code_init_file.html

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    void <font color="#008800">Compress</font>();  <font color="#886600">// Remove all Comments and Whitespace.</font>
  
    void <font color="#008800">AddLine</font>(<font color="#880000">cString</font> & <font color="#000088">in_string</font>);  <font color="#886600">// Add a line to beginning of memory.</font>
    <font color="#880000">cString</font> <font color="#008800">RemoveLine</font>();               <font color="#886600">// Remove first line from memory.</font>
    <font color="#880000">cString</font> <font color="#008800">GetLine</font>(<font color="#880000">int</font> <font color="#000088">line_num</font>=0);    <font color="#886600">// Get specified line from memory.</font>

    <font color="#880000">int</font> <font color="#008800">GetNumLines</font>() const { return <font color="#000088">line_list</font>.<font color="#008800">GetSize</font>(); }

    <font color="#886600">// Find a keyword in the specified column. Stop at first occurrence and
    // set in_string to the full line it was found in.</font>
    <font color="#880000">bool</font> <font color="#008800">Find</font>(<font color="#880000">cString</font> & <font color="#000088">in_string</font>, const <font color="#880000">cString</font> & <font color="#000088">keyword</font>, <font color="#880000">int</font> <font color="#000088">col</font>) const;
  
    <font color="#886600">// Find an entry the keyword in first column.  Return the *remainder* of
    // the line.  If not found, just return the default value given.</font>
    <font color="#880000">cString</font> <font color="#008800">ReadString</font>(const <font color="#880000">cString</font> & <font color="#000088">keyword</font>, <font color="#880000">cString</font> <font color="#000088">def</font>="") const;
  };
</pre>

<p>
The cInitFile class has a <font color="#880000">cStringList</font> data
member called <font color="#000088">line_list</font> that can contain a
collection of "strings", in this case lines loaded from the file in question.
The <font color="#008800">Load()</font> method is the one that copies all of
the lines from the file into line_list, and then the
<font color="#008800">Compress()</font> method will remove all comments
(in this case, anything after a <tt>#</tt> on a line), compress all
sequential spaces and tabs down to a single space, and completely remove any
lines that then have nothing left on them.  The
<font color="#008800">AddLine()</font> and
<font color="#008800">RemoveLine()</font> methods allow you to directly
change the contents of memory, while, <font color="#008800">GetLine()</font>
allows you to retrieve a line at a specified position.
The next method in this group is <font color="#008800">GetNumLines()</font>,
which is exactly what it sounds -- it will return the number of lines
currently in memory.


<p>
Finally, we have a pair of methods that allow us to search through the memory
in a more useful manner.  The <font color="#008800">Find()</font> method
seeks out a keyword in a specific column from the loaded file.  It 
returns <tt>true</tt> or <tt>false</tt> depending on if that keyword
was found, and it will fill out the input variable
<font color="#000088">in_string</font> with the contents of the full line
that the keyword was found in.  The other method,
<font color="#008800">ReadString()</font>, is only a slight variation on
Find().  It takes a keyword, searches for it as the first word on any line
in the file, and then returns the remainder of the line.  If the keyword was
nowhere to be found in the file, it will instead return a default value
specified by the user.  Below is the definition of these two functions,
as found in <tt>file.cc</tt>.

<p>
<pre>
  <font color="#880000">bool</font> <font color="#880000">cInitFile</font>::<font color="#008800">Find</font>(<font color="#880000">cString</font> & <font color="#000088">in_string</font>, const <font color="#880000">cString</font> & <font color="#000088">keyword</font>,
                       <font color="#880000">int</font> <font color="#000088">col</font>) const
  {
    <font color="#886600">// Loop through all of the lines until we find our keyword.</font>
    <font color="#880000">cStringIterator</font> <font color="#000088">list_it</font>(<font color="#000088">line_list</font>);
    while ( <font color="#000088">list_it</font>.<font color="#008800">AtEnd</font>() == false ) {
      <font color="#000088">list_it</font>.<font color="#008800">Next</font>();
      <font color="#880000">cString</font> <font color="#000088">cur_string</font> = <font color="#000088">list_it</font>.<font color="#008800">Get</font>();
      if (<font color="#000088">cur_string</font>.<font color="#008800">GetWord</font>(<font color="#000088">col</font>) == <font color="#000088">keyword</font>) {
        <font color="#000088">in_string</font> = <font color="#000088">cur_string</font>;
        return true;
      }
    }

    return false;    <font color="#886600">// Not Found...</font>
  }


  <font color="#880000">cString</font> <font color="#880000">cInitFile</font>::<font color="#008800">ReadString</font>(const <font color="#880000">cString</font> & <font color="#000088">name</font>, <font color="#880000">cString</font> <font color="#000088">def</font>) const
  {
    <font color="#886600">// See if we definitely can't find the keyword.</font>
    if (<font color="#000088">name</font> == "" || <font color="#008800">IsOpen</font>() == false) return <font color="#000088">def</font>;

