// 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.

// This package implements translation between
// unsigned integer values and byte sequences.
package binary

import (
	"math";
	"io";
	"os";
	"reflect";
)

// A ByteOrder specifies how to convert byte sequences into
// 16-, 32-, or 64-bit unsigned integers.
type ByteOrder interface {
	Uint16(b []byte) uint16;
	Uint32(b []byte) uint32;
	Uint64(b []byte) uint64;
	PutUint16([]byte, uint16);
	PutUint32([]byte, uint32);
	PutUint64([]byte, uint64);
	String() string;
}

// This is byte instead of struct{} so that it can be compared,
// allowing, e.g., order == binary.LittleEndian.
type unused byte

var LittleEndian ByteOrder = littleEndian(0)
var BigEndian ByteOrder = bigEndian(0)

type littleEndian unused

func (littleEndian) Uint16(b []byte) uint16	{ return uint16(b[0]) | uint16(b[1])<<8 }

func (littleEndian) PutUint16(b []byte, v uint16) {
	b[0] = byte(v);
	b[1] = byte(v >> 8);
}

func (littleEndian) Uint32(b []byte) uint32 {
	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
}

func (littleEndian) PutUint32(b []byte, v uint32) {
	b[0] = byte(v);
	b[1] = byte(v >> 8);
	b[2] = byte(v >> 16);
	b[3] = byte(v >> 24);
}

func (littleEndian) Uint64(b []byte) uint64 {
	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
}

func (littleEndian) PutUint64(b []byte, v uint64) {
	b[0] = byte(v);
	b[1] = byte(v >> 8);
	b[2] = byte(v >> 16);
	b[3] = byte(v >> 24);
	b[4] = byte(v >> 32);
	b[5] = byte(v >> 40);
	b[6] = byte(v >> 48);
	b[7] = byte(v >> 56);
}

func (littleEndian) String() string	{ return "LittleEndian" }

func (littleEndian) GoString() string	{ return "binary.LittleEndian" }

type bigEndian unused

func (bigEndian) Uint16(b []byte) uint16	{ return uint16(b[1]) | uint16(b[0])<<8 }

func (bigEndian) PutUint16(b []byte, v uint16) {
	b[0] = byte(v >> 8);
	b[1] = byte(v);
}

func (bigEndian) Uint32(b []byte) uint32 {
	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
}

func (bigEndian) PutUint32(b []byte, v uint32) {
	b[0] = byte(v >> 24);
	b[1] = byte(v >> 16);
	b[2] = byte(v >> 8);
	b[3] = byte(v);
}

func (bigEndian) Uint64(b []byte) uint64 {
	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
}

func (bigEndian) PutUint64(b []byte, v uint64) {
	b[0] = byte(v >> 56);
	b[1] = byte(v >> 48);
	b[2] = byte(v >> 40);
	b[3] = byte(v >> 32);
	b[4] = byte(v >> 24);
	b[5] = byte(v >> 16);
	b[6] = byte(v >> 8);
	b[7] = byte(v);
}

func (bigEndian) String() string	{ return "BigEndian" }

func (bigEndian) GoString() string	{ return "binary.BigEndian" }

// Read reads structured binary data from r into data.
// Data must be a pointer to a fixed-size value.
// A fixed-size value is either a fixed-size integer
// (int8, uint8, int16, uint16, ...) or an array or struct
// containing only fixed-size values.  Bytes read from
// r are decoded using the specified byte order and written
// to successive fields of the data.
func Read(r io.Reader, order ByteOrder, data interface{}) os.Error {
	v := reflect.NewValue(data).(*reflect.PtrValue).Elem();
	size := sizeof(v.Type());
	if size < 0 {
		return os.NewError("binary.Read: invalid type " + v.Type().String())
	}
	d := &decoder{order: order, buf: make([]byte, size)};
	if _, err := io.ReadFull(r, d.buf); err != nil {
		return err
	}
	d.value(v);
	return nil;
}

// Write writes the binary representation of data into w.
// Data must be a fixed-size value or a pointer to
// a fixed-size value.
// A fixed-size value is either a fixed-size integer
// (int8, uint8, int16, uint16, ...) or an array or struct
// containing only fixed-size values.  Bytes written to
// w are encoded using the specified byte order and read
// from successive fields of the data.
func Write(w io.Writer, order ByteOrder, data interface{}) os.Error {
	v := reflect.Indirect(reflect.NewValue(data));
	size := sizeof(v.Type());
	if size < 0 {
		return os.NewError("binary.Write: invalid type " + v.Type().String())
	}
	buf := make([]byte, size);
	e := &encoder{order: order, buf: buf};
	e.value(v);
	_, err := w.Write(buf);
	return err;
}

func sizeof(t reflect.Type) int {
	switch t := t.(type) {
	case *reflect.ArrayType:
		n := sizeof(t.Elem());
		if n < 0 {
			return -1
		}
		return t.Len() * n;

