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package exifcommon
import (
"bytes"
"encoding/binary"
"github.com/dsoprea/go-logging"
)
var (
parserLogger = log.NewLogger("exifcommon.parser")
)
// Parser knows how to parse all well-defined, encoded EXIF types.
type Parser struct {
}
// ParseBytesknows how to parse a byte-type value.
func (p *Parser) ParseBytes(data []byte, unitCount uint32) (value []uint8, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeByte.Size() * count) {
log.Panic(ErrNotEnoughData)
}
value = []uint8(data[:count])
return value, nil
}
// ParseAscii returns a string and auto-strips the trailing NUL character that
// should be at the end of the encoding.
func (p *Parser) ParseAscii(data []byte, unitCount uint32) (value string, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeAscii.Size() * count) {
log.Panic(ErrNotEnoughData)
}
if len(data) == 0 || data[count-1] != 0 {
s := string(data[:count])
parserLogger.Warningf(nil, "ascii not terminated with nul as expected: [%v]", s)
return s, nil
}
// Auto-strip the NUL from the end. It serves no purpose outside of
// encoding semantics.
return string(data[:count-1]), nil
}
// ParseAsciiNoNul returns a string without any consideration for a trailing NUL
// character.
func (p *Parser) ParseAsciiNoNul(data []byte, unitCount uint32) (value string, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeAscii.Size() * count) {
log.Panic(ErrNotEnoughData)
}
return string(data[:count]), nil
}
// ParseShorts knows how to parse an encoded list of shorts.
func (p *Parser) ParseShorts(data []byte, unitCount uint32, byteOrder binary.ByteOrder) (value []uint16, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeShort.Size() * count) {
log.Panic(ErrNotEnoughData)
}
value = make([]uint16, count)
for i := 0; i < count; i++ {
value[i] = byteOrder.Uint16(data[i*2:])
}
return value, nil
}
// ParseLongs knows how to encode an encoded list of unsigned longs.
func (p *Parser) ParseLongs(data []byte, unitCount uint32, byteOrder binary.ByteOrder) (value []uint32, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeLong.Size() * count) {
log.Panic(ErrNotEnoughData)
}
value = make([]uint32, count)
for i := 0; i < count; i++ {
value[i] = byteOrder.Uint32(data[i*4:])
}
return value, nil
}
// ParseRationals knows how to parse an encoded list of unsigned rationals.
func (p *Parser) ParseRationals(data []byte, unitCount uint32, byteOrder binary.ByteOrder) (value []Rational, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeRational.Size() * count) {
log.Panic(ErrNotEnoughData)
}
value = make([]Rational, count)
for i := 0; i < count; i++ {
value[i].Numerator = byteOrder.Uint32(data[i*8:])
value[i].Denominator = byteOrder.Uint32(data[i*8+4:])
}
return value, nil
}
// ParseSignedLongs knows how to parse an encoded list of signed longs.
func (p *Parser) ParseSignedLongs(data []byte, unitCount uint32, byteOrder binary.ByteOrder) (value []int32, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeSignedLong.Size() * count) {
log.Panic(ErrNotEnoughData)
}
b := bytes.NewBuffer(data)
value = make([]int32, count)
for i := 0; i < count; i++ {
err := binary.Read(b, byteOrder, &value[i])
log.PanicIf(err)
}
return value, nil
}
// ParseSignedRationals knows how to parse an encoded list of signed
// rationals.
func (p *Parser) ParseSignedRationals(data []byte, unitCount uint32, byteOrder binary.ByteOrder) (value []SignedRational, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
count := int(unitCount)
if len(data) < (TypeSignedRational.Size() * count) {
log.Panic(ErrNotEnoughData)
}
b := bytes.NewBuffer(data)
value = make([]SignedRational, count)
for i := 0; i < count; i++ {
err = binary.Read(b, byteOrder, &value[i].Numerator)
log.PanicIf(err)
err = binary.Read(b, byteOrder, &value[i].Denominator)
log.PanicIf(err)
}
return value, nil
}
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