/// <summary>
/// Gets a <see cref="MetadataReader"/> from a <see cref="MetadataReaderProvider"/>.
/// </summary>
/// <remarks>
/// The caller must keep the <see cref="MetadataReaderProvider"/> undisposed throughout the lifetime of the metadata reader.
///
/// If this method is called multiple times each call with arguments equal to the arguments passed to the previous successful call
/// returns the same instance of <see cref="MetadataReader"/> as the previous call.
/// </remarks>
/// <exception cref="ArgumentException">The encoding of <paramref name="utf8Decoder"/> is not <see cref="UTF8Encoding"/>.</exception>
/// <exception cref="PlatformNotSupportedException">The current platform is big-endian.</exception>
/// <exception cref="IOException">IO error while reading from the underlying stream.</exception>
/// <exception cref="ObjectDisposedException">Provider has been disposed.</exception>
public unsafe MetadataReader GetMetadataReader(MetadataReaderOptions options = MetadataReaderOptions.Default, MetadataStringDecoder utf8Decoder = null)
{
var cachedReader = _lazyMetadataReader;
if (CanReuseReader(cachedReader, options, utf8Decoder))
{
return(cachedReader);
}
// If multiple threads attempt to open a metadata reader with the same options and decoder
// it's cheaper to wait for the other thread to finish initializing the reader than to open
// two readers and discard one.
// Note that it's rare to reader the same metadata using different options.
lock (_metadataReaderGuard)
{
cachedReader = _lazyMetadataReader;
if (CanReuseReader(cachedReader, options, utf8Decoder))
{
return(cachedReader);
}
AbstractMemoryBlock metadata = GetMetadataBlock();
var newReader = new MetadataReader(metadata.Pointer, metadata.Size, options, utf8Decoder, memoryOwner: this);
_lazyMetadataReader = newReader;
return(newReader);
}
}
private static bool CanReuseReader(MetadataReader reader, MetadataReaderOptions options, MetadataStringDecoder utf8DecoderOpt)
{
return(reader != null && reader.Options == options && ReferenceEquals(reader.UTF8Decoder, utf8DecoderOpt ?? MetadataStringDecoder.DefaultUTF8));
}
/// <summary>
/// Gets a <see cref="MetadataReader"/> from a <see cref="PEReader"/>.
/// </summary>
/// <remarks>
/// The caller must keep the <see cref="PEReader"/> undisposed throughout the lifetime of the metadata reader.
/// </remarks>
/// <exception cref="ArgumentNullException"><paramref name="peReader"/> is null</exception>
/// <exception cref="ArgumentException">The encoding of <paramref name="utf8Decoder"/> is not <see cref="UTF8Encoding"/>.</exception>
/// <exception cref="PlatformNotSupportedException">The current platform is big-endian.</exception>
/// <exception cref="IOException">IO error while reading from the underlying stream.</exception>
public static unsafe MetadataReader GetMetadataReader(this PEReader peReader, MetadataReaderOptions options, MetadataStringDecoder utf8Decoder)
{
if (peReader == null)
{
throw new ArgumentNullException(nameof(peReader));
}
var metadata = peReader.GetMetadata();
return(new MetadataReader(metadata.Pointer, metadata.Length, options, utf8Decoder, memoryOwner: peReader));
}