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ColumnWriter.d

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00001 /*******************************************************************************
00002 
00003         @file ColumnWriter.d
00004         
00005         Copyright (c) 2004 Kris Bell
00006         
00007         This software is provided 'as-is', without any express or implied
00008         warranty. In no event will the authors be held liable for damages
00009         of any kind arising from the use of this software.
00010         
00011         Permission is hereby granted to anyone to use this software for any 
00012         purpose, including commercial applications, and to alter it and/or 
00013         redistribute it freely, subject to the following restrictions:
00014         
00015         1. The origin of this software must not be misrepresented; you must 
00016            not claim that you wrote the original software. If you use this 
00017            software in a product, an acknowledgment within documentation of 
00018            said product would be appreciated but is not required.
00019 
00020         2. Altered source versions must be plainly marked as such, and must 
00021            not be misrepresented as being the original software.
00022 
00023         3. This notice may not be removed or altered from any distribution
00024            of the source.
00025 
00026         4. Derivative works are permitted, but they must carry this notice
00027            in full and credit the original source.
00028 
00029 
00030                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00031 
00032 
00033         @version        Initial version, March 2004      
00034         @author         Kris
00035 
00036 
00037 *******************************************************************************/
00038 
00039 module mango.io.ColumnWriter;
00040 
00041 private import  mango.io.Exception;
00042 
00043 public  import  mango.io.DisplayWriter;
00044 
00045 /*******************************************************************************
00046 
00047         Print readable output to an IWriter, distributed across a set of
00048         columns. Columns start at zero rather than one, so adjust counts
00049         appropriately. All output is currently left-aligned. 
00050 
00051         This is how one might use ColumnWriter:
00052         
00053         @code
00054         static int[] columns = [0, 4, 14, 24];
00055 
00056         // map a ColumnWriter directly onto Stdout
00057         ColumnWriter cw = new ColumnWriter (Stdout.getBuffer(), new ColumnList(columns));
00058 
00059         // set 2 digits of precision
00060         cw.setPrecision (2);
00061 
00062         // opShl style     
00063         cw << 1 << 20.34944 << "test" << cw.newline;
00064         
00065         // put() style
00066         cw.put(1).put(20.34944).put("test").cr();
00067         @endcode
00068 
00069         Note that ColumnWriter may be used with files, sockets, or any other
00070         buffer-oriented construct.
00071 
00072 *******************************************************************************/
00073 
00074 class ColumnWriter : DisplayWriter
00075 {
00076         private int             output;
00077         private ColumnList      columns;
00078         private static ubyte    spaces[256];
00079 
00080         alias opShl put;
00081         alias DisplayWriter.opShl opShl;
00082 
00083         /***********************************************************************
00084         
00085                 Construct a ColumnWriter upon the given IBuffer, with the
00086                 specified set of columns.
00087                 
00088         ***********************************************************************/
00089 
00090         this (IBuffer buffer, ColumnList columns)
00091         in {
00092            assert (buffer);
00093            assert (columns);
00094            }
00095         body
00096         {
00097                 super (buffer);
00098                 
00099                 this.columns = columns;
00100                 reset ();
00101         }
00102      
00103         /***********************************************************************
00104         
00105                 Populate the space padding with valid spaces.
00106 
00107         ***********************************************************************/
00108 
00109         static this ()
00110         {
00111                 spaces[] = ' ';
00112         }
00113      
00114         /***********************************************************************
00115         
00116                 Reset everything back to zero. Typical usage will invoke
00117                 this whenever a Newline is emitted. 
00118                 
00119                 Note that we maintain our own internal count of how many 
00120                 bytes have been output: this is because we cannot depend 
00121                 on the Buffer to provide that for us if (a) the buffer is 
00122                 very small, or (b) the buffer is flushed after each write 
00123                 (Stdout etc).
00124 
00125         ***********************************************************************/
00126 
00127         void reset ()
00128         {
00129                 output = 0;
00130                 columns.reset ();
00131         }
00132 /+     
00133         /***********************************************************************
00134         
00135                 Return the width of the current column.
00136 
00137         ***********************************************************************/
00138 
00139         override int getWidth ()
00140         {
00141                 return columns.getWidth;
00142         }
00143 +/
00144         /***********************************************************************
00145         
00146                 Intercept the IWritable type so we can reset our columns
00147                 when a newline is emitted.
00148 
00149         ***********************************************************************/
00150 
00151         override IWriter opShl (IWritable x)
00152         {                       
00153                // have superclass print the IWritable
00154                 super.opShl (x);
00155 
00156                 // reset columns on a newline
00157                 if (cast (INewlineWriter) x)
00158                     reset ();
00159 
00160                 return this;
00161         }
00162      
00163         /***********************************************************************
00164         
00165                 Intercept the output so we can write some spaces first. 
00166                 Note that our superclass (DisplayWriter) converts each
00167                 of its arguments to a char[] first, so this override is
00168                 able to catch everything emitted.
00169 
00170                 @todo - add the equivalent intercepts for both wchar[] 
00171                         and dchar[] methods.
00172 
00173         ***********************************************************************/
00174 
00175         override IWriter opShl (char[] x)
00176         {    
00177                 pad ();
00178                 output += x.length;
00179                 return super.opShl (x);
00180         }
00181 
00182         /***********************************************************************
00183 
00184                 Pad the output with spaces to reach the next column
00185                 position. This should be invoked before anything is
00186                 written to the buffer.
00187         
00188         ***********************************************************************/
00189 
00190         private final void pad ()
00191         {    
00192                 int padding = columns.next() - output;
00193 
00194                 // pad output to next column position?
00195                 if (padding > 0)
00196                    if (padding <= spaces.sizeof)
00197                       {
00198                       // yep - write a set of spaces
00199                       encode.char8 (spaces, padding);
00200                       output += padding;
00201                       }
00202                    else
00203                       throw new IOException ("Invalid column step (> 256)");
00204         }
00205 }
00206 
00207 
00208 /*******************************************************************************
00209 
00210         A list of columns for the ColumnWriter to utilize.
00211 
00212 *******************************************************************************/
00213 
00214 class ColumnList
00215 {
00216         private int     index;
00217         private int[]   columns;
00218 
00219         private bool    rightAlign;  // this needs to be per column instead
00220 
00221         /***********************************************************************
00222         
00223                 Construct a ColumnList via an array of integers.
00224 
00225         ***********************************************************************/
00226 
00227         this (int[] columns)
00228         in {
00229            assert (columns);
00230            }
00231         body
00232         {
00233                 reset ();
00234                 this.columns = columns;
00235         }
00236 
00237         /***********************************************************************
00238         
00239                 Start returning columns from the beginning.
00240 
00241         ***********************************************************************/
00242 
00243         void reset ()
00244         {
00245                 index = 0;
00246         }
00247 
00248         /***********************************************************************
00249         
00250                 Return width of the current column
00251 
00252         ***********************************************************************/
00253 
00254         int getWidth ()
00255         {
00256                 if (rightAlign)
00257                    {
00258                    int i = index;
00259                 
00260                    if (i == 0)
00261                        ++i;
00262 
00263                    if (i < columns.length)
00264                        return columns[i] - columns[i-1];
00265                    }
00266                 return 0;
00267         }
00268 
00269         /***********************************************************************
00270         
00271                 Returns next column in the sequence. Assume that we'll be
00272                 invoked (quasi-legally) when there's no more columns left.
00273 
00274         ***********************************************************************/
00275 
00276         int next ()
00277         {
00278                 if (index < columns.length)
00279                     ++index;
00280 
00281                 return columns [index-1];
00282         }
00283 }
00284 

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