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package exifcommon
import (
"bytes"
"math"
"reflect"
"time"
"encoding/binary"
"github.com/dsoprea/go-logging"
)
var (
typeEncodeLogger = log.NewLogger("exif.type_encode")
)
// EncodedData encapsulates the compound output of an encoding operation.
type EncodedData struct {
Type TagTypePrimitive
Encoded []byte
// TODO(dustin): Is this really necessary? We might have this just to correlate to the incoming stream format (raw bytes and a unit-count both for incoming and outgoing).
UnitCount uint32
}
// ValueEncoder knows how to encode values of every type to bytes.
type ValueEncoder struct {
byteOrder binary.ByteOrder
}
// NewValueEncoder returns a new ValueEncoder.
func NewValueEncoder(byteOrder binary.ByteOrder) *ValueEncoder {
return &ValueEncoder{
byteOrder: byteOrder,
}
}
func (ve *ValueEncoder) encodeBytes(value []uint8) (ed EncodedData, err error) {
ed.Type = TypeByte
ed.Encoded = []byte(value)
ed.UnitCount = uint32(len(value))
return ed, nil
}
func (ve *ValueEncoder) encodeAscii(value string) (ed EncodedData, err error) {
ed.Type = TypeAscii
ed.Encoded = []byte(value)
ed.Encoded = append(ed.Encoded, 0)
ed.UnitCount = uint32(len(ed.Encoded))
return ed, nil
}
// encodeAsciiNoNul returns a string encoded as a byte-string without a trailing
// NUL byte.
//
// Note that:
//
// 1. This type can not be automatically encoded using `Encode()`. The default
// mode is to encode *with* a trailing NUL byte using `encodeAscii`. Only
// certain undefined-type tags using an unterminated ASCII string and these
// are exceptional in nature.
//
// 2. The presence of this method allows us to completely test the complimentary
// no-nul parser.
//
func (ve *ValueEncoder) encodeAsciiNoNul(value string) (ed EncodedData, err error) {
ed.Type = TypeAsciiNoNul
ed.Encoded = []byte(value)
ed.UnitCount = uint32(len(ed.Encoded))
return ed, nil
}
func (ve *ValueEncoder) encodeShorts(value []uint16) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
ed.UnitCount = uint32(len(value))
ed.Encoded = make([]byte, ed.UnitCount*2)
for i := uint32(0); i < ed.UnitCount; i++ {
ve.byteOrder.PutUint16(ed.Encoded[i*2:(i+1)*2], value[i])
}
ed.Type = TypeShort
return ed, nil
}
func (ve *ValueEncoder) encodeLongs(value []uint32) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
ed.UnitCount = uint32(len(value))
ed.Encoded = make([]byte, ed.UnitCount*4)
for i := uint32(0); i < ed.UnitCount; i++ {
ve.byteOrder.PutUint32(ed.Encoded[i*4:(i+1)*4], value[i])
}
ed.Type = TypeLong
return ed, nil
}
func (ve *ValueEncoder) encodeFloats(value []float32) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
ed.UnitCount = uint32(len(value))
ed.Encoded = make([]byte, ed.UnitCount*4)
for i := uint32(0); i < ed.UnitCount; i++ {
ve.byteOrder.PutUint32(ed.Encoded[i*4:(i+1)*4], math.Float32bits(value[i]))
}
ed.Type = TypeFloat
return ed, nil
}
func (ve *ValueEncoder) encodeDoubles(value []float64) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
ed.UnitCount = uint32(len(value))
ed.Encoded = make([]byte, ed.UnitCount*8)
for i := uint32(0); i < ed.UnitCount; i++ {
ve.byteOrder.PutUint64(ed.Encoded[i*8:(i+1)*8], math.Float64bits(value[i]))
}
ed.Type = TypeDouble
return ed, nil
}
func (ve *ValueEncoder) encodeRationals(value []Rational) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
ed.UnitCount = uint32(len(value))
ed.Encoded = make([]byte, ed.UnitCount*8)
for i := uint32(0); i < ed.UnitCount; i++ {
ve.byteOrder.PutUint32(ed.Encoded[i*8+0:i*8+4], value[i].Numerator)
ve.byteOrder.PutUint32(ed.Encoded[i*8+4:i*8+8], value[i].Denominator)
}
ed.Type = TypeRational
return ed, nil
}
func (ve *ValueEncoder) encodeSignedLongs(value []int32) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
ed.UnitCount = uint32(len(value))
b := bytes.NewBuffer(make([]byte, 0, 8*ed.UnitCount))
for i := uint32(0); i < ed.UnitCount; i++ {
err := binary.Write(b, ve.byteOrder, value[i])
log.PanicIf(err)
}
ed.Type = TypeSignedLong
ed.Encoded = b.Bytes()
return ed, nil
}
func (ve *ValueEncoder) encodeSignedRationals(value []SignedRational) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
ed.UnitCount = uint32(len(value))
b := bytes.NewBuffer(make([]byte, 0, 8*ed.UnitCount))
for i := uint32(0); i < ed.UnitCount; i++ {
err := binary.Write(b, ve.byteOrder, value[i].Numerator)
log.PanicIf(err)
err = binary.Write(b, ve.byteOrder, value[i].Denominator)
log.PanicIf(err)
}
ed.Type = TypeSignedRational
ed.Encoded = b.Bytes()
return ed, nil
}
// Encode returns bytes for the given value, infering type from the actual
// value. This does not support `TypeAsciiNoNull` (all strings are encoded as
// `TypeAscii`).
func (ve *ValueEncoder) Encode(value interface{}) (ed EncodedData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
switch t := value.(type) {
case []byte:
ed, err = ve.encodeBytes(t)
log.PanicIf(err)
case string:
ed, err = ve.encodeAscii(t)
log.PanicIf(err)
case []uint16:
ed, err = ve.encodeShorts(t)
log.PanicIf(err)
case []uint32:
ed, err = ve.encodeLongs(t)
log.PanicIf(err)
case []float32:
ed, err = ve.encodeFloats(t)
log.PanicIf(err)
case []float64:
ed, err = ve.encodeDoubles(t)
log.PanicIf(err)
case []Rational:
ed, err = ve.encodeRationals(t)
log.PanicIf(err)
case []int32:
ed, err = ve.encodeSignedLongs(t)
log.PanicIf(err)
case []SignedRational:
ed, err = ve.encodeSignedRationals(t)
log.PanicIf(err)
case time.Time:
// For convenience, if the user doesn't want to deal with translation
// semantics with timestamps.
s := ExifFullTimestampString(t)
ed, err = ve.encodeAscii(s)
log.PanicIf(err)
default:
log.Panicf("value not encodable: [%s] [%v]", reflect.TypeOf(value), value)
}
return ed, nil
}
|
