/// <summary>
/// Reads an IFD from file at position <paramref name="offset"/> relative
/// to <paramref name="baseOffset"/>.
/// </summary>
/// <param name="baseOffset">
/// A <see cref="System.Int64"/> with the base offset which every offset
/// in IFD is relative to.
/// </param>
/// <param name="offset">
/// A <see cref="System.UInt32"/> with the offset of the IFD relative to
/// <paramref name="baseOffset"/>
/// </param>
/// <param name="maxOffset">
/// A <see cref="System.UInt32"/> with the maximal offset to consider for
/// the IFD.
/// </param>
/// <returns>
/// A <see cref="System.UInt32"/> with the offset of the next IFD, the
/// offset is also relative to <paramref name="baseOffset"/>
/// </returns>
uint ReadIFD(long baseOffset, uint offset, uint maxOffset)
{
long length = 0;
try {
length = file.Length;
} catch (Exception) {
// Use a safety-value of 4 gigabyte.
length = 1073741824L * 4;
}
if (baseOffset + offset > length)
{
file.MarkAsCorrupt("Invalid IFD offset");
return(0);
}
var directory = new IFDDirectory();
file.Seek(baseOffset + offset, SeekOrigin.Begin);
ushort entry_count = ReadUShort();
if (file.Tell + 12 * entry_count > baseOffset + maxOffset)
{
file.MarkAsCorrupt("Size of entries exceeds possible data size");
return(0);
}
ByteVector entry_datas = file.ReadBlock(12 * entry_count);
uint next_offset = ReadUInt();
for (int i = 0; i < entry_count; i++)
{
ByteVector entry_data = entry_datas.Mid(i * 12, 12);
ushort entry_tag = entry_data.Mid(0, 2).ToUShort(is_bigendian);
ushort type = entry_data.Mid(2, 2).ToUShort(is_bigendian);
uint value_count = entry_data.Mid(4, 4).ToUInt(is_bigendian);
ByteVector offset_data = entry_data.Mid(8, 4);
IFDEntry entry = CreateIFDEntry(entry_tag, type, value_count, baseOffset, offset_data, maxOffset);
if (entry == null)
{
continue;
}
if (directory.ContainsKey(entry.Tag))
{
directory.Remove(entry.Tag);
}
directory.Add(entry.Tag, entry);
}
FixupDirectory(baseOffset, directory);
structure.directories.Add(directory);
return(next_offset);
}
/// <summary>
/// Renders the IFD to an ByteVector where the offset of the IFD
/// itself is <paramref name="ifd_offset"/> and all offsets
/// contained in the IFD are adjusted accroding it.
/// </summary>
/// <param name="directory">
/// A <see cref="IFDDirectory"/> with the directory to render.
/// </param>
/// <param name="ifd_offset">
/// A <see cref="System.UInt32"/> with the offset of the IFD
/// </param>
/// <param name="last">
/// A <see cref="System.Boolean"/> which is true, if the IFD is
/// the last one, i.e. the offset to the next IFD, which is
/// stored inside the IFD, is 0. If the value is false, the
/// offset to the next IFD is set that it starts directly after
/// the current one.
/// </param>
/// <returns>
/// A <see cref="ByteVector"/> with the rendered IFD.
/// </returns>
private ByteVector RenderIFD(IFDDirectory directory, uint ifd_offset, bool last)
{
if (directory.Count > (int)UInt16.MaxValue)
{
throw new Exception(String.Format("Directory has too much entries: {0}", directory.Count));
}
// Remove empty SUB ifds.
