add memory allocation functions

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 134 insertions, 0 deletions

diff --git a/src/stdlib/malloc.c b/src/stdlib/malloc.c
new file mode 100644
index 0000000..82a6f54
--- /dev/null
+++ b/src/stdlib/malloc.c
@@ -0,0 +1,134 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <stdlib.h>
+#include <slibc-alloc.h>
+#include <strings.h>
+#include <sys/mman.h>
+
+
+
+/**
+ * Create a new memory allocation on the heap.
+ * The allocation will not be initialised.
+ * 
+ * @param   size  The size of the allocation.
+ * @return        Pointer to the beginning of the new allocation.
+ *                If `size` is zero, this function will either return
+ *                `NULL` (that is what this implement does) or return
+ *                a unique pointer that can later be freed with `free`.
+ *                `NULL` is returned on error, and `errno` is set to
+ *                indicate the error.
+ * 
+ * @throws  ENOMEM  The process cannot allocate more memory.
+ */
+void* malloc(size_t size)
+{
+  /* TODO implement implementation of malloc */
+  char* ptr;
+  if (size == 0)
+    return NULL;
+  ptr = mmap(NULL, sizeof(size_t) + size, (PROT_READ | PROT_WRITE),
+	     (MAP_PRIVATE | MAP_ANONYMOUS), -1, 0);
+  *(size_t*)ptr = size;
+  return ptr + sizeof(size_t);
+}
+
+
+/**
+ * Variant of `malloc` that clears the allocation with zeroes.
+ * 
+ * `p = calloc(n, m)` is equivalent to
+ * `(p = malloc(n * m), p ? (explicit_bzero(p, n * m), p) : NULL)`
+ * 
+ * @param   elem_count  The number of elements to allocate.
+ * @param   elem_size   The size of each element.
+ * @return              Pointer to the beginning of the new allocation.
+ *                      If `elem_count` or `elem_size` is zero, this function
+ *                      will either return `NULL` (that is what this implement
+ *                      does) or return a unique pointer that can later be
+ *                      freed with `free`. `NULL` is returned on error, and
+ *                      `errno` is set to indicate the error.
+ * 
+ * @throws  ENOMEM  The process cannot allocate more memory.
+ */
+void* calloc(size_t elem_count, size_t elem_size)
+{
+  void* ptr = malloc(elem_count * elem_size);
+  if (ptr != NULL)
+    explicit_bzero(ptr, elem_count * elem_size);
+  return ptr;
+}
+
+
+/**
+ * Variant of `malloc` that extends, or shrinks, an existing allocation,
+ * if beneficial and possible, or creates a new allocation with the new
+ * size, copies the data, and frees the old allocation.
+ * 
+ * On error, `ptr` is not freed.
+ * 
+ * @param   ptr   Pointer to the beginning of the old memory allocation.
+ *                The process may crash if it does not point to the
+ *                beginning of a memory allocation on the heap.
+ *                However, if it is `NULL`, this function will behave
+ *                like `malloc`.
+ * @param   size  The new allocation size. If zero, this function will
+ *                behave like `free`, and will return `NULL`.
+ * @return        Pointer to the beginning of the new allocation.
+ *                If `size` is zero, `NULL` is returned. On error `NULL`
+ *                is returned and `errno` is set to indicate the error.
+ * 
+ * @throws  ENOMEM  The process cannot allocate more memory.
+ */
+void* realloc(void* ptr, size_t size)
+{
+  return fast_realloc(ptr, size);
+}
+
+
+/**
+ * Free a memory allocation.
+ * 
+ * @param  ptr  Pointer to the beginning of the memory allocation.
+ *              The process may crash if it does not point to the
+ *              beginning of a memory allocation on the heap.
+ *              However, if it is `NULL`, nothing will happen.
+ */
+void free(void* ptr)
+{
+  fast_free(ptr);
+}
+
+
+/**
+ * This function is identical to `free`.
+ * Any argument beyond the first argument, is ignored.
+ * 
+ * This function uses variadic arguments because there
+ * there are multiple conflicting specifications for `cfree`.
+ * 
+ * @param  ptr  Pointer to the beginning of the memory allocation.
+ *              The process may crash if it does not point to the
+ *              beginning of a memory allocation on the heap.
+ *              However, if it is `NULL`, nothing will happen.
+ */
+void cfree(void* ptr, ...)
+{
+  fast_free(ptr);
+}
+