robertwb commented on code in PR #22137:
URL: https://github.com/apache/beam/pull/22137#discussion_r917016828
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sdks/typescript/src/apache_beam/coders/standard_coders.ts:
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@@ -123,9 +123,9 @@ export class DoubleCoder implements Coder<number> {
}
decode(reader: Reader, context: Context): number {
- const barr = new Uint8Array(reader.buf, reader.pos, 8);
- const dView = new DataView(barr.buffer);
- reader.float();
+ const barr = new Uint8Array(reader.buf);
+ const dView = new DataView(barr.buffer.slice(reader.pos, reader.pos + 8));
Review Comment:
The problem was that despite constructing the `barr` as new
`Uint8Array(reader.buf, reader.pos, 8)`, `barr.buffer` still refers to the
entire (non-cropped) underlying buffer. This means the coder failed whenever
the value was not the first element in the stream (as it is in js_coders, hence
the added test, as well as in iterables, as a second element, etc.) I didn't
see a way to avoid the extra copy, but it's only 8 bytes (as opposed to an
unbounded amount) so hopefully that should be relatively cheap.
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