var tags = new List <ushort>(directory.Keys);
foreach (var tag in tags)
{
var entry = directory[tag];
if (entry is SubIFDEntry && (entry as SubIFDEntry).ChildCount == 0)
{
directory.Remove(tag);
}
}
ushort entry_count = (ushort)directory.Count;
// ifd_offset + size of entry_count + entries + next ifd offset
uint data_offset = ifd_offset + 2 + 12 * (uint)entry_count + 4;
// store the entries itself
ByteVector entry_data = new ByteVector();
// store the data referenced by the entries
ByteVector offset_data = new ByteVector();
entry_data.Add(ByteVector.FromUShort(entry_count, is_bigendian));
foreach (IFDEntry entry in directory.Values)
{
RenderEntryData(entry, entry_data, offset_data, data_offset);
}
if (last)
{
entry_data.Add("\0\0\0\0");
}
else
{
entry_data.Add(ByteVector.FromUInt((uint)(data_offset + offset_data.Count), is_bigendian));
}
if (data_offset - ifd_offset != entry_data.Count)
{
throw new Exception(String.Format("Expected IFD data size was {0} but is {1}", data_offset - ifd_offset, entry_data.Count));
}
entry_data.Add(offset_data);
return(entry_data);
}
/// <summary>
/// Performs some fixups to a read <see cref="IFDDirectory"/>. For some
/// special cases multiple <see cref="IFDEntry"/> instances contained
/// in the directory are needed. Therfore, we do the fixups after reading the
/// whole directory to be sure, all entries are present.
/// </summary>
/// <param name="base_offset">
/// A <see cref="System.Int64"/> value with the base offset, all offsets in the
/// directory refers to.
/// </param>
/// <param name="directory">
/// A <see cref="IFDDirectory"/> instance which was read and needs fixes.
/// </param>
private void FixupDirectory (long base_offset, IFDDirectory directory)
{
// The following two entries refer to thumbnail data, where one is the offset
// to the data and the other is the length. Unnaturally both are used to describe
// the data. So it is needed to keep both entries in sync and keep the thumbnail data
// for writing it back.
// We determine the position of the data, read it and store it in an ThumbnailDataIFDEntry
// which replaces the offset-entry to thumbnail data.
ushort offset_tag = (ushort) IFDEntryTag.JPEGInterchangeFormat;
ushort length_tag = (ushort) IFDEntryTag.JPEGInterchangeFormatLength;
if (directory.ContainsKey (offset_tag) && directory.ContainsKey (length_tag)) {
var offset_entry = directory [offset_tag] as LongIFDEntry;
var length_entry = directory [length_tag] as LongIFDEntry;
if (offset_entry != null && length_entry != null) {
uint offset = offset_entry.Value;
uint length = length_entry.Value;
file.Seek (base_offset + offset, SeekOrigin.Begin);
ByteVector data = file.ReadBlock ((int) length);
directory.Remove (offset_tag);
directory.Add (offset_tag, new ThumbnailDataIFDEntry (offset_tag, data));
}
}
// create a StripOffsetIFDEntry if necessary
ushort strip_offsets_tag = (ushort) IFDEntryTag.StripOffsets;
ushort strip_byte_counts_tag = (ushort) IFDEntryTag.StripByteCounts;
if (directory.ContainsKey (strip_offsets_tag) && directory.ContainsKey (strip_byte_counts_tag)) {
uint [] strip_offsets = null;
uint [] strip_byte_counts = null;
var strip_offsets_entry = directory [strip_offsets_tag];
var strip_byte_counts_entry = directory [strip_byte_counts_tag];
if (strip_offsets_entry is LongIFDEntry)
strip_offsets = new uint[] {(strip_offsets_entry as LongIFDEntry).Value};
else if (strip_offsets_entry is LongArrayIFDEntry)
strip_offsets = (strip_offsets_entry as LongArrayIFDEntry).Values;
if (strip_offsets == null)
return;
if (strip_byte_counts_entry is LongIFDEntry)
strip_byte_counts = new uint[] {(strip_byte_counts_entry as LongIFDEntry).Value};
else if (strip_byte_counts_entry is LongArrayIFDEntry)
strip_byte_counts = (strip_byte_counts_entry as LongArrayIFDEntry).Values;
if (strip_byte_counts == null)
return;
directory.Remove (strip_offsets_tag);
directory.Add (strip_offsets_tag, new StripOffsetsIFDEntry (strip_offsets_tag, strip_offsets, strip_byte_counts, file));
}
}
/// <summary>
/// Reads an IFD from file at position <paramref name="offset"/> relative
/// to <paramref name="base_offset"/>.
/// </summary>
/// <param name="base_offset">
/// A <see cref="System.Int64"/> with the base offset which every offset
/// in IFD is relative to.
