On 2015-10-03 12:09, Axel Burri wrote:
>
>
> On 2015-10-03 11:56, Goffredo Baroncelli wrote:
>> On 2015-10-02 18:41, axel@xxxxxxx wrote:
>>> Old implementation used tabs "\t", and tried to work around problems
>>> by guessing amount of tabs needed (e.g. "\t\t" after top level", with
>>> buggy output as soon as empty uuids are printed). This will never work
>>> correctly, as tab width is a user-defined setting in the terminal.
>>
>>
>> Why not use string_table() and table_*() functions ?
>
> string_table(), as well as all table functions by nature, needs to know
> the maximum size of all cells in a row before printing, and therefore
> buffers all the output before printing. It would eat up a lot of memory
> for large tables (it is not unusual to have 1000+ subvolumes in btrfs if
> you make heavy use of snapshotting). Furthermore, it would slow down
> things by not printing the output linewise.
Assuming 200bytes per row (== subvolume) x 1000 subvolumes = 200kB... I don't think that this could be a problem, nor in terms of memory used nor in terms of speed: if you have 1000+ subvolumes the most time consuming activity is traversing the filesystem looking at the snapshot...
>
>>
>>>
>>> Keep it simple and don't reimplement the wheel, for nice tabular
>>> output we have the "column" command from util-linux:
>>>
>>> btrfs subvolume list -t <path> | column -t
>>>
>>> Signed-off-by: Axel Burri <axel@xxxxxxx>
>>> ---
>>> btrfs-list.c | 40 ++++++++++++----------------------------
>>> 1 file changed, 12 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/btrfs-list.c b/btrfs-list.c
>>> index f8396e7..c09257a 100644
>>> --- a/btrfs-list.c
>>> +++ b/btrfs-list.c
>>> @@ -45,12 +45,12 @@ struct root_lookup {
>>> };
>>>
>>> static struct {
>>> - char *name;
>>> + char *name; /* machine-readable column identifier: [a-z_]+ */
>>> char *column_name;
>>> int need_print;
>>> } btrfs_list_columns[] = {
>>> {
>>> - .name = "ID",
>>> + .name = "id",
>>> .column_name = "ID",
>>> .need_print = 0,
>>> },
>>> @@ -70,7 +70,7 @@ static struct {
>>> .need_print = 0,
>>> },
>>> {
>>> - .name = "top level",
>>> + .name = "top_level",
>>> .column_name = "Top Level",
>>> .need_print = 0,
>>> },
>>> @@ -1465,13 +1465,10 @@ static void print_single_volume_info_table(struct root_info *subv)
>>> if (!btrfs_list_columns[i].need_print)
>>> continue;
>>>
>>> - print_subvolume_column(subv, i);
>>> -
>>> - if (i != BTRFS_LIST_PATH)
>>> - printf("\t");
>>> + if (i != 0)
>>> + printf(" ");
>>>
>>> - if (i == BTRFS_LIST_TOP_LEVEL)
>>> - printf("\t");
>>> + print_subvolume_column(subv, i);
>>> }
>>> printf("\n");
>>> }
>>> @@ -1496,30 +1493,17 @@ static void print_single_volume_info_default(struct root_info *subv)
>>> static void print_all_volume_info_tab_head(void)
>>> {
>>> int i;
>>> - int len;
>>> - char barrier[20];
>>> -
>>> - for (i = 0; i < BTRFS_LIST_ALL; i++) {
>>> - if (btrfs_list_columns[i].need_print)
>>> - printf("%s\t", btrfs_list_columns[i].name);
>>> -
>>> - if (i == BTRFS_LIST_ALL-1)
>>> - printf("\n");
>>> - }
>>>
>>> for (i = 0; i < BTRFS_LIST_ALL; i++) {
>>> - memset(barrier, 0, sizeof(barrier));
>>> + if (!btrfs_list_columns[i].need_print)
>>> + continue;
>>>
>>> - if (btrfs_list_columns[i].need_print) {
>>> - len = strlen(btrfs_list_columns[i].name);
>>> - while (len--)
>>> - strcat(barrier, "-");
>>> + if (i != 0)
>>> + printf(" ");
>>>
>>> - printf("%s\t", barrier);
>>> - }
>>> - if (i == BTRFS_LIST_ALL-1)
>>> - printf("\n");
>>> + printf(btrfs_list_columns[i].name);
>>> }
>>> + printf("\n");
>>> }
>>>
>>> static void print_all_volume_info(struct root_lookup *sorted_tree,
>>>
>>
>>
>
--
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5
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