/// <summary>
/// Writes the given <see cref="byte[]"/> data into a <see cref="SharedMemoryMap"/>.
/// Note:
/// Tracks the reference to the <see cref="SharedMemoryMap"/> after creating it and does not close it.
/// </summary>
/// <param name="content">Content to write into shared memory.</param>
/// <returns>Metadata of the shared memory map into which data is written if successful, <see cref="null"/> otherwise.</returns>
private async Task <SharedMemoryMetadata> PutBytesAsync(byte[] content)
{
// Generate name of shared memory map to write content into
string mapName = Guid.NewGuid().ToString();
// Create shared memory map which can hold the content
long contentSize = content.Length;
SharedMemoryMap sharedMemoryMap = Create(mapName, contentSize);
// Ensure the shared memory map was created
if (sharedMemoryMap == null)
{
_logger.LogError("Cannot write content into shared memory");
return(null);
}
// Write content into shared memory map
long bytesWritten = await sharedMemoryMap.PutBytesAsync(content);
// Ensure that the entire content has been written into the shared memory map
if (bytesWritten != contentSize)
{
_logger.LogError("Cannot write complete content into shared memory map: {MapName}; wrote: {BytesWritten} bytes out of total: {ContentSize} bytes", mapName, bytesWritten, contentSize);
return(null);
}
// Track the shared memory map (to keep a reference open so that the OS does not free the memory)
if (!AllocatedSharedMemoryMaps.TryAdd(mapName, sharedMemoryMap))
{
_logger.LogError("Cannot add shared memory map: {MapName} to list of allocated maps", mapName);
sharedMemoryMap.Dispose();
return(null);
}
// Respond back with metadata about the created and written shared memory map
SharedMemoryMetadata response = new SharedMemoryMetadata
{
Name = mapName,
Count = contentSize
};
return(response);
}
/// <summary>
/// Reads data as <see cref="byte[]"/> from the <see cref="SharedMemoryMap"/> with the given name.
/// </summary>
/// <param name="mapName">Name of the <see cref="MemoryMappedFile"/> to read from.</param>
/// <param name="offset">Offset to start reading data from in the <see cref="SharedMemoryMap"/>.</param>
/// <param name="count">Number of bytes to read from, starting from the offset, in the <see cref="SharedMemoryMap"/>.</param>
/// <returns>Data read as <see cref="byte[]"/> if successful, <see cref="null"/> otherwise.
/// </returns>
private async Task <byte[]> GetBytesAsync(string mapName, int offset, int count)
{
SharedMemoryMap sharedMemoryMap = Open(mapName);
try
{
byte[] content = await sharedMemoryMap.GetBytesAsync(offset, count);
if (content == null)
{
_logger.LogError($"Cannot read content from MemoryMappedFile: {mapName}");
throw new Exception($"Cannot read content from MemoryMappedFile: {mapName} with offset: {offset} and count: {count}");
}
return(content);
}
finally
{
sharedMemoryMap.Dispose(deleteFile: false);
}
}
