Adding &[u8] support. #117
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This change adds specifically, support for &[u8] with a corresponding rust::Slice<uint8_t> type. No other types of slice are permitted. The rationale is that it may be common to pass binary data back and forth across the FFI boundary, so it's more urgent to get this in place sooner. Broader support for other slices can wait for the future. But, both C and Rust-side bindings should allow the existing support to be broadened to other Slice types in future without code changes. A few specific notes: * The name "rust::Slice" might be better as "rust::SliceRef" but I'm following the precedent of "rust::Str". * It would be good to add constructors from std::span but as that's a C 20 feature, that may have to wait until C feature detection is resolved. * Internally, this follows the pattern of &str, where the parser will initially recognize this as Type::Ref (of Type::Slice) but then will replace that with Type::SliceRefU8. Type::Slice should not persist through later stages. As we later come to support other types of slice, we would probably want to remove Type::SliceRefU8.
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Thanks -- my work codebase just needed the same thing yesterday. Will review ASAP. In the meantime, it looks like the Bazel, Buck, and Windows builds are all failing with the same error: function tests$cxxbridge02$c_try_return_sliceu8: error: undefined reference to 'tests::c_try_return_sliceu8(rust::cxxbridge02::Slice<unsigned char>)Would you be able to take a look? |
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Yes, I'll take a look - but probably not for ~ 3 hours due to meetings. (My day job, sigh :) ) |
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for C feature detection, the following should work: #ifdef __has_include
#if __has_include(<version>)
#include <version>
#endif
#endif
#if __cpp_lib_span >= 202002L
#include <span>
void has_span(std::span<char>) {}
#endif |
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@programmerjake Thanks for that suggestion. There's some discussion on feature detection over here - #80 - which is why I didn't attempt to do it on this PR. |
dtolnay
approved these changes
Apr 14, 2020
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This change adds specifically, support for
&[u8]with a correspondingrust::Slice<uint8_t>type. No other types of slice are permitted. Therationale is that it may be common to pass binary data back and forth
across the FFI boundary, so it's more urgent to get this in place sooner.
Broader support for other slices can wait for the future.
But, both C and Rust-side bindings should allow the existing support
to be broadened to other Slice types in future without code changes.
A few specific notes:
rust::Slicemight be better asrust::SliceRefbut I'mfollowing the precedent of
rust::Str.std::spanbut as that'sa C 20 feature, that may have to wait until C feature detection
is resolved. Meanwhile,
rust::Slice<uint8_t>can be constructedfrom a raw pointer and a length.
&str, where the parser willinitially recognize this as
Type::Ref(ofType::Slice) but thenwill replace that with
Type::SliceRefU8. Type::Slice should notpersist through later stages. As we later come to support other
types of slice, we would probably want to remove
Type::SliceRefU8.