Implemented macros for iterating over memblock regions, including free regions

sandbox/memblock/memblock.c

@@ -1,7 +1,18 @@
 #include <stdbool.h>
+#include <limits.h>
 #include <string.h>
 #include "memblock.h"
 
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+
+#define ITER(a, b) ((uint64_t)(a) | ((uint64_t)(b) << 32))
+#define ITER_END ULLONG_MAX
+#define IDX_A(idx) ((idx) & 0xFFFFFFFF)
+#define IDX_B(idx) (((idx) >> 32) & 0xFFFFFFFF)
+
+#define ADDR_MAX 0xFFFFFFFF
+
 static memblock_region_t init_memory_regions[MEMBLOCK_INIT_MEMORY_REGION_COUNT];
 static memblock_region_t init_reserved_regions[MEMBLOCK_INIT_RESERVED_REGION_COUNT];
 
@@ -142,3 +153,52 @@ uintptr_t memblock_alloc(size_t size)
 {
 	return 0;
 }
+
+void __next_memory_region(memblock_iter_t *it, memblock_type_t *type_a, memblock_type_t *type_b, uintptr_t start, uintptr_t end)
+{
+	unsigned int idx_a = IDX_A(it->idx);
+	unsigned int idx_b = IDX_B(it->idx);
+
+	for (; idx_a < type_a->count; idx_a++) {
+		memblock_region_t *m = &type_a->regions[idx_a];
+		if (!type_b) {
+			it->base = m->base;
+			it->limit = m->limit;
+
+			it->idx = ITER(idx_a + 1, idx_b);
+			return;
+		}
+
+		uintptr_t m_start = m->base;
+		uintptr_t m_end = m->limit;
+
+		for (; idx_b < type_b->count + 1; idx_b++) {
+			memblock_region_t *r = &type_b->regions[idx_b];
+
+			/* r_start and r_end delimit the region of memory between the current and previous reserved regions */
+			uintptr_t r_start = idx_b > 0 ? r[-1].limit + 1 : 0;
+			uintptr_t r_end = idx_b < type_b->count ? r->base - 1 : ADDR_MAX;
+
+			if (r_start >= m_end) {
+				/* we've gone past the end of the current memory region, and need to go to the next one */
+				break;
+			}
+
+			if (m_start < r_end) {
+				it->base = MAX(m_start, r_start);
+				it->limit = MIN(m_end, r_end);
+
+				if (m_end <= r_end) {
+					idx_a++;
+				} else {
+					idx_b++;
+				}
+
+				it->idx = ITER(idx_a, idx_b);
+				return;
+			}
+		}
+	}
+
+	it->idx = ITER_END;
+}