/// </param>
/// <param name="offset">
/// A <see cref="System.UInt32"/> with the offset of the IFD relative to
/// <paramref name="base_offset"/>
/// </param>
/// <param name="max_offset">
/// A <see cref="System.UInt32"/> with the maximal offset to consider for
/// the IFD.
/// </param>
/// <returns>
/// A <see cref="System.UInt32"/> with the offset of the next IFD, the
/// offset is also relative to <paramref name="base_offset"/>
/// </returns>
private uint ReadIFD (long base_offset, uint offset, uint max_offset)
{
long length = 0;
try {
length = file.Length;
} catch (Exception) {
// Use a safety-value of 4 gigabyte.
length = 1073741824L * 4;
}
if (base_offset + offset > length) {
file.MarkAsCorrupt ("Invalid IFD offset");
return 0;
}
var directory = new IFDDirectory ();
file.Seek (base_offset + offset, SeekOrigin.Begin);
ushort entry_count = ReadUShort ();
if (file.Tell + 12 * entry_count > base_offset + max_offset) {
file.MarkAsCorrupt ("Size of entries exceeds possible data size");
return 0;
}
ByteVector entry_datas = file.ReadBlock (12 * entry_count);
uint next_offset = ReadUInt ();
for (int i = 0; i < entry_count; i++) {
ByteVector entry_data = entry_datas.Mid (i * 12, 12);
ushort entry_tag = entry_data.Mid (0, 2).ToUShort (is_bigendian);
ushort type = entry_data.Mid (2, 2).ToUShort (is_bigendian);
uint value_count = entry_data.Mid (4, 4).ToUInt (is_bigendian);
ByteVector offset_data = entry_data.Mid (8, 4);
IFDEntry entry = CreateIFDEntry (entry_tag, type, value_count, base_offset, offset_data, max_offset);
if (entry == null)
continue;
if (directory.ContainsKey (entry.Tag))
directory.Remove (entry.Tag);
directory.Add (entry.Tag, entry);
}
FixupDirectory (base_offset, directory);
structure.directories.Add (directory);
return next_offset;
}
/// <summary>
/// Performs some fixups to a read <see cref="IFDDirectory"/>. For some
/// special cases multiple <see cref="IFDEntry"/> instances contained
/// in the directory are needed. Therfore, we do the fixups after reading the
/// whole directory to be sure, all entries are present.
/// </summary>
/// <param name="baseOffset">
/// A <see cref="System.Int64"/> value with the base offset, all offsets in the
/// directory refers to.
/// </param>
/// <param name="directory">
/// A <see cref="IFDDirectory"/> instance which was read and needs fixes.
/// </param>
void FixupDirectory(long baseOffset, IFDDirectory directory)
{
// The following two entries refer to thumbnail data, where one is the offset
// to the data and the other is the length. Unnaturally both are used to describe
// the data. So it is needed to keep both entries in sync and keep the thumbnail data
// for writing it back.
// We determine the position of the data, read it and store it in an ThumbnailDataIFDEntry
// which replaces the offset-entry to thumbnail data.
