perf tools: Add gzip_is_compressed function

Add implementation of the is_compressed callback for gzip.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180817094813.15086-13-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/zlib.c b/tools/perf/util/zlib.c
index e683172..902ce63 100644 (file)
--- a/tools/perf/util/zlib.c
+++ b/tools/perf/util/zlib.c
@@ -6,6 +6,7 @@
 #include <sys/mman.h>
 #include <zlib.h>
 #include <linux/compiler.h>
+#include <unistd.h>
 
 #include "util/compress.h"
 #include "util/util.h"
@@ -81,7 +82,18 @@ out_close:
        return ret == Z_STREAM_END ? 0 : -1;
 }
 
-bool gzip_is_compressed(const char *input __maybe_unused)
+bool gzip_is_compressed(const char *input)
 {
-       return true;
+       int fd = open(input, O_RDONLY);
+       const uint8_t magic[2] = { 0x1f, 0x8b };
+       char buf[2] = { 0 };
+       ssize_t rc;
+
+       if (fd < 0)
+               return -1;
+
+       rc = read(fd, buf, sizeof(buf));
+       close(fd);
+       return rc == sizeof(buf) ?
+              memcmp(buf, magic, sizeof(buf)) == 0 : false;
 }