructHandler for decoding.
func Unmarshal(data []byte, v interface{}) (err error) {
h, ok := v.(Handler)
if !ok {
h, err = NewStructHandler(v)
if err != nil {
return err
}
}
return gotoScanner(data, h)
}
// StructHandler unmarshals logfmt into a struct. It matches incoming keys to
// the the struct's fields (either the struct field name or its tag, preferring
// an exact match but also accepting a case-insensitive match.
//
// Field types supported by StructHandler are:
//
// all numeric types (e.g. float32, int, etc.)
// []byte
// string
// bool - true if key is present, false otherwise (the value is ignored).
// time.Duration - uses time.ParseDuration
//
// If a field is a pointer to an above type, and a matching key is not present
// in the logfmt data, the pointer will be untouched.
//
// If v is not a pointer to an Handler or struct, Unmarshal will return an
// error.
type StructHandler struct {
rv reflect.Value
}
func NewStructHandler(v interface{}) (Handler, error) {
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Ptr || rv.IsNil() {
return nil, &InvalidUnmarshalError{reflect.TypeOf(v)}
}
return &StructHandler{rv: rv}, nil
}
func (h *StructHandler) HandleLogfmt(key, val []byte) error {
el := h.rv.Elem()
skey := string(key)
for i := 0; i < el.NumField(); i++ {
fv := el.Field(i)
ft := el.Type().Field(i)
switch {
case ft.Name == skey:
case ft.Tag.Get("logfmt") == skey:
case strings.EqualFold(ft.Name, skey):
default:
continue
}
if fv.Kind() == reflect.Ptr {
if fv.IsNil() {
t := fv.Type().Elem()
v := reflect.New(t)
fv.Set(v)
fv = v
}
fv = fv.Elem()
}
switch fv.Interface().(type) {
case time.Duration:
d, err := time.ParseDuration(string(val))
if err != nil {
return &UnmarshalTypeError{string(val), fv.Type()}
}
fv.Set(reflect.ValueOf(d))
case string:
fv.SetString(string(val))
case []byte:
b := make([]byte, len(val))
copy(b, val)
fv.SetBytes(b)
case bool:
fv.SetBool(true)
default:
switch {
case reflect.Int <= fv.Kind() && fv.Kind() <= reflect.Int64:
v, err := strconv.ParseInt(string(val), 10, 64)
if err != nil {
return err
}
fv.SetInt(v)
case reflect.Uint32 <= fv.Kind() && fv.Kind() <= reflect.Uint64:
v, err := strconv.ParseUint(string(val), 10, 64)
if err != nil {
return err
}
fv.SetUint(v)
case reflect.Float32 <= fv.Kind() && fv.Kind() <= reflect.Float64:
v, err := strconv.ParseFloat(string(val), 10)
if err != nil {
return err
}
fv.SetFloat(v)
default:
return &UnmarshalTypeError{string(val), fv.Type()}
}
}
}
return nil
}
// An InvalidUnmarshalError describes an invalid argument passed to Unmarshal.
// (The argument to Unmarshal must be a non-nil pointer.)
type InvalidUnmarshalError struct {
Type reflect.Type
}
func (e *InvalidUnmarshalError) Error() string {
if e.Type == nil {
return "logfmt: Unmarshal(nil)"
}
if e.Type.Kind() != reflect.Ptr {
return "logfmt: Unmarshal(non-pointer " + e.Type.String() + ")"
}
return "logfmt: Unmarshal(nil " + e.Type.String() + ")"
}
// An UnmarshalTypeError describes a logfmt value that was
// not appropriate for a value of a specific Go type.
type UnmarshalTypeError struct {
Value string // the logfmt value
Type reflect.Type // type of Go value it could not be assigned to
}
func (e *UnmarshalTypeError) Error() string {
return "logfmt: cannot unmarshal " + e.Value + " into Go value of type " + e.Type.String()
}
|
