From dbae5c29917fec23ae75a34672d36eadef68e5a8 Mon Sep 17 00:00:00 2001
From: bugobliterator <siddharthbharatpurohit@gmail.com>
Date: Wed, 7 Jun 2023 19:59:25 +1000
Subject: [PATCH] add support for semaphores around allocate and freeing blocks
 of memory

---
 canard.c | 16 +++++++++++++++-
 canard.h | 12 ++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/canard.c b/canard.c
index c9f210b..3463a8d 100644
--- a/canard.c
+++ b/canard.c
@@ -1837,10 +1837,16 @@ CANARD_INTERNAL void initPoolAllocator(CanardPoolAllocator* allocator,
     allocator->statistics.capacity_blocks = buf_len;
     allocator->statistics.current_usage_blocks = 0;
     allocator->statistics.peak_usage_blocks = 0;
+    // user should initialize semaphore after the canardInit
+    // or at first call of canard_allocate_sem_take
+    allocator->semaphore = NULL;
 }
 
 CANARD_INTERNAL void* allocateBlock(CanardPoolAllocator* allocator)
 {
+#if CANARD_ALLOCATE_SEM
+    canard_allocate_sem_take(allocator);
+#endif
     // Check if there are any blocks available in the free list.
     if (allocator->free_list == NULL)
     {
@@ -1857,12 +1863,17 @@ CANARD_INTERNAL void* allocateBlock(CanardPoolAllocator* allocator)
     {
         allocator->statistics.peak_usage_blocks = allocator->statistics.current_usage_blocks;
     }
-
+#if CANARD_ALLOCATE_SEM
+    canard_allocate_sem_give(allocator);
+#endif
     return result;
 }
 
 CANARD_INTERNAL void freeBlock(CanardPoolAllocator* allocator, void* p)
 {
+#if CANARD_ALLOCATE_SEM
+    canard_allocate_sem_take(allocator);
+#endif
     CanardPoolAllocatorBlock* block = (CanardPoolAllocatorBlock*) p;
 
     block->next = allocator->free_list;
@@ -1870,4 +1881,7 @@ CANARD_INTERNAL void freeBlock(CanardPoolAllocator* allocator, void* p)
 
     CANARD_ASSERT(allocator->statistics.current_usage_blocks > 0);
     allocator->statistics.current_usage_blocks--;
+#if CANARD_ALLOCATE_SEM
+    canard_allocate_sem_give(allocator);
+#endif
 }
diff --git a/canard.h b/canard.h
index 676ecca..fa59694 100644
--- a/canard.h
+++ b/canard.h
@@ -90,6 +90,9 @@ extern "C" {
 # endif
 #endif
 
+#ifndef CANARD_ALLOCATE_SEM
+#define CANARD_ALLOCATE_SEM 0
+#endif
 /// Error code definitions; inverse of these values may be returned from API calls.
 #define CANARD_OK                                      0
 // Value 1 is omitted intentionally, since -1 is often used in 3rd party code
@@ -335,6 +338,9 @@ typedef struct CanardBufferBlock
  */
 typedef struct
 {
+    // user should initialize semaphore after the canardInit
+    // or at first call of canard_allocate_sem_take
+    void *semaphore;
     CanardPoolAllocatorBlock* free_list;
     CanardPoolAllocatorStatistics statistics;
     void *arena;
@@ -717,6 +723,12 @@ CANARD_STATIC_ASSERT(((uint32_t)CANARD_MULTIFRAME_RX_PAYLOAD_HEAD_SIZE) < 32,
                      "Please define CANARD_64_BIT=1 for 64 bit builds");
 #endif
 
+#if CANARD_ALLOCATE_SEM
+// user implemented functions for taking and freeing semaphores
+void canard_allocate_sem_take(CanardPoolAllocator *allocator);
+void canard_allocate_sem_give(CanardPoolAllocator *allocator);
+#endif
+
 #ifdef __cplusplus
 }
 #endif