12 files changed, 74 insertions, 72 deletions

diff --git a/cstring/src/cstring.c b/cstring/src/cstring.c
index e308589..100c130 100644
--- a/cstring/src/cstring.c
+++ b/cstring/src/cstring.c
@@ -23,7 +23,7 @@ string string_new(const char* cstr) {
 void string_del(string* str) {
   if (str->data) {
     free((void*)str->data);
-    str->data   = 0;
+    str->data   = nullptr;
     str->length = 0;
   }
 }
diff --git a/filesystem/src/filesystem.c b/filesystem/src/filesystem.c
index b228e85..b0c207a 100644
--- a/filesystem/src/filesystem.c
+++ b/filesystem/src/filesystem.c
@@ -27,11 +27,11 @@ size_t get_file_size(FILE* file) {
 void* read_file(const char* filepath) {
   assert(filepath);
 
-  void* data = 0;
+  void* data = nullptr;
 
   FILE* file = fopen(filepath, "rb");
   if (!file) {
-    return 0;
+    return nullptr;
   }
   const size_t file_size = get_file_size(file);
   if (file_size == (size_t)-1) {
@@ -53,5 +53,5 @@ cleanup:
   if (data) {
     free(data);
   }
-  return 0;
+  return nullptr;
 }
diff --git a/filesystem/src/path.c b/filesystem/src/path.c
index 2ce5a04..544a5d1 100644
--- a/filesystem/src/path.c
+++ b/filesystem/src/path.c
@@ -21,7 +21,7 @@ path path_new(const char* str) {
 void path_del(path* path) {
   if (path) {
     free(path->data);
-    path->data = 0;
+    path->data = nullptr;
     path->size = 0;
   }
 }
diff --git a/list/include/list.h b/list/include/list.h
index 24291e1..aadcb88 100644
--- a/list/include/list.h
+++ b/list/include/list.h
@@ -23,7 +23,7 @@ static inline void* alloc(size_t size) {
 
 /// Create a new empty list.
 #define make_list(type) \
-  (type##_list) { 0 }
+  (type##_list) { nullptr }
 
 /// Delete the list.
 #define del_list(list)                                  \
@@ -32,7 +32,7 @@ static inline void* alloc(size_t size) {
     node                 = node->next;                  \
     free(cur);                                          \
   }                                                     \
-  list.head = 0;
+  list.head = nullptr;
 
 /// Prepend a value to the list.
 #define list_add(list, value)                               \
@@ -76,10 +76,10 @@ static inline void* alloc(size_t size) {
       node->next->prev = node->prev; \
     }                                \
     if (list.head == node) {         \
-      list.head = 0;                 \
+      list.head = nullptr;           \
     }                                \
     free(node);                      \
-    node = 0;                        \
+    node = nullptr;                  \
   }
 
 /// Iterate over all the items in the list.
diff --git a/list/test/list_test.c b/list/test/list_test.c
index 418e156..4ac5b5b 100644
--- a/list/test/list_test.c
+++ b/list/test/list_test.c
@@ -52,7 +52,7 @@ TEST_CASE(list_remove_by_value) {
 TEST_CASE(list_remove_by_address) {
   const int N = 3;
 
-  int* ptrs[3] = {0};
+  int* ptrs[3] = {nullptr};
 
   int_list list = make_list(int);
   for (int i = 0; i < N; ++i) {
diff --git a/mem/src/mem.c b/mem/src/mem.c
index 4f5e5ef..9169a9f 100644
--- a/mem/src/mem.c
+++ b/mem/src/mem.c
@@ -46,17 +46,18 @@ void mem_del_(Memory* mem) {
   if (mem->dynamic) {
     if (mem->chunks) {
       free(mem->chunks);
-      mem->chunks = 0;
+      mem->chunks = nullptr;
     }
     if (mem->blocks) {
       free(mem->blocks);
-      mem->blocks = 0;
+      mem->blocks = nullptr;
     }
   }
 }
 
 void mem_clear_(Memory* mem) {
   assert(mem);
+  mem->num_used_blocks = 0;
   mem->next_free_chunk = 0;
   memset(mem->blocks, 0, mem->num_blocks * mem->block_size_bytes);
   memset(mem->chunks, 0, mem->num_blocks * sizeof(Chunk));
@@ -113,10 +114,11 @@ void* mem_alloc_(Memory* mem, size_t num_blocks) {
     return &mem->blocks[chunk_idx * mem->block_size_bytes];
   } else {
     if (mem->trap) {
-      FAIL("Memory allocation failed, increase the allocator's capacity or "
-           "avoid fragmentation.");
+      FAIL(
+          "Memory allocation failed, increase the allocator's capacity or "
+          "avoid fragmentation.");
     }
-    return 0; // Large-enough free chunk not found.
+    return nullptr; // Large-enough free chunk not found.
   }
 }
 
