[PATCH v5 04/16] perf util: add const modifier to buf in "writen" function

David Carrillo-Cisneros
2017-07-11T23:56:27Z

Make buf in helper function "writen" constant to simplify
the life of its callers.

This requires to hack a cast of buf prior to passing it to "ion"
which is simpler than the alternative of reworking the "ion"
function to provide a read and a write paths, the latter with
constant buf argument.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
tools/perf/util/util.c | 6 ++++--
tools/perf/util/util.h | 2 +-
2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 28c9f335006c..0d8d7b8b2949 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -259,6 +259,7 @@ static ssize_t ion(bool is_read, int fd, void *buf, size_t n)
size_t left = n;

while (left) {
+ /* buf must be treated as const if !is_read. */
ssize_t ret = is_read ? read(fd, buf, left) :
write(fd, buf, left);

@@ -286,9 +287,10 @@ ssize_t readn(int fd, void *buf, size_t n)
/*
* Write exactly 'n' bytes or return an error.
*/
-ssize_t writen(int fd, void *buf, size_t n)
+ssize_t writen(int fd, const void *buf, size_t n)
{
- return ion(false, fd, buf, n);
+ /* ion does not modify buf. */
+ return ion(false, fd, (void *)buf, n);
}

size_t hex_width(u64 v)
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 5dfb9bb6482d..fc6555e48422 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -49,7 +49,7 @@ int copyfile_mode(const char *from, const char *to, mode_t mode);
int copyfile_offset(int fromfd, loff_t from_ofs, int tofd, loff_t to_ofs, u64 size);

ssize_t readn(int fd, void *buf, size_t n);
-ssize_t writen(int fd, void *buf, size_t n);
+ssize_t writen(int fd, const void *buf, size_t n);

size_t hex_width(u64 v);
int hex2u64(const char *ptr, u64 *val);
--
2.13.2.725.g09c95d1e9-goog