move generate_uuid from mkswap to libbb

Signed-off-by: Vladimir Dronnikov <dronnikov@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index aa0812914..e47b01dc1 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -209,3 +209,66 @@ int FAST_FUNC tcsetattr_stdin_TCSANOW(const struct termios *tp)
 {
 	return tcsetattr(STDIN_FILENO, TCSANOW, tp);
 }
+
+void FAST_FUNC generate_uuid(uint8_t *buf)
+{
+	/* http://www.ietf.org/rfc/rfc4122.txt
+	 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                          time_low                             |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |       time_mid                |         time_hi_and_version   |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |clk_seq_and_variant            |         node (0-1)            |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                         node (2-5)                            |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * IOW, uuid has this layout:
+	 * uint32_t time_low (big endian)
+	 * uint16_t time_mid (big endian)
+	 * uint16_t time_hi_and_version (big endian)
+	 *  version is a 4-bit field:
+	 *   1 Time-based
+	 *   2 DCE Security, with embedded POSIX UIDs
+	 *   3 Name-based (MD5)
+	 *   4 Randomly generated
+	 *   5 Name-based (SHA-1)
+	 * uint16_t clk_seq_and_variant (big endian)
+	 *  variant is a 3-bit field:
+	 *   0xx Reserved, NCS backward compatibility
+	 *   10x The variant specified in rfc4122
+	 *   110 Reserved, Microsoft backward compatibility
+	 *   111 Reserved for future definition
+	 * uint8_t node[6]
+	 *
+	 * For version 4, these bits are set/cleared:
+	 * time_hi_and_version & 0x0fff | 0x4000
+	 * clk_seq_and_variant & 0x3fff | 0x8000
+	 */
+	pid_t pid;
+	int i;
+
+	i = open("/dev/urandom", O_RDONLY);
+	if (i >= 0) {
+		read(i, buf, 16);
+		close(i);
+	}
+	/* Paranoia. /dev/urandom may be missing.
+	 * rand() is guaranteed to generate at least [0, 2^15) range,
+	 * but lowest bits in some libc are not so "random".  */
+	srand(monotonic_us());
+	pid = getpid();
+	while (1) {
+		for (i = 0; i < 16; i++)
+			buf[i] ^= rand() >> 5;
+		if (pid == 0)
+			break;
+		srand(pid);
+		pid = 0;
+	}
+
+	/* version = 4 */
+	buf[4 + 2    ] = (buf[4 + 2    ] & 0x0f) | 0x40;
+	/* variant = 10x */
+	buf[4 + 2 + 2] = (buf[4 + 2 + 2] & 0x3f) | 0x80;
+}