ShockwaveFlash 1.2.0

ShockwaveFlash

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

Disassemble a .swf into a strongly-typed tag tree, inspect or edit it in code, then assemble it back — the round-trip is lossless: byte-identical for canonically-encoded SWFs and byte-stable on re-encode, validated on a real corpus of production files.

Install

dotnet add package ShockwaveFlash

Read

using ShockwaveFlash;

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

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

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

Edit & write

The movie and its tags are mutable, so edit them in place — Tags is a List<Tag> and every tag exposes settable properties:

using ShockwaveFlash;
using ShockwaveFlash.Tags;

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

swf.Tags.RemoveAll(tag => tag.Metadata.Code is TagCode.Metadata);

File.WriteAllBytes("movie.trimmed.swf", swf.Assemble().ToArray());

Round-trip

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

// true for canonically-encoded SWFs; always byte-stable on a second pass.
bool identical = rebuilt.Span.SequenceEqual(original);

Error handling

Malformed input throws a typed SwfException rather than corrupting state:

using ShockwaveFlash.Exceptions;

try
{
    var swf = ShockwaveFlashFile.Disassemble(bytes);
}
catch (SwfTruncatedException) { /* buffer ended mid-record */ }
catch (SwfFormatException)    { /* not a valid SWF */ }

Notes

• Coverage — shapes, fonts, text, sounds, bitmaps, sprites, buttons, morph shapes, video, ABC, filters and control tags. Unknown tags are preserved verbatim, so nothing is lost on round-trip.
• Exact wire model — fixed-point types (Fixed16 16.16, Fixed8 8.8); no lossy float conversions.
• Compression — FWS (uncompressed), CWS (zlib) and ZWS (LZMA), all read and write.
• No unsafe, no Span plumbing — the public surface works over ReadOnlyMemory<byte>.

Part of the ShockwaveFlash project · MIT © Aerafal