	case *reflect.StructType:
		sum := 0;
		for i, n := 0, t.NumField(); i < n; i++ {
			s := sizeof(t.Field(i).Type);
			if s < 0 {
				return -1
			}
			sum += s;
		}
		return sum;

	case *reflect.Uint8Type:
		return 1
	case *reflect.Uint16Type:
		return 2
	case *reflect.Uint32Type:
		return 4
	case *reflect.Uint64Type:
		return 8
	case *reflect.Int8Type:
		return 1
	case *reflect.Int16Type:
		return 2
	case *reflect.Int32Type:
		return 4
	case *reflect.Int64Type:
		return 8
	case *reflect.Float32Type:
		return 4
	case *reflect.Float64Type:
		return 8
	}
	return -1;
}

type decoder struct {
	order	ByteOrder;
	buf	[]byte;
}

type encoder struct {
	order	ByteOrder;
	buf	[]byte;
}

func (d *decoder) uint8() uint8 {
	x := d.buf[0];
	d.buf = d.buf[1:len(d.buf)];
	return x;
}

func (e *encoder) uint8(x uint8) {
	e.buf[0] = x;
	e.buf = e.buf[1:len(e.buf)];
}

func (d *decoder) uint16() uint16 {
	x := d.order.Uint16(d.buf[0:2]);
	d.buf = d.buf[2:len(d.buf)];
	return x;
}

func (e *encoder) uint16(x uint16) {
	e.order.PutUint16(e.buf[0:2], x);
	e.buf = e.buf[2:len(e.buf)];
}

func (d *decoder) uint32() uint32 {
	x := d.order.Uint32(d.buf[0:4]);
	d.buf = d.buf[4:len(d.buf)];
	return x;
}

func (e *encoder) uint32(x uint32) {
	e.order.PutUint32(e.buf[0:4], x);
	e.buf = e.buf[4:len(e.buf)];
}

func (d *decoder) uint64() uint64 {
	x := d.order.Uint64(d.buf[0:8]);
	d.buf = d.buf[8:len(d.buf)];
	return x;
}

func (e *encoder) uint64(x uint64) {
	e.order.PutUint64(e.buf[0:8], x);
	e.buf = e.buf[8:len(e.buf)];
}

func (d *decoder) int8() int8	{ return int8(d.uint8()) }

func (e *encoder) int8(x int8)	{ e.uint8(uint8(x)) }

func (d *decoder) int16() int16	{ return int16(d.uint16()) }

func (e *encoder) int16(x int16)	{ e.uint16(uint16(x)) }

func (d *decoder) int32() int32	{ return int32(d.uint32()) }

func (e *encoder) int32(x int32)	{ e.uint32(uint32(x)) }

func (d *decoder) int64() int64	{ return int64(d.uint64()) }

func (e *encoder) int64(x int64)	{ e.uint64(uint64(x)) }

func (d *decoder) value(v reflect.Value) {
	switch v := v.(type) {
	case *reflect.ArrayValue:
		l := v.Len();
		for i := 0; i < l; i++ {
			d.value(v.Elem(i))
		}
	case *reflect.StructValue:
		l := v.NumField();
		for i := 0; i < l; i++ {
			d.value(v.Field(i))
		}

	case *reflect.Uint8Value:
		v.Set(d.uint8())
	case *reflect.Uint16Value:
		v.Set(d.uint16())
	case *reflect.Uint32Value:
		v.Set(d.uint32())
	case *reflect.Uint64Value:
		v.Set(d.uint64())
	case *reflect.Int8Value:
		v.Set(d.int8())
	case *reflect.Int16Value:
		v.Set(d.int16())
	case *reflect.Int32Value:
		v.Set(d.int32())
	case *reflect.Int64Value:
		v.Set(d.int64())
	case *reflect.Float32Value:
		v.Set(math.Float32frombits(d.uint32()))
	case *reflect.Float64Value:
		v.Set(math.Float64frombits(d.uint64()))
	}
}

func (e *encoder) value(v reflect.Value) {
	switch v := v.(type) {
	case *reflect.ArrayValue:
		l := v.Len();
		for i := 0; i < l; i++ {
			e.value(v.Elem(i))
		}
	case *reflect.StructValue:
		l := v.NumField();
		for i := 0; i < l; i++ {
			e.value(v.Field(i))
		}

	case *reflect.Uint8Value:
		e.uint8(v.Get())
	case *reflect.Uint16Value:
		e.uint16(v.Get())
	case *reflect.Uint32Value:
		e.uint32(v.Get())
	case *reflect.Uint64Value:
		e.uint64(v.Get())
	case *reflect.Int8Value:
		e.int8(v.Get())
	case *reflect.Int16Value:
		e.int16(v.Get())
	case *reflect.Int32Value:
		e.int32(v.Get())
	case *reflect.Int64Value:
		e.int64(v.Get())
	case *reflect.Float32Value:
		e.uint32(math.Float32bits(v.Get()))
	case *reflect.Float64Value:
		e.uint64(math.Float64bits(v.Get()))
	}
}