@@ -172,7 +174,7 @@ void mem_free_(Memory* mem, void** chunk_ptr) {
 
   mem->num_used_blocks--;
 
-  *chunk_ptr = 0;
+  *chunk_ptr = nullptr;
 }
 
 // The handle is the chunk's index. We don't call it an index in the public API
diff --git a/mem/test/mem_test.c b/mem/test/mem_test.c
index 14718a5..a8d482f 100644
--- a/mem/test/mem_test.c
+++ b/mem/test/mem_test.c
@@ -39,7 +39,7 @@ TEST_CASE(mem_fully_allocate) {
 
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     const int* block = mem_alloc(&mem, 1);
-    TEST_TRUE(block != 0);
+    TEST_TRUE(block != nullptr);
   }
 
   TEST_TRUE(mem_size(&mem) == NUM_BLOCKS);
@@ -50,15 +50,15 @@ TEST_CASE(mem_fill_then_free) {
   test_mem mem;
   mem_make(&mem);
 
-  int* blocks[NUM_BLOCKS] = {0};
+  int* blocks[NUM_BLOCKS] = {nullptr};
   for (int i = 0; i < NUM_BLOCKS; i++) {
     blocks[i] = mem_alloc(&mem, 1);
-    TEST_TRUE(blocks[i] != 0);
+    TEST_TRUE(blocks[i] != nullptr);
   }
 
   for (int i = 0; i < NUM_BLOCKS; i++) {
     mem_free(&mem, &blocks[i]);
-    TEST_EQUAL(blocks[i], 0); // Pointer should be set to 0 on free.
+    TEST_EQUAL(blocks[i], nullptr); // Pointer should be set to 0 on free.
   }
 
   TEST_EQUAL(count(&mem), 0);
@@ -74,12 +74,12 @@ TEST_CASE(mem_allocate_beyond_max_size) {
 
   // Fully allocate the mem.
   for (int i = 0; i < NUM_BLOCKS; ++i) {
-    TEST_TRUE(mem_alloc(&mem, 1) != 0);
+    TEST_TRUE(mem_alloc(&mem, 1) != nullptr);
   }
 
   // Past the end.
   for (int i = 0; i < NUM_BLOCKS; ++i) {
-    TEST_EQUAL(mem_alloc(&mem, 1), 0);
+    TEST_EQUAL(mem_alloc(&mem, 1), nullptr);
   }
 
   TEST_TRUE(mem_size(&mem) == NUM_BLOCKS);
@@ -105,7 +105,7 @@ TEST_CASE(mem_zero_free_block_after_free) {
   mem_make(&mem);
 
   int* val = mem_alloc(&mem, 1);
-  TEST_TRUE(val != 0);
+  TEST_TRUE(val != nullptr);
   *val = 177;
 
   int* old_val = val;
@@ -131,7 +131,7 @@ TEST_CASE(mem_traverse_partially_full) {
 
   for (int i = 0; i < N; ++i) {
     int* val = mem_alloc(&mem, 1);
-    TEST_TRUE(val != 0);
+    TEST_TRUE(val != nullptr);
     *val = i + 1;
   }
 
@@ -146,7 +146,7 @@ TEST_CASE(mem_traverse_full) {
 
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     int* val = mem_alloc(&mem, 1);
-    TEST_TRUE(val != 0);
+    TEST_TRUE(val != nullptr);
     *val = i + 1;
   }
 