ushort offset_tag = (ushort)IFDEntryTag.JPEGInterchangeFormat;
ushort length_tag = (ushort)IFDEntryTag.JPEGInterchangeFormatLength;
if (directory.ContainsKey(offset_tag) && directory.ContainsKey(length_tag))
{
if (directory[offset_tag] is LongIFDEntry offset_entry && directory[length_tag] is LongIFDEntry length_entry)
{
uint offset = offset_entry.Value;
uint length = length_entry.Value;
file.Seek(baseOffset + offset, SeekOrigin.Begin);
var data = file.ReadBlock((int)length);
directory.Remove(offset_tag);
directory.Add(offset_tag, new ThumbnailDataIFDEntry(offset_tag, data));
}
}
// create a StripOffsetIFDEntry if necessary
ushort strip_offsets_tag = (ushort)IFDEntryTag.StripOffsets;
ushort strip_byte_counts_tag = (ushort)IFDEntryTag.StripByteCounts;
if (directory.ContainsKey(strip_offsets_tag) && directory.ContainsKey(strip_byte_counts_tag))
{
uint[] strip_offsets = null;
uint[] strip_byte_counts = null;
var strip_offsets_entry = directory[strip_offsets_tag];
var strip_byte_counts_entry = directory[strip_byte_counts_tag];
if (strip_offsets_entry is LongIFDEntry)
{
strip_offsets = new[] { (strip_offsets_entry as LongIFDEntry).Value }
}
;
else if (strip_offsets_entry is LongArrayIFDEntry)
{
strip_offsets = (strip_offsets_entry as LongArrayIFDEntry).Values;
}
if (strip_offsets == null)
{
return;
}
if (strip_byte_counts_entry is LongIFDEntry)
{
strip_byte_counts = new[] { (strip_byte_counts_entry as LongIFDEntry).Value }
}
;
else if (strip_byte_counts_entry is LongArrayIFDEntry)
{
strip_byte_counts = (strip_byte_counts_entry as LongArrayIFDEntry).Values;
}
if (strip_byte_counts == null)
{
return;
}
directory.Remove(strip_offsets_tag);
directory.Add(strip_offsets_tag, new StripOffsetsIFDEntry(strip_offsets_tag, strip_offsets, strip_byte_counts, file));
}
}
/// <summary>
/// Renders the IFD to an ByteVector where the offset of the IFD
/// itself is <paramref name="ifd_offset"/> and all offsets
/// contained in the IFD are adjusted accroding it.
/// </summary>
/// <param name="directory">
/// A <see cref="IFDDirectory"/> with the directory to render.
/// </param>
/// <param name="ifd_offset">
/// A <see cref="System.UInt32"/> with the offset of the IFD
/// </param>
/// <param name="last">
/// A <see cref="System.Boolean"/> which is true, if the IFD is
/// the last one, i.e. the offset to the next IFD, which is
/// stored inside the IFD, is 0. If the value is false, the
/// offset to the next IFD is set that it starts directly after
/// the current one.
/// </param>
/// <returns>
/// A <see cref="ByteVector"/> with the rendered IFD.
/// </returns>
private ByteVector RenderIFD(IFDDirectory directory, uint ifd_offset, bool last)
{
if (directory.Count > (int)UInt16.MaxValue)
throw new Exception (String.Format ("Directory has too much entries: {0}", directory.Count));
// Remove empty SUB ifds.
var tags = new List<ushort> (directory.Keys);
foreach (var tag in tags) {
var entry = directory [tag];
if (entry is SubIFDEntry && (entry as SubIFDEntry).ChildCount == 0) {
directory.Remove (tag);
}
}
ushort entry_count = (ushort) directory.Count;
// ifd_offset + size of entry_count + entries + next ifd offset
uint data_offset = ifd_offset + 2 + 12 * (uint) entry_count + 4;
// store the entries itself
ByteVector entry_data = new ByteVector ();
// store the data referenced by the entries
ByteVector offset_data = new ByteVector ();
entry_data.Add (ByteVector.FromUShort (entry_count, is_bigendian));
foreach (IFDEntry entry in directory.Values)
RenderEntryData (entry, entry_data, offset_data, data_offset);
if (last)
entry_data.Add ("\0\0\0\0");
else
entry_data.Add (ByteVector.FromUInt ((uint) (data_offset + offset_data.Count), is_bigendian));
if (data_offset - ifd_offset != entry_data.Count)
throw new Exception (String.Format ("Expected IFD data size was {0} but is {1}", data_offset - ifd_offset, entry_data.Count));
entry_data.Add (offset_data);
return entry_data;
}
/// <summary>
/// Reads an IFD from file at position <paramref name="offset"/> relative
/// to <paramref name="base_offset"/>.
/// </summary>
/// <param name="base_offset">
/// A <see cref="System.Int64"/> with the base offset which every offset
/// in IFD is relative to.
/// </param>
/// <param name="offset">
/// A <see cref="System.UInt32"/> with the offset of the IFD relative to
/// <paramref name="base_offset"/>
/// </param>
/// <param name="max_offset">
/// A <see cref="System.UInt32"/> with the maximal offset to consider for
/// the IFD.
