From 73e1855b9de7530980a393594230e35a8a9078d2 Mon Sep 17 00:00:00 2001
From: 0x1abin <0x1abin@gmail.com>
Date: Fri, 20 Aug 2021 16:02:46 +0800
Subject: [PATCH] Check if timer's expiry time is greater than time and care
 about uint32_t wraparounds.

---
 MultiTimer.c          | 13 +++++++++----
 MultiTimer.h          |  4 ++--
 examples/test_linux.c | 10 +++++-----
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/MultiTimer.c b/MultiTimer.c
index 75de835..99d1d37 100644
--- a/MultiTimer.c
+++ b/MultiTimer.c
@@ -1,10 +1,15 @@
 #include "MultiTimer.h"
 #include <stdio.h>
 
-// Timer handle list head.
+#define MULTIMER_MAX_TIMEOUT  0x7fffffff
+
+/* Check if timer's expiry time is greater than time and care about uint32_t wraparounds */
+#define CHECK_TIME_LESS_THAN(t, compare_to) ( (((uint32_t)((t)-(compare_to))) > MULTIMER_MAX_TIMEOUT) ? 1 : 0 )
+
+/* Timer handle list head. */
 static MultiTimer* timerList = NULL;
 
-// Timer tick
+/* Timer tick */
 static PlatformTicksFunction_t platformTicksFunction = NULL;
 
 int MultiTimerInstall(PlatformTicksFunction_t ticksFunc)
@@ -15,7 +20,7 @@ int MultiTimerInstall(PlatformTicksFunction_t ticksFunc)
 
 int MultiTimerStart(MultiTimer* timer, uint32_t timing, MultiTimerCallback_t callback, void* userData)
 {
-    if (!timer || !callback) {
+    if (!timer || !callback || timing > MULTIMER_MAX_TIMEOUT) {
         return -1;
     }
     MultiTimer** nextTimer = &timerList;
@@ -68,7 +73,7 @@ int MultiTimerYield(void)
     for (; *nextTimer; nextTimer = &(*nextTimer)->next) {
         MultiTimer* entry = *nextTimer;
         /* Sorted list, just process with the front part. */
-        if (entry->deadline > platformTicksFunction()) {
+        if (CHECK_TIME_LESS_THAN(platformTicksFunction(), entry->deadline)) {
             return (int)(entry->deadline - platformTicksFunction());
         }
         /* remove expired timer from list */
diff --git a/MultiTimer.h b/MultiTimer.h
index 60eb45f..23926ef 100644
--- a/MultiTimer.h
+++ b/MultiTimer.h
@@ -7,7 +7,7 @@
 extern "C" {  
 #endif
 
-typedef uint64_t (*PlatformTicksFunction_t)(void);
+typedef uint32_t (*PlatformTicksFunction_t)(void);
 
 typedef struct MultiTimerHandle MultiTimer;
 
@@ -15,7 +15,7 @@ typedef void (*MultiTimerCallback_t)(MultiTimer* timer, void* userData);
 
 struct MultiTimerHandle {
     MultiTimer* next;
-    uint64_t deadline;
+    uint32_t deadline;
     MultiTimerCallback_t callback;
     void* userData;
 };
diff --git a/examples/test_linux.c b/examples/test_linux.c
index 30ff5ad..d945b34 100755
--- a/examples/test_linux.c
+++ b/examples/test_linux.c
@@ -7,27 +7,27 @@ MultiTimer timer1;
 MultiTimer timer2;
 MultiTimer timer3;
 
-uint64_t PlatformTicksGetFunc(void)
+uint32_t PlatformTicksGetFunc(void)
 {
     struct timespec current_time;
     clock_gettime(CLOCK_MONOTONIC, &current_time);
-    return (uint64_t)((current_time.tv_sec * 1000) + (current_time.tv_nsec / 1000000));
+    return (uint32_t)((current_time.tv_sec * 1000) + (current_time.tv_nsec / 1000000));
 }
 
 void exampleTimer1Callback(MultiTimer* timer, void *userData)
 {
-    printf("[T:%012ld] Timer:%p callback-> %s.\r\n", PlatformTicksGetFunc(), timer, (char*)userData);
+    printf("[T:%010d] Timer:%p callback-> %s.\r\n", PlatformTicksGetFunc(), timer, (char*)userData);
     MultiTimerStart(timer, 1000, exampleTimer1Callback, userData);
 }
 
 void exampleTimer2Callback(MultiTimer* timer, void *userData)
 {
-    printf("[T:%012ld] Timer:%p callback-> %s.\r\n", PlatformTicksGetFunc(), timer, (char*)userData);
+    printf("[T:%010d] Timer:%p callback-> %s.\r\n", PlatformTicksGetFunc(), timer, (char*)userData);
 }
 
 void exampleTimer3Callback(MultiTimer* timer, void *userData)
 {
-    printf("[T:%012ld] Timer:%p callback-> %s.\r\n", PlatformTicksGetFunc(), timer, (char*)userData);
+    printf("[T:%010d] Timer:%p callback-> %s.\r\n", PlatformTicksGetFunc(), timer, (char*)userData);
     MultiTimerStart(timer, 4567, exampleTimer3Callback, userData);
 }