Tableprinter
============

The table.h provides table printing facility. We need to print table
with arbitrary column types (e.g. int, uint, u64, etc.). The table
columns have names and the order of the columns is configurable. The
table checks that the user writes correct type into a cell of the
table. Additionally, the table allows to print string to an arbitrary
cell (in order to make the table slightly more flexible).

We should be able to print the table in various formats. Currently
there is a human readable format

We demonstrate the table on a table that contains music recordings:

The following enum defines the column indices (the enum is indexed
starting from 0):

// definition of columns
enum table_columns {
   TBL_REC_ID,
   TBL_REC_ALBUM_NAME,
   TBL_REC_ARTIST,
   TBL_REC_YEAR
};

The following structure contains definition of the table. The table
columns are defined using the TBL_COL_xxx and TBL_COL_xxx_FMT
macros. The TBL_COL_xxx macro has two arguments: (1) column name; (2)
width of the table column. The TBL_COL_xxx_FMT has an additional
format argument. There exists flags that causes the column to be
left-aligned (see TBL_REC_ALBUM_NAME for a reference). An example of
the table follows:

struct table recording_table = {
  TBL_COLUMNS {
     [TBL_REC_ID] = TBL_COL_UINT("id", 16),
     [TBL_REC_ALBUM_NAME] = TBL_COL_STR_FMT("album-name", 20 | CELL_ALIGN_LEFT, "%s"),
     [TBL_REC_ARTIST] = TBL_COL_STR("artist", 20),
     [TBL_REC_YEAR] = TBL_COL_UINT("year", 10),
     TBL_COL_END
  }
};

The table struct can be reused for printing of multiple tables.  The
usage of the table is used as follows. After the table init is called:

table_init(&recording_table);

the table is initialized and ready to use. To start printing of the
table, the user has to initialize the fastbuf (which is used for
output) and call table_start:

struct fastbuf *out = bfdopen_shared(1, 4096);

table_start(&recording_table, out);

after the table_start is called, we can start filling the rows. Each
row is ended by table_end_row:

table_col_uint(&recording_table, TBL_REC_ID, 0);
table_col_str(&recording_table, TBL_REC_ALBUM_NAME, "The Wall");
table_col_str(&recording_table, TBL_REC_ARTIST, "Pink Floyd");
table_col_uint(&recording_table, TBL_REC_YEAR, 1979);
table_end_row(&recording_table);

table_col_uint(&recording_table, TBL_REC_ID, 1);
table_col_str(&recording_table, TBL_REC_ALBUM_NAME, "Rio Grande Mud");
table_col_str(&recording_table, TBL_REC_ARTIST, "ZZ Top");
table_col_uint(&recording_table, TBL_REC_YEAR, 1972);
table_end_row(&recording_table);

Printing of the whole table is endded by calling of the table_end():

table_end(&recording_table);


To reuse the recording_table, we just call table_start followed by
table_end once again.

At the end of the lifetime of the struct recording_table we call:
table_cleanup(&recording_table);