agrego practicas

c/arena5/main.c

@@ -0,0 +1,120 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+#define ARENA_ALIGN 8
+
+typedef struct{
+    unsigned char *buffer;
+    size_t size;
+    size_t offset;
+}Arena;
+
+Arena arena_create(size_t);
+void* arena_alloc(Arena *, size_t);
+void arena_reset(Arena *);
+void arena_destroy(Arena *);
+bool arena_is_aligned(size_t);
+size_t arena_checkpoint(Arena*);
+void arena_restore(Arena*, size_t);
+
+int main(void){
+    Arena  arena =  arena_create(32);
+
+    size_t cp0 = arena_checkpoint(&arena);
+    int* x = (int*)arena_alloc(&arena, 8);
+
+*x = 21;
+
+    arena_alloc(&arena, 8);
+    size_t cp1 = arena_checkpoint(&arena);
+    int* tmp = (int*)arena_alloc(&arena, 8);
+
+    arena_restore(&arena, cp1);
+
+    printf("x:%d\n", *x);
+
+    arena_alloc(&arena, 16);
+
+    arena_restore(&arena, cp0);
+
+    arena_alloc(&arena, 32);
+
+    arena_destroy(&arena);
+
+    return 0;
+}
+
+void arena_restore(Arena* ref_arena, size_t chk){
+    ref_arena->offset = chk;
+}
+
+size_t arena_checkpoint(Arena* ref_arena){
+    return ref_arena->offset;
+}
+
+bool arena_is_aligned(size_t pos){
+    size_t mask = 7;
+    return (pos & mask) == 0;
+}
+
+Arena arena_create( size_t bytes){
+    Arena new_arena = {
+        .buffer = NULL,
+        .size = bytes,
+        .offset = 0
+    };
+
+    new_arena.buffer = (unsigned char *)malloc(bytes);
+
+    if(new_arena.buffer == NULL){
+        perror("Error asignando memoria");
+        exit(1);
+    }
+
+    return new_arena;
+
+}
+void* arena_alloc(Arena *ref_arena, size_t bytes){
+
+    if(ref_arena->buffer == NULL){
+        return NULL;
+    }
+
+    size_t aligned = ((ref_arena->offset + (size_t)((ARENA_ALIGN - 1))) & ~(ARENA_ALIGN - 1));
+
+    if(aligned + bytes > ref_arena->size){
+        printf("arena_alloc(%d): NULL \n", (int) bytes);
+        return NULL;
+    }
+    void* ptr_ref = ref_arena->buffer + aligned;
+
+    printf("arena_alloc(%d) ", (int) bytes);
+
+    if(arena_is_aligned((size_t)ptr_ref)){
+        printf("aligned: true ");
+    }else{
+        printf("aligned: false ");
+    }
+
+    printf(" base + %d", (int)aligned);
+    printf(" offset: %d -> %d \n", (int)ref_arena->offset, (int)aligned);
+
+    ref_arena->offset = aligned + bytes;
+
+    return ptr_ref;
+}
+
+void arena_reset(Arena *ref_arena){
+    ref_arena->offset = 0;
+}
+
+void arena_destroy(Arena *ref_arena){
+    if(ref_arena->buffer != NULL){
+        free(ref_arena->buffer);
+        ref_arena->buffer = NULL;
+    }
+}
+