@@ -161,7 +161,7 @@ TEST_CASE(mem_get_block) {
 
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     int* block = mem_alloc(&mem, 1);
-    TEST_TRUE(block != 0);
+    TEST_TRUE(block != nullptr);
     *block = i;
     TEST_EQUAL(mem_get_chunk_handle(&mem, block), (size_t)i);
   }
@@ -179,7 +179,7 @@ TEST_CASE(mem_fragmentation) {
   test_mem mem;
   mem_make(&mem);
 
-  int* blocks[NUM_BLOCKS] = {0};
+  int* blocks[NUM_BLOCKS] = {nullptr};
   int  next_block         = 0;
 
 #define ALLOC(num_blocks)                           \
@@ -205,7 +205,7 @@ TEST_CASE(mem_fragmentation) {
 
   // Should be able to allocate 1 chunk of N blocks.
   const void* chunk = mem_alloc(&mem, NUM_BLOCKS);
-  TEST_TRUE(chunk != 0);
+  TEST_TRUE(chunk != nullptr);
 }
 
 // Clear and re-use an allocator.
@@ -216,15 +216,17 @@ TEST_CASE(mem_clear_then_reuse) {
   // Allocate chunks, contents not important.
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     int* chunk = mem_alloc(&mem, 1);
-    TEST_TRUE(chunk != 0);
+    TEST_TRUE(chunk != nullptr);
   }
 
   mem_clear(&mem);
+  TEST_EQUAL(mem_size(&mem), 0);
+  TEST_EQUAL(mem_capacity(&mem), NUM_BLOCKS);
 
   // Allocate chunks and assign values 0..N.
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     int* chunk = mem_alloc(&mem, 1);
-    TEST_TRUE(chunk != 0);
+    TEST_TRUE(chunk != nullptr);
     *chunk = i + 1;
   }
 
diff --git a/mempool/README.md b/mempool/README.md
index ed2935e..7eb950e 100644
--- a/mempool/README.md
+++ b/mempool/README.md
@@ -1,20 +1,15 @@
 # Mempool
 
-A memory pool implementation.
+A memory pool of fixed-sized blocks with O(1) allocation and deallocation.
 
 Each block in the pool is tagged with a boolean value that indicates whether the
-block is free or in use. The allocator otherwise maintains little additional
-information. Therefore, some operations have linear-time complexity.
-Specifically:
+block is free or in use, as well as a pointer to the next free/used block.
+Blocks thus form two lists, a free list and a used list. The allocator
+maintains the two lists when allocating/deallocating blocks.
 
-- Allocating a block scans the pool for the next free block in linear time.
-- Freeing a block runs in constant time.
-- Iterating over the pool's used blocks is linear over the number of blocks in
-  the pool, as opposed to just the number of used blocks.
+The allocator's internal data is stored separately from the block data so that
+the data remains tightly packed.
 
-The allocator's internal data is also stored separately from the main array of
-blocks so that the block data remains tightly packed.
-
-For convenience of programming and debugging, free blocks in the mempool always
-remain zeroed out. If your data structures are valid when zeroed out, then you
-do not need to explicitly initialize them.
+Free blocks in the mempool always remain zeroed out for convenience of
+programming and debugging. If the application's data structures are valid when
+zeroed out, then they do not need to be explicitly initialized.
diff --git a/mempool/include/mempool.h b/mempool/include/mempool.h
index 245173b..04d0313 100644
--- a/mempool/include/mempool.h
+++ b/mempool/include/mempool.h
@@ -106,8 +106,8 @@
 /// It is valid to mempool_free() the object at each step of the iteration.
 #define mempool_foreach(POOL, ITER, BODY)                                  \
   {                                                                        \
-    size_t i = (POOL)->pool.used;                                          \
     if ((POOL)->pool.num_used_blocks > 0) {                                \
+      size_t i = (POOL)->pool.used;                                        \
       do {                                                                 \
         if ((POOL)->pool.block_info[i].used) {                             \
           __typeof__((POOL)->object[0])* ITER =                            \
diff --git a/mempool/src/mempool.c b/mempool/src/mempool.c
index 46f1053..c398c4f 100644
--- a/mempool/src/mempool.c
+++ b/mempool/src/mempool.c
@@ -34,7 +34,7 @@ bool mempool_make_(
     block_info    = calloc(num_blocks, sizeof(BlockInfo));
     blocks        = calloc(num_blocks, block_size_bytes);
     pool->dynamic = true;
-    if ((block_info == 0) || (blocks == 0)) {
+    if ((block_info == nullptr) || (blocks == nullptr)) {
       return false;
     }
   } else {
@@ -55,19 +55,20 @@ void mempool_del_(mempool* pool) {
   if (pool->dynamic) {
     if (pool->block_info) {
       free(pool->block_info);
-      pool->block_info = 0;
+      pool->block_info = nullptr;
     }
     if (pool->blocks) {
       free(pool->blocks);
-      pool->blocks = 0;
+      pool->blocks = nullptr;
     }
   }
 }
 
