libsmartcols: add lines grouping support

For some use-case we need to describe M:N relation between output
lines. The nice examples are RAIDs or multi-path devices in lsblk
output.

    NAME                 MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
    loop0                  7:0    0 955.7M  0 loop
┌┈▶ ├─test-thin-metadata 253:0    0     2M  0 dm
└┬▶ └─test-thin-data     253:1    0 953.7M  0 dm
 └┈┈test-thin-pool       253:2    0 953.7M  0 dm

In this example two line (test-thin-metadata and test-thin-data) are
parents for another line (test-thin-pool). The new API uses term "group"
for parental line -- the number of group members is unlimited and every
group has at least one child.

It's possible that group's child is member of another group:

       NAME                 MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
       loop0                  7:0    0 955.7M  0 loop
   ┌┈▶ ├─test-thin-metadata 253:0    0     2M  0 dm
   └┬▶ └─test-thin-data     253:1    0 953.7M  0 dm
┌┈▶ └┈┈test-thin-pool       253:2    0 953.7M  0 dm
┆      └─test-thin          253:3    0 190.8M  0 dm
└┬▶    loop1                  7:1    0 190.8M  0 loop
 └┈┈┈┈┈test-thin-extsnap    253:4    0 190.8M  0 dm

For now multi-group relation is unsupported and one line can be member
of one group only. The library API and printing code is ready to
support this feature, but not sure if we really need it. All what is
necessary is to create array of groups in the line struct.

Note that grouping is independent on standard parent->child relations
between lines and grouping can connect arbitrary lines. The
restriction is only that group child cannot be child of another line
or child of another group. These cross reference are (and probably
will be) impossible.

The patch is relative large, but easy to review. Changes:

* add new UTF symbols
* add scols_symbols_set_group_* public API to modify new symbols
* add struct libscols_group, used only internally

* add "grpset" array to table struct -- the array is used to keep
position of the group in the output. Every active group uses three
items in the grpset. If there is more overlapping groups than bigger
grpset is allocated.

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/libsmartcols/src/init.c b/libsmartcols/src/init.c
index 104e43b64..dfd7510dc 100644
--- a/libsmartcols/src/init.c
+++ b/libsmartcols/src/init.c
@@ -25,6 +25,7 @@ UL_DEBUG_DEFINE_MASKNAMES(libsmartcols) =
 	{ "cell", SCOLS_DEBUG_CELL,	"table cell utils" },
 	{ "col", SCOLS_DEBUG_COL,	"cols utils" },
 	{ "help", SCOLS_DEBUG_HELP,	"this help" },
+	{ "group", SCOLS_DEBUG_GROUP,	"lines grouping utils" },
 	{ "line", SCOLS_DEBUG_LINE,	"table line utils" },
 	{ "tab", SCOLS_DEBUG_TAB,	"table utils" },
 	{ NULL, 0, NULL }