Improve SDT checksum functions

src/types.c

@@ -0,0 +1,37 @@
+#include "types.h"
+
+UINT8 SumBytes(const UINT8* arr, UINTN size) {
+	UINT8 sum = 0;
+	for (UINTN i = 0; i < size; ++i) {
+		sum += arr[i];
+	}
+	return sum;
+}
+
+int VerifyAcpiRsdp2Checksums(const void* data) {
+	const UINT8* arr = data;
+	UINTN size = *(const UINT32*)&arr[20];
+	return SumBytes(arr, 20) == 0 && SumBytes(arr, size) == 0;
+}
+
+void SetAcpiRsdp2Checksums(void* data) {
+	UINT8* arr = data;
+	UINTN size = *(const UINT32*)&arr[20];
+	arr[9] = 0;
+	arr[32] = 0;
+	arr[9] = -SumBytes(arr, 20);
+	arr[32] = -SumBytes(arr, size);
+}
+
+int VerifyAcpiSdtChecksum(const void* data) {
+	const UINT8* arr = data;
+	UINTN size = *(const UINT32*)&arr[4];
+	return SumBytes(arr, size) == 0;
+}
+
+void SetAcpiSdtChecksum(void* data) {
+	UINT8* arr = data;
+	UINTN size = *(const UINT32*)&arr[4];
+	arr[9] = 0;
+	arr[9] = -SumBytes(arr, size);
+}