The following code implements buffering on top of datatool
, in order to allow you to process the rows n by n. This works via an environment called lfbuffering
which is called this way:
\begin{lfbuffering}{n}{macro names for needed columns}{code}
\DTLforeach*{database}% Database
{\macro1=colname1, \macro2=colname2, ..., \macrop=colnamep}
{\lfbufProcessOneRow}
\end{lfbuffering}
This will call the code in the third argument of the lfbuffering
environment every time n rows have been read (buffered) by \DTLforeach*
. If less than n rows are available for the last execution of code, it will still be executed; \lfbufNbBufferedRows
tells how many rows are available in the buffer (technically, \lfbufNbBufferedRows
is a \countdef
token; in particular, it is a TeX 〈number〉, i.e., an integer).
So, for instance, if n is 4 and \DTLforeach*
provides 11 database rows in total, the successive invocations of code will see \lfbufNbBufferedRows
equal to 4, 4 then 3 (4 + 4 + 3 = 11). code can be a macro name or more tokens. It has access to the buffered fields using \lfbufField{k}{macroName}
where
k is 1 for the first buffered row, 2 for the second buffered row, etc. (k must be less than or equal to \lfbufNbBufferedRows
);
macroName is any of macro1
, macro2
, ... (elements from the second argument of lfbuffering
, corresponding to part or all of the macro names defined in the \DTLforeach*
call's second mandatory argument, without the leading backslashes).
Let's take a simple example:
\begin{lfbuffering}{3}{Type, Name, Description}{\myPrintBufferedData}
\DTLforeach*{products}% Database
{\NoCoding=No,\Type=Type,\Name=Name,\Description=Description,\Break=Break}
{\lfbufProcessOneRow}
\end{lfbuffering}
Here, we process the rows (records of your products
database) 3 by 3. \lfbufProcessOneRow
is the only token in the third mandatory argument of \DTLforeach*
: its role is to gather in memory the rows read by \DTLforeach*
until it has 3, at which point it will call \myPrintBufferedData
(contents of the code argument of the lfbuffering
environment). You have to define \myPrintBufferedData
to say what you want to do with the buffered rows. Its definition can look like this (given the value used for the second argument of lfbuffering
in this example, \myPrintBufferedData
can access the Type
, Name
and Description
fields):
\newcommand*{\myPrintBufferedData}{%
\setlength{\parindent}{0pt}% for instance
\ifnum\lfbufNbBufferedRows>0 % <-- space or end-of-line here, important!
\lfbufField{1}{Type}, \lfbufField{1}{Name},
\lfbufField{1}{Description}\par
\fi
%
\ifnum\lfbufNbBufferedRows>1 % here too
\lfbufField{2}{Type}, \lfbufField{2}{Name},
\lfbufField{2}{Description}\par
\fi
%
\ifnum\lfbufNbBufferedRows>2 % and here
\lfbufField{3}{Type}, \lfbufField{3}{Name},
\lfbufField{3}{Description}\par\medskip
\fi
}
Since the code argument of the lfbuffering
environment is never called with an empty buffer, the first test (\ifnum\lfbufNbBufferedRows>0
[ended by a space]) could be omitted. But this way, all cases follow the same pattern. Here is a complete example similar to what we just explained:
\RequirePackage{filecontents}
\begin{filecontents*}{product.tex}
%Type =1,2...10
No,Type,Name,Description,Break
1,1,A1,D1,xx
2,1,A1,D2,yy
3,1,A1,D3,break
4,1,A1,D30,ll
5,1,A2,D31,mm
6,1,A2,D131,break
7,1,A3,D132,bb
8,1,A3,D133,tt
9,1,A3,D134,break
10,1,A4,D249,ii
11,1,A10,D1000,bb
12,1,A2,D11,break
13,1,A3,D13,qq
14,1,A3,D135,gg
