/// <summary>
/// Function to determine if a physical file system can be read by this provider.
/// </summary>
/// <param name="physicalPath">Path to the packed file containing the file system.</param>
/// <returns><b>true</b> if the provider can read the packed file, <b>false</b> if not.</returns>
/// <exception cref="ArgumentNullException">Thrown when the <paramref name="physicalPath"/> parameter is <b>null</b>.</exception>
/// <exception cref="ArgumentEmptyException">Thrown when the <paramref name="physicalPath"/> parameter is an empty string.</exception>
/// <remarks>
/// <para>
/// This will test a physical file system (e.g. a Zip file) to see if the provider can open it or not. If used with a directory on an operating system file system, this method should always return
/// <b>false</b>.
/// </para>
/// <para>
/// When used with a <see cref="IGorgonFileSystemProvider"/> that supports a non operating system based physical file system, such as the <see cref="GorgonFileSystemRamDiskProvider"/>, then this
/// method should compare the <paramref name="physicalPath"/> with its <see cref="IGorgonFileSystemProvider.Prefix"/> to ensure that the <see cref="IGorgonFileSystem"/> requesting the provider is using the correct provider.
/// </para>
/// <para>
/// Implementors of a <see cref="GorgonFileSystemProvider"/> should override this method to determine if a packed file can be read by reading the header of the file specified in <paramref name="physicalPath"/>.
/// </para>
/// </remarks>
protected override bool OnCanReadFile(string physicalPath)
{
string header;
using (var reader = new GorgonBinaryReader(File.Open(physicalPath, FileMode.Open, FileAccess.Read, FileShare.Read)))
{
// If the length of the stream is less or equal to the header size, it's unlikely that we can read this file.
if (reader.BaseStream.Length <= GorPackHeader.Length)
{
return(false);
}
reader.ReadByte();
header = new string(reader.ReadChars(GorPackHeader.Length));
}
return(string.Equals(header, GorPackHeader));
}
/// <summary>
/// Function to determine if a file can be read by this provider.
/// </summary>
/// <param name="physicalPath">Path to the file containing the file system.</param>
/// <returns>
/// TRUE if the provider can read the packed file, FALSE if not.
/// </returns>
/// <remarks>This method is applicable to packed files only.
/// <para>Implementors must use this method to determine if a packed file can be read by reading the header of the file.</para>
/// </remarks>
/// <exception cref="System.ArgumentNullException">Thrown when the <paramref name="physicalPath"/> parameter is NULL (Nothing in VB.Net).</exception>
/// <exception cref="System.ArgumentException">Thrown when the <paramref name="physicalPath"/> parameter is an empty string.</exception>
public override bool CanReadFile(string physicalPath)
{
string header;
if (physicalPath == null)
{
throw new ArgumentNullException("physicalPath");
}
if (string.IsNullOrWhiteSpace(physicalPath))
{
throw new ArgumentException(Resources.GORFS_PARAMETER_MUST_NOT_BE_EMPTY, "physicalPath");
}
using (var reader = new GorgonBinaryReader(File.Open(physicalPath, FileMode.Open, FileAccess.Read, FileShare.Read), false))
{
reader.ReadByte();
header = new string(reader.ReadChars(GorgonGorPackPlugIn.GorPackHeader.Length));
}
return(string.Equals(header, GorgonGorPackPlugIn.GorPackHeader));
}