 void mempool_clear_(mempool* pool) {
   assert(pool);
-  pool->head = 0;
-  pool->used = 0;
+  pool->head            = 0;
+  pool->used            = 0;
+  pool->num_used_blocks = 0;
   memset(pool->blocks, 0, pool->num_blocks * pool->block_size_bytes);
   memset(pool->block_info, 0, pool->num_blocks * sizeof(BlockInfo));
   init_free_list(pool);
@@ -81,7 +82,7 @@ void* mempool_alloc_(mempool* pool) {
     if (pool->trap) {
       FAIL("mempool allocation failed, increase the pool's capacity.");
     }
-    return 0; // Pool is full.
+    return nullptr; // Pool is full.
   }
 
   // Allocate the block.
@@ -124,7 +125,7 @@ void mempool_free_(mempool* pool, void** block_ptr) {
 
   pool->num_used_blocks--;
 
-  *block_ptr = 0;
+  *block_ptr = nullptr;
 }
 
 void* mempool_get_block_(const mempool* pool, size_t block_index) {
diff --git a/mempool/test/mempool_test.c b/mempool/test/mempool_test.c
index 843f7e7..6d904bc 100644
--- a/mempool/test/mempool_test.c
+++ b/mempool/test/mempool_test.c
@@ -39,7 +39,7 @@ TEST_CASE(mempool_allocate_until_full) {
 
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     const int* block = mempool_alloc(&pool);
-    TEST_TRUE(block != 0);
+    TEST_TRUE(block != nullptr);
   }
 
   TEST_TRUE(mempool_size(&pool) == NUM_BLOCKS);
@@ -50,10 +50,10 @@ TEST_CASE(mempool_fill_then_free) {
   test_pool pool;
   mempool_make(&pool);
 
-  int* blocks[NUM_BLOCKS] = {0};
+  int* blocks[NUM_BLOCKS] = {nullptr};
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     blocks[i] = mempool_alloc(&pool);
-    TEST_TRUE(blocks[i] != 0);
+    TEST_TRUE(blocks[i] != nullptr);
   }
 
   for (int i = 0; i < NUM_BLOCKS; ++i) {
@@ -74,7 +74,7 @@ TEST_CASE(mempool_allocate_beyond_max_size) {
 
   // Fully allocate the pool.
   for (int i = 0; i < NUM_BLOCKS; ++i) {
-    TEST_TRUE(mempool_alloc(&pool) != 0);
+    TEST_TRUE(mempool_alloc(&pool) != nullptr);
   }
 
   // Past the end.
@@ -105,7 +105,7 @@ TEST_CASE(mempool_zero_free_block_after_free) {
   mempool_make(&pool);
 
   int* val = mempool_alloc(&pool);
-  TEST_TRUE(val != 0);
+  TEST_TRUE(val != nullptr);
   *val = 177;
 
   int* old_val = val;
@@ -131,7 +131,7 @@ TEST_CASE(mempool_traverse_partially_full) {
 
   for (int i = 0; i < N; ++i) {
     int* val = mempool_alloc(&pool);
-    TEST_TRUE(val != 0);
+    TEST_TRUE(val != nullptr);
     *val = i + 1;
   }
 
@@ -146,7 +146,7 @@ TEST_CASE(mempool_traverse_full) {
 
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     int* val = mempool_alloc(&pool);
-    TEST_TRUE(val != 0);
+    TEST_TRUE(val != nullptr);
     *val = i + 1;
   }
 
