Pool allocator

README.md

@@ -4,7 +4,8 @@ My personal library of common C data structures and algorithms. Supports Linux,
 
 ## Documentation
 
-Extensive documentation can be found [here](https://fputs.com/docs/libflint/)
+Extensive documentation can be found [here](https://fputs.com/docs/libflint/). You can also check out `tests/tests.c` to
+see example usage from most of the library's API.
 
 ## Requirements
 

docs/memory.md

@@ -2,7 +2,7 @@
 
 Custom allocators and memory functions
 
-# Arena Allocator
+## Arena Allocator
 
 A simple arena-style allocator
 
@@ -11,7 +11,7 @@ A simple arena-style allocator
 ### ArenaAllocator
 
 Represents an arena allocator. `ArenaAllocator` holds its own buffer, but managing its size is left to the user. Like
-most structs in `libflint`, it must be malloced first before being passed to `arena_init()`.
+most structs in `libflint`, it must be malloc'd first before being passed to `arena_init()`.
 
 ```c
 typedef struct {
@@ -97,3 +97,98 @@ Convenience macro for getting the size of the arena's buffer
 ```c
 #define arena_sz(a) (a)->buf_sz
 ```
+
+## Pool Allocator
+
+A pool-based allocator for chunks of the same size. Useful for quickly allocating and using memory of the same size
+without worrying about order; most operations are `O(1)`
+
+## Structs
+
+### PoolAllocator
+
+Represents a pool allocator. `PoolAllocator` holds its own buffer, but managing its size is left to the user. Like
+most structs in `libflint`, it must be malloc'd first before being passed to `pool_init()`.
+
+```c
+typedef struct {
+	unsigned char *buf;
+    size_t buf_sz;
+    size_t chunk_size;
+
+    List *free_list;
+} PoolAllocator;
+```
+
+## Functions
+
+### pool_init
+
+Initializes the `PoolAllocator`. The struct must first be created by the user using `malloc()`, see the example below.
+
+- `buf_sz`: Size of the underlying buffer in bytes
+- `chunk_sz`: Size of each chunk in bytes
+- `chunk_align`: The alignment of the chunks. The`LF_DEFAULT_ALIGNMENT` macro is available as a good default for basic types
+
+```c
+void pool_init(PoolAllocator *allocator, size_t buf_sz, size_t chunk_sz, size_t chunk_align);
+
+/* Usage */
+PoolAllocator *pool = malloc(sizeof(PoolAllocator));
+pool_init(pool, 64, 16, LF_DEFAULT_ALIGNMENT);
+```
+
+### pool_free
+
+Return a single chunk back to the pool. `ptr` is a pointer to the allocated chunk.
+
+```c
+void pool_free(PoolAllocator *allocator, void *ptr);
+```
+
+### pool_free_all
+
+Returns all chunks back to the pool. Any pointers received before this call are now invalid and must be reasigned with 
+`pool_alloc` or set to `NULL`.
+
+```c
+void pool_free_all(PoolAllocator *allocator);
+```
+
+### pool_alloc
+
+Allocate a chunk from the pool. Returns `NULL` on failure.
+
+```c
+void *pool_alloc(PoolAllocator *allocator);
+```
+
+### pool_destroy
+
+Destroys the underlying buffer and `List` in `allocator`, then frees it. User is responsible for setting `allocator` to
+`NULL` afterwards.
+
+```c
+void pool_destroy(PoolAllocator *allocator);
+```
+
+## Macros
+
+### pool_count_available
+
+Returns the amount of chunks left available in the pool
+
+```c
+#define pool_count_available(x) (x)->free_list->size
+```
+
+### LF_DEFAULT_ALIGNMENT
+
+The default alignment for allocators. Use this as a simple default (defaults to 16 bytes on amd64 systems) when storing
+basic types
+
+```c
+#ifndef DEFAULT_ALIGNMENT
+#define LF_DEFAULT_ALIGNMENT (2*sizeof(void*))
+#endif // DEFAULT_ALIGNMENT
+```

include/lfmemory.h

@@ -3,6 +3,12 @@
 
 #include <stddef.h>
 
+#include "lflinkedlist.h"
+
+#ifndef DEFAULT_ALIGNMENT
+#define LF_DEFAULT_ALIGNMENT (2*sizeof(void*))
+#endif // DEFAULT_ALIGNMENT
+
 typedef struct {
     unsigned char* buf;
     size_t buf_sz;
@@ -17,4 +23,20 @@ void arena_resize_buf(ArenaAllocator *allocator, size_t new_sz);
 void *arena_resize(ArenaAllocator *allocator, void *mem, size_t old_sz, size_t new_sz);
