libtf: Add model ops hash.

libtf.cc

@@ -9,6 +9,7 @@
 #include "tensorflow/lite/micro/cortex_m_generic/debug_log_callback.h"
 #include "tensorflow/lite/micro/examples/micro_speech/micro_features/micro_features_generator.h"
 #include "tensorflow/lite/micro/micro_interpreter.h"
+#include "tensorflow/lite/schema/schema_utils.h"
 
 #include "libtf.h"
 #define LIBTF_MAX_OPS 80
@@ -239,6 +240,19 @@ extern "C" {
         resolver.AddZerosLike();
     }
 
+    static uint32_t libtf_ops_hash(const tflite::Model *model) {
+        uint32_t hash = 5381;
+        const auto *subgraph = model->subgraphs()->Get(0);
+        for (size_t i = 0; i < subgraph->operators()->size(); i++) {
+            const auto *op = subgraph->operators()->Get(i);
+            uint32_t opcode = GetBuiltinCode(model->operator_codes()->Get(op->opcode_index()));
+            for (size_t x=0; x<4; x++) {
+                hash = ((hash << 5) + hash) + ((uint8_t*) &opcode)[x];
+            }
+        }
+        return hash;
+    }
+
     static int libtf_get_parameters(const unsigned char *model_data,
                                     unsigned char *tensor_arena, size_t tensor_arena_size,
                                     libtf_parameters_t *params,
@@ -265,6 +279,7 @@ extern "C" {
 
         tflite::MicroInterpreter interpreter(model, resolver, tensor_arena, tensor_arena_size, error_reporter);
         params->operators_size = interpreter.operators_size();
+        params->operators_hash = libtf_ops_hash(model);
 
         if (interpreter.AllocateTensors() != kTfLiteOk) {
             error_reporter->Report("AllocateTensors() failed!");

libtf.h

@@ -29,6 +29,7 @@ typedef struct libtf_parameters {
     float output_scale;
     int output_zero_point;
     size_t operators_size;
+    uint32_t operators_hash;
 } libtf_parameters_t;
 
 // Call this first to get the model parameters.