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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.IO;
using System.Runtime.InteropServices;
using MS.Internal.PresentationCore;
using MS.Internal.FontCache;
// Since we disable PreSharp warnings in this file, we first need to disable warnings about unknown message numbers and unknown pragmas.
#pragma warning disable 1634, 1691
namespace MS.Internal.FontFace
{
/// <summary>
/// Font technology.
/// </summary>
internal enum FontTechnology
{
// this enum need to be kept in order of preference that we want to use with duplicate font face,
// highest value will win in case of duplicate
PostscriptOpenType,
TrueType,
TrueTypeCollection
}
internal class TrueTypeFontDriver
{
#region Font constants, structures and enumerations
private struct DirectoryEntry
{
internal TrueTypeTags tag;
internal CheckedPointer pointer;
}
private enum TrueTypeTags : int
{
CharToIndexMap = 0x636d6170, /* 'cmap' */
ControlValue = 0x63767420, /* 'cvt ' */
BitmapData = 0x45424454, /* 'EBDT' */
BitmapLocation = 0x45424c43, /* 'EBLC' */
BitmapScale = 0x45425343, /* 'EBSC' */
Editor0 = 0x65647430, /* 'edt0' */
Editor1 = 0x65647431, /* 'edt1' */
Encryption = 0x63727970, /* 'cryp' */
FontHeader = 0x68656164, /* 'head' */
FontProgram = 0x6670676d, /* 'fpgm' */
GridfitAndScanProc = 0x67617370, /* 'gasp' */
GlyphDirectory = 0x67646972, /* 'gdir' */
GlyphData = 0x676c7966, /* 'glyf' */
HoriDeviceMetrics = 0x68646d78, /* 'hdmx' */
HoriHeader = 0x68686561, /* 'hhea' */
HorizontalMetrics = 0x686d7478, /* 'hmtx' */
IndexToLoc = 0x6c6f6361, /* 'loca' */
Kerning = 0x6b65726e, /* 'kern' */
LinearThreshold = 0x4c545348, /* 'LTSH' */
MaxProfile = 0x6d617870, /* 'maxp' */
NamingTable = 0x6e616d65, /* 'name' */
OS_2 = 0x4f532f32, /* 'OS/2' */
Postscript = 0x706f7374, /* 'post' */
PreProgram = 0x70726570, /* 'prep' */
VertDeviceMetrics = 0x56444d58, /* 'VDMX' */
VertHeader = 0x76686561, /* 'vhea' */
VerticalMetrics = 0x766d7478, /* 'vmtx' */
PCLT = 0x50434C54, /* 'PCLT' */
TTO_GSUB = 0x47535542, /* 'GSUB' */
TTO_GPOS = 0x47504F53, /* 'GPOS' */
TTO_GDEF = 0x47444546, /* 'GDEF' */
TTO_BASE = 0x42415345, /* 'BASE' */
TTO_JSTF = 0x4A535446, /* 'JSTF' */
OTTO = 0x4f54544f, // Adobe OpenType 'OTTO'
TTC_TTCF = 0x74746366 // 'ttcf'
}
#endregion
#region Byte, Short, Long etc. accesss to CheckedPointers
/// <summary>
/// The follwoing APIs extract OpenType variable types from OpenType font
/// files. OpenType variables are stored big-endian, and the type are named
/// as follows:
/// Byte - signed 8 bit
/// UShort - unsigned 16 bit
/// Short - signed 16 bit
/// ULong - unsigned 32 bit
/// Long - signed 32 bit
/// </summary>
private static ushort ReadOpenTypeUShort(CheckedPointer pointer)
{
unsafe
{
byte * readBuffer = (byte *)pointer.Probe(0, 2);
ushort result = (ushort)((readBuffer[0] << 8) + readBuffer[1]);
return result;
}
}
private static int ReadOpenTypeLong(CheckedPointer pointer)
{
unsafe
{
byte * readBuffer = (byte *)pointer.Probe(0, 4);
int result = (int)((((((readBuffer[0] << 8) + readBuffer[1]) << 8) + readBuffer[2]) << 8) + readBuffer[3]);
return result;
}
}
#endregion Byte, Short, Long etc. accesss to CheckedPointers
#region Constructor and general helpers
internal TrueTypeFontDriver(UnmanagedMemoryStream unmanagedMemoryStream, Uri sourceUri)
{
_sourceUri = sourceUri;
_unmanagedMemoryStream = unmanagedMemoryStream;
_fileStream = new CheckedPointer(unmanagedMemoryStream);
try
{
CheckedPointer seekPosition = _fileStream;
TrueTypeTags typeTag = (TrueTypeTags)ReadOpenTypeLong(seekPosition);
seekPosition += 4;
if (typeTag == TrueTypeTags.TTC_TTCF)
{
// this is a TTC file, we need to decode the ttc header
_technology = FontTechnology.TrueTypeCollection;
