io: add Err field to LimitedReader #134
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Add an Err field to LimitedReader that allows callers to return a custom error when the read limit is exceeded, instead of always returning EOF. When Err is set to a non-nil, non-EOF value, and the limit is reached, LimitedReader.Read probes the underlying reader with a 1-byte read to distinguish two cases: stream had exactly N bytes (returns EOF), or stream has more data (returns the custom Err). The probe result is cached using negative N values to avoid repeated reads. When Err is nil or EOF, Read returns EOF, maintaining backward compatibility. Zero-length reads return (0, nil) without side effects. Fixes golang#51115
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Add an Err field to LimitedReader that allows callers to return a custom error when the read limit is exceeded, instead of always returning EOF.
When Err is set to a non-nil, non-EOF value, and the limit is reached, LimitedReader.Read probes the underlying reader with a 1-byte read to distinguish two cases: stream had exactly N bytes (returns EOF), or stream has more data (returns the custom Err). The probe result is cached using negative N values to avoid repeated reads.
When Err is nil or EOF, Read returns EOF, maintaining backward compatibility. Zero-length reads return (0, nil) without side effects.
Fixes golang#51115
🔄 This is a mirror of upstream PR golang#76156