1 files changed, 464 insertions, 0 deletions
diff --git a/vendor/github.com/dsoprea/go-exif/v3/common/value_context.go b/vendor/github.com/dsoprea/go-exif/v3/common/value_context.go
new file mode 100644
index 000000000..b9e634106
--- /dev/null
+++ b/vendor/github.com/dsoprea/go-exif/v3/common/value_context.go
@@ -0,0 +1,464 @@
+package exifcommon
+
+import (
+	"errors"
+	"io"
+
+	"encoding/binary"
+
+	"github.com/dsoprea/go-logging"
+)
+
+var (
+	parser *Parser
+)
+
+var (
+	// ErrNotFarValue indicates that an offset-based lookup was attempted for a
+	// non-offset-based (embedded) value.
+	ErrNotFarValue = errors.New("not a far value")
+)
+
+// ValueContext embeds all of the parameters required to find and extract the
+// actual tag value.
+type ValueContext struct {
+	unitCount      uint32
+	valueOffset    uint32
+	rawValueOffset []byte
+	rs             io.ReadSeeker
+
+	tagType   TagTypePrimitive
+	byteOrder binary.ByteOrder
+
+	// undefinedValueTagType is the effective type to use if this is an
+	// "undefined" value.
+	undefinedValueTagType TagTypePrimitive
+
+	ifdPath string
+	tagId   uint16
+}
+
+// TODO(dustin): We can update newValueContext() to derive `valueOffset` itself (from `rawValueOffset`).
+
+// NewValueContext returns a new ValueContext struct.
+func NewValueContext(ifdPath string, tagId uint16, unitCount, valueOffset uint32, rawValueOffset []byte, rs io.ReadSeeker, tagType TagTypePrimitive, byteOrder binary.ByteOrder) *ValueContext {
+	return &ValueContext{
+		unitCount:      unitCount,
+		valueOffset:    valueOffset,
+		rawValueOffset: rawValueOffset,
+		rs:             rs,
+
+		tagType:   tagType,
+		byteOrder: byteOrder,
+
+		ifdPath: ifdPath,
+		tagId:   tagId,
+	}
+}
+
+// SetUndefinedValueType sets the effective type if this is an unknown-type tag.
+func (vc *ValueContext) SetUndefinedValueType(tagType TagTypePrimitive) {
+	if vc.tagType != TypeUndefined {
+		log.Panicf("can not set effective type for unknown-type tag because this is *not* an unknown-type tag")
+	}
+
+	vc.undefinedValueTagType = tagType
+}
+
+// UnitCount returns the embedded unit-count.
+func (vc *ValueContext) UnitCount() uint32 {
+	return vc.unitCount
+}
+
+// ValueOffset returns the value-offset decoded as a `uint32`.
+func (vc *ValueContext) ValueOffset() uint32 {
+	return vc.valueOffset
+}
+
+// RawValueOffset returns the uninterpreted value-offset. This is used for
+// embedded values (values small enough to fit within the offset bytes rather
+// than needing to be stored elsewhere and referred to by an actual offset).
+func (vc *ValueContext) RawValueOffset() []byte {
+	return vc.rawValueOffset
+}
+
+// AddressableData returns the block of data that we can dereference into.
+func (vc *ValueContext) AddressableData() io.ReadSeeker {
+
+	// RELEASE)dustin): Rename from AddressableData() to ReadSeeker()
+
+	return vc.rs
+}
+
+// ByteOrder returns the byte-order of numbers.
+func (vc *ValueContext) ByteOrder() binary.ByteOrder {
+	return vc.byteOrder
+}
+
+// IfdPath returns the path of the IFD containing this tag.
+func (vc *ValueContext) IfdPath() string {
+	return vc.ifdPath
+}
+
+// TagId returns the ID of the tag that we represent.
+func (vc *ValueContext) TagId() uint16 {
+	return vc.tagId
+}
+
+// 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
+}
+
+// SizeInBytes returns the number of bytes that this value requires. The
+// underlying call will panic if the type is UNDEFINED. It is the
+// responsibility of the caller to preemptively check that.
