(maybe) decompresses a stream
jsr.io/@mary/maybe-decompression-stream
jsr
typescript
initial commit
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.vscode/settings.json
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.vscode/settings.json
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LICENSE
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LICENSE
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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README.md
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README.md
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# maybe-decompression-stream
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decompresses a stream of data if it is compressed with gzip, otherwise it passes the data through.
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```ts
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const response = await fetch('resource.tgz');
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const stream = response.body.pipeThrough(new MaybeDecompressionStream());
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for await (const chunk of stream) {
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// ...
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}
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```
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deno.json
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deno.json
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{
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"name": "@mary/maybe-decompression-stream",
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"version": "0.1.0",
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"exports": "./lib/mod.ts",
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"fmt": {
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"useTabs": true,
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"indentWidth": 2,
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"lineWidth": 110,
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"semiColons": true,
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"singleQuote": true
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},
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"publish": {
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"include": ["lib/", "LICENSE", "README.md", "deno.json"]
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}
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}
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lib/mod.ts
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lib/mod.ts
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const enum CompressionState {
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Undetermined,
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Compressed,
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Passthrough,
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}
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type State =
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| { status: CompressionState.Undetermined; buffer: Uint8Array | undefined }
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| { status: CompressionState.Compressed; writer: WritableStreamDefaultWriter<Uint8Array> }
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| { status: CompressionState.Passthrough };
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/**
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* decompresses a stream of data if it is compressed with gzip, otherwise it passes the data through.
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*/
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export class MaybeDecompressionStream extends TransformStream<Uint8Array, Uint8Array> {
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constructor() {
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let state: State = { status: CompressionState.Undetermined, buffer: undefined };
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super({
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transform(chunk, controller) {
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switch (state.status) {
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case CompressionState.Passthrough: {
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controller.enqueue(chunk);
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return;
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}
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case CompressionState.Compressed: {
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state.writer.write(chunk);
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return;
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}
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case CompressionState.Undetermined: {
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let buffer = state.buffer;
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if (buffer === undefined) {
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buffer = chunk;
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} else {
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const concat = new Uint8Array(buffer.length + chunk.length);
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concat.set(buffer);
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concat.set(chunk, buffer.length);
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buffer = concat;
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}
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if (buffer.length < 2) {
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state.buffer = buffer;
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return;
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}
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const isGzip = buffer[0] === 0x1f && buffer[1] === 0x8b;
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if (isGzip) {
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const { readable, writable } = new DecompressionStream('gzip');
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const writer = writable.getWriter();
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writer.write(buffer);
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readable.pipeTo(
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new WritableStream({
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write(chunk) {
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controller.enqueue(chunk);
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},
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close() {
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controller.terminate();
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},
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abort(err) {
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controller.error(err);
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},
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}),
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);
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state = { status: CompressionState.Compressed, writer };
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} else {
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controller.enqueue(buffer);
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state = { status: CompressionState.Passthrough };
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}
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return;
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}
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}
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},
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async flush(controller) {
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if (state.status === CompressionState.Undetermined) {
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if (state.buffer) {
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controller.enqueue(state.buffer);
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}
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}
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if (state.status === CompressionState.Compressed) {
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await state.writer.close();
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}
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},
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async cancel(reason) {
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if (state.status === CompressionState.Compressed) {
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await state.writer.abort(reason);
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}
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},
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});
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}
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}