c-ares / c-ares / 12341005525

91%

Build Type

push

github

Committed by web-flow

Commit Message

ares_buf: turn off buffering when loading a file (#939)

The commit is a small optimization in how a file is loaded into memory.

`FILE` buffering is just a libc (or user) provided buffer that
transparently reduces (typically) the number of system calls to I/O.
`fseek()` is not affected (not because `fseek()` will not perform I/O
but because it won't use that buffer, apart from potentially flushing
it).

In this case we predetermine the number of bytes to read (the entire
file) and then we load the entire file in one `fread()`, and in this
case buffering can only hurt: it results in multiple system `read()`
calls instead of a single `read()`, as well as copying each read byte
from the I/O buffer to the `fread()` buffer.

Furthermore, the `setvbuf()` call eagerly (before `fclose()`) releases
the buffer memory back to the system (at least `BUFSIZ` >= 256 bytes).
Releasing memory eagerly before performing I/O may be advantageous on a
low-memory system with slow I/O.

Signed-off-by: Nikolaos Chatzikonstantinou (@createyourpersonalaccount)

Run Details

1 of 1 new or added line in 1 file covered. (100.0%)

4 existing lines in 2 files now uncovered.

22200 of 24314 relevant lines covered (91.31%)

11885.66 hits per line