15,1,A3,D137,break
16,1,A4,D249,ff
17,1,A10,D100,gg
18,1,A43,D318,break
19,1,A44,D319,ss
20,1,A40,D320,ww
21,1,A43,D318,break
22,2,A44,D319,as
23,2,A40,D320,aw
\end{filecontents*}
\documentclass{article}
\usepackage{xparse}
\usepackage{datatool}
\DTLloaddb[autokeys=false]{products}{product.tex}
\ExplSyntaxOn
\int_new:N \l_lfbuf_buffer_depth_int
\seq_new:N \l_lfbuf_colnames_seq
\tl_new:N \l_lfbuf_output_callback_tl
% #1: zero-based index of buffered row
% #2: field name
% #3: value
\cs_new_protected:Npn \lfbuf_store_field_aux:nnn #1#2#3
{
\tl_set:cn { l_lfbuf_data_#1_#2_tl } {#3}
}
\cs_generate_variant:Nn \lfbuf_store_field_aux:nnn { nnV }
% #1: zero-based index of buffered row
% #2: field name
\cs_new_protected:Npn \lfbuf_store_field:nn #1#2
{
% Get the field contents; this requires 3 expansion steps
\tl_set:No \l_tmpa_tl { \use:c {#2} }
\exp_args:NNNo \exp_args:NNo \tl_set:No \l_tmpa_tl { \l_tmpa_tl}
\lfbuf_store_field_aux:nnV {#1} {#2} \l_tmpa_tl
}
\cs_generate_variant:Nn \lfbuf_store_field:nn { Vn }
\cs_new_protected:Npn \lfbuf_clear_buffer_vars:
{
\int_step_inline:nnn { 0 } { \l_lfbuf_buffer_depth_int - 1 }
{
\seq_map_inline:Nn \l_lfbuf_colnames_seq
{ \tl_clear_new:c { l_lfbuf_data_##1_####1_tl } }
}
}
% These two are often identical, but not always
\int_new:N \l_lfbuf_buffered_row_index_int
\int_new:N \lfbufNbBufferedRows % user-accessible from callback code
\cs_new_protected:Npn \lfbuf_process_one_row:
{
\seq_map_inline:Nn \l_lfbuf_colnames_seq
{ \lfbuf_store_field:Vn \l_lfbuf_buffered_row_index_int {##1} }
% Advance the index, but stay modulo \l_lfbuf_buffer_depth_int
\int_set:Nn \l_lfbuf_buffered_row_index_int
{ \int_mod:nn
{ \l_lfbuf_buffered_row_index_int + 1 }
{ \l_lfbuf_buffer_depth_int }
}
% Is the buffer full?
\int_compare:nNnT { \l_lfbuf_buffered_row_index_int } = { 0 }
{
% Print output and start over with an empty buffer.
\int_set_eq:NN \lfbufNbBufferedRows \l_lfbuf_buffer_depth_int
\tl_use:N \l_lfbuf_output_callback_tl
}
}
\cs_new:Npn \lfbuf_get_field:nn #1#2
{
\use:c { l_lfbuf_data_#1_#2_tl }
}
\cs_generate_variant:Nn \lfbuf_get_field:nn { f }
% *********************************************************************
% As opposed to all code-level functions, document commands use 1-based
% indexing (datatool also uses 1-based indexing for rows and columns).
% *********************************************************************
% Expand to field #2 (column title) of buffered row #1 (index starting from 1).
\NewExpandableDocumentCommand \lfbufField { m m }
{
\lfbuf_get_field:fn { \int_eval:n {#1-1} } {#2}
}
\NewDocumentCommand \lfbufProcessOneRow { }
{
\lfbuf_process_one_row:
}
\NewDocumentEnvironment { lfbuffering } { m m +m }
{
\int_set:Nn \l_lfbuf_buffer_depth_int {#1}
\seq_set_from_clist:Nn \l_lfbuf_colnames_seq {#2}
\tl_set:Nn \l_lfbuf_output_callback_tl {#3}
\int_set:Nn \l_lfbuf_buffered_row_index_int { 0 }
\lfbuf_clear_buffer_vars:
\ignorespaces
}
{
\unskip
% If there is buffered data that hasn't been output, process it now (this
% means that the last row of the datatool table didn't fill the buffer).
\int_compare:nNnT { \l_lfbuf_buffered_row_index_int } > { 0 }
{
\int_set_eq:NN \lfbufNbBufferedRows \l_lfbuf_buffered_row_index_int
\tl_use:N \l_lfbuf_output_callback_tl
}
}
\ExplSyntaxOff
\newcommand*{\myPrintBufferedData}{%
\setlength{\parindent}{0pt}%
% I keep this test for symmetry with the other cases, but it is always true.
% You can remove it if you prefer.
