+
+/* Returns the value of the bit with offset 'ofs' in 'src', which is 'len'
+ * bytes long.
+ *
+ * If you consider all of 'src' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in src[len - 1], bit 1 is the bit with value 2, bit 2 is the
+ * bit with value 4, ..., bit 8 is the bit with value 1 in src[len - 2], and so
+ * on.
+ *
+ * Required invariants:
+ * ofs < len * 8
+ */
+bool
+bitwise_get_bit(const void *src_, unsigned int len, unsigned int ofs)
+{
+ const uint8_t *src = src_;
+
+ return (src[len - (ofs / 8 + 1)] & (1u << (ofs % 8))) != 0;
+}
+
+/* Sets the bit with offset 'ofs' in 'dst', which is 'len' bytes long, to 0.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[len - 1], bit 1 is the bit with value 2, bit 2 is the
+ * bit with value 4, ..., bit 8 is the bit with value 1 in dst[len - 2], and so
+ * on.
+ *
+ * Required invariants:
+ * ofs < len * 8
+ */
+void
+bitwise_put0(void *dst_, unsigned int len, unsigned int ofs)
+{
+ uint8_t *dst = dst_;
+
+ dst[len - (ofs / 8 + 1)] &= ~(1u << (ofs % 8));
+}
+
+/* Sets the bit with offset 'ofs' in 'dst', which is 'len' bytes long, to 1.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[len - 1], bit 1 is the bit with value 2, bit 2 is the
+ * bit with value 4, ..., bit 8 is the bit with value 1 in dst[len - 2], and so
+ * on.
+ *
+ * Required invariants:
+ * ofs < len * 8
+ */
+void
+bitwise_put1(void *dst_, unsigned int len, unsigned int ofs)
+{
+ uint8_t *dst = dst_;
+
+ dst[len - (ofs / 8 + 1)] |= 1u << (ofs % 8);
+}
+
+/* Sets the bit with offset 'ofs' in 'dst', which is 'len' bytes long, to 'b'.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[len - 1], bit 1 is the bit with value 2, bit 2 is the
+ * bit with value 4, ..., bit 8 is the bit with value 1 in dst[len - 2], and so
+ * on.
+ *
+ * Required invariants:
+ * ofs < len * 8
+ */
+void
+bitwise_put_bit(void *dst, unsigned int len, unsigned int ofs, bool b)
+{
+ if (b) {
+ bitwise_put1(dst, len, ofs);
+ } else {
+ bitwise_put0(dst, len, ofs);
+ }
+}
+
+/* Flips the bit with offset 'ofs' in 'dst', which is 'len' bytes long.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[len - 1], bit 1 is the bit with value 2, bit 2 is the
+ * bit with value 4, ..., bit 8 is the bit with value 1 in dst[len - 2], and so
+ * on.
+ *
+ * Required invariants:
+ * ofs < len * 8
+ */
+void
+bitwise_toggle_bit(void *dst_, unsigned int len, unsigned int ofs)
+{
+ uint8_t *dst = dst_;
+
+ dst[len - (ofs / 8 + 1)] ^= 1u << (ofs % 8);
+}