Arena allocation

include/ci2.h

@@ -32,6 +32,7 @@ You get to decide which parts of that platform layer you'd like to use.
 
 /* Then you import which parts of the platform layer, you'd like. */
 #include "./platform/error/ci2_exception.h"
+#include "./platform/mem/ci2_arena.h"
 #include "./platform/mem/ci2_mem.h"
 #include "./platform/try/ci2_try.h"
 

include/platform/mem/ci2_arena.h

@@ -0,0 +1,62 @@
+/* - | Copyright / About | ----------------------------------------------------
+   Copyright (c) 2026 Randy Jordan
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+ * --------------------------------------------------------------------------*/
+#ifndef CI2_ARENA_H
+#define CI2_ARENA_H
+
+#include "../ci2_platform.h"
+#include <stddef.h>
+
+struct Arena
+{
+  char* beg;
+  char* end;
+};
+typedef struct Arena Arena;
+
+/* Initialize an Arena with an existing buffer  */
+CI2_DEF void
+ci2_arena_back(struct Arena* a, char* buf, ptrdiff_t len);
+
+/* Allocate a new Arena */
+CI2_DEF struct Arena
+ci2_arena_new(ptrdiff_t cap);
+
+/* Get the current capacity of an Arena */
+CI2_DEF ptrdiff_t
+ci2_arena_capacity(struct Arena a);
+
+/* Make an allocation from an Arena and do not zero.*/
+CI2_DEF void*
+ci2_arena_malloc(struct Arena* a,
+                 ptrdiff_t size,
+                 ptrdiff_t align,
+                 ptrdiff_t count);
+
+/* Make an allocation from an Arena and zero.*/
+CI2_DEF void*
+ci2_arena_calloc(struct Arena* a,
+                 ptrdiff_t size,
+                 ptrdiff_t align,
+                 ptrdiff_t count);
+
+#endif // ci2_arena.h

src/ci2_arena.c

@@ -0,0 +1,91 @@
+/* - | Copyright / About | ----------------------------------------------------
+   Copyright (c) 2026 Randy Jordan
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+ * --------------------------------------------------------------------------*/
+
+#include "../include/platform/mem/ci2_arena.h"
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* Initialize an Arena with an existing buffer  */
+void
+ci2_arena_back(struct Arena* a, char* buf, ptrdiff_t len)
+{
+  CI2_ASSERT(a != NULL);
+  CI2_ASSERT(buf != NULL);
+  a->beg = buf;
+  a->end = buf + len;
+}
+
+/* Allocate a new Arena */
+struct Arena
+ci2_arena_new(ptrdiff_t cap)
+{
+  struct Arena a = { 0 };
+  a.beg = malloc(cap);
+  a.end = a.beg ? a.beg + cap : 0;
+  return a;
+}
+
+/* Get the current capacity of an Arena */
+ptrdiff_t
+ci2_arena_capacity(struct Arena a)
+{
+  ptrdiff_t res = a.end - a.beg;
+  return res;
+}
+
+/* Make an allocation from an Arena and do not zero.*/
+void*
+ci2_arena_calloc(struct Arena* a,
+                 ptrdiff_t size,
+                 ptrdiff_t align,
+                 ptrdiff_t count)
+{
+  ptrdiff_t padding = -(uintptr_t)a->beg & (align - 1);
+  ptrdiff_t available = a->end - a->beg - padding;
+  if (available < 0 || count > available / size) {
+    return NULL;
+  }
+  ptrdiff_t total = padding + count * size;
+  void* p = a->beg + total;
+  a->beg += total;
+  return memset(p, 0, total);
+}
+
+/* Make an allocation from an Arena and zero.*/
+void*
+ci2_arena_malloc(struct Arena* a,
+                 ptrdiff_t size,
+                 ptrdiff_t align,
+                 ptrdiff_t count)
+{
+  ptrdiff_t padding = -(uintptr_t)a->beg & (align - 1);
+  ptrdiff_t available = a->end - a->beg - padding;
+  if (available < 0 || count > available / size) {
+    return NULL;
+  }
+  ptrdiff_t total = padding + count * size;
+  void* p = a->beg + total;
+  a->beg += total;
+  return p;
+}

src/ci2_mem.c

@@ -34,7 +34,7 @@ void*
 ci2_alloc(size_t nbytes, const char* file, int line)
 {
   void* ptr;
-  ci2_rt_assert(nbytes > 0);
+  CI2_ASSERT(nbytes > 0);
   ptr = malloc(nbytes);
   if (ptr == NULL) {
     if (file == NULL)
@@ -49,8 +49,8 @@ void*
 ci2_calloc(size_t count, size_t nbytes, const char* file, int line)
 {
   void* ptr;
-  ci2_rt_assert(count > 0);
-  ci2_rt_assert(nbytes > 0);
+  CI2_ASSERT(count > 0);
+  CI2_ASSERT(nbytes > 0);
   ptr = calloc(count, nbytes);
   if (ptr == NULL) {
     if (file == NULL)
@@ -74,8 +74,8 @@ ci2_free(void* ptr, const char* file, int line)
 void*
 ci2_resize(void* ptr, size_t nbytes, const char* file, int line)
 {
-  // ci2_rt_assert(ptr); // ? Maybe
-  // ci2_rt_assert(nbytes > 0);// ? Maybe
+  // CI2_ASSERT(ptr); // ? Maybe
+  // CI2_ASSERT(nbytes > 0);// ? Maybe
   void* tmp = realloc(ptr, nbytes);
   if (tmp == NULL) {
     if (file == NULL)