Re: [PATCH 1/2] hexdump: minimize the output width of the offset

[Randy Dunlap]

On 8/7/23 18:10, Leizhen (ThunderTown) wrote:
> 
> 
> On 2023/8/8 6:37, Randy Dunlap wrote:
>> Hi--
>>
>> On 8/5/23 00:21, thunder.leizhen@xxxxxxxxxxxxxxx wrote:
>>> 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. But we usually dump only tens or hundreds
>>> of bytes, occasionally thousands of bytes. Therefore, the output offset
>>> value always has a number of leading zeros, which increases the number of
>>> bytes printed and reduces readability. Let's minimize the output width of
>>> the offset based on the number of significant bits of its maximum value.
>>>
>>> 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 06833d404398d74..86cb4cc3eec485a 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 - 1;	/* offset start from 0, so minus 1 */
>>> +
>>> +		do {
>>> +			width++;
>>> +			tmp >>= 4;
>>> +		} while (tmp);
>>> +	}
>>> +
>>
>> You could put all of that ^^^ in the case DUMP_PREFIX_OFFSET below.
> 
> for (i = 0; i < len; i += rowsize) {
> 
> "case DUMP_PREFIX_OFFSET" is in the loop, and moving the code above
> to the case DUMP_PREFIX_OFFSET will be calculate multiple times. But
> following your prompt, I thought again, I can control it with the
> local variable width. I will post v2 right away.

Ah I see. My apologies.

>> Otherwise LGTM.
>>
>> Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
>> Thanks.
>>
>>>  	for (i = 0; i < len; i += rowsize) {
>>>  		linelen = min(remaining, rowsize);
>>>  		remaining -= rowsize;
>>> @@ -282,7 +291,7 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
>>>  			       level, prefix_str, 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);
>>
> 

-- 
~Randy