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encode.go
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encode.go
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package toml
// TODO: Build a decent encoder.
// Interestingly, this isn't as trivial as recursing down the type of the
// value given and outputting the corresponding TOML. In particular, multiple
// TOML types (especially if tuples are added) can map to a single Go type, so
// that the reverse correspondence isn't clear.
//
// One possible avenue is to choose a reasonable default (like structs map
// to hashes), but allow the user to override with struct tags. But this seems
// like a mess.
//
// The other possibility is to scrap an encoder altogether. After all, TOML
// is a configuration file format, and not a data exchange format.
import (
"bufio"
"fmt"
"io"
"reflect"
"strings"
)
type encoder struct {
// A single indentation level. By default it is two spaces.
Indent string
w *bufio.Writer
}
func newEncoder(w io.Writer) *encoder {
return &encoder{
w: bufio.NewWriter(w),
Indent: " ",
}
}
func (enc *encoder) Encode(v interface{}) error {
rv := eindirect(reflect.ValueOf(v))
if err := enc.encode(Key([]string{}), rv); err != nil {
return err
}
return enc.w.Flush()
}
func (enc *encoder) encode(key Key, rv reflect.Value) error {
k := rv.Kind()
switch k {
case reflect.Struct:
return enc.eStruct(key, rv)
case reflect.String:
return enc.eString(key, rv)
}
return e("Unsupported type for key '%s': %s", key, k)
}
func (enc *encoder) eStruct(key Key, rv reflect.Value) error {
rt := rv.Type()
for i := 0; i < rt.NumField(); i++ {
sft := rt.Field(i)
sf := rv.Field(i)
if err := enc.encode(key.add(sft.Name), sf); err != nil {
return err
}
}
return nil
}
func (enc *encoder) eString(key Key, rv reflect.Value) error {
s := rv.String()
s = strings.NewReplacer(
"\t", "\\t",
"\n", "\\n",
"\r", "\\r",
"\"", "\\\"",
"\\", "\\\\",
).Replace(s)
s = "\"" + s + "\""
if err := enc.eKeyVal(key, s); err != nil {
return err
}
return nil
}
func (enc *encoder) eKeyVal(key Key, value string) error {
out := fmt.Sprintf("%s%s = %s",
strings.Repeat(enc.Indent, len(key)-1), key[len(key)-1], value)
if _, err := fmt.Fprintln(enc.w, out); err != nil {
return err
}
return nil
}
func eindirect(v reflect.Value) reflect.Value {
if v.Kind() != reflect.Ptr {
return v
}
return eindirect(reflect.Indirect(v))
}