[PATCH 4/7] kernel-shark-qt: Add an example showing how to load trace data

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

This patch introduces a basic example, showing how to use the
C API of KernelShark and open a new session, load a trace data
file, produced by trace-cmd, print some data to the screen,
cleanup and then exit.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 kernel-shark-qt/CMakeLists.txt          |  1 +
 kernel-shark-qt/build/cmake_clean.sh    |  1 +
 kernel-shark-qt/examples/CMakeLists.txt |  5 ++
 kernel-shark-qt/examples/dataload.c     | 80 +++++++++++++++++++++++++
 4 files changed, 87 insertions(+)
 create mode 100644 kernel-shark-qt/examples/CMakeLists.txt
 create mode 100644 kernel-shark-qt/examples/dataload.c

diff --git a/kernel-shark-qt/CMakeLists.txt b/kernel-shark-qt/CMakeLists.txt
index 9929937..9ff12a1 100644
--- a/kernel-shark-qt/CMakeLists.txt
+++ b/kernel-shark-qt/CMakeLists.txt
@@ -33,6 +33,7 @@ message(STATUS "CXX flags    : " ${CMAKE_CXX_FLAGS})
 message(STATUS "Linker flags : " ${CMAKE_EXE_LINKER_FLAGS})
 
 add_subdirectory(${KS_DIR}/src)
+add_subdirectory(${KS_DIR}/examples)
 
 if (_DOXYGEN_DOC AND DOXYGEN_FOUND)
 
diff --git a/kernel-shark-qt/build/cmake_clean.sh b/kernel-shark-qt/build/cmake_clean.sh
index 57c40a4..acdbb43 100755
--- a/kernel-shark-qt/build/cmake_clean.sh
+++ b/kernel-shark-qt/build/cmake_clean.sh
@@ -4,6 +4,7 @@ rm cmake_install.cmake
 rm Makefile
 rm -rf CMakeFiles/
 rm -rf src/
+rm -rf examples/
 rm -f ../lib/*
 rm -f ../src/KsDeff.h
 rm -f CMakeDoxyfile.in
diff --git a/kernel-shark-qt/examples/CMakeLists.txt b/kernel-shark-qt/examples/CMakeLists.txt
new file mode 100644
index 0000000..98df9d8
--- /dev/null
+++ b/kernel-shark-qt/examples/CMakeLists.txt
@@ -0,0 +1,5 @@
+message("\n examples ...")
+
+message(STATUS "dataload")
+add_executable(dload          dataload.c)
+target_link_libraries(dload   kshark)
diff --git a/kernel-shark-qt/examples/dataload.c b/kernel-shark-qt/examples/dataload.c
new file mode 100644
index 0000000..a5c0ed3
--- /dev/null
+++ b/kernel-shark-qt/examples/dataload.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2018 VMware Inc, Yordan Karadzhov <y.karadz@gmail.com>
+ */
+
+// C
+#include <stdio.h>
+#include <stdlib.h>
+
+// KernelShark
+#include "libkshark.h"
+
+const char *default_file = "trace.dat";
+
+int main(int argc, char **argv)
+{
+	// Create a new kshark session.
+	struct kshark_context *kshark_ctx = NULL;
+	kshark_instance(&kshark_ctx);
+
+	// Open a trace data file produced by trace-cmd.
+	bool status;
+	if (argc > 1)
+		status = kshark_open(kshark_ctx, argv[1]);
+	else
+		status = kshark_open(kshark_ctx, default_file);
+
+	if (!status) {
+		kshark_free(kshark_ctx);
+		return 1;
+	}
+
+	// Load the content of the file into an array of entries.
+	struct kshark_entry **data = NULL;
+	size_t r, n_rows;
+	n_rows = kshark_load_data_entries(kshark_ctx, &data);
+
+	// Print to the screen the list of all tasks.
+	struct kshark_task_list* task = kshark_ctx->tasks;
+	while (task) {
+		const char *task_str = pevent_data_comm_from_pid(kshark_ctx->pevt,
+								 task->pid);
+		printf("task: %s-%i\n", task_str, task->pid);
+		task = task->next;
+	}
+
+	puts("\n\n");
+
+	// Print to the screen the first 10 entries.
+	char *entry_str;
+	for (r = 0; r < 10; ++r) {
+		entry_str = kshark_dump_entry(data[r]);
+		puts(entry_str);
+		free(entry_str);
+	}
+
+	puts("\n...\n");
+
+	// Print the last 10 entries.
+	for (r = n_rows - 10; r < n_rows; ++r) {
+		entry_str = kshark_dump_entry(data[r]);
+		puts(entry_str);
+		free(entry_str);
+	}
+
+	// Free the memory.
+	for (r = 0; r < n_rows; ++r)
+		free(data[r]);
+
+	free(data);
+
+	// Close the file.
+	kshark_close(kshark_ctx);
+
+	// Close the session.
+	kshark_free(kshark_ctx);
+
+	return 0;
+}
-- 
2.17.1