#include "include/acpi.h"
#include "include/utils.h"

OS_ACPI_Header* acpi_rsdt;
OS_ACPI_Header** acpi_root_tables;
os_u32 acpi_root_tables_amount;

os_bool os_check_acpi(OS_ACPI_Header* header) {
	os_u32 len = header->length;
	os_u8* ptr = (os_u8*)header;
	os_u8 sum = 0;
	for(os_u32 i = 0; i < len; i++) {
		sum += *ptr;
		++ptr;
	}

	return sum == 0 ? OS_TRUE : OS_FALSE;
}

os_bool os_acpi_init(OS_RSDPDescriptor* desc) {
	OS_ACPI_Header* rsdt_header = (OS_ACPI_Header*)desc->rsdt_address;

	if (os_check_acpi(rsdt_header) == OS_FALSE) {
		return OS_FALSE;
	}

	acpi_rsdt = rsdt_header;
	acpi_root_tables = (OS_ACPI_Header**) (((os_u32)acpi_rsdt) + sizeof(OS_ACPI_Header));
	acpi_root_tables_amount = (acpi_rsdt->length - sizeof(OS_ACPI_Header)) / sizeof(OS_ACPI_Header*);

	return OS_TRUE;
}

OS_ACPI_Header* os_acpi_find_table(os_u8* sig) {
	for(os_u32 i = 0; i < acpi_root_tables_amount; i++) {
		OS_ACPI_Header* h = acpi_root_tables[i];

		if(os_data_compare(sig, (os_u8*)h->signature, 4) == OS_TRUE &&
			os_check_acpi(h) == OS_TRUE) {
			return h;
		}
	}

	return (OS_ACPI_Header*)0;
}