bitset: add functions to manipulate bitsets

Makefile

@@ -16,6 +16,7 @@ CFLAGS += -Iinclude
 CFLAGS += -Wall -Wundef -Wextra -Wshadow -Wimplicit-function-declaration
 CFLAGS += -Wredundant-decls -Wmissing-prototypes -Wstrict-prototypes
 
+obj-y += source/bitset.o
 obj-y += source/main.o
 obj-y += source/shell/cmd.o
 obj-y += source/shell/flash.o

include/bitset.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdlib.h>
+
+int is_bit_set(uint8_t *set, size_t n);
+void set_bit(uint8_t *set, size_t n);
+void clear_bit(uint8_t *set, size_t n);

source/bitset.c

@@ -0,0 +1,32 @@
+#include <bitset.h>
+#include <macros.h>
+
+int is_bit_set(uint8_t *set, size_t n)
+{
+	uint8_t *word, mask;
+
+	word = set + n / BIT_SIZE(*set);
+	mask = (1 << (n % BIT_SIZE(*set)));
+
+	return (*word & mask) ? 1 : 0;
+}
+
+void set_bit(uint8_t *set, size_t n)
+{
+	uint8_t *word, mask;
+
+	word = set + n / BIT_SIZE(*set);
+	mask = (1 << (n % BIT_SIZE(*set)));
+
+	*word |= mask;
+}
+
+void clear_bit(uint8_t *set, size_t n)
+{
+	uint8_t *word, mask;
+
+	word = set + n / BIT_SIZE(*set);
+	mask = (1 << (n % BIT_SIZE(*set)));
+
+	*word &= ~mask;
+}