Code review request: cdcontrol status label additon

[M. Warner Losh]

Please find enclosed patches to enable printing of the ISO-9660 Volume
label, if present, for a CD.  I've connected this to the 'status
label' command.  Please comment.

Warner
-------------- next part --------------
Index: cdcontrol.1
===================================================================
--- cdcontrol.1	(revision 187760)
+++ cdcontrol.1	(working copy)
@@ -156,12 +156,14 @@
 Play the right subtrack on both left and right channels.
 .It Ic info
 Print the table of contents.
-.It Ic status Op Cm audio | media | volume
+.It Ic status Op Cm audio | label | media | volume
 Print the information about the disc:
 .Pp
 .Bl -tag -width ".Cm volume" -compact
 .It Cm audio
 the current playing status and position
+.It Cm label
+the current ISO 9660 volume label, if present
 .It Cm media
 the current media catalog status
 .It Cm volume
Index: cdcontrol.c
===================================================================
--- cdcontrol.c	(revision 187760)
+++ cdcontrol.c	(working copy)
@@ -86,6 +86,7 @@
 #define STATUS_AUDIO	0x1
 #define STATUS_MEDIA	0x2
 #define STATUS_VOLUME	0x4
+#define STATUS_LABEL	0x8
 
 struct cmdtab {
 	int command;
@@ -801,6 +802,8 @@
 		what |= STATUS_MEDIA;
 	    else if (!strncasecmp(p, "volume", strlen(p)))
 		what |= STATUS_VOLUME;
+	    else if (!strncasecmp(p, "label", strlen(p)))
+		what |= STATUS_LABEL;
 	    else {
 		warnx("invalid command arguments");
 		return 0;
@@ -851,6 +854,32 @@
 	    else
 		printf ("No volume level info available\n");
 	}
+	if (what & STATUS_LABEL) {
+#define	ISO9660_MAGIC	"\x01" "CD001" "\x01\x00"
+#define	ISO9660_OFFSET	0x8000
+#define	VOLUME_LEN	32
+#define CD_SECTOR_LEN	2048
+#define LABEL_NAME_OFF	0x28
+#define LABEL_NAME_LEN	32
+	    char *sp, *ep, buffer[CD_SECTOR_LEN];
+
+	    lseek(fd, ISO9660_OFFSET, SEEK_SET);
+	    rc = read (fd, buffer, CD_SECTOR_LEN);
+	    if (rc == CD_SECTOR_LEN &&
+	      memcmp(buffer, ISO9660_MAGIC, sizeof(ISO9660_MAGIC) - 1) == 0) {
+		sp = buffer + LABEL_NAME_OFF;
+		ep = sp + LABEL_NAME_LEN - 1;
+		while (*ep == ' ' && ep >= sp)
+		    *ep-- = '\0';
+		if (verbose)
+		    printf("ISO 9660 Label is: %s\n", sp);
+		else
+		    printf("%s\n", sp);
+	    }
+	    else
+		printf("No ISO 9660 label found\n");
+	}
+		
 	return(0);
 }