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Implement size_hint for BufReader #81052
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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @dtolnay (or someone else) soon. If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes. Please see the contribution instructions for more information. |
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I am confused about this error:
Does anyone understand why it won't compile? The compiler says here that it allows specializing on explicitly marked traits with no associated items. Is that what is happening? |
That's part of the restrictions on min_specialization since full specialization is not ready for dogfooding yet. You might (i'm not sure!) be able to work around this by creating a private helper trait to which |
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Honestly, I am debating whether this would be worth including now or I should just wait until full specialization is available. The original implementation was so nice and required no dynamic dispatch. It might make more sense to just wait for full specialization so that it can be implemented with a simple:
Is there a way to conditionally compile this extension only on nightly branches with the |
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It's a shame that you need to call Sorry for the many pushes, fmt locally was causing issues when it was on. |
…ramertj Improved IO Bytes Size Hint After trying to implement better `size_hint()` return values for `File` in [this PR](rust-lang#81044) and changing to implementing it for `BufReader` in [this PR](rust-lang#81052), I have arrived at this implementation that provides tighter bounds for the `Bytes` iterator of various readers including `BufReader`, `Empty`, and `Chain`. Unfortunately, for `BufReader`, the size_hint only improves after calling `fill_buffer` due to it using the contents of the buffer for the hint. Nevertheless, the the tighter bounds should result in better pre-allocation of space to handle the contents of the `Bytes` iterator. Closes rust-lang#81052
…ramertj Improved IO Bytes Size Hint After trying to implement better `size_hint()` return values for `File` in [this PR](rust-lang#81044) and changing to implementing it for `BufReader` in [this PR](rust-lang#81052), I have arrived at this implementation that provides tighter bounds for the `Bytes` iterator of various readers including `BufReader`, `Empty`, and `Chain`. Unfortunately, for `BufReader`, the size_hint only improves after calling `fill_buffer` due to it using the contents of the buffer for the hint. Nevertheless, the the tighter bounds should result in better pre-allocation of space to handle the contents of the `Bytes` iterator. Closes rust-lang#81052
…ramertj Improved IO Bytes Size Hint After trying to implement better `size_hint()` return values for `File` in [this PR](rust-lang#81044) and changing to implementing it for `BufReader` in [this PR](rust-lang#81052), I have arrived at this implementation that provides tighter bounds for the `Bytes` iterator of various readers including `BufReader`, `Empty`, and `Chain`. Unfortunately, for `BufReader`, the size_hint only improves after calling `fill_buffer` due to it using the contents of the buffer for the hint. Nevertheless, the the tighter bounds should result in better pre-allocation of space to handle the contents of the `Bytes` iterator. Closes rust-lang#81052
…ramertj Improved IO Bytes Size Hint After trying to implement better `size_hint()` return values for `File` in [this PR](rust-lang#81044) and changing to implementing it for `BufReader` in [this PR](rust-lang#81052), I have arrived at this implementation that provides tighter bounds for the `Bytes` iterator of various readers including `BufReader`, `Empty`, and `Chain`. Unfortunately, for `BufReader`, the size_hint only improves after calling `fill_buffer` due to it using the contents of the buffer for the hint. Nevertheless, the the tighter bounds should result in better pre-allocation of space to handle the contents of the `Bytes` iterator. Closes rust-lang#81052
…ramertj Improved IO Bytes Size Hint After trying to implement better `size_hint()` return values for `File` in [this PR](rust-lang#81044) and changing to implementing it for `BufReader` in [this PR](rust-lang#81052), I have arrived at this implementation that provides tighter bounds for the `Bytes` iterator of various readers including `BufReader`, `Empty`, and `Chain`. Unfortunately, for `BufReader`, the size_hint only improves after calling `fill_buffer` due to it using the contents of the buffer for the hint. Nevertheless, the the tighter bounds should result in better pre-allocation of space to handle the contents of the `Bytes` iterator. Closes rust-lang#81052
…ramertj Improved IO Bytes Size Hint After trying to implement better `size_hint()` return values for `File` in [this PR](rust-lang#81044) and changing to implementing it for `BufReader` in [this PR](rust-lang#81052), I have arrived at this implementation that provides tighter bounds for the `Bytes` iterator of various readers including `BufReader`, `Empty`, and `Chain`. Unfortunately, for `BufReader`, the size_hint only improves after calling `fill_buffer` due to it using the contents of the buffer for the hint. Nevertheless, the the tighter bounds should result in better pre-allocation of space to handle the contents of the `Bytes` iterator. Closes rust-lang#81052
After trying to implement better
size_hint()
return values forFile
in this PR, it was recommended that I implement this instead. Due to buffering, theIterator
Bytes
is guaranteed to produce at least as manyu8
s as are currently in the buffer. This allows thesize_hint()
to provide a tighter lower bound than the default of0
.