// Create a new archive with the files specified in filesToPack
public static void CreateArchive(string volumeFilename, IEnumerable <string> filesToPack)
{
List <string> filesToPackSorted = new List <string>(filesToPack);
// Sort files alphabetically based on the filename only (not including the full path).
// Packed files must be locatable by a binary search of their filename.
filesToPackSorted.Sort(new System.Comparison <string>((s1, s2) => Path.GetFileName(s1).CompareTo(Path.GetFileName(s2))));
CreateVolumeInfo volInfo = new CreateVolumeInfo();
volInfo.filesToPack = filesToPackSorted;
volInfo.names = GetNamesFromPaths(filesToPackSorted);
// Allowing duplicate names when packing may cause unintended results during binary search and file extraction.
VerifySortedContainerHasNoDuplicateNames(volInfo.names);
// Open input files and prepare header and indexing info
PrepareHeader(volInfo, volumeFilename);
WriteVolume(volumeFilename, volInfo);
// Dispose of open readers
foreach (BinaryReader reader in volInfo.fileStreamReaders)
{
reader.Dispose();
}
}
private static void PrepareHeader(CreateVolumeInfo volInfo, string volumeFilename)
{
OpenAllInputFiles(volInfo, volumeFilename);
volInfo.stringTableLength = 0;
// Get file sizes and calculate length of string table
for (int i = 0; i < volInfo.fileCount(); ++i)
{
IndexEntry indexEntry = new IndexEntry();
long fileSize = volInfo.fileStreamReaders[i].BaseStream.Length;
if (fileSize > uint.MaxValue)
{
throw new System.Exception("File " + volInfo.filesToPack[i] +
" is too large to fit inside a volume archive. Writing volume " + volumeFilename + " aborted.");
}
indexEntry.fileSize = (int)(fileSize);
indexEntry.filenameOffset = volInfo.stringTableLength;
indexEntry.compressionType = CompressionType.Uncompressed;
volInfo.indexEntries.Add(indexEntry);
// Add length of internal filename plus null terminator to string table length.
if (volInfo.stringTableLength + (ulong)volInfo.names[i].Length + 1 > uint.MaxValue)
{
throw new System.Exception("String table length is too long to create volume " + volumeFilename);
}
volInfo.stringTableLength += (uint)(volInfo.names[i].Length) + 1;
}
// Calculate size of index table
if ((ulong)volInfo.fileCount() * IndexEntry.SizeInBytes > uint.MaxValue)
{
throw new System.Exception("Index table length is too long to create volume " + volumeFilename);
}
volInfo.indexTableLength = (uint)volInfo.fileCount() * IndexEntry.SizeInBytes;
// Calculate the zero padded length of the string table and index table
volInfo.paddedStringTableLength = (uint)((volInfo.stringTableLength + 7) & ~3);
volInfo.paddedIndexTableLength = (uint)((volInfo.indexTableLength + 3) & ~3);
if (volInfo.indexEntries.Count == 0)
{
return;
}
volInfo.indexEntries[0].dataBlockOffset = volInfo.paddedStringTableLength + volInfo.paddedIndexTableLength + 32;
// Calculate offsets to the files
for (int i = 1; i < volInfo.fileCount(); ++i)
{
IndexEntry previousIndex = volInfo.indexEntries[i - 1];
volInfo.indexEntries[i].dataBlockOffset = (uint)((previousIndex.dataBlockOffset + previousIndex.fileSize + 11) & ~3);
}
}
private static void OpenAllInputFiles(CreateVolumeInfo volInfo, string volumeFilename)
{
volInfo.fileStreamReaders.Clear();
foreach (string filename in volInfo.filesToPack)
{
try {
FileStream fs = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
volInfo.fileStreamReaders.Add(new BinaryReader(fs));
}
catch (System.Exception e) {
throw new System.Exception("Error attempting to open " + filename +
" for reading into volume " + volumeFilename + ". Internal Error: " + e);
}
}
}
private static void WriteVolume(string filename, CreateVolumeInfo volInfo)
{
foreach (string path in volInfo.filesToPack)
{
if (string.Compare(filename, path, true) == 0) // NOTE: Case insensitive comparison
{
throw new System.Exception("Cannot include a volume being overwritten in new volume " + filename);
}
}
using (FileStream fs = new FileStream(filename, FileMode.Create, FileAccess.Write, FileShare.None))
using (BinaryWriter volWriter = new BinaryWriter(fs))
{
WriteHeader(volWriter, volInfo);
WriteFiles(volWriter, volInfo);
}
}
private static void WriteHeader(BinaryWriter volWriter, CreateVolumeInfo volInfo)
{
// Write the header
new SectionHeader(TagVOL_, volInfo.paddedStringTableLength + volInfo.paddedIndexTableLength + 24).Serialize(volWriter);
new SectionHeader(TagVOLH, 0).Serialize(volWriter);
// Write the string table
new SectionHeader(TagVOLS, volInfo.paddedStringTableLength).Serialize(volWriter);
volWriter.Write(volInfo.stringTableLength);
// Write out all internal file name strings (including NULL terminator)
for (int i = 0; i < volInfo.fileCount(); ++i)
{
// Account for the null terminator in the size.
byte[] stringBuffer = System.Text.Encoding.ASCII.GetBytes(volInfo.names[i] + "\0");
volWriter.Write(stringBuffer, 0, stringBuffer.Length);
}
byte[] padding = new byte[4]; // Pad with 0 bytes
volWriter.Write(padding, 0, (int)(volInfo.paddedStringTableLength - (volInfo.stringTableLength + 4)));
// Write the index table
new SectionHeader(TagVOLI, volInfo.indexTableLength).Serialize(volWriter);
int bytesWritten = 0;
foreach (IndexEntry entry in volInfo.indexEntries)
{
if (bytesWritten >= volInfo.indexTableLength)
{
break;
}
entry.Serialize(volWriter);
bytesWritten += IndexEntry.SizeInBytes;
}
volWriter.Write(padding, 0, (int)(volInfo.paddedIndexTableLength - volInfo.indexTableLength));
}
private static void WriteFiles(BinaryWriter volWriter, CreateVolumeInfo volInfo)
{
// Write each file header and contents
for (int i = 0; i < volInfo.fileCount(); ++i)
{
new SectionHeader(TagVBLK, (uint)volInfo.indexEntries[i].fileSize).Serialize(volWriter);
try {
volInfo.fileStreamReaders[i].BaseStream.Seek(0, SeekOrigin.Begin);
volWriter.Write(volInfo.fileStreamReaders[i].ReadBytes((int)volInfo.fileStreamReaders[i].BaseStream.Length));
// Add padding after the file, ensuring it ends on a 4 byte boundary
// Use a bitmask to quickly calculate the modulo 4 (remainder) of fileSize
byte[] padding = new byte[4];
volWriter.Write(padding, 0, (-volInfo.indexEntries[i].fileSize) & 3);
}
catch (System.Exception e) {
throw new System.Exception("Unable to pack file " + volInfo.names[i] + ". Internal error: " + e);
}
}
}
