1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include <sys/time.h> 6 7 // Timer helper for fps. Returns seconds elapsed since first call to 8 // getseconds(), as a double. 9 static inline double getseconds() { 10 static int first_call = 1; 11 static struct timeval start_tv; 12 static int start_tv_retv; 13 const double usec_to_sec = 0.000001; 14 15 if (first_call) { 16 first_call = 0; 17 start_tv_retv = gettimeofday(&start_tv, NULL); 18 } 19 20 struct timeval tv; 21 if ((0 == start_tv_retv) && (0 == gettimeofday(&tv, NULL))) 22 return (tv.tv_sec - start_tv.tv_sec) + tv.tv_usec * usec_to_sec; 23 return 0.0; 24 } 25 26 struct FpsState { 27 double last_time; 28 int frame_count; 29 }; 30 31 /** 32 * Initialize the FpsState object. 33 */ 34 inline void FpsInit(struct FpsState* state) { 35 state->last_time = getseconds(); 36 state->frame_count = 0; 37 } 38 39 /** 40 * Call this whenever you render, after calling FpsInit above. 41 * 42 * Returns 1 if the value should be displayed. In this case, the result will 43 * be written to the |out_fps| parameter. 44 */ 45 inline int FpsStep(struct FpsState* state, double* out_fps) { 46 const double kFpsUpdateSecs = 1.0f; 47 double current_time = getseconds(); 48 49 state->frame_count++; 50 51 if (current_time < state->last_time + kFpsUpdateSecs) 52 return 0; 53 54 *out_fps = state->frame_count / (current_time - state->last_time); 55 state->last_time = current_time; 56 state->frame_count = 0; 57 return 1; 58 } 59
