prototypes for malloc impl

include/ni_alloc/vm.h

@@ -0,0 +1,59 @@
+#ifndef __NICKEL_VM_H
+#define __NICKEL_VM_H
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* VM layer: portable-ish page allocation based on mmap/munmap (Linux + macOS). */
+
+typedef struct ni_vm_stats {
+    size_t page_size;
+
+    /* cumulative counters */
+    uint64_t reserves;      /* number of reserve calls */
+    uint64_t releases;      /* number of release calls */
+    uint64_t commits;       /* if supported by impl (optional), else 0 */
+    uint64_t decommits;     /* if supported by impl (optional), else 0 */
+
+    size_t bytes_reserved;  /* current bytes reserved */
+    size_t bytes_peak;      /* peak reserved */
+} ni_vm_stats;
+
+/* Returns OS page size (usually sysconf(_SC_PAGESIZE)). Never returns 0. */
+size_t ni_vm_page_size(void);
+
+/* Reserve anonymous virtual memory.
+   - bytes will be rounded up to a page multiple.
+   - returns NULL on failure.
+*/
+void* ni_vm_reserve(size_t bytes);
+
+/* Release a region previously returned by ni_vm_reserve (page-multiple size). */
+bool ni_vm_release(void* addr, size_t bytes);
+
+/* Optional: “commit/decommit” for platforms where it’s meaningful.
+   On many Unix systems, reserve implies commit; implementations may no-op.
+*/
+bool ni_vm_commit(void* addr, size_t bytes);
+bool ni_vm_decommit(void* addr, size_t bytes);
+
+/* Optional: set guard pages (mprotect) for debug.
+   Returns false if unsupported or fails.
+*/
+bool ni_vm_protect_none(void* addr, size_t bytes);
+bool ni_vm_protect_rw(void* addr, size_t bytes);
+
+/* Stats are optional but very useful for tests/tools. */
+void ni_vm_get_stats(ni_vm_stats* out_stats);
+void ni_vm_reset_stats(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __NICKEL_VM_H */