libperf: Add preadn()

Add preadn() to provide pread() and readn() semantics.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/ab8918a4-7ac8-a37e-2e2c-28438c422d87@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/perf/include/internal/lib.h b/tools/lib/perf/include/internal/lib.h
index 5175d49..85471a4 100644 (file)
--- 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 1865893..696fb0e 100644 (file)
--- 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.
  */