reftable/blocksource: adjust `read_block()` to return `ssize_t`

The `block_source_read_block()` function and its implementations return
an integer as a result that reflects either the number of bytes read, or
an error. As such its return type, a signed integer, isn't wrong, but it
doesn't give the reader a good hint what it actually returns.

Refactor the function to return an `ssize_t` instead, which is typical
for functions similar to read(3p) and should thus give readers a better
signal what they can expect as a result.

Adjust callers to better handle the returned value to avoid warnings
with -Wsign-compare. One of these callers is `reader_get_block()`, whose
return value is only ever used by its callers to figure out whether or
not the read was successful. So instead of bubbling up the `ssize_t`
there, too, we adapt it to only indicate success or errors.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/reftable/reader.h b/reftable/reader.h
index d2b48a4849..bb72108a6f 100644
--- a/reftable/reader.h
+++ b/reftable/reader.h
@@ -16,9 +16,9 @@ https://developers.google.com/open-source/licenses/bsd
 
 uint64_t block_source_size(struct reftable_block_source *source);
 
-int block_source_read_block(struct reftable_block_source *source,
-			    struct reftable_block *dest, uint64_t off,
-			    uint32_t size);
+ssize_t block_source_read_block(struct reftable_block_source *source,
+				struct reftable_block *dest, uint64_t off,
+				uint32_t size);
 void block_source_close(struct reftable_block_source *source);
 
 /* metadata for a block type */