Arenas and start work on strings

1 files changed, 197 insertions, 0 deletions

diff --git a/src/smrt_arena.c b/src/smrt_arena.c
new file mode 100644
index 0000000..683afcd
--- /dev/null
+++ b/src/smrt_arena.c
@@ -0,0 +1,197 @@
+#if defined(__linux__)
+#define _DEFAULT_SOURCE
+#endif
+
+#include "common.h"
+#include "smrt_arena.h"
+
+#include <string.h>
+
+smrt_arena_t *smrt_arena_create(u64 reserve_size, u64 commit_size, b32 auto_decommit) {
+    u32 pagesize = plat_get_pagesize();
+
+    reserve_size = ALIGN_UP_POW2(reserve_size + sizeof(smrt_arena_t), pagesize);
+     commit_size = ALIGN_UP_POW2( commit_size, pagesize);
+
+    smrt_arena_t *arena = plat_mem_reserve(reserve_size);
+
+    if (!plat_mem_commit(arena, commit_size)) {
+        return NULL;
+    }
+
+    arena->reserve_size = reserve_size;
+     arena->commit_size = commit_size;
+      arena->commit_pos = commit_size;
+             arena->pos = SMRT_ARENA_BASE_POS;
+        arena->mark_pos = 0;
+    arena->auto_decommit = auto_decommit;
+
+    return arena;
+
+}
+
+static void smrt_arena__shrink_commit(smrt_arena_t *arena) {
+    if (!arena->auto_decommit) { return; }
+
+    u64 target_commit_pos = arena->pos + arena->commit_size - 1;
+    target_commit_pos -= target_commit_pos % arena->commit_size;
+
+    if (target_commit_pos >= arena->commit_pos) { return; }
+
+    u64 decommit_size = arena->commit_pos - target_commit_pos;
+    u8 *decommit_start = (u8*)arena + target_commit_pos;
+
+    if (plat_mem_decommit(decommit_start, decommit_size)) {
+        arena->commit_pos = target_commit_pos;
+
+        if (arena->mark_pos > arena->commit_pos) {
+            arena->mark_pos = 0;
+        }
+    }
+}
+
+void *smrt_arena_push(smrt_arena_t *arena, u64 alloc_amount, b32 zero_out) {
+    u64 pos_aligned = ALIGN_UP_POW2(arena->pos, ARENA_ALIGN);
+    u64     new_pos = pos_aligned + alloc_amount;
+
+    if (new_pos > arena->reserve_size) { return NULL; }
+
+    if (new_pos > arena->commit_pos) {
+        u64 new_commit_pos = new_pos;
+        new_commit_pos += arena->commit_size - 1;
+        new_commit_pos -= new_commit_pos % arena->commit_size;
+        new_commit_pos =  MIN(new_commit_pos, arena->reserve_size);
+
+        u8 *mem = (u8*)arena + arena->commit_pos;
+        u64 commit_size = new_commit_pos - arena->commit_pos;
+
+        if (!plat_mem_commit(mem, commit_size)) {
+            return NULL;
+        }
+
+        arena->commit_pos = new_commit_pos;
+    }
+
+    arena->pos = new_pos;
+
+    u8 *out = (u8*)arena + pos_aligned;
+
+    if (zero_out) {
+        memset(out, 0, alloc_amount);
+    }
+
+    return out;
+}
+
+void *smrt_arena_mark_push(smrt_arena_t *arena, u64 alloc_amount, b32 zero_out) {
+    u64 orig_pos = arena->pos;
+
+    void *mem = smrt_arena_push(arena, alloc_amount, zero_out);
+
+    if (mem) {
+        arena->mark_pos = orig_pos;
+    }
+
+    return mem;
+}
+
+void smrt_arena_pop(smrt_arena_t *arena, u64 pop_amount) {
+    pop_amount = MIN(pop_amount, arena->pos - SMRT_ARENA_BASE_POS);
+    arena->pos -= pop_amount;
+
+    smrt_arena__shrink_commit(arena);
+}
+
+void smrt_arena_pop_to(smrt_arena_t *arena, u64 pos) {
+    u64 size = pos < arena->pos ? arena->pos - pos : 0;
+    smrt_arena_pop(arena, size);
+}
+
+b32 smrt_arena_pop_to_mark(smrt_arena_t *arena) {
+    if (arena->mark_pos == 0) {
+        return false;
+    }
+
+    smrt_arena_pop_to(arena, arena->mark_pos);
+
+    return true;
+}
+
+void smrt_arena_clear(smrt_arena_t *arena, b32 zero_out) {
+    arena->pos = SMRT_ARENA_BASE_POS;
+
+    if (zero_out) {
+        memset((u8*)arena + SMRT_ARENA_BASE_POS, 0, arena->commit_size - SMRT_ARENA_BASE_POS);
+    }
+
+    smrt_arena__shrink_commit(arena);
+}
+
+void smrt_arena_destroy(smrt_arena_t *arena) {
+    plat_mem_release(arena, arena->reserve_size);
+}
+
+#if defined(_WIN32)
+
+#include <windows.h>
+
+u32 plat_get_pagesize(void) {
+    SYSTEM_INFO sysinfo = { 0 };
+    GetSystemInfo(&sysinfo);
+
+    return sysinfo.dwPageSize;
+}
+
+void* plat_mem_reserve(u64 size) {
+    return VirtualAlloc(NULL, size, MEM_RESERVE, PAGE_READWRITE);
+}
+
+b32 plat_mem_commit(void* ptr, u64 size) {
+    void* ret = VirtualAlloc(ptr, size, MEM_COMMIT, PAGE_READWRITE);
+    return ret != NULL;
+}
+
+b32 plat_mem_decommit(void* ptr, u64 size) {
+    return VirtualFree(ptr, size, MEM_DECOMMIT);
+}
+
+b32 plat_mem_release(void* ptr, u64 size) {
+    return VirtualFree(ptr, size, MEM_RELEASE);
+}
+
+
+#elif defined(__linux__)
+
+#include <unistd.h>
+#include <sys/mman.h>
+
+u32 plat_get_pagesize(void) {
+    return (u32)sysconf(_SC_PAGESIZE);
+}
+
+void* plat_mem_reserve(u64 size) {
+    void* out = mmap(NULL, size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    if (out == MAP_FAILED) {
+        return NULL;
+    }
+    return out;
+}
+
+b32 plat_mem_commit(void* ptr, u64 size) {
+    i32 ret = mprotect(ptr, size, PROT_READ | PROT_WRITE);
+    return ret == 0;
+}
+
+b32 plat_mem_decommit(void* ptr, u64 size) {
+    i32 ret = mprotect(ptr, size, PROT_NONE);
+    if (ret != 0) return false;
+    ret = madvise(ptr, size, MADV_DONTNEED);
+    return ret == 0;
+}
+
+b32 plat_mem_release(void* ptr, u64 size) {
+    i32 ret = munmap(ptr, size);
+    return ret == 0;
+}
+
+#endif