diff --git a/src/rvprof_internal.h b/src/rvprof_internal.h
index 7681045..c8457ff 100644
--- a/src/rvprof_internal.h
+++ b/src/rvprof_internal.h
@@ -52,6 +52,24 @@ typedef struct {
     void* func_addr;
 } region_t;
 
+// function stats
+typedef struct {
+    char name [MAX_NAME_LEN];
+    char caller [MAX_NAME_LEN];
+    uint64_t total_inclusive_time;
+    uint64_t total_exclusive_time;
+    uint64_t total_inclusive_cycles;
+    uint64_t total_exclusive_cycles;
+    uint64_t call_count;
+    int* stack_ids;
+    int num_stack_ids;
+    int max_stack_ids;
+    char** callers;
+    int num_callers;
+    int max_callers;
+    double exclusive_percent;
+    double inclusive_percent;
+} function_stats_t;
 
 #ifdef __cplusplus
 }