/// </param>
/// <returns>
/// A <see cref="System.UInt32"/> with the offset of the next IFD, the
/// offset is also relative to <paramref name="base_offset"/>
/// </returns>
private uint ReadIFD(long base_offset, uint offset, uint max_offset)
{
long length = 0;
try {
length = file.Length;
} catch (Exception) {
// Use a safety-value of 4 gigabyte.
length = 1073741824L * 4;
}
if (base_offset + offset > length)
{
file.MarkAsCorrupt("Invalid IFD offset");
return(0);
}
var directory = new IFDDirectory();
file.Seek(base_offset + offset, SeekOrigin.Begin);
ushort entry_count = ReadUShort();
if (file.Tell + 12 * entry_count > base_offset + max_offset)
{
file.MarkAsCorrupt("Size of entries exceeds possible data size");
return(0);
}
ByteVector entry_datas = file.ReadBlock(12 * entry_count);
uint next_offset = ReadUInt();
for (int i = 0; i < entry_count; i++)
{
ByteVector entry_data = entry_datas.Mid(i * 12, 12);
ushort entry_tag = entry_data.Mid(0, 2).ToUShort(is_bigendian);
ushort type = entry_data.Mid(2, 2).ToUShort(is_bigendian);
uint value_count = entry_data.Mid(4, 4).ToUInt(is_bigendian);
ByteVector offset_data = entry_data.Mid(8, 4);
// Even if the value count represents a single bytes it's impossible
// for the count plus the base offset to be bigger than the entire file,
// ignore this entry and keep going
if (value_count + base_offset > max_offset)
{
file.MarkAsCorrupt("Value count + base offset is greater than the maximum possible offset");
continue;
}
IFDEntry entry = CreateIFDEntry(entry_tag, type, value_count, base_offset, offset_data, max_offset);
if (entry == null)
{
continue;
}
if (directory.ContainsKey(entry.Tag))
{
directory.Remove(entry.Tag);
}
directory.Add(entry.Tag, entry);
}
FixupDirectory(base_offset, directory);
structure.directories.Add(directory);
return(next_offset);
}
/// <summary>
/// Performs some fixups to a read <see cref="IFDDirectory"/>. For some
/// special cases multiple <see cref="IFDEntry"/> instances contained
/// in the directory are needed. Therfore, we do the fixups after reading the
/// whole directory to be sure, all entries are present.
/// </summary>
/// <param name="base_offset">
/// A <see cref="System.Int64"/> value with the base offset, all offsets in the
/// directory refers to.
/// </param>
/// <param name="directory">
/// A <see cref="IFDDirectory"/> instance which was read and needs fixes.
/// </param>
private void FixupDirectory (long base_offset, IFDDirectory directory)
{
// The following two entries refer to thumbnail data, where one is the offset
// to the data and the other is the length. Unnaturally both are used to describe
// the data. So it is needed to keep both entries in sync and keep the thumbnail data
// for writing it back.
// We determine the position of the data, read it and store it in an ThumbnailDataIFDEntry
// which replaces the offset-entry to thumbnail data.
ushort offset_tag = (ushort) IFDEntryTag.JPEGInterchangeFormat;
ushort length_tag = (ushort) IFDEntryTag.JPEGInterchangeFormatLength;
if (directory.ContainsKey (offset_tag) && directory.ContainsKey (length_tag)) {
var offset_entry = directory [offset_tag] as LongIFDEntry;
var length_entry = directory [length_tag] as LongIFDEntry;
if (offset_entry != null && length_entry != null) {
uint offset = offset_entry.Value;
uint length = length_entry.Value;
file.Seek (base_offset + offset, SeekOrigin.Begin);
ByteVector data = file.ReadBlock ((int) length);
directory.Remove (offset_tag);
directory.Add (offset_tag, new ThumbnailDataIFDEntry (offset_tag, data));
}
}
}
/// <summary>
/// Reads an IFD from file at position <paramref name="offset"/> relative
/// to <paramref name="base_offset"/>.
/// </summary>
/// <param name="base_offset">
/// A <see cref="System.Int64"/> with the base offset which every offset
/// in IFD is relative to.
/// </param>
/// <param name="offset">
/// A <see cref="System.UInt32"/> with the offset of the IFD relative to
/// <paramref name="base_offset"/>
/// </param>
/// <param name="max_offset">
/// A <see cref="System.UInt32"/> with the maximal offset to consider for
/// the IFD.