\ifnum\lfbufNbBufferedRows>0 % if there remains at least one row
\lfbufField{1}{NoCoding}, \lfbufField{1}{Type}, \lfbufField{1}{Name},
\lfbufField{1}{Description}, \lfbufField{1}{Break}\par
\fi
%
\ifnum\lfbufNbBufferedRows>1
\lfbufField{2}{NoCoding}, \lfbufField{2}{Type}, \lfbufField{2}{Name},
\lfbufField{2}{Description}, \lfbufField{2}{Break}\par
\fi
%
\ifnum\lfbufNbBufferedRows>2
\lfbufField{3}{NoCoding}, \lfbufField{3}{Type}, \lfbufField{3}{Name},
\lfbufField{3}{Description}, \lfbufField{3}{Break}\par\medskip
\fi
}
\begin{document}
% Read and process 3 lines at a time. Call \myPrintBufferedData every time
% the buffer is full as well as at the end (i.e., the last call can have 1,
% 2 or 3 lines, as indicated by \lfbufNbBufferedRows).
\begin{lfbuffering}{3}{NoCoding, Type, Name, Description, Break}
{\myPrintBufferedData}
\DTLforeach*{products}% Database
{\NoCoding=No,\Type=Type,\Name=Name,\Description=Description,\Break=Break}
{\lfbufProcessOneRow}
\end{lfbuffering}
\end{document}

And here is the example with your tcbposter
:
\RequirePackage{filecontents}
\begin{filecontents*}{product.tex}
%Type =1,2...10
No,Type,Name,Description,Break
1,1,A1,D1,xx
2,1,A1,D2,yy
3,1,A1,D3,break
4,1,A1,D30,ll
5,1,A2,D31,mm
6,1,A2,D131,break
7,1,A3,D132,bb
8,1,A3,D133,tt
9,1,A3,D134,break
10,1,A4,D249,ii
11,1,A10,D1000,bb
12,1,A2,D11,break
13,1,A3,D13,qq
14,1,A3,D135,gg
15,1,A3,D137,break
16,1,A4,D249,ff
17,1,A10,D100,gg
18,1,A43,D318,break
19,1,A44,D319,ss
20,1,A40,D320,ww
21,1,A43,D318,break
22,2,A44,D319,as
23,2,A40,D320,aw
\end{filecontents*}
\documentclass{article}
\usepackage[landscape,hscale=0.8]{geometry}
\usepackage{tcolorbox}
\tcbuselibrary{poster}
\usepackage{xparse}
\usepackage{datatool}
\DTLloaddb[autokeys=false]{products}{product.tex}
\ExplSyntaxOn
\int_new:N \l_lfbuf_buffer_depth_int
\seq_new:N \l_lfbuf_colnames_seq
\tl_new:N \l_lfbuf_output_callback_tl
% #1: zero-based index of buffered row
% #2: field name
% #3: value
\cs_new_protected:Npn \lfbuf_store_field_aux:nnn #1#2#3
{
\tl_set:cn { l_lfbuf_data_#1_#2_tl } {#3}
}
\cs_generate_variant:Nn \lfbuf_store_field_aux:nnn { nnV }
% #1: zero-based index of buffered row
% #2: field name
\cs_new_protected:Npn \lfbuf_store_field:nn #1#2
{
% Get the field contents; this requires 3 expansion steps
\tl_set:No \l_tmpa_tl { \use:c {#2} }
\exp_args:NNNo \exp_args:NNo \tl_set:No \l_tmpa_tl { \l_tmpa_tl}
\lfbuf_store_field_aux:nnV {#1} {#2} \l_tmpa_tl
}
\cs_generate_variant:Nn \lfbuf_store_field:nn { Vn }
\cs_new_protected:Npn \lfbuf_clear_buffer_vars:
{
\int_step_inline:nnn { 0 } { \l_lfbuf_buffer_depth_int - 1 }
{
\seq_map_inline:Nn \l_lfbuf_colnames_seq
{ \tl_clear_new:c { l_lfbuf_data_##1_####1_tl } }
}
}
% These two are often identical, but not always
\int_new:N \l_lfbuf_buffered_row_index_int
\int_new:N \lfbufNbBufferedRows % user-accessible from callback code
\cs_new_protected:Npn \lfbuf_process_one_row:
{
\seq_map_inline:Nn \l_lfbuf_colnames_seq
{ \lfbuf_store_field:Vn \l_lfbuf_buffered_row_index_int {##1} }
% Advance the index, but stay modulo \l_lfbuf_buffer_depth_int
\int_set:Nn \l_lfbuf_buffered_row_index_int
{ \int_mod:nn
{ \l_lfbuf_buffered_row_index_int + 1 }
{ \l_lfbuf_buffer_depth_int }
}
% Is the buffer full?
