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Subject[PATCH V2 2/5] libperf: Add preadn()
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Add preadn() to provide pread() and readn() semantics.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---


Changes in V2:

Make preadn() thread-safe in case someone infers
from the name that it is.


tools/lib/perf/include/internal/lib.h | 2 ++
tools/lib/perf/lib.c | 20 ++++++++++++++++++++
2 files changed, 22 insertions(+)

diff --git a/tools/lib/perf/include/internal/lib.h b/tools/lib/perf/include/internal/lib.h
index 5175d491b2d49..85471a4b900f7 100644
--- a/tools/lib/perf/include/internal/lib.h
+++ b/tools/lib/perf/include/internal/lib.h
@@ -9,4 +9,6 @@ extern unsigned int page_size;
ssize_t readn(int fd, void *buf, size_t n);
ssize_t writen(int fd, const void *buf, size_t n);

+ssize_t preadn(int fd, void *buf, size_t n, off_t offs);
+
#endif /* __LIBPERF_INTERNAL_CPUMAP_H */
diff --git a/tools/lib/perf/lib.c b/tools/lib/perf/lib.c
index 18658931fc714..696fb0ea67c6e 100644
--- a/tools/lib/perf/lib.c
+++ b/tools/lib/perf/lib.c
@@ -38,6 +38,26 @@ ssize_t readn(int fd, void *buf, size_t n)
return ion(true, fd, buf, n);
}

+ssize_t preadn(int fd, void *buf, size_t n, off_t offs)
+{
+ size_t left = n;
+
+ while (left) {
+ ssize_t ret = pread(fd, buf, left, offs);
+
+ if (ret < 0 && errno == EINTR)
+ continue;
+ if (ret <= 0)
+ return ret;
+
+ left -= ret;
+ buf += ret;
+ offs += ret;
+ }
+
+ return n;
+}
+
/*
* Write exactly 'n' bytes or return an error.
*/
--
2.34.1
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