char/avril

git clone https://git.t4t.associates/char/avril

Charlotte Somport compression extension to typescriptec742cf2026-10-19

import { safePromise } from "ext:core/promises";
import {
  ArrayBuffer,
  ArrayBufferPrototypeGetResizable as resizable,
  getter,
  ObjectGetOwnPropertyDescriptor as descriptor,
  ReflectApply as apply,
  Set,
  SetPrototypeHas as has,
  TypedArrayPrototypeGetBuffer as typedArrayBuffer,
  TypedArrayPrototypeGetByteLength as typedArrayLength,
  TypedArrayPrototypeGetByteOffset as typedArrayOffset,
  TypeError,
  Uint8Array,
  uncurryThis,
  WeakMap,
  WeakMapPrototypeSet as set,
} from "ext:core/primordials";
import {
  op_compression_dispose as dispose,
  op_compression_finish as finishCodec,
  op_compression_new as newCodec,
  op_compression_transform as transformCodec,
} from "ext:core/ops";
import { installInterface } from "ext:web/interface.js";
import { required, state, string } from "ext:web/idl.js";
import { registerUncloneable } from "ext:web/serialization.js";
import {
  ReadableStream,
  TransformStream,
  TransformStreamDefaultController,
  WritableStream,
} from "ext:webstreams/streams.js";

import type {
  ReadableStreamDefaultReader as Reader,
  ReadableStreamDefaultController as ReadableController,
} from "ext:webstreams/streams.js";

type Bytes = Uint8Array<ArrayBuffer>;
interface CodecState {
  id: number | null;
  owner: object;
  stream: TransformStream<unknown, Bytes> | null;
  readable?: ReadableStream<Bytes>;
  writable?: WritableStream<unknown>;
}

const isView = ArrayBuffer.isView;
const arrayBufferLength = getter(ArrayBuffer.prototype, "byteLength");
const dataViewBuffer = getter(DataView.prototype, "buffer");
const dataViewLength = getter(DataView.prototype, "byteLength");
const dataViewOffset = getter(DataView.prototype, "byteOffset");
const enqueue: (controller: TransformStreamDefaultController<Bytes>, chunk: Bytes) => void =
  uncurryThis(TransformStreamDefaultController.prototype.enqueue);
const readable = descriptor(TransformStream.prototype, "readable")!.get!;
const writable = descriptor(TransformStream.prototype, "writable")!.get!;
const getReader = uncurryThis((ReadableStream.prototype as ReadableStream<Bytes>).getReader);
const read = uncurryThis((ReadableStreamDefaultReader.prototype as Reader<Bytes>).read);
const readerCancel = uncurryThis(ReadableStreamDefaultReader.prototype.cancel);
const enqueueReadable: (controller: ReadableController<Bytes>, chunk: Bytes) => void = uncurryThis(
  ReadableStreamDefaultController.prototype.enqueue,
);
const closeReadable = uncurryThis(
  ReadableStreamDefaultController.prototype.close,
);
const getWriter = uncurryThis(WritableStream.prototype.getWriter);
const write = uncurryThis(WritableStreamDefaultWriter.prototype.write);
const closeWriter = uncurryThis(WritableStreamDefaultWriter.prototype.close);
const abortWriter = uncurryThis(WritableStreamDefaultWriter.prototype.abort);
const register: (registry: FinalizationRegistry<number>, target: WeakKey, id: number) => void =
  uncurryThis(FinalizationRegistry.prototype.register);
const compressionStates = new WeakMap<object, Required<CodecState>>(),
  decompressionStates = new WeakMap<object, Required<CodecState>>();
registerUncloneable(compressionStates);
registerUncloneable(decompressionStates);
const finalizer = new FinalizationRegistry<number>((id) => dispose(id));
const formats = new Set(["deflate", "deflate-raw", "gzip", "brotli"]);

