gotosocial/vendor/github.com/dsoprea/go-exif/value_context.go
Tobi Smethurst 98263a7de6
Grand test fixup (#138)
* start fixing up tests

* fix up tests + automate with drone

* fiddle with linting

* messing about with drone.yml

* some more fiddling

* hmmm

* add cache

* add vendor directory

* verbose

* ci updates

* update some little things

* update sig
2021-08-12 21:03:24 +02:00

367 lines
8.4 KiB
Go

package exif
import (
"encoding/binary"
"github.com/dsoprea/go-logging"
)
var (
parser *Parser
)
// ValueContext describes all of the parameters required to find and extract
// the actual tag value.
type ValueContext struct {
unitCount uint32
valueOffset uint32
rawValueOffset []byte
addressableData []byte
tagType TagTypePrimitive
byteOrder binary.ByteOrder
// undefinedValueTagType is the effective type to use if this is an
// "undefined" value.
undefinedValueTagType TagTypePrimitive
ifdPath string
tagId uint16
}
func newValueContext(ifdPath string, tagId uint16, unitCount, valueOffset uint32, rawValueOffset, addressableData []byte, tagType TagTypePrimitive, byteOrder binary.ByteOrder) *ValueContext {
return &ValueContext{
unitCount: unitCount,
valueOffset: valueOffset,
rawValueOffset: rawValueOffset,
addressableData: addressableData,
tagType: tagType,
byteOrder: byteOrder,
ifdPath: ifdPath,
tagId: tagId,
}
}
func newValueContextFromTag(ite *IfdTagEntry, addressableData []byte, byteOrder binary.ByteOrder) *ValueContext {
return newValueContext(
ite.IfdPath,
ite.TagId,
ite.UnitCount,
ite.ValueOffset,
ite.RawValueOffset,
addressableData,
ite.TagType,
byteOrder)
}
func (vc *ValueContext) SetUnknownValueType(tagType TagTypePrimitive) {
vc.undefinedValueTagType = tagType
}
func (vc *ValueContext) UnitCount() uint32 {
return vc.unitCount
}
func (vc *ValueContext) ValueOffset() uint32 {
return vc.valueOffset
}
func (vc *ValueContext) RawValueOffset() []byte {
return vc.rawValueOffset
}
func (vc *ValueContext) AddressableData() []byte {
return vc.addressableData
}
// isEmbedded returns whether the value is embedded or a reference. This can't
// be precalculated since the size is not defined for all types (namely the
// "undefined" types).
func (vc *ValueContext) isEmbedded() bool {
tagType := vc.effectiveValueType()
return (tagType.Size() * int(vc.unitCount)) <= 4
}
func (vc *ValueContext) effectiveValueType() (tagType TagTypePrimitive) {
if vc.tagType == TypeUndefined {
tagType = vc.undefinedValueTagType
if tagType == 0 {
log.Panicf("undefined-value type not set")
}
} else {
tagType = vc.tagType
}
return tagType
}
func (vc *ValueContext) readRawEncoded() (rawBytes []byte, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
tagType := vc.effectiveValueType()
unitSizeRaw := uint32(tagType.Size())
if vc.isEmbedded() == true {
byteLength := unitSizeRaw * vc.unitCount
return vc.rawValueOffset[:byteLength], nil
} else {
return vc.addressableData[vc.valueOffset : vc.valueOffset+vc.unitCount*unitSizeRaw], nil
}
}
// Format returns a string representation for the value.
//
// Where the type is not ASCII, `justFirst` indicates whether to just stringify
// the first item in the slice (or return an empty string if the slice is
// empty).
//
// Since this method lacks the information to process undefined-type tags (e.g.
// byte-order, tag-ID, IFD type), it will return an error if attempted. See
// `Undefined()`.
func (vc *ValueContext) Format() (value string, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawBytes, err := vc.readRawEncoded()
log.PanicIf(err)
phrase, err := Format(rawBytes, vc.tagType, false, vc.byteOrder)
log.PanicIf(err)
return phrase, nil
}
// FormatOne is similar to `Format` but only gets and stringifies the first
