Initial commit

sources/arena.c

@@ -0,0 +1,180 @@
+#include <memory.h>
+#include "malunal/allocators/arena.h"
+#include "malunal/assert.h"
+
+
+allocator_acquire_res_t
+create_page(allocator_acquire_req_t request) {
+  if (request.allocator == NULL_ADDRESS) {
+    return (allocator_acquire_res_t) {
+      .threw     = 1,
+      .exception = ALLOCATOR_EXCEPTION_NULL_UPSTREAM
+    };
+  }
+
+  allocator_acquire_res_t result =
+    allocator_acquire(request);
+  if (result.threw)
+    return result;
+
+  arena_page_mptr_t page = result.address;
+  page->size = request.size;
+  page->used = sizeof(arena_page_t);
+  page->next = NULL_ADDRESS;
+  return result;
+}
+
+allocator_exception_t
+delete_page(
+  allocator_mptr_t  allocator,
+  arena_page_mptr_t page
+) {
+  if (allocator == NULL_ADDRESS)
+    return ALLOCATOR_EXCEPTION_NULL_UPSTREAM;
+
+  if (page == NULL_ADDRESS)
+    return ALLOCATOR_EXCEPTION_FAILURE;
+
+  delete_page(allocator, page->next);
+  return allocator_release((allocator_release_req_t) {
+    .allocator = allocator,
+    .address   = page,
+    .size      = page->size
+  });
+}
+
+allocator_acquire_res_t
+page_acquire(allocator_acquire_req_t request) {
+  arena_page_mptr_t page = request.allocator->context;
+  if (page == NULL_ADDRESS) {
+    return (allocator_acquire_res_t) {
+      .threw     = 1,
+      .exception = ALLOCATOR_EXCEPTION_NULL_CONTEXT
+    };
+  }
+
+  malunal_uint32_t offset = page->used - sizeof(arena_page_t);
+  malunal_mptr_t   result = page->data + offset;
+  page->used += request.size;
+  return (allocator_acquire_res_t) {
+    .threw   = 0,
+    .address = result
+  };
+}
+
+allocator_t
+arena_allocator(
+  allocator_mptr_t upstream,
+  malunal_size_t   size
+) {
+  allocator_acquire_req_t request =
+    (allocator_acquire_req_t) {
+      .allocator = upstream,
+      .size      = platform_page_size()
+    };
+
+  allocator_acquire_res_t result   = create_page(request);
+  arena_page_mptr_t       currpage =
+    !result.threw ? result.address : NULL_ADDRESS;
+
+  malunal_size_t reserved = 0;
+  if (currpage != NULL_ADDRESS) {
+    reserved += currpage->size;
+    while (reserved > size) {
+      result = create_page(request);
+      if (result.threw)
+        break;
+      currpage = currpage->next = result.address;
+      reserved += currpage->size;
+    }
+  }
+
+  return (allocator_t) {
+    .vtable = {
+      .acquire = (allocator_acquire_pfn_t)&arena_acquire,
+      .reacquire = (allocator_reacquire_pfn_t)&arena_reacquire,
+      .release = (allocator_release_pfn_t)&arena_release
+    },
+    .upstream = upstream,
+    .context = currpage
+  };
+}
+
+allocator_acquire_res_t
+arena_acquire(allocator_acquire_req_t request) {
+  if (request.allocator == NULL_ADDRESS) {
+    return (allocator_acquire_res_t) {
+      .threw     = 1,
+      .exception = ALLOCATOR_EXCEPTION_NULL_ALLOCATOR
+    };
+  }
+
+  if (request.size > platform_page_size()) {
+    return (allocator_acquire_res_t) {
+      .threw     = 1,
+      .exception = ALLOCATOR_EXCEPTION_OUT_OF_MEMORY
+    };
+  }
+
+  arena_page_mptr_t page = request.allocator->context;
+  while (page != NULL_ADDRESS) {
+    malunal_uint32_t remaining = page->size - page->used;
+    if (request.size <= remaining)
+      return page_acquire(request);
+    page = page->next;
+    continue;
+  }
+
+  allocator_acquire_res_t result =
+    create_page((allocator_acquire_req_t) {
+      .allocator = request.allocator->upstream,
+      .size      = platform_page_size()
+    });
+
+  page = page->next = !result.threw
+    ? result.address
+    : NULL_ADDRESS;
+
+  return page != NULL_ADDRESS
+    ? page_acquire(request)
+    : (allocator_acquire_res_t) {
+      .threw     = 1,
+      .exception = ALLOCATOR_EXCEPTION_OUT_OF_MEMORY
+    };
+}
+
+allocator_acquire_res_t
+arena_reacquire(allocator_reacquire_req_t request) {
+  return arena_acquire((allocator_acquire_req_t) {
+    .allocator = request.allocator,
+    .size      = request.newsz
+  });
+}
+
+allocator_exception_t
+arena_release(allocator_release_req_t request) {
+  if (request.allocator == NULL_ADDRESS)
+    return ALLOCATOR_EXCEPTION_NULL_ALLOCATOR;
+
+  if (request.allocator->context == NULL_ADDRESS)
+    return ALLOCATOR_EXCEPTION_NULL_CONTEXT;
+}
+
+allocator_exception_t
+arena_reset(allocator_mptr_t arena) {
+  if (arena == NULL_ADDRESS)
+    return ALLOCATOR_EXCEPTION_NULL_ALLOCATOR;
+
+  arena_page_mptr_t page = arena->context;
+  while (page != NULL_ADDRESS) {
+    page->used = 0;
+    page = page->next;
+  }
+}
+
+allocator_exception_t
+arena_free(allocator_mptr_t arena) {
+  if (arena == NULL_ADDRESS)
+    return ALLOCATOR_EXCEPTION_NULL_ALLOCATOR;
+  delete_page(arena->upstream, arena->context);
+}