[PATCH v6 2/5] hexdump: minimize the output width of the offset

[thunder . leizhen]

From: Zhen Lei <thunder.leizhen@xxxxxxxxxx>

The offset of case DUMP_PREFIX_OFFSET always starts from 0. Currently,
the output width is fixed to 8. Therefore, the high-order bits filled
with zeros are meaningless except for increasing the number of characters
to be printed. Let's minimize the output width of the offset to improve
readability.

Before:
dump_size=36:
00000000: c0 ba 8c 80 00 80 ff ff 6c 93 ee 2f ee bf ff ff
00000010: 00 50 1e 98 ff 27 ff ff 01 00 00 00 00 00 00 00
00000020: 80 ca 2f 98

After:
dump_size=8:
0: c0 ba 89 80 00 80 ff ff

dump_size=36:
00: c0 3a 91 80 00 80 ff ff 6c 93 ae 76 30 ce ff ff
10: 00 60 cd 60 7d 4e ff ff 01 00 00 00 00 00 00 00
20: 40 9e 29 40

dump_size=300:
000: c0 ba 8d 80 00 80 ff ff 6c 93 ce d4 78 a7 ff ff
010: 00 00 16 18 0c 40 ff ff 01 00 00 00 00 00 00 00
020: 01 00 00 00 00 00 00 00 e8 bc 8d 80 00 80 ff ff
... ...
110: 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
120: 00 08 12 01 0c 40 ff ff 00 00 01 00

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
 lib/hexdump.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/lib/hexdump.c b/lib/hexdump.c
index 247c8765cc7ca3f..d3c5b7bb1b8813b 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -263,12 +263,21 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
 		    const void *buf, size_t len, bool ascii)
 {
 	const u8 *ptr = buf;
-	int i, linelen, remaining = len;
+	int i, linelen, width = 0, remaining = len;
 	unsigned char linebuf[32 * 3 + 2 + 32 + 1];
 
 	if (rowsize != 16 && rowsize != 32)
 		rowsize = 16;
 
+	if (prefix_type == DUMP_PREFIX_OFFSET) {
+		unsigned long tmp = len;
+
+		do {
+			width++;
+			tmp >>= 4;
+		} while (tmp);
+	}
+
 	for (i = 0; i < len; i += rowsize) {
 		linelen = min(remaining, rowsize);
 		remaining -= rowsize;
@@ -286,7 +295,7 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
 			       prefix_str, 0xffff & (unsigned long)(ptr + i), linebuf);
 			break;
 		case DUMP_PREFIX_OFFSET:
-			printk("%s%s%.8x: %s\n", level, prefix_str, i, linebuf);
+			printk("%s%s%0*x: %s\n", level, prefix_str, width, i, linebuf);
 			break;
 		default:
 			printk("%s%s%s\n", level, prefix_str, linebuf);
-- 
2.34.1