[PATCH v2 05/10] trace-cmd library: New API to inherit parameters from an existing trace file

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

The new API initializes previously allocated output handler with
parameters from an input handler to a trace file.
 tracecmd_output_set_from_input()

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 .../include/private/trace-cmd-private.h       |  1 +
 lib/trace-cmd/trace-output.c                  | 33 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/lib/trace-cmd/include/private/trace-cmd-private.h b/lib/trace-cmd/include/private/trace-cmd-private.h
index 23e86107..41876195 100644
--- a/lib/trace-cmd/include/private/trace-cmd-private.h
+++ b/lib/trace-cmd/include/private/trace-cmd-private.h
@@ -274,6 +274,7 @@ int tracecmd_output_set_msg(struct tracecmd_output *handler,
 			    struct tracecmd_msg_handle *msg_handle);
 int tracecmd_output_set_trace_dir(struct tracecmd_output *handler, const char *tracing_dir);
 int tracecmd_output_set_kallsyms(struct tracecmd_output *handler, const char *kallsyms);
+int tracecmd_output_set_from_input(struct tracecmd_output *handler, struct tracecmd_input *ihandle);
 struct tracecmd_output *tracecmd_create_file_latency(const char *output_file, int cpus);
 struct tracecmd_output *
 tracecmd_create_init_file_glob(const char *output_file,
diff --git a/lib/trace-cmd/trace-output.c b/lib/trace-cmd/trace-output.c
index c654561a..7db3729b 100644
--- a/lib/trace-cmd/trace-output.c
+++ b/lib/trace-cmd/trace-output.c
@@ -996,6 +996,39 @@ int tracecmd_output_set_kallsyms(struct tracecmd_output *handler, const char *ka
 	return 0;
 }
 
+/**
+ * tracecmd_output_set_from_input - Inherit parameters from an existing trace file
+ * @handle: output handler to a trace file.
+ * @ihandle: input handler to an existing trace file.
+ *
+ * This API copies parameters from input handler @ihandle, associated with an existing trace file,
+ * to the output handler @handle, associated with file that is going to be created.
+ * These parameters are copied:
+ *  - tep handler
+ *  - page size
+ *  - file endian
+ *  - file version
+ *  - file compression protocol
+ * This API must be called before tracecmd_output_write_init().
+ *
+ * Returns 0 on success, or -1 if the output file handler is not allocated or not in expected state.
+ */
+int tracecmd_output_set_from_input(struct tracecmd_output *handler, struct tracecmd_input *ihandle)
+{
+	if (!handler || !ihandle || handler->file_state != TRACECMD_FILE_ALLOCATED)
+		return -1;
+
+	/* get endian, page size, file version and compression */
+	/* Use the pevent of the ihandle for later writes */
+	handler->pevent = tracecmd_get_tep(ihandle);
+	tep_ref(handler->pevent);
+	handler->page_size = tracecmd_page_size(ihandle);
+	handler->file_version = tracecmd_get_in_file_version(ihandle);
+	handler->big_endian = tep_is_file_bigendian(handler->pevent);
+
+	return 0;
+}
+
 static int select_file_version(struct tracecmd_output *handle,
 				struct tracecmd_input *ihandle)
 {
-- 
2.33.1