// item.
func (vc *ValueContext) FormatFirst() (value string, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawBytes, err := vc.readRawEncoded()
log.PanicIf(err)
phrase, err := Format(rawBytes, vc.tagType, true, vc.byteOrder)
log.PanicIf(err)
return phrase, nil
}
func (vc *ValueContext) ReadBytes() (value []byte, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseBytes(rawValue, vc.unitCount)
log.PanicIf(err)
return value, nil
}
func (vc *ValueContext) ReadAscii() (value string, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseAscii(rawValue, vc.unitCount)
log.PanicIf(err)
return value, nil
}
func (vc *ValueContext) ReadAsciiNoNul() (value string, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseAsciiNoNul(rawValue, vc.unitCount)
log.PanicIf(err)
return value, nil
}
func (vc *ValueContext) ReadShorts() (value []uint16, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseShorts(rawValue, vc.unitCount, vc.byteOrder)
log.PanicIf(err)
return value, nil
}
func (vc *ValueContext) ReadLongs() (value []uint32, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseLongs(rawValue, vc.unitCount, vc.byteOrder)
log.PanicIf(err)
return value, nil
}
func (vc *ValueContext) ReadRationals() (value []Rational, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseRationals(rawValue, vc.unitCount, vc.byteOrder)
log.PanicIf(err)
return value, nil
}
func (vc *ValueContext) ReadSignedLongs() (value []int32, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseSignedLongs(rawValue, vc.unitCount, vc.byteOrder)
log.PanicIf(err)
return value, nil
}
func (vc *ValueContext) ReadSignedRationals() (value []SignedRational, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
rawValue, err := vc.readRawEncoded()
log.PanicIf(err)
value, err = parser.ParseSignedRationals(rawValue, vc.unitCount, vc.byteOrder)
log.PanicIf(err)
return value, nil
}
// Values knows how to resolve the given value. This value is always a list
// (undefined-values aside), so we're named accordingly.
//
// Since this method lacks the information to process unknown-type tags (e.g.
// byte-order, tag-ID, IFD type), it will return an error if attempted. See
// `Undefined()`.
func (vc *ValueContext) Values() (values interface{}, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
if vc.tagType == TypeByte {
values, err = vc.ReadBytes()
log.PanicIf(err)
} else if vc.tagType == TypeAscii {
values, err = vc.ReadAscii()
log.PanicIf(err)
} else if vc.tagType == TypeAsciiNoNul {
values, err = vc.ReadAsciiNoNul()
log.PanicIf(err)
} else if vc.tagType == TypeShort {
values, err = vc.ReadShorts()
log.PanicIf(err)
} else if vc.tagType == TypeLong {
values, err = vc.ReadLongs()
log.PanicIf(err)
} else if vc.tagType == TypeRational {
values, err = vc.ReadRationals()
log.PanicIf(err)
} else if vc.tagType == TypeSignedLong {
values, err = vc.ReadSignedLongs()
log.PanicIf(err)
} else if vc.tagType == TypeSignedRational {
values, err = vc.ReadSignedRationals()
log.PanicIf(err)
} else if vc.tagType == TypeUndefined {
log.Panicf("will not parse undefined-type value")
// Never called.
return nil, nil
} else {
log.Panicf("value of type [%s] is unparseable", vc.tagType)
// Never called.
return nil, nil
}
return values, nil
}
// Undefined attempts to identify and decode supported undefined-type fields.
// This is the primary, preferred interface to reading undefined values.
func (vc *ValueContext) Undefined() (value interface{}, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
value, err = UndefinedValue(vc.ifdPath, vc.tagId, vc, vc.byteOrder)
if err != nil {
if err == ErrUnhandledUnknownTypedTag {
return nil, err
}
log.Panic(err)
}
return value, nil
}
func init() {
parser = &Parser{}
}