RFC: Add limited read - #7945
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Which issue does this PR close?
Refs #7938.
Rationale for this change
A bounded read range is exact, so callers that only need up to a small number of bytes must stat the object first or handle a short object as an error. OpenDAL needs an at-most read for probes such as file header and format detection without an extra metadata request.
What changes are included in this PR?
This PR proposes
ReadOptions::limitandOperator::read_with(...).limit(n). The proposal keeps exact bounded range behavior, uses the existing rawopenandreadsplit, and carries only a privateexactboolean in core instead of adding a new raw operation or planning abstraction.Are there any user-facing changes?
Yes. The proposed API returns between zero and the configured limit on clean EOF. Existing reads that do not set
limitkeep their current behavior. This PR contains the RFC only; it does not implement the API.AI Usage Statement
This proposal was drafted with assistance from OpenAI Codex powered by GPT-5.