seekPosition += 4; // skip version
_numFaces = ReadOpenTypeLong(seekPosition);
}
else if (typeTag == TrueTypeTags.OTTO)
{
_technology = FontTechnology.PostscriptOpenType;
_numFaces = 1;
}
else
{
_technology = FontTechnology.TrueType;
_numFaces = 1;
}
}
catch (ArgumentOutOfRangeException e)
{
// convert exceptions from CheckedPointer to FileFormatException
throw new FileFormatException(SourceUri, e);
}
}
internal void SetFace(int faceIndex)
{
if (_technology == FontTechnology.TrueTypeCollection)
{
ArgumentOutOfRangeException.ThrowIfNegative(faceIndex);
ArgumentOutOfRangeException.ThrowIfGreaterThanOrEqual(faceIndex, _numFaces);
}
else
{
if (faceIndex != 0)
throw new ArgumentOutOfRangeException("faceIndex", SR.FaceIndexValidOnlyForTTC);
}
try
{
CheckedPointer seekPosition = _fileStream + 4;
if (_technology == FontTechnology.TrueTypeCollection)
{
// this is a TTC file, we need to decode the ttc header
// skip version, num faces, OffsetTable array
seekPosition += (4 + 4 + 4 * faceIndex);
_directoryOffset = ReadOpenTypeLong(seekPosition);
seekPosition = _fileStream + (_directoryOffset + 4);
// 4 means that we skip the version number
}
_faceIndex = faceIndex;
int numTables = ReadOpenTypeUShort(seekPosition);
seekPosition += 2;
// quick check for malformed fonts, see if numTables is too large
// file size should be >= sizeof(offset table) + numTables * (sizeof(directory entry) + minimum table size (4))
long minimumFileSize = (4 + 2 + 2 + 2 + 2) + numTables * (4 + 4 + 4 + 4 + 4);
if (_fileStream.Size < minimumFileSize)
{
throw new FileFormatException(SourceUri);
}
_tableDirectory = new DirectoryEntry[numTables];
// skip searchRange, entrySelector and rangeShift
seekPosition += 6;
// I can't use foreach here because C# disallows modifying the current value
for (int i = 0; i < _tableDirectory.Length; ++i)
{
_tableDirectory[i].tag = (TrueTypeTags)ReadOpenTypeLong(seekPosition);
seekPosition += 8; // skip checksum
int offset = ReadOpenTypeLong(seekPosition);
seekPosition += 4;
int length = ReadOpenTypeLong(seekPosition);
seekPosition += 4;
_tableDirectory[i].pointer = _fileStream.CheckedProbe(offset, length);
}
}
catch (ArgumentOutOfRangeException e)
{
// convert exceptions from CheckedPointer to FileFormatException
throw new FileFormatException(SourceUri, e);
}
}
#endregion
#region Public methods and properties
internal int NumFaces
{
get
{
return _numFaces;
}
}
private Uri SourceUri
{
get
{
return _sourceUri;
}
}
/// <summary>
/// Create font subset that includes glyphs in the input collection.
/// </summary>
internal byte[] ComputeFontSubset(ICollection<ushort> glyphs)
{
int fileSize = _fileStream.Size;
unsafe
{
void* fontData = _fileStream.Probe(0, fileSize);
// Since we currently don't have a way to subset CFF fonts, just return a copy of the font.
if (_technology == FontTechnology.PostscriptOpenType)
{
byte[] fontCopy = new byte[fileSize];
Marshal.Copy((IntPtr)fontData, fontCopy, 0, fileSize);
return fontCopy;
}
ushort[] glyphArray;
if (glyphs == null || glyphs.Count == 0)
glyphArray = null;
else
{
glyphArray = new ushort[glyphs.Count];
glyphs.CopyTo(glyphArray, 0);
}
return TrueTypeSubsetter.ComputeSubset(fontData, fileSize, SourceUri, _directoryOffset, glyphArray);
}
}
#endregion Public methods and properties
#region Fields
// file-specific state
private CheckedPointer _fileStream;
private UnmanagedMemoryStream _unmanagedMemoryStream;
private Uri _sourceUri;
private int _numFaces;
private FontTechnology _technology;
// face-specific state
private int _faceIndex;
private int _directoryOffset; // table directory offset for TTC, 0 for TTF
private DirectoryEntry[] _tableDirectory;
#endregion
}
}
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