perf tools: Fine tune readn function
Added a 'left' variable to make the flow clearer, and added a debug
check for the return value - returning 'n' is more obvious.
Added small comment for readn.
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Original-patch-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1385634619-8129-4-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 9440481..6ea0b4a 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -6,6 +6,7 @@
#endif
#include <stdio.h>
#include <stdlib.h>
+#include <linux/kernel.h>
/*
* XXX We need to find a better place for these things...
@@ -151,21 +152,26 @@
return value;
}
+/*
+ * Read exactly 'n' bytes or return an error.
+ */
ssize_t readn(int fd, void *buf, size_t n)
{
void *buf_start = buf;
+ size_t left = n;
- while (n) {
- ssize_t ret = read(fd, buf, n);
+ while (left) {
+ ssize_t ret = read(fd, buf, left);
if (ret <= 0)
return ret;
- n -= ret;
- buf += ret;
+ left -= ret;
+ buf += ret;
}
- return buf - buf_start;
+ BUG_ON((size_t)(buf - buf_start) != n);
+ return n;
}
size_t hex_width(u64 v)