ShowTable - routines to display tabular data in several


       use Data::ShowTable;

       ShowTable \@titles, \@types, \@widths, \&row_sub [,
       \&fmt_sub ];

       $Data::ShowTable::Show_Mode = 'mode';

       $Data::ShowTable::Term_Columns = NNN;

       $Data::ShowTable::Max_Table_Width = NNN;

       $Data::ShowTable::No_Escape = flag;

       %Data::ShowTable::URL_Keys = { "$colname" => "$col_URL",
       ... };

       ShowRow $rewindflag, \$index, $col_array_1 [,
       $col_array_2, ...;]

       ShowDatabases \@dbnames;

       ShowTables \@tblnames;

       ShowColumns \@columns, \@col_types, \@col_lengths,

       ShowBoxTable \@titles, \@types, \@widths, \&row_sub [,
       \&fmt_sub ];

       ShowSimpleTable \@titles, \@types, \@widths, \&row_sub [,

       ShowHTMLTable \@titles, \@types, \@widths, \&row_sub [,

       ShowListTable \@titles, \@types, \@widths, \&row_sub [,

       $fmt = ShowTableValue $value, $type, $max_width, $width,


       The ShowTable module provides subroutines to display
       tabular data, typially from a database, in nicely
       formatted columns, in several formats.  The output format
       for any one invocation can be one of four possible styles:

       Box       A tabular format, with the column titles and the
                 ShowBoxTable for details.

       Table     A simple tabular format, with columns
                 automatically aligned, with column titles.  See
                 the section on ShowSimpleTable.

       List      A list style, where columns of data are listed
                 as a name:value pair, one pair per line, with
                 rows being one or more column values, separated
                 by an empty line.  See the section on

       HTML      The data is output as an HTML TABLE, suitable
                 for display through a Web-client.  See the
                 section on ShowHTMLTable.

       The subroutines which perform these displays are listed


       This module exports the following subroutines:

        ShowDatabases    - show list of databases
        ShowTables       - show list of tables
        ShowColumns      - show table of column info
        ShowTable        - show a table of data
        ShowRow          - show a row from one or more columns
        ShowTableValue   - show a single column's value
        ShowBoxTable     - show a table of data in a box
        ShowListTable    - show a table of data in a list
        ShowSimpleTable  - show a table of data in a simple table
        ShowHTMLTable    - show a table of data using HTML

       All of these subroutines, and others, are described in
       detail in the following sections.



       Format and display the contents of one or more rows of

         ShowTable \@titles, \@types, \@widths, \&row_sub [,
       \&fmt_sub ];

         $Data::ShowTable::Show_Mode = 'mode';

         $Data::ShowTable::Term_Columns = NNN;

         $Data::ShowTable::Max_Table_Width = NNN;

         $Data::ShowTable::No_Escape = flag;

       display: Box, Table, List, and HTML.  Each mode is
       described separately below.

       The arguments to ShowTable are:

       \@titles  A reference to an array of column names, or
                 titles.  If a particular column name is null,
                 then the string Column num is used by default.
                 To have a column have no title, use the empty

       \@types   A reference to an array of types, one for each
                 column.  These types are passed to the fmt_sub
                 for appropriate formatting.  Also, if a column
                 type matches the regexp "/text|char|string/i",
                 then the column alignment will be left-
                 justified, otherwise it will be right-justified.

       \@widths  A reference to an array of column widths, which
                 may be given as an integer, or as a string of
                 the form: "width.precision".

       \&row_sub A reference to a subroutine which successively
                 returns rows of values in an array.  It is
                 called for two purposes, each described

                 * To fetch successive rows of data:

                     @row = &$row_sub(0);

                 When given a null, zero, or empty argument, the
                 next row is returned.

                 * To initialize or rewind the data traversal.

                     $rewindable = &$row_sub(1);

                 When invoked with a non-null argument, the
                 subroutine should rewind its row pointer to
                 start at the first row of data.  If the data
                 which row_sub is traversing is not rewindable,
                 it must return zero or null.  If the data is
                 rewindable, a non-null, non-zero value should be

                 The row_sub must expect to be invoked once with
                 a non-null argument, in order to discover
                 whether or not the data is rewindable.  If the
                 data cannot be rewound, row_sub will thereafter
                 only be called with a zero argument.

