Clarify BufRead::fill_buf doesn't consume data #150584
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The previous documentation said 'via Read methods' which incorrectly implied that fill_buf consumes the data. This restores the historical clarification that read() can return the same contents as fill_buf, and emphasizes the relationship with consume(). This addresses the concerns raised in the issue where implementations like BufReader and Cursor do not actually consume data when fill_buf is called - subsequent read() calls can still read the same bytes until consume() is explicitly called.
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r? @ChrisDenton rustbot has assigned @ChrisDenton. Use |
ChrisDenton
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Jan 8, 2026
| /// Returns the contents of the internal buffer, filling it with more data from the underlying reader if it is empty. | ||
| /// | ||
| /// This function will not read data into the buffer if some is already present. | ||
| /// When calling this method, none of the contents will be "read" in the sense that later |
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Perhaps this could use the same phrasing as used for consume below? So something like:
When calling this method, none of the contents will be marked as "read"...
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Issue #149000
The previous documentation said 'via Read methods' which incorrectly implied that fill_buf consumes the data. This restores the historical clarification that read() can return the same contents as fill_buf, and emphasizes the relationship with consume().
This addresses the concerns raised in the issue where implementations like BufReader and Cursor do not actually consume data when fill_buf is called - subsequent read() calls can still read the same bytes until consume() is explicitly called.