 void arena_clear(ArenaAllocator *allocator);
 
+typedef struct {
+	unsigned char *buf;
+    size_t buf_sz;
+    size_t chunk_size;
+
+    List *free_list;
+} PoolAllocator;
+
+void pool_init(PoolAllocator *allocator, size_t buf_sz, size_t chunk_sz, size_t chunk_align);
+void pool_free(PoolAllocator *allocator, void *ptr);
+void pool_free_all(PoolAllocator *allocator);
+void *pool_alloc(PoolAllocator *allocator);
+void pool_destroy(PoolAllocator *allocator);
+
+#define pool_count_available(x) (x)->free_list->size
+
 #endif // LIBFLINT_H_MEMORY

mkdocs.yml

@@ -12,6 +12,7 @@ nav:
     - 'Linked List': 'linkedlist.md'
     - 'Math': 'math.md'
     - 'macOS': 'macos.md'
+    - 'Memory': 'memory.md'
     - 'Network': 'network.md'
     - 'Parsing': 'parsing.md'
     - 'Set': 'set.md'

src/memory.c

@@ -28,26 +28,37 @@ void arena_clear(ArenaAllocator *allocator) {
     allocator->offset_prev = 0;
 }
 
-static uintptr_t align_forward(uintptr_t ptr, size_t align) {
+static uintptr_t align_forward_uintptr(const uintptr_t ptr, const uintptr_t align) {
-    uintptr_t p, a, m;
     if (!is_power_of_two(align)) {
         // TODO: Error
     }
-    p = ptr;
+    uintptr_t p = ptr;
-    a = (uintptr_t)align;
+    const uintptr_t m = p & (align - 1);
-    m = p & (a - 1);
 
     if (m != 0) {
-        p += a - m;
+        p += align - m;
     }
     return p;
 }
 
-static void *arena_malloc_align(ArenaAllocator *allocator, size_t size, size_t align) {
+static uintptr_t align_forward_size(const size_t ptr, const size_t align) {
-    uintptr_t cur_ptr = (uintptr_t)allocator->buf + (uintptr_t)allocator->offset_cur;
+    if (!is_power_of_two(align)) {
+        // TODO: Error
+    }
+    uintptr_t p = ptr;
+    const uintptr_t m = p & (align - 1);
+
+    if (m != 0) {
+        p += align - m;
+    }
+    return p;
+}
+
+static void *arena_malloc_align(ArenaAllocator *allocator, const size_t size, size_t align) {
+    uintptr_t cur_ptr = (uintptr_t)allocator->buf + allocator->offset_cur;
 
     // Push forward to align, then change to relative offset
-    uintptr_t offset = align_forward(cur_ptr, align);
+    uintptr_t offset = align_forward_uintptr(cur_ptr, align);
     offset -= (uintptr_t)allocator->buf;
 
     if (offset + size <= allocator->buf_sz) {
@@ -62,8 +73,8 @@ static void *arena_malloc_align(ArenaAllocator *allocator, size_t size, size_t a
     return NULL;
 }
 
-static void *arena_resize_align(ArenaAllocator *allocator, void *mem, size_t old_sz, size_t new_sz, size_t align) {
+static void *arena_resize_align(ArenaAllocator *allocator, void *mem, const size_t old_sz, const size_t new_sz, size_t align) {
-    unsigned char *old_mem = (unsigned char *)mem;
+    unsigned char *old_mem = mem;
     if (!is_power_of_two(align)) {
         // TODO: Error handling
     }
@@ -91,19 +102,79 @@ static void *arena_resize_align(ArenaAllocator *allocator, void *mem, size_t old
     return NULL;
 }
 
-void arena_resize_buf(ArenaAllocator *allocator, size_t new_sz) {
+void arena_resize_buf(ArenaAllocator *allocator, const size_t new_sz) {
     allocator->buf = realloc(allocator->buf, sizeof(unsigned char) * new_sz);
 }
 
-#ifndef DEFAULT_ALIGNMENT
+void *arena_malloc(ArenaAllocator *allocator, const size_t size) {
-#define DEFAULT_ALIGNMENT (2*sizeof(void*))
+    return arena_malloc_align(allocator, size, LF_DEFAULT_ALIGNMENT);
-#endif // DEFAULT_ALIGNMENT
-
-void *arena_malloc(ArenaAllocator *allocator, size_t size) {
-    return arena_malloc_align(allocator, size, DEFAULT_ALIGNMENT);
 }
 
-void *arena_resize(ArenaAllocator *allocator, void *mem, size_t old_sz, size_t new_sz) {
+void *arena_resize(ArenaAllocator *allocator, void *mem, const size_t old_sz, const size_t new_sz) {
-    return arena_resize_align(allocator, mem, old_sz, new_sz, DEFAULT_ALIGNMENT);
+    return arena_resize_align(allocator, mem, old_sz, new_sz, LF_DEFAULT_ALIGNMENT);