                     $rewindable = &$row_sub(1);
                     if ($rewindable) {
                         while ((@row = &$row_sub(0)), $#row >= 0) {
                             # examine lengths for optimal formatting
                         &$row_sub(1);   # rewind
                     while ((@row = &$row_sub(0)), $#row >= 0) {
                         # format the data

                 The consequence of data that is not rewindable,
                 a reasonably nice table will still be formatted,
                 but it may contain fairly large amounts of
                 whitespace for wide columns.

       \&fmt_sub A reference to a subroutine which formats a
                 value, according to its type, width, precision,
                 and the current column width.  It is invoked
                 this way:

                   $string = &fmt_sub($value, $type, $max_width, $width, $precision)

                 The $max_width is the maximum width for the
                 column currently being formatted.

                 If $width is omitted, $max_width is assumed.

                 If $precision is omitted, zero is assumed.

                 If \&fmt_sub is omitted, then a default
                 subroutine, ShowTableValue, will be used, which
                 will use Perl's standard string formatting


       Fetch rows successively from one or more columns of data.

         ShowRow $rewindflag, \$index, $col_array_1 [,
       $col_array_2, ...;]

       The ShowRow subroutine returns a row of data from one or
       more columns of data.  It is designed to be used as a
       callback routine, within the ShowTable routine.   It can
       be used to select elements from one or more array
       reference arguments.

       If passed two or more array references as arguments,
       elements of the arrays selected by $index are returned as
       the "row" of data.

       the "row" of data.

       If the $rewindflag flag is set, then the $index pointer is
       reset to zero, and "true" is returned (a scalar 1).  This
       indicates that the data is rewindable to the ShowTable

       When the $rewindflag is not set, then the current row of
       data, as determined by $index is returned, and $index will
       have been incremented.

       An actual invocation (from ShowColumns) is:

         ShowTable \@titles, \@types, \@lengths,
             sub { &ShowRow( $_[0], \$current_row, $col_names, $col_types,
                             $col_lengths, \@col_attrs); };

       In the example above, after each invocation, the
       $current_row argument will have been incremented.


       Show a list of database names.

         ShowDatabases \@dbnames;

       ShowDatabases is intended to be used to display a list of
       database names, under the column heading of "Databases".
       It is a special case usage of ShowTable.

       The argument, \@dbnames, is a reference to an array of


       Show an array of table names.

         ShowTables \@tblnames;

       ShowTables is used to display a list of table names, under
       the column heading of "Tables".  It is a special case
       usage of ShowTable.


       Display a table of column names, types, and attributes.

         ShowColumns \@columns, \@col_types, \@col_lengths,

       The ShowColumns subroutine displays a table of column
       names, types, lengths, and other attributes in a nicely
       formatted table.  It is a special case usage of ShowTable.

       The arguments are:

                 An array of column types names.

                 An array of maximum lengths for corresponding

                 An array of column attributes array references
                 (ie: an array of arrays).  The attributes array
                 for the first column are at "$col_attrs-\>[0]".
                 The first attribute of the second column is

       The columns, types, lengths, and attributes are displayed
       in a table with the column headings: "Column", "Type",
       "Length", and "Attributes".  This is a special case usage
       of ShowTable.


       Show tabular data in a box.

         ShowBoxTable \@titles, \@types, \@widths, \&row_sub [,
       \&fmt_sub ];

       The ShowBoxTable displays tabular data in titled columns
       using a "box" of ASCII graphics, looking something like

           | Column1    | Column2  | ... | ColumnN  |
           | Value11    | Value12  | ... | Value 1M |
           | Value21    | Value22  | ... | Value 2M |
           | Value31    | Value32  | ... | Value 3M |
           |  ...       |  ...     | ... |  ...     |
           | ValueN1    | ValueN2  | ... | Value NM |

       The arguments are the same as with ShowTable.  If the
       @titles array is empty, the header row is omitted.


       Display a table of data using a simple table format.

         ShowSimpleTable \@titles, \@types, \@widths, \&row_sub
       [, \&fmt_sub];

       The ShowSimpleTable subroutine formats data into a simple
       table of aligned columns, in the following example:

          -------  -------  -------
          Value1   Value2   Value3
          Value12  Value22  Value32

       Columns are auto-sized by the data's widths, plus two
       spaces between columns.  Values which are too long for the
       maximum colulmn width are wrapped within the column.


       Display a table of data nicely using HTML tables.

