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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>
This commit is contained in:
Adrian Hunter 2022-05-20 18:56:04 +03:00 committed by Arnaldo Carvalho de Melo
parent 237c96b8c1
commit 618ee7838e
2 changed files with 22 additions and 0 deletions
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2
tools/lib/perf/include/internal/lib.h
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@ -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 */

20
tools/lib/perf/lib.c
View File

@ -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.
*/