smart_ulltoa5: make available in libbb

1 files changed, 54 insertions, 6 deletions

diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index c72265003..352515af4 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -201,23 +201,71 @@ void xsetenv(const char *key, const char *value)
 		bb_error_msg_and_die(bb_msg_memory_exhausted);
 }
 
+
+// Converts unsigned long long value into compact 4-char
+// representation. Examples: "1234", "1.2k", " 27M", "123T"
+// Fifth char is always '\0'
+void smart_ulltoa5(unsigned long long ul, char buf[5])
+{
+	char *fmt;
+	char c;
+	unsigned v,idx = 0;
+	ul *= 10;
+	if (ul > 9999*10) { // do not scale if 9999 or less
+		while (ul >= 10000) {
+			ul /= 1024;
+			idx++;
+		}
+	}
+	v = ul; // ullong divisions are expensive, avoid them
+
+	fmt = " 123456789";
+	if (!idx) {		// 9999 or less: use 1234 format
+		c = buf[0] = " 123456789"[v/10000];
+		if (c!=' ') fmt = "0123456789";
+		c = buf[1] = fmt[v/1000%10];
+		if (c!=' ') fmt = "0123456789";
+		buf[2] = fmt[v/100%10];
+		buf[3] = "0123456789"[v/10%10];
+	} else {
+		if (v>=10*10) {	// scaled value is >=10: use 123M format
+			c = buf[0] = " 123456789"[v/1000];
+			if (c!=' ') fmt = "0123456789";
+			buf[1] = fmt[v/100%10];
+			buf[2] = "0123456789"[v/10%10];
+		} else {	// scaled value is <10: use 1.2M format
+			buf[0] = "0123456789"[v/10];
+			buf[1] = '.';
+			buf[2] = "0123456789"[v%10];
+		}
+		// see http://en.wikipedia.org/wiki/Tera
+		buf[3] = " kMGTPEZY"[idx];
+	}
+	buf[4] = '\0';
+}
+
+
 // Convert unsigned integer to ascii, writing into supplied buffer.  A
 // truncated result is always null terminated (unless buflen is 0), and
 // contains the first few digits of the result ala strncpy.
+void BUG_sizeof_unsigned_not_4(void);
 void utoa_to_buf(unsigned n, char *buf, unsigned buflen)
 {
-	int i, out = 0;
+	unsigned i, out, res;
+	if (sizeof(unsigned) != 4)
+		BUG_sizeof_unsigned_not_4();
 	if (buflen) {
-		for (i=1000000000; i; i/=10) {
-			int res = n/i;
-
-			if ((res || out || i == 1) && --buflen>0) {
+		out = 0;
+		for (i = 1000000000; i; i /= 10) {
+			res = n / i;
+			if (res || out || i == 1) {
+				if (!--buflen) break;
 				out++;
 				n -= res*i;
 				*buf++ = '0' + res;
 			}
 		}
-		*buf = 0;
+		*buf = '\0';
 	}
 }