@@ -161,7 +161,7 @@ TEST_CASE(mempool_get_block) {
 
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     int* block = mempool_alloc(&pool);
-    TEST_TRUE(block != 0);
+    TEST_TRUE(block != nullptr);
     *block = i;
     TEST_EQUAL(mempool_get_block_index(&pool, block), (size_t)i);
   }
@@ -178,16 +178,18 @@ TEST_CASE(mem_clear_then_reuse) {
 
   // Allocate chunks, contents not important.
   for (int i = 0; i < NUM_BLOCKS; ++i) {
-    int* chunk = mempool_alloc(&mem);
-    TEST_TRUE(chunk != 0);
+    const int* chunk = mempool_alloc(&mem);
+    TEST_TRUE(chunk != nullptr);
   }
 
   mempool_clear(&mem);
+  TEST_EQUAL(mempool_size(&mem), 0);
+  TEST_EQUAL(mempool_capacity(&mem), NUM_BLOCKS);
 
   // Allocate chunks and assign values 0..N.
   for (int i = 0; i < NUM_BLOCKS; ++i) {
     int* chunk = mempool_alloc(&mem);
-    TEST_TRUE(chunk != 0);
+    TEST_TRUE(chunk != nullptr);
     *chunk = i + 1;
   }
 
diff --git a/plugin/src/plugin.c b/plugin/src/plugin.c
index e2aae1f..3a0ef5d 100644
--- a/plugin/src/plugin.c
+++ b/plugin/src/plugin.c
@@ -64,14 +64,14 @@ static bool load_library(Plugin* plugin) {
   // Handle reloading a previously-loaded library.
   if (plugin->handle) {
     dlclose(plugin->handle);
-    plugin->handle = 0;
+    plugin->handle = nullptr;
   }
 
   const mstring lib = plugin_lib_path(plugin);
 
   // If the plugin fails to load, make sure to keep the plugin's old handle to
   // handle the error gracefully. This handles reload failures, specifically.
-  void* handle = 0;
+  void* handle = nullptr;
   if ((handle = dlopen(mstring_cstr(&lib), RTLD_NOW))) {
     LOGD("Plugin [%s] loaded successfully", mstring_cstr(&plugin->filename));
     plugin->handle = handle;
@@ -86,7 +86,7 @@ static bool load_library(Plugin* plugin) {
 static void delete_plugin_state(Plugin* plugin) {
   if (plugin->state) {
     free(plugin->state);
-    plugin->state = 0;
+    plugin->state = nullptr;
   }
 }
 
@@ -105,7 +105,7 @@ static void destroy_plugin(Plugin* plugin) {
   if (plugin) {
     if (plugin->handle) {
       dlclose(plugin->handle);
-      plugin->handle = 0;
+      plugin->handle = nullptr;
     }
     delete_plugin_state(plugin);
   }
@@ -118,7 +118,7 @@ Plugin* load_plugin(PluginEngine* eng, const char* filename) {
   Plugin plugin = (Plugin){.eng = eng, .filename = mstring_make(filename)};
 
   if (!load_library(&plugin)) {
-    return 0;
+    return nullptr;
   }
 
   list_add(eng->plugins, plugin);
@@ -132,7 +132,7 @@ void delete_plugin(Plugin** pPlugin) {
     assert(plugin->eng);
     destroy_plugin(plugin);
     list_remove_ptr(plugin->eng->plugins, plugin);
-    *pPlugin = 0;
+    *pPlugin = nullptr;
   }
 }
 
@@ -148,7 +148,7 @@ bool plugin_reloaded(Plugin* plugin) {
 // -----------------------------------------------------------------------------
 
 PluginEngine* new_plugin_engine(const PluginEngineDesc* desc) {
-  PluginEngine* eng = 0;
+  PluginEngine* eng = nullptr;
 
   if (!(eng = calloc(1, sizeof(PluginEngine)))) {
     goto cleanup;
@@ -173,7 +173,7 @@ PluginEngine* new_plugin_engine(const PluginEngineDesc* desc) {
 
 cleanup:
   delete_plugin_engine(&eng);
-  return 0;
+  return nullptr;
 }
 
 void delete_plugin_engine(PluginEngine** pEng) {
@@ -191,7 +191,7 @@ void delete_plugin_engine(PluginEngine** pEng) {
       close(eng->inotify_instance);
     }
     free(eng);
-    *pEng = 0;
+    *pEng = nullptr;
   }
 }