perf tools: Add perf_data_file__open interface to data object

Adding perf_data_file__open interface to data object to open the
perf.data file for both read and write.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1381847254-28809-3-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/data.c

@@ -0,0 +1,120 @@
+#include <linux/compiler.h>
+#include <linux/kernel.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "data.h"
+#include "util.h"
+
+static bool check_pipe(struct perf_data_file *file)
+{
+	struct stat st;
+	bool is_pipe = false;
+	int fd = perf_data_file__is_read(file) ?
+		 STDIN_FILENO : STDOUT_FILENO;
+
+	if (!file->path) {
+		if (!fstat(fd, &st) && S_ISFIFO(st.st_mode))
+			is_pipe = true;
+	} else {
+		if (!strcmp(file->path, "-"))
+			is_pipe = true;
+	}
+
+	if (is_pipe)
+		file->fd = fd;
+
+	return file->is_pipe = is_pipe;
+}
+
+static int check_backup(struct perf_data_file *file)
+{
+	struct stat st;
+
+	if (!stat(file->path, &st) && st.st_size) {
+		/* TODO check errors properly */
+		char oldname[PATH_MAX];
+		snprintf(oldname, sizeof(oldname), "%s.old",
+			 file->path);
+		unlink(oldname);
+		rename(file->path, oldname);
+	}
+
+	return 0;
+}
+
+static int open_file_read(struct perf_data_file *file)
+{
+	struct stat st;
+	int fd;
+
+	fd = open(file->path, O_RDONLY);
+	if (fd < 0) {
+		int err = errno;
+
+		pr_err("failed to open %s: %s", file->path, strerror(err));
+		if (err == ENOENT && !strcmp(file->path, "perf.data"))
+			pr_err("  (try 'perf record' first)");
+		pr_err("\n");
+		return -err;
+	}
+
+	if (fstat(fd, &st) < 0)
+		goto out_close;
+
+	if (!file->force && st.st_uid && (st.st_uid != geteuid())) {
+		pr_err("file %s not owned by current user or root\n",
+		       file->path);
+		goto out_close;
+	}
+
+	if (!st.st_size) {
+		pr_info("zero-sized file (%s), nothing to do!\n",
+			file->path);
+		goto out_close;
+	}
+
+	file->size = st.st_size;
+	return fd;
+
+ out_close:
+	close(fd);
+	return -1;
+}
+
+static int open_file_write(struct perf_data_file *file)
+{
+	if (check_backup(file))
+		return -1;
+
+	return open(file->path, O_CREAT|O_RDWR|O_TRUNC, S_IRUSR|S_IWUSR);
+}
+
+static int open_file(struct perf_data_file *file)
+{
+	int fd;
+
+	fd = perf_data_file__is_read(file) ?
+	     open_file_read(file) : open_file_write(file);
+
+	file->fd = fd;
+	return fd < 0 ? -1 : 0;
+}
+
+int perf_data_file__open(struct perf_data_file *file)
+{
+	if (check_pipe(file))
+		return 0;
+
+	if (!file->path)
+		file->path = "perf.data";
+
+	return open_file(file);
+}
+
+void perf_data_file__close(struct perf_data_file *file)
+{
+	close(file->fd);
+}