dart: Return dart:typed_data equivalent where possible #8289
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I'm not opposed to that, but I'd like to see some insight from one of the Dart maintainers to see if this aligns with their view for the Dart side. Ideally, we could expand the same to |
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Ready for review. I tested using @tompark's example code, with the latest version of flatbuffers on pub.dev as well as this fork, and this fork prints the expected |
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I can provide a test repo if you'd like as well, although setting up Tom's example code also takes <10 minutes, assuming you have Flutter and Python already installed. |
NotTsunami
changed the title
* Remove _FbUint8List, _FbInt8List and _FbUint16List to return typed_data types * Add test for Int8List * Test Int8List, Uint8List and Uint16List for type equivalence * Remove unnecessary cast in _writeUTFString to silence linting warning
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I squashed the changes and removed a change related to my other PR to prevent conflicts between the two. @vaind Hi Ivan, is there any way you might be able to spare some bandwidth in the relatively near future to help review and potentially land both of my open PRs? Cheers. |
I think I'd rather add a separate path or built-in for big-endian, otherwise the newly added conditions to the tests will cause the tests to fail on big-endian, as the old classes do not return Uint8List, Int8List, Uint16List, etc on the lazy path. I think the only supported test environment (theoretically) would be ARM on Linux running in big-endian mode? I'll try and set up a qemu environment to test. |
I think it's OK to have different actual return type on big endian, the only contract is that it is compatible with List, everything else is "just" an optimization. It's OK for tests to assert the return value is the expected type based on endianness though |
Sounds good to me. Sorry for the delay. I'll get this updated this week, hopefully on the earlier half as opposed to the later half. |
I'll extend this to other types! I'll expand the tests as well. |
| List<double> read(BufferContext bc, int offset) { | ||
| if (Endian.host == Endian.little) { | ||
| final listOffset = bc.derefObject(offset); | ||
| final length = bc._getUint32(listOffset); | ||
| return bc._asFloat64List(listOffset + _sizeofUint32, length); | ||
| } else { | ||
| return _FbFloat64List(bc, bc.derefObject(offset)); | ||
| } | ||
| } |
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With this change, test_writeList_ofFloat64 is failing as the offset must be a multiple of BYTES_PER_ELEMENT (8). I'm absolutely missing something simple here, need to wrap my head around what it is (or grab another coffee, maybe).
For this PR specifically, it has been expanded out to the existing List types in the code already. I don't know enough about the flatbuffers library to understand how to expand this out for types that do not already have a Reader class, eg Int16ListReader, Int32ListReader. Note though, the float implementation needs to be corrected, but after that the PR should be complete. |
Stems from discussion in #8183. This should allow users to be able to access a Uint8List directly without copying over from a list, thus actually offering zero-copy access (for this class, at least) in both the lazy path and the non-lazy path. This is pretty important for signal processing and image processing where we want to avoid any unnecessary list copies.