153 lines
4.7 KiB
TypeScript
153 lines
4.7 KiB
TypeScript
/**
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* Low-level SWF file parsing: decompression, tag reading, symbol class.
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*/
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import { inflateSync } from "node:zlib";
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import LZMA from "lzma";
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// ── SWF Tag Types ──────────────────────────────────────────────────
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export const TAG_END = 0;
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export const TAG_DEFINE_BITS_LOSSLESS = 20;
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export const TAG_DEFINE_BITS_JPEG2 = 21;
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export const TAG_DEFINE_BITS_JPEG3 = 35;
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export const TAG_DEFINE_BITS_LOSSLESS2 = 36;
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export const TAG_SYMBOL_CLASS = 76;
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export const TAG_DEFINE_BINARY_DATA = 87;
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// ── Interfaces ─────────────────────────────────────────────────────
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export interface SwfTag {
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type: number;
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data: Buffer;
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}
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export interface SymbolClassResult {
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/** charID → first symbol name (canonical name) */
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classNames: Map<number, string>;
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/** symbol name → charID (all symbols including aliases) */
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symbols: Map<string, number>;
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}
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// ── SWF Header Parsing ─────────────────────────────────────────────
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export function decompressSwf(buffer: Buffer): Buffer {
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const sig = buffer.toString("ascii", 0, 3);
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if (sig === "FWS") {
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return buffer;
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}
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if (sig === "CWS") {
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const header = Buffer.alloc(8);
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buffer.copy(header, 0, 0, 8);
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header.write("FWS", 0, 3, "ascii");
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const compressed = buffer.subarray(8);
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const decompressed = inflateSync(compressed);
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return Buffer.concat([header, decompressed]);
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}
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if (sig === "ZWS") {
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const fileLength = buffer.readUInt32LE(4);
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const compressedSize = buffer.readUInt32LE(8);
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const lzmaData = buffer.subarray(12, 12 + compressedSize);
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const props = lzmaData.subarray(0, 5);
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const compressedPayload = lzmaData.subarray(5);
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const uncompressedSize = fileLength - 8;
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const lzmaHeader = Buffer.alloc(13);
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props.copy(lzmaHeader, 0);
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lzmaHeader.writeUInt32LE(uncompressedSize, 5);
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lzmaHeader.writeUInt32LE(0, 9);
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const lzmaStream = Buffer.concat([lzmaHeader, compressedPayload]);
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const decompressed = Buffer.from(LZMA.decompress(lzmaStream) as number[]);
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const header = Buffer.alloc(8);
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buffer.copy(header, 0, 0, 8);
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header.write("FWS", 0, 3, "ascii");
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return Buffer.concat([header, decompressed]);
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}
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throw new Error(`Unknown SWF signature: ${sig}`);
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}
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function readRect(buf: Buffer, offset: number): number {
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const nbits = (buf[offset] >> 3) & 0x1f;
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const totalBits = 5 + nbits * 4;
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const totalBytes = Math.ceil(totalBits / 8);
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return offset + totalBytes;
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}
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// ── SWF Tag Reader ─────────────────────────────────────────────────
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export function parseSwfTags(swfBuffer: Buffer): SwfTag[] {
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const tags: SwfTag[] = [];
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let offset = 8;
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offset = readRect(swfBuffer, offset);
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offset += 4;
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while (offset < swfBuffer.length) {
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if (offset + 2 > swfBuffer.length) break;
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const tagCodeAndLength = swfBuffer.readUInt16LE(offset);
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offset += 2;
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const tagType = (tagCodeAndLength >> 6) & 0x3ff;
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let tagLength = tagCodeAndLength & 0x3f;
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if (tagLength === 0x3f) {
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if (offset + 4 > swfBuffer.length) break;
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tagLength = swfBuffer.readUInt32LE(offset);
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offset += 4;
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}
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if (tagType === TAG_END) break;
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if (offset + tagLength > swfBuffer.length) break;
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const tagData = swfBuffer.subarray(offset, offset + tagLength);
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tags.push({ type: tagType, data: Buffer.from(tagData) });
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offset += tagLength;
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}
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return tags;
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}
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// ── SymbolClass Parser ─────────────────────────────────────────────
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export function parseSymbolClass(data: Buffer): SymbolClassResult {
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const classNames = new Map<number, string>();
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const symbols = new Map<string, number>();
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let offset = 0;
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const numSymbols = data.readUInt16LE(offset);
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offset += 2;
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for (let i = 0; i < numSymbols; i++) {
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if (offset + 2 > data.length) break;
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const charId = data.readUInt16LE(offset);
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offset += 2;
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const strStart = offset;
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while (offset < data.length && data[offset] !== 0) offset++;
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const name = data.toString("utf-8", strStart, offset);
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offset++;
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symbols.set(name, charId);
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if (!classNames.has(charId)) {
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classNames.set(charId, name);
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}
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}
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return { classNames, symbols };
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}
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// ── DefineBinaryData Parser ────────────────────────────────────────
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export function parseBinaryData(data: Buffer): { id: number; content: Buffer } {
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const id = data.readUInt16LE(0);
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const content = data.subarray(6);
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return { id, content };
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}
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