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.
>
>>
>> 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,
>>
>
>
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