function bufferSource(value: unknown): Bytes {
  let buffer, offset = 0, length;
  if (isView(value)) {
    try {
      buffer = typedArrayBuffer(value);
      offset = typedArrayOffset(value);
      length = typedArrayLength(value);
    } catch {
      try {
        buffer = dataViewBuffer(value);
        offset = dataViewOffset(value);
        length = dataViewLength(value);
      } catch {
        throw new TypeError("Expected an attached BufferSource");
      }
    }
  } else {
    buffer = value;
    try {
      length = arrayBufferLength(buffer);
    } catch {
      throw new TypeError("Expected a non-shared BufferSource");
    }
  }
  try {
    arrayBufferLength(buffer);
  } catch {
    throw new TypeError("Expected a non-shared BufferSource");
  }
  try {
    const bytes = new Uint8Array(buffer as ArrayBuffer, offset, length);
    return resizable(buffer) ? new Uint8Array(bytes) : bytes;
  } catch {
    throw new TypeError("Expected an attached BufferSource");
  }
}

function disposeState(internal: CodecState): void {
  const id = internal.id;
  if (id !== null) {
    internal.id = null;
    dispose(id);
  }
}

function create(receiver: object, rawFormat: unknown, decompress: boolean, states: WeakMap<object, Required<CodecState>>): void {
  const format = string(rawFormat);
  if (!has(formats, format)) {
    throw new TypeError("Unsupported compression format");
  }
  const id = newCodec([format, decompress]);
  const internal: CodecState = { id, owner: receiver, stream: null };
  const stream = new TransformStream<unknown, Bytes>({
    async transform(chunk, controller) {
      try {
        const input = bufferSource(chunk);
        // Cancellation can clear the handle; preserve the native rejection/catch path.
        const result = await safePromise(transformCodec([internal.id!, input]));
        const output = result[0];
        if (output.byteLength !== 0) enqueue(controller, output);
        if (result[1]) {
          throw new TypeError("Invalid or unsupported compressed data");
        }
      } catch {
        disposeState(internal);
        throw new TypeError("Invalid or unsupported compressed data");
      }
    },
    async flush(controller) {
      if (internal.id === null) return;
      try {
        const result = await safePromise(finishCodec(internal.id));
        const output = result[0];
        if (output.byteLength !== 0) enqueue(controller, output);
      } catch {
        disposeState(internal);
        throw new TypeError("Invalid or truncated compressed data");
      }
      disposeState(internal);
    },
    cancel() {
      disposeState(internal);
    },
  });
  const outputReader = getReader(apply(readable, stream, []) as ReadableStream<Bytes>);
  const inputWriter = getWriter(apply(writable, stream, []) as WritableStream<unknown>);
  internal.readable = new ReadableStream<Bytes>({
    async pull(controller) {
      try {
        const result = await safePromise(read(outputReader));
        if (result.done) closeReadable(controller);
        else enqueueReadable(controller, result.value);
      } catch (error) {
        disposeState(internal);
        throw error;
      }
    },
    cancel(reason) {
      disposeState(internal);
      return readerCancel(outputReader, reason);
    },
  });
  internal.writable = new WritableStream<unknown>({
    write(chunk) {
      return write(inputWriter, chunk);
    },
    close() {
      return closeWriter(inputWriter);
    },
    abort(reason) {
      disposeState(internal);
      return abortWriter(inputWriter, reason);
    },
  });
  internal.stream = stream;
  // Publish the brand only after both stream endpoints have been installed.
  set(states, receiver, internal as Required<CodecState>);
  register(finalizer, receiver, id);
}

class CompressionStream {
  constructor(format: unknown) {
    required(arguments.length, 1);
    create(this, format, false, compressionStates);
  }
  get readable(): ReadableStream<Bytes> {
    return state(compressionStates, this).readable;
  }
  get writable(): WritableStream<unknown> {
    return state(compressionStates, this).writable;
  }
}

class DecompressionStream {
  constructor(format: unknown) {
    required(arguments.length, 1);
    create(this, format, true, decompressionStates);
  }
  get readable(): ReadableStream<Bytes> {
    return state(decompressionStates, this).readable;
  }
  get writable(): WritableStream<unknown> {
    return state(decompressionStates, this).writable;
  }
}

export type { CompressionStream, DecompressionStream };

for (const ctor of [CompressionStream, DecompressionStream]) {
  installInterface(ctor.name, ctor);
}