\int_compare:nNnT { \l_lfbuf_buffered_row_index_int } = { 0 }
{
% Print output and start over with an empty buffer.
\int_set_eq:NN \lfbufNbBufferedRows \l_lfbuf_buffer_depth_int
\tl_use:N \l_lfbuf_output_callback_tl
}
}
\cs_new:Npn \lfbuf_get_field:nn #1#2
{
\use:c { l_lfbuf_data_#1_#2_tl }
}
\cs_generate_variant:Nn \lfbuf_get_field:nn { f }
% *********************************************************************
% As opposed to all code-level functions, document commands use 1-based
% indexing (datatool also uses 1-based indexing for rows and columns).
% *********************************************************************
% Expand to field #2 (column title) of buffered row #1 (index starting from 1).
\NewExpandableDocumentCommand \lfbufField { m m }
{
\lfbuf_get_field:fn { \int_eval:n {#1-1} } {#2}
}
\NewDocumentCommand \lfbufProcessOneRow { }
{
\lfbuf_process_one_row:
}
\NewDocumentEnvironment { lfbuffering } { m m +m }
{
\int_set:Nn \l_lfbuf_buffer_depth_int {#1}
\seq_set_from_clist:Nn \l_lfbuf_colnames_seq {#2}
\tl_set:Nn \l_lfbuf_output_callback_tl {#3}
\int_set:Nn \l_lfbuf_buffered_row_index_int { 0 }
\lfbuf_clear_buffer_vars:
\ignorespaces
}
{
\unskip
% If there is buffered data that hasn't been output, process it now (this
% means that the last row of the datatool table didn't fill the buffer).
\int_compare:nNnT { \l_lfbuf_buffered_row_index_int } > { 0 }
{
\int_set_eq:NN \lfbufNbBufferedRows \l_lfbuf_buffered_row_index_int
\tl_use:N \l_lfbuf_output_callback_tl
}
}
\ExplSyntaxOff
\newcommand*{\myPrintBufferedData}{%
\begin{tcbposter}[poster={columns=1, rows=2, spacing=3mm,
height=14cm, width=12cm}]
% Box A
\posterbox[colframe=red, width=6cm, height=5cm]{xshift=0cm, yshift=-3cm}
{% I keep this test for symmetry with the other cases, but it is always
% true. You can remove it if you prefer.
\ifnum\lfbufNbBufferedRows>0
\includegraphics[width=4cm]{example-image-a}\\
\noindent
\lfbufField{1}{NoCoding}\quad
\lfbufField{1}{Name}\quad
\lfbufField{1}{Break}%
\fi
}%
% Box B
\posterbox[colframe=blue, width=6cm, height=5cm]{xshift=8cm, yshift=-3cm}
{%
\ifnum\lfbufNbBufferedRows>1
\includegraphics[width=4cm]{example-image-b}\\
\noindent
\lfbufField{2}{NoCoding}\quad
\lfbufField{2}{Name}\quad
\lfbufField{2}{Break}%
\fi
}%
% Box C
\posterbox[colframe=green, width=6cm, height=5cm]{xshift=16cm, yshift=-3cm}
{%
\ifnum\lfbufNbBufferedRows>2
\includegraphics[width=4cm]{example-image-c}\\
\noindent
\lfbufField{3}{NoCoding}\quad
\lfbufField{3}{Name}\quad
\lfbufField{3}{Break}%
\fi
}%
\end{tcbposter}%
\newpage
}
\newcommand{\printtype}[1]{%
% Read and process 3 lines at a time. Call \myPrintBufferedData every time
% the buffer is full as well as at the end (i.e., the last call can have 1,
% 2 or 3 lines, as indicated by \lfbufNbBufferedRows).
\begin{lfbuffering}{3}{NoCoding, Type, Name, Description, Break}
{\myPrintBufferedData}
\DTLforeach*
[\DTLiseq{\Type}{#1}]% Condition
{products}% Database
{\NoCoding=No,\Type=Type,\Name=Name,\Description=Description,\Break=Break}
{\lfbufProcessOneRow}
\end{lfbuffering}%
}
\begin{document}
\printtype{1}
\end{document}
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