/// </param>
/// <returns>
/// A <see cref="System.UInt32"/> with the offset of the next IFD, the
/// offset is also relative to <paramref name="base_offset"/>
/// </returns>
private uint ReadIFD (long base_offset, uint offset, uint max_offset)
{
if (base_offset + offset > file.Length)
throw new Exception (String.Format ("Invalid IFD offset {0}, length: {1}", offset, file.Length));
var directory = new IFDDirectory ();
file.Seek (base_offset + offset, SeekOrigin.Begin);
ushort entry_count = ReadUShort ();
if (file.Tell + 12 * entry_count > base_offset + max_offset)
throw new Exception (String.Format ("Size of entries exceeds possible data size"));
ByteVector entry_datas = file.ReadBlock (12 * entry_count);
uint next_offset = ReadUInt ();
for (int i = 0; i < entry_count; i++) {
ByteVector entry_data = entry_datas.Mid (i * 12, 12);
ushort entry_tag = entry_data.Mid (0, 2).ToUShort (is_bigendian);
ushort type = entry_data.Mid (2, 2).ToUShort (is_bigendian);
uint value_count = entry_data.Mid (4, 4).ToUInt (is_bigendian);
ByteVector offset_data = entry_data.Mid (8, 4);
IFDEntry entry = CreateIFDEntry (entry_tag, type, value_count, base_offset, offset_data, max_offset);
if (entry == null)
continue;
if (directory.ContainsKey (entry.Tag))
directory.Remove (entry.Tag);
directory.Add (entry.Tag, entry);
}
FixupDirectory (base_offset, directory);
structure.directories.Add (directory);
return next_offset;
}
private void FixupDirectory(long base_offset, IFDDirectory directory)
{
ushort offset_tag = (ushort)IFDEntryTag.JPEGInterchangeFormat;
ushort length_tag = (ushort)IFDEntryTag.JPEGInterchangeFormatLength;
if (directory.ContainsKey(offset_tag) && directory.ContainsKey(length_tag))
{
var offset_entry = directory[offset_tag] as LongIFDEntry;
var length_entry = directory[length_tag] as LongIFDEntry;
if (offset_entry != null && length_entry != null)
{
uint offset = offset_entry.Value;
uint length = length_entry.Value;
file.Seek(base_offset + offset, SeekOrigin.Begin);
ByteVector data = file.ReadBlock((int)length);
directory.Remove(offset_tag);
directory.Add(offset_tag, new ThumbnailDataIFDEntry(offset_tag, data));
}
}
ushort strip_offsets_tag = (ushort)IFDEntryTag.StripOffsets;
ushort strip_byte_counts_tag = (ushort)IFDEntryTag.StripByteCounts;
if (directory.ContainsKey(strip_offsets_tag) && directory.ContainsKey(strip_byte_counts_tag))
{
uint[] strip_offsets = null;
uint[] strip_byte_counts = null;
var strip_offsets_entry = directory[strip_offsets_tag];
var strip_byte_counts_entry = directory[strip_byte_counts_tag];
if (strip_offsets_entry is LongIFDEntry)
{
strip_offsets = new uint[]
{
(strip_offsets_entry as LongIFDEntry).Value
};
}
else if (strip_offsets_entry is LongArrayIFDEntry)
{
strip_offsets = (strip_offsets_entry as LongArrayIFDEntry).Values;
}
if (strip_offsets == null)
{
return;
}
if (strip_byte_counts_entry is LongIFDEntry)
{
strip_byte_counts = new uint[]
{
(strip_byte_counts_entry as LongIFDEntry).Value
};
}
else if (strip_byte_counts_entry is LongArrayIFDEntry)
{
strip_byte_counts = (strip_byte_counts_entry as LongArrayIFDEntry).Values;
}
if (strip_byte_counts == null)
{
return;
}
directory.Remove(strip_offsets_tag);
directory.Add(strip_offsets_tag, new StripOffsetsIFDEntry(strip_offsets_tag, strip_offsets, strip_byte_counts, file));
}
}
