make "dd -iseek 0x200" iseek to 512, rather than 0,
also improve checking of numbers and include more
binary multipliers.


Reference: /n/sources/patch/maybe/dd-hex
Date: Fri Dec 10 16:57:41 CET 2010
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/dd.c	Fri Dec 10 16:57:29 2010
+++ /sys/src/cmd/dd.c	Fri Dec 10 16:57:27 2010
@@ -341,40 +341,45 @@
 	return 1;
 }
 
+static	char	power[]	= "kmgtpezy";
+
 vlong
 number(vlong big)
 {
-	char *cs;
+	char *cs, *q, ch;
+	int c;
 	uvlong n;
 
-	cs = string;
-	n = 0;
-	while(*cs >= '0' && *cs <= '9')
-		n = n*10 + *cs++ - '0';
-	for(;;)
-	switch(*cs++) {
-
-	case 'k':
-		n *= 1024;
-		continue;
-
-	case 'b':
-		n *= 512;
-		continue;
-
-/*	case '*':*/
-	case 'x':
-		string = cs;
-		n *= number(VBIG);
-
-	case '\0':
-		if(n > big) {
-			fprint(2, "dd: argument %llud out of range\n", n);
-			exits("range");
+	n = strtoull(string, &cs, 0);
+	if(cs == string){
+bad:
+		fprint(2, "dd: bad number %s\n", string);
+		exits("badnum");
+	}
+	for(;;){
+		switch(ch = *cs++){
+		default:
+			q = strchr(power, ch);
+			if(q == nil)
+				goto bad;
+			for(c = q - power + 1; c--; )
+				n *= 1024;
+			break;
+		case 'b':
+			n *= 512;
+			break;
+		case 'x':
+/*		case '*':*/
+			string = cs;
+			n *= number(VBIG);
+		case '\0':
+			if(n > big) {
+				fprint(2, "dd: argument %llud out of range\n", n);
+				exits("range");
+			}
+			return n;
 		}
-		return n;
 	}
-	/* never gets here */
 }
 
 void
--- /sys/man/1/dd	Fri Dec 10 16:57:35 2010
+++ /sys/man/1/dd	Fri Dec 10 16:57:34 2010
@@ -142,12 +142,20 @@
 .fi
 Where sizes are specified,
 a number of bytes is expected.
-A number may end with
-.L k
-or
+A number may end with a sequence
+of
+.LR k ,
+.LR m ,
+.LR g ,
+.LR t ,
+.LR e ,
+.LR z ,
+.L y 
+to specify multiplication by
+1KiB, 1MiB, etc., or
 .LR b
 to specify multiplication by
-1024 or 512 respectively;
+512;
 a pair of numbers may be separated by
 .L x
 to indicate a product.