 }
 
+void pool_init(PoolAllocator *allocator, size_t buf_sz, size_t chunk_sz, size_t chunk_align) {
+    if (allocator == NULL) {
+        return;
+    }
+
+    allocator->buf = malloc(sizeof(unsigned char) * buf_sz);
+    uintptr_t istart = (uintptr_t)allocator->buf;
+    uintptr_t start = align_forward_uintptr(istart, chunk_align);
+    allocator->buf_sz = buf_sz - (start - istart);
+
+    allocator->chunk_size = align_forward_size(chunk_sz, chunk_align);
+    if (allocator->chunk_size < sizeof(void *) || allocator->buf_sz < allocator->chunk_size) {
+        //TODO: Handle error better
+        return;
+    }
+
+    allocator->free_list = malloc(sizeof(List));
+    ll_init(allocator->free_list, NULL);
+
+    pool_free_all(allocator);
+}
+
+void pool_free(PoolAllocator *allocator, void *ptr) {
+    ListNode *node = NULL;
+    const void *start = allocator->buf;
+    const void *end = &allocator->buf[allocator->buf_sz];
+
+    if (ptr == NULL) {
+        return;
+    }
+
+    if (!(start <= ptr && ptr < end)) {
+        // TODO: Handle error better
+        return;
+    }
+
+    ll_ins_next(allocator->free_list, allocator->free_list->tail, ptr);
+}
+
+void pool_free_all(PoolAllocator *allocator) {
+    size_t chunk_count = allocator->buf_sz / allocator->chunk_size;
+    for (size_t i = 0; i < chunk_count; ++i) {
+        ll_ins_next(allocator->free_list, allocator->free_list->head, &allocator->buf[i * allocator->chunk_size]);
+    }
+}
+
+void *pool_alloc(PoolAllocator *allocator) {
+    ListNode *node = allocator->free_list->head;
+    if (node == NULL) {
+        // TODO: Handle error better
+        return NULL;
+    }
+
+    void *tmp;
+    ll_remove(allocator->free_list, allocator->free_list->head, &tmp);
+    return memset(tmp, 0, allocator->chunk_size);
+}
+
+void pool_destroy(PoolAllocator *allocator) {
+    ll_destroy(allocator->free_list);
+    free(allocator->free_list);
+    free(allocator->buf);
+    free(allocator);
+}

src/vector.c

@@ -113,7 +113,7 @@ int vec_shrink(Vector *vec) {
 
     vec->capacity = vec_len(vec);
 
-#ifdef __OpenBSD__
+#if !defined(__OpenBSD__) || defined(__linux)
     vec->elements = reallocarray(vec->elements, vec->capacity, sizeof(void *));
 #else
     vec->elements = reallocf(vec->elements, sizeof(void *) * vec->capacity);

tests/tests.c

@@ -471,11 +471,11 @@ void test_macos() {
 
 void test_memory() {
     printf("\n--- MEMORY TEST ---\n");
-    ArenaAllocator *a = malloc(sizeof(ArenaAllocator));
+    ArenaAllocator *arena = malloc(sizeof(ArenaAllocator));
-    arena_init(a, 1024);
+    arena_init(arena, 1024);
 
-    int *i1 = arena_malloc(a, sizeof(int));
+    int *i1 = arena_malloc(arena, sizeof(int));
-    int *i2 = arena_malloc(a, sizeof(int));
+    int *i2 = arena_malloc(arena, sizeof(int));
 
     *i1 = 1;
     *i2 = 2;
@@ -483,13 +483,33 @@ void test_memory() {
     assert(i1 < i2);
     assert(*i1 < *i2);
 
-    long *l = arena_resize(a, i1, sizeof(int), sizeof(long));
+    long *l = arena_resize(arena, i1, sizeof(int), sizeof(long));
     assert(*l == 1);
 
-    unsigned char *c = arena_resize(a, i2, sizeof(int), sizeof(unsigned char));
+    unsigned char *char_test = arena_resize(arena, i2, sizeof(int), sizeof(unsigned char));
-    assert(*c == 2);
+    assert(*char_test == 2);
 
-    arena_free(a);
+    arena_free(arena);
+    arena = NULL;
+
+    PoolAllocator *pool = malloc(sizeof(PoolAllocator));
+    pool_init(pool, 64, 16, LF_DEFAULT_ALIGNMENT);
+    void *a = pool_alloc(pool);
+    void *b = pool_alloc(pool);
+    void *c = pool_alloc(pool);
+    void *d = pool_alloc(pool);
+
+    assert(a != NULL);
+    assert(b != NULL);
+    assert(c != NULL);
+    assert(d != NULL);
+
+    assert(pool_count_available(pool) == 0);
+    pool_free(pool, d);
+    d = NULL;
+    assert(pool_count_available(pool) == 1);
+
+    pool_destroy(pool);
     printf("Passes all memory tests\n");
 }