+func (vc *ValueContext) SizeInBytes() int {
+	tagType := vc.effectiveValueType()
+
+	return tagType.Size() * int(vc.unitCount)
+}
+
+// effectiveValueType returns the effective type of the unknown-type tag or, if
+// not unknown, the actual type.
+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
+}
+
+// readRawEncoded returns the encoded bytes for the value that we represent.
+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
+	}
+
+	_, err = vc.rs.Seek(int64(vc.valueOffset), io.SeekStart)
+	log.PanicIf(err)
+
+	rawBytes = make([]byte, vc.unitCount*unitSizeRaw)
+
+	_, err = io.ReadFull(vc.rs, rawBytes)
+	log.PanicIf(err)
+
+	return rawBytes, nil
+}
+
+// GetFarOffset returns the offset if the value is not embedded [within the
+// pointer itself] or an error if an embedded value.
+func (vc *ValueContext) GetFarOffset() (offset uint32, err error) {
+	if vc.isEmbedded() == true {
+		return 0, ErrNotFarValue
+	}
+
+	return vc.valueOffset, nil
+}
+
+// ReadRawEncoded returns the encoded bytes for the value that we represent.
+func (vc *ValueContext) ReadRawEncoded() (rawBytes []byte, err error) {
+
+	// TODO(dustin): Remove this method and rename readRawEncoded in its place.
+
+	return vc.readRawEncoded()
+}
+
+// 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 := FormatFromBytes(rawBytes, vc.effectiveValueType(), false, vc.byteOrder)
+	log.PanicIf(err)
+
+	return phrase, nil
+}
+
+// FormatFirst 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 := FormatFromBytes(rawBytes, vc.tagType, true, vc.byteOrder)
+	log.PanicIf(err)
+
+	return phrase, nil
+}
+
+// ReadBytes parses the encoded byte-array from the value-context.
+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
+}
+
+// ReadAscii parses the encoded NUL-terminated ASCII string from the value-
+// context.
+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
+}
+
+// ReadAsciiNoNul parses the non-NUL-terminated encoded ASCII string from the
+// value-context.
+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
+}
+
+// ReadShorts parses the list of encoded shorts from the value-context.
+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
+}
+
+// ReadLongs parses the list of encoded, unsigned longs from the value-context.
+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
+}
+
+// ReadFloats parses the list of encoded, floats from the value-context.
+func (vc *ValueContext) ReadFloats() (value []float32, err error) {
+	defer func() {
+		if state := recover(); state != nil {
+			err = log.Wrap(state.(error))
+		}
+	}()
+
+	rawValue, err := vc.readRawEncoded()
+	log.PanicIf(err)
+
+	value, err = parser.ParseFloats(rawValue, vc.unitCount, vc.byteOrder)
+	log.PanicIf(err)
+
+	return value, nil
+}
+
+// ReadDoubles parses the list of encoded, doubles from the value-context.
+func (vc *ValueContext) ReadDoubles() (value []float64, err error) {
+	defer func() {
+		if state := recover(); state != nil {
+			err = log.Wrap(state.(error))
+		}
+	}()
+
+	rawValue, err := vc.readRawEncoded()
+	log.PanicIf(err)
+
+	value, err = parser.ParseDoubles(rawValue, vc.unitCount, vc.byteOrder)
+	log.PanicIf(err)
+
+	return value, nil
+}
+
+// ReadRationals parses the list of encoded, unsigned rationals from the value-
+// context.
+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
+}
+
+// ReadSignedLongs parses the list of encoded, signed longs from the value-context.
+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
+}
+
+// ReadSignedRationals parses the list of encoded, signed rationals from the
+// value-context.
+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 == TypeFloat {
+		values, err = vc.ReadFloats()
+		log.PanicIf(err)
+	} else if vc.tagType == TypeDouble {
+		values, err = vc.ReadDoubles()
+		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
+}
+
+func init() {
+	parser = new(Parser)
+}