         ShowHTMLTable \@titles, \@types, \@widths, \&row_sub [,

       The ShowHTMLTable displays one or more rows of columns of
       data using the HTML C<\ShowTable.

       If the @titles array is empty, no header row is generated.

       There is a variable which controls if and how hypertext
       links are generated within the table:

       %URL_Keys This is a hash array of column names (titles)
                 and corresponding base URLs.  The values of any
                 columns occuring as keys in the hash array will
                 be generated as hypertext anchors using the
                 associated base URL and the column name and
                 value as a querystring for the "col" and "val"
                 parameters, respectively.

       For example, if we define the array:

           $base_url = "http://www.$domain/cgi/lookup";
           %url_cols = ('Author' => $base_url,
                        'Name'   => $base_url);

       Then, the values in the Author column will be generated
       with the following HTML text:

           <A HREF="http://www.$domain/cgi/lookup?col=Author?val=somevalue>somevalue</A>

       and the values in the Name column will be generated with
       the URL:

           <A HREF="http://www.$domain/cgi/lookup?col=Name?val=othervalue>othervalue</A>


       Display a table of data using a list format.

         ShowListTable \@titles, \@types, \@widths, \&row_sub [,

       displayed wth a field name and value pair per line, with
       records being one or more fields .  In other words, the
       output of a table would look something like this:

           Field1-1: Value1-1
           Field1-2: Value1-2
           Field1-3: Value1-3
           Field1-N: Value1-M
           <empty line>
           Field2-1: Value2-1
           Field2-2: Value2-2
           Field2-3: Value2-3
           Field2-N: Value2-N
           FieldM-1: ValueM-1
           FieldM-2: ValueM-2
           FieldM-N: ValueM-N
           <empty line>
           <empty line>

       Characteristics of List mode:

       o         two empty lines indicate the end of data.

       o         An empty field (column) may be omitted, or may
                 have a label, but no data.

       o         A long line can be continue by a null field

                     Field2: blah blah blah
                           : blah blah blah

       o         On a continuation, the null field is an
                 arbitrary number of leading white space, a colon
                 ':', a single blank or tab, followed by the
                 continued text.

       o         Embedded newlines are indicated by the escape
                 mechanism "\n".  Similarly, embedded tabs are
                 indicated with "\t", returns with "\r".

       o         If the @Titles array is empty, the field names
                 "Field NN" are used instead.


       Prepare and return a formatted representation of a value.
       A value argument, using its corresponding type, effective

         $fmt = ShowTableValue $value, $type, $max_width, $width,

       $value    The value to be formatted.

       $type     The type name of the value; eg: char, varchar,
                 int, etc.

                 The maximum width of any value in the current
                 value's column.  If $width is zero or null,
                 $max_width is used by default.  $max_width is
                 also used as a minimum width, in case $width is
                 a smaller value.

       $width    The default width of the value, obtained from
                 the width specification of the column in which
                 this value occurs.

                 The precision specification, if any, from the
                 column width specification.


       The following variables may be set by the user to affect
       the display (with the defaults enclosed in square brackets

       $Show_Mode [Box]
                 This is the default display mode when using
                 ShowTable.  The environment variable,
                 $ENV{'SHOWMODE'}, is used when this variable is
                 null or the empty string.  The possible values
                 for this variable are: "Box", "List", "Table",
                 and "HTML".  Case is insignificant.

       $List_Wrap_Margin [2]
                 This variable's value determines how large a
                 margin to keep before wrarpping a long value's
                 display in a column.  This value is only used in
                 "List" mode.

       $Term_Columns [80]
                 This variable, used in "List" mode, is used to
                 determine how long an output line may be before
                 wrapping it.  The environment variable,
                 $ENV{'COLUMNS'}, is used to define this value
                 when it is null.

       $Max_Table_Width ['']
                 This variable, when set, causes all tables to
                 this variable is not set, which is the default
                 case, there is no maximum table width, and no
                 scaling will be done.

       $No_Escape ['']
                 If set, allows embedded HTML text to be included
                 in the data displayed in an HTML-formatted
                 table.  By default, the HTML formatting
                 characters ("<", ">", and "&") occuring in
                 values are escaped.

       %URL_Keys In HTML mode, this variable is used to recognize
                 which columns are to be displayed with a
                 corresponding hypertext anchor.  See the section
                 on ShowHTMLTable for more details.



