153 lines
4.8 KiB
TypeScript
153 lines
4.8 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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