ShockwaveFlash 1.0.0

ShockwaveFlash

A fast, allocation-light reader and writer for the SWF (Shockwave Flash) binary format, written for .NET 10.

Disassemble a .swf file into a strongly-typed tag tree, inspect or edit it in code, then assemble it back. Re-assembly is byte-identical to the input it was parsed from — validated by round-tripping a real corpus of production files.

Features

• Reader and writer for the SWF container and its tag stream — every supported tag round-trips.
• Byte-identical assembly: parse then assemble reproduces the original bytes exactly.
• Broad tag coverage (shapes, fonts, text, sounds, bitmaps, sprites, buttons, morph shapes, video, ABC, filters, control tags). Unknown tags are preserved verbatim, so nothing is lost on round-trip.
• Exact fixed-point types (Fixed16 16.16, Fixed8 8.8) — no lossy float conversions in the wire model.
• Compression: reads FWS (uncompressed), CWS (zlib) and ZWS (LZMA); writes uncompressed and zlib.
• Typed exceptions (SwfFormatException, SwfTruncatedException, SwfUnsupportedException, SwfCompressionException) for precise error handling on malformed input.
• No unsafe in your code path, no Span plumbing — the public surface works over ReadOnlyMemory<byte>.

Install

dotnet add package ShockwaveFlash

Quick start

Read

using ShockwaveFlash;

var bytes = File.ReadAllBytes("movie.swf");
var swf = ShockwaveFlashFile.Disassemble(bytes);

Console.WriteLine($"SWF v{swf.Header.Version} ({swf.Header.Compression})");
Console.WriteLine($"Frame size : {swf.Header.FrameSize}");
Console.WriteLine($"Frame rate : {swf.Header.FrameRate.ToSingle()} fps");
Console.WriteLine($"Frames     : {swf.Header.FrameCount}");
Console.WriteLine($"Tags       : {swf.Tags.Count}");

foreach (var tag in swf.Tags)
    Console.WriteLine($"  {tag.Metadata.Code} ({tag.Metadata.Length} bytes)");

Write

ShockwaveFlashFile is an immutable record, so edits are expressed with with:

using ShockwaveFlash;
using ShockwaveFlash.Tags;

var swf = ShockwaveFlashFile.Disassemble(File.ReadAllBytes("movie.swf"));

var trimmed = swf with
{
    Tags = swf.Tags.Where(tag => tag.Metadata.Code is not TagCode.Metadata).ToList()
};

ReadOnlyMemory<byte> output = trimmed.Assemble();
File.WriteAllBytes("movie.trimmed.swf", output.ToArray());

Round-trip

var original = File.ReadAllBytes("movie.swf");
var rebuilt = ShockwaveFlashFile.Disassemble(original).Assemble();

// Reproduces the original bytes exactly.
bool identical = rebuilt.Span.SequenceEqual(original);

Error handling

Malformed input throws a SwfException (or one of its derived types) rather than corrupting state:

using ShockwaveFlash.Exceptions;

try
{
    var swf = ShockwaveFlashFile.Disassemble(bytes);
}
catch (SwfTruncatedException)
{
    // the buffer ended before a record was complete
}
catch (SwfFormatException)
{
    // the bytes are not a valid SWF
}

License

MIT © Aerafal