         ($num_cols, $widths, $precision, $max_widths) =
               &calc_widths( $widthspec, $titles, $rewindable,
               $row_sub, $fmt_sub, $types, $showmode);


       calc_widths is a generalized subroutine used by all the
       ShowTable variant subroutines to setup internal variables
       prior to formatting for display.  Calc_widths handles the
       column width and precision analysis, including scanning
       the data (if rewindable) for appropriate default values.

       The number of columns in the data is returned, as well as
       three arrays: the declared column widths, the column
       precision values, and the maximum column widths.


       $num_cols is the number of columns in the data.  If the
                 data is not rewindable, this is computed as the
                 maximum of the number of elements in the
                 $widthspec array and the number of elements in
                 the $titles array.  When the data is rewindable,
                 this is the maximum of the number of columns of
                 each row of data.

       $widths   is the column widths array ref, without the
                 precision specs (if any).  Each column's width
                 value is determined by the original $widthspec
                 value and/or the maximum length of the formatted
                 data for the column.

                 original precision component from the
                 $widthspec, and the data is rewindable, then the
                 data is examined to determine the maximum
                 default precision.

                 is the ref to the array of maximum widths for
                 the given columns.


                 A reference to an array of column width (or
                 length) values, each given as an integer, real
                 number, or a string value of "width.precision".
                 If a value is zero or null, the length of the
                 corresponding formatted data (if rewindable) and
                 column title length are used to determine a
                 reasonable default.

                 If a column's width portion is a positive, non-
                 zero number, then the column will be this wide,
                 regardless of the values lengths of the data in
                 the column.

                 If the column's width portion is given as a
                 negative number, then the positive value is used
                 as a minimum column width, with no limit on the
                 maximum column width.  In other words, the
                 column will be at least width characters wide.

                 If the data is not rewindable, and a column's
                 width value is null or zero, then the length of
                 the column title is used.  This may cause severe
                 wrapping of data in the column, if the column
                 data lengths are much greater than the column
                 title widths.

       $titles   The array ref to the column titles; used to
                 determine the minimum acceptable width, as well
                 as the default number of columns.  If the
                 $titles array is empty, then the $widthspec
                 array is used to determine the default number of

                 A flag indicating whether or not the data being
                 formatted is rewindable.  If this is true, a
                 pass over the data will be done in order to
                 calculate the maximum lengths of the actual
                 formatted data, using $fmt_sub (below), rather
                 (ie: the actual column widths may be less than
                 the declared column widths).

                 If it is not desired to have the column widths
                 dynamically adjusted, then set the $rewindable
                 argument to 0, even if the data is rewindable.

       $row_sub  The code reference to the subroutine which
                 returns the data; invoked only if $rewindable is

       $fmt_sub  The subroutine used to determine the length of
                 the data when formatted; if this is omitted or
                 null, the length of the data is used by default.
                 The $fmt_sub is used only when the data is

       $types    An array reference to the types of each of the
                 value columns; used only when $fmt_sub is

       $showmode A string indicating the mode of the eventual
                 display; one of four strings: "box", "table",
                 "list", and "html".  Used to adjust widths for
                 formatting requirements.


         $wrapped = &putcell( \@cells, $c, $cell_width, \@prefix,
       \@suffix, $wrap_flag );

       Output the contents of an array cell at $cell[$c], causing
       text longer than $cell_width to be saved for output on
       subsequent calls.  Prefixing the output of each cell's
       value is a string from the two-element array @prefix.
       Suffixing each cell's value is a string from the two-
       element array @suffix.  The first element of either array
       is selected when $wrap_flag is zero or null, or when there
       is no more text in the current to be output.  The second
       element is selected when $wrap_flag is non-zero, and when
       there is more text in the current cell to be output.

       In the case of text longer than $cell_width, a non-zero
       value is returned.

       Cells with undefined data are not output, nor are the
       prefix or suffix strings.


       Center a string within a given width.

         $field = center $string, $width;

       Compute the maximum value from a list of values.

         $max = &max( @values );


       Compute the minum value from a list of values.

         $min = &min( @values );


       Compute the maximum length of a set of strings in an array

         $maxlength = &max_length( \@array_ref );


       Translate regular text for output into an HTML document.
       This means certain characters, such as "&", ">", and "<"
       must be escaped.

         $output = &htmltext( $input );


       Alan K. Stebbens <>