coomdev
2 years ago
11 changed files with 187 additions and 43 deletions
@ -0,0 +1,149 @@ |
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import { buf } from "crc-32"; |
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import { Buffer } from "buffer"; |
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import type { ImageProcessor } from "./main"; |
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import { PNGDecoder, PNGEncoder } from "./png"; |
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import { decodeCoom3Payload } from "./utils"; |
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const CUM0 = Buffer.from("CUM\0" + "0"); |
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const CUM3 = Buffer.from("CUM\0" + "3"); |
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const BufferReadStream = (b: Buffer) => { |
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const ret = new ReadableStream<Buffer>({ |
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pull(cont) { |
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cont.enqueue(b); |
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cont.close(); |
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} |
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}); |
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return ret; |
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}; |
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const extract = async (png: Buffer) => { |
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let magic = false; |
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let coom3 = false; |
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const reader = BufferReadStream(png).getReader(); |
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const sneed = new PNGDecoder(reader); |
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try { |
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let lastIDAT: Buffer | null = null; |
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for await (const [name, chunk, crc, offset] of sneed.chunks()) { |
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let buff: Buffer; |
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switch (name) { |
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// should exist at the beginning of file to signal decoders if the file indeed has an embedded chunk
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case 'tEXt': |
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buff = chunk; |
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if (buff.slice(4, 4 + CUM0.length).equals(CUM0)) |
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magic = true; |
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if (buff.slice(4, 4 + CUM0.length).equals(CUM3)) { |
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coom3 = true; |
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magic = true; |
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} |
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break; |
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case 'IDAT': |
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if (magic) { |
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lastIDAT = chunk; |
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break; |
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} |
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// eslint-disable-next-line no-fallthrough
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case 'IEND': |
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if (!magic) |
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return; // Didn't find tExt Chunk;
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// eslint-disable-next-line no-fallthrough
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default: |
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break; |
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} |
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} |
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if (lastIDAT) { |
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let data = (lastIDAT as Buffer).slice(4); |
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if (coom3) |
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return decodeCoom3Payload(data); |
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const fnsize = data.readUInt32LE(0); |
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const fn = data.slice(4, 4 + fnsize).toString(); |
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// Todo: xor the buffer to prevent scanning for file signatures (4chan embedded file detection)?
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data = data.slice(4 + fnsize); |
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return [{ filename: fn, data }]; |
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} |
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} catch (e) { |
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console.error(e); |
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} finally { |
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reader.releaseLock(); |
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} |
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}; |
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|
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const buildChunk = (tag: string, data: Buffer) => { |
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const ret = Buffer.alloc(data.byteLength + 4); |
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ret.write(tag.slice(0, 4), 0); |
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data.copy(ret, 4); |
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return ret; |
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}; |
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export const BufferWriteStream = () => { |
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let b = Buffer.from([]); |
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const ret = new WritableStream<Buffer>({ |
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write(chunk) { |
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b = Buffer.concat([b, chunk]); |
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} |
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}); |
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return [ret, () => b] as [WritableStream<Buffer>, () => Buffer]; |
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}; |
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const inject = async (container: File, inj: File) => { |
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const [writestream, extract] = BufferWriteStream(); |
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const encoder = new PNGEncoder(writestream); |
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const decoder = new PNGDecoder(container.stream().getReader()); |
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let magic = false; |
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for await (const [name, chunk, crc, offset] of decoder.chunks()) { |
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if (magic && name != "IDAT") |
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break; |
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if (!magic && name == "IDAT") { |
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await encoder.insertchunk(["tEXt", buildChunk("tEXt", CUM0), 0, 0]); |
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magic = true; |
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} |
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await encoder.insertchunk([name, chunk, crc, offset]); |
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} |
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const injb = Buffer.alloc(4 + inj.name.length + inj.size); |
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injb.writeInt32LE(inj.name.length, 0); |
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injb.write(inj.name, 4); |
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Buffer.from(await inj.arrayBuffer()).copy(injb, 4 + inj.name.length); |
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await encoder.insertchunk(["IDAT", buildChunk("IDAT", injb), 0, 0]); |
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await encoder.insertchunk(["IEND", buildChunk("IEND", Buffer.from([])), 0, 0]); |
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return extract(); |
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}; |
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const has_embed = async (png: Buffer) => { |
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const reader = BufferReadStream(png).getReader(); |
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const sneed = new PNGDecoder(reader); |
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try { |
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for await (const [name, chunk, crc, offset] of sneed.chunks()) { |
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let buff: Buffer; |
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switch (name) { |
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// should exist at the beginning of file to signal decoders if the file indeed has an embedded chunk
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case 'tEXt': |
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buff = chunk; |
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if (buff.slice(4, 4 + CUM0.length).equals(CUM0)) |
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return true; |
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if (buff.slice(4, 4 + CUM0.length).equals(CUM3)) |
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return true; |
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break; |
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case 'IDAT': |
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// eslint-disable-next-line no-fallthrough
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case 'IEND': |
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return false; // Didn't find tExt Chunk; Definite no
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// eslint-disable-next-line no-fallthrough
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default: |
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break; |
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} |
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} |
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// stream ended on chunk boundary, so no unexpected EOF was fired, need more data anyway
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} catch (e) { |
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return; // possibly unexpected EOF, need more data to decide
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} finally { |
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reader.releaseLock(); |
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} |
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}; |
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export default { |
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extract, |
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has_embed, |
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inject, |
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match: fn => !!fn.match(/\.png$/) |
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} as ImageProcessor; |
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@ -0,0 +1,5 @@ |
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import type { Buffer } from "buffer"; |
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export const decodeCoom3Payload = (buff: Buffer) => { |
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//
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}; |
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