1 files changed, 78 insertions, 0 deletions
diff --git a/hello_os/bits.h b/hello_os/bits.h
new file mode 100644
index 0000000..f0f16a2
--- /dev/null
+++ b/hello_os/bits.h
@@ -0,0 +1,78 @@
+#pragma once
+
+#include <stdint.h>
+
+static inline uint32_t bit_clr(uint32_t x, unsigned bit) {
+    return x & ~(1 << bit);
+}
+
+static inline uint32_t bit_set(uint32_t x, unsigned bit) {
+    return x | (1 << bit);
+}
+
+static inline uint32_t bit_assign(uint32_t x, unsigned bit, unsigned val) {
+    x = bit_clr(x, bit);
+    return x | (val << bit);
+}
+
+#define bit_isset bit_is_on
+#define bit_get   bit_is_on
+
+static inline unsigned bit_is_on(uint32_t x, unsigned bit) {
+    return (x >> bit) & 1;
+}
+static inline unsigned bit_is_off(uint32_t x, unsigned bit) {
+    return bit_is_on(x, bit) == 0;
+}
+
+static inline uint32_t bits_mask(unsigned nbits) {
+    if (nbits == 32)
+        return ~0;
+    return (1 << nbits) - 1;
+}
+
+static inline uint32_t bits_get(uint32_t x, unsigned lb, unsigned ub) {
+    return (x >> lb) & bits_mask(ub - lb + 1);
+}
+
+static inline uint32_t bits_clr(uint32_t x, unsigned lb, unsigned ub) {
+    uint32_t mask = bits_mask(ub - lb + 1);
+    return x & ~(mask << lb);
+}
+
+static inline uint32_t bits_set(uint32_t x,
+                                unsigned lb,
+                                unsigned ub,
+                                uint32_t v) {
+    return bits_clr(x, lb, ub) | (v << lb);
+}
+
+static inline unsigned bits_eq(uint32_t x,
+                               unsigned lb,
+                               unsigned ub,
+                               uint32_t val) {
+    return bits_get(x, lb, ub) == val;
+}
+
+static inline unsigned bit_count(uint32_t x) {
+    unsigned cnt = 0;
+    for (unsigned i = 0; i < 32; i++)
+        if (bit_is_on(x, i))
+            cnt++;
+    return cnt;
+}
+
+static inline uint32_t bits_union(uint32_t x, uint32_t y) {
+    return x | y;
+}
+
+static inline uint32_t bits_intersect(uint32_t x, uint32_t y) {
+    return x & y;
+}
+static inline uint32_t bits_not(uint32_t x) {
+    return ~x;
+}
+
+static inline uint32_t bits_diff(uint32_t A, uint32_t B) {
+    return bits_intersect(A, bits_not(B));
+}