go-bt/decode.go

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2010-01-06 15:38:33 +00:00
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Represents JSON data structure using native Go types: booleans, floats,
// strings, arrays, and maps.
package bencode
import (
"container/vector"
"io"
"os"
)
// Decode a bencode stream
// Decode parses the stream r and returns the
// generic bencode object representation. The object representation is a tree
// of Go data types. The data return value may be one of string,
// int64, uint64, []interface{} or map[string]interface{}. The array and map
// elements may in turn contain any of the types listed above and so on.
//
// If Decode encounters a syntax error, it returns with err set to an
// instance of ParseError. See ParseError documentation for details.
func Decode(r io.Reader) (data interface{}, err os.Error) {
jb := newDecoder(nil, nil)
err = Parse(r, jb)
if err == nil {
data = jb.Data()
}
return
}
type decoder struct {
// A value being constructed.
value interface{}
// Container entity to flush into. Can be either vector.Vector or
// map[string]interface{}.
container interface{}
// The index into the container interface. Either int or string.
index interface{}
}
func newDecoder(container interface{}, key interface{}) *decoder {
return &decoder{container: container, index: key}
}
func (j *decoder) Int64(i int64) { j.value = int64(i) }
func (j *decoder) Uint64(i uint64) { j.value = uint64(i) }
func (j *decoder) Float64(f float64) { j.value = float64(f) }
func (j *decoder) String(s string) { j.value = s }
func (j *decoder) Bool(b bool) { j.value = b }
func (j *decoder) Null() { j.value = nil }
func (j *decoder) Array() { j.value = new(vector.Vector) }
func (j *decoder) Map() { j.value = make(map[string]interface{}) }
func (j *decoder) Elem(i int) Builder {
v, ok := j.value.(*vector.Vector)
if !ok {
v = new(vector.Vector)
j.value = v
}
if v.Len() <= i {
v.Resize(i+1, (i+1)*2)
}
return newDecoder(v, i)
}
func (j *decoder) Key(s string) Builder {
m, ok := j.value.(map[string]interface{})
if !ok {
m = make(map[string]interface{})
j.value = m
}
return newDecoder(m, s)
}
func (j *decoder) Flush() {
switch c := j.container.(type) {
case *vector.Vector:
index := j.index.(int)
c.Set(index, j.Data())
case map[string]interface{}:
index := j.index.(string)
c[index] = j.Data()
}
}
// Get the value built by this builder.
func (j *decoder) Data() interface{} {
switch v := j.value.(type) {
case *vector.Vector:
return v.Data()
}
return j.value
}