    <font color="#886600">// Search for the keyword.</font>
    <font color="#880000">cString</font> <font color="#000088">cur_line</font>;
    if ( <font color="#008800">Find</font>(<font color="#000088">cur_line</font>, <font color="#000088">name</font>, 0) == false ) {
      if (<font color="#000088">verbose</font> == true) {
        <font color="#000088">cerr</font> &lt;&lt; "Warning: " &lt;&lt; <font color="#000088">name</font> &lt;&lt; " not in \"" &lt;&lt; <font color="#008800">GetFilename</font>()
             &lt;&lt; "\", defaulting to: " &lt;&lt; <font color="#000088">def</font> &lt;&lt; endl;
      }
      return <font color="#000088">def</font>;
    }

    <font color="#886600">// Pop off the keyword, and return the remainder of the line.</font>
    <font color="#000088">cur_line</font>.<font color="#008800">PopWord</font>();
    return <font color="#000088">cur_line</font>;
  }

</pre>


<p>
This ReadString() method is one of the main ones that we use when
dealing with the genesis file.  In order to find the value of a specific
setting in genesis, we can run ReadString() with the name of that setting as
a keyword, and its value will be returned.  We can specify a default
for everything in case the user does not fill out genesis fully.  This will
all be explained in more detail in the next document.


<h3>The <font color="#880000">cGenesis</font> class</h3>

<p>
The cGenesis class extends cInitFile to add additional functionality that is 
specific to reading in the genesis file.  It does not contain 
new data, but it does have new methods.  Here is a simplified version of the
class declaration:

<pre>
  class <font color="#880000">cGenesis</font> : public <font color="#880000">cInitFile</font> {
  public:
    <font color="#008800">cGenesis</font>(const <font color="#880000">cString</font> & <font color="#000088">_fname</font>);
    <font color="#008800">~cGenesis</font>();

    <font color="#886600">// This Open command will run Open() from cInitFile, but then it will
    // also automatically Load() and Compress() the contents.</font>
    <font color="#880000">int</font> <font color="#008800">Open</font>(<font color="#880000">cString</font> <font color="#000088">_fname</font>, <font color="#880000">int</font> <font color="#000088">mode</font>=(<font color="#880000">ios</font>::<font color="#000088">in</font>|<font color="#880000">ios</font>::<font color="#000088">nocreate</font>));

    <font color="#886600">// Functions to add more data to a loaded genesis file (they use AddLine())</font>
    void <font color="#008800">AddInput</font>(const <font color="#880000">cString</font> & <font color="#000088">in_name</font>, <font color="#880000">int</font> <font color="#000088">in_value</font>);
    void <font color="#008800">AddInput</font>(const <font color="#880000">cString</font> & <font color="#000088">in_name</font>, const <font color="#880000">cString</font> & <font color="#000088">in_value</font>);

    <font color="#886600">// Functions to read in integer or floating point values set in genesis.</font>
    <font color="#880000">int</font> <font color="#008800">ReadInt</font>(const <font color="#880000">cString</font> & <font color="#000088">name</font>, <font color="#880000">int</font> <font color="#000088">base</font>=0, <font color="#880000">bool</font> <font color="#000088">warn</font>=true) const;
    <font color="#880000">double</font> <font color="#008800">ReadFloat</font>(const <font color="#880000">cString</font> & <font color="#000088">name</font>, <font color="#880000">float</font> <font color="#000088">base</font>=0.0, <font color="#880000">bool</font> <font color="#000088">warn</font>=true) const;
};
</pre>

<p>
In this class, the <font color="#008800">Open()</font> method overloads the
one from cInitFile such that it will automatically also call
<font color="#880000">cInitFile</font>::<font color="#008800">Load()</font>
and
<font color="#880000">cInitFile</font>::<font color="#008800">Compress()</font>
inside of it.

<p>
The two <font color="#008800">AddInput</font>() methods are used to add new
values to the memory image of the genesis file that will take precedence over
any loaded directly from the file.  This is made use of when the user
activates Avida with a command line option that has higher priority than a
genesis setting.  Note
that even though both of these methods go by the identical name, C++ knows
which one you are intending to call by the variables passed into
it.  In this case, either an integer or a string will be used as the
second argument.

<p>
Finally, the <font color="#008800">ReadInt</font>() and
<font color="#008800">ReadFloat</font>() methods are used to obtain settings
from the genesis file that are in integer or floating point form respectively.
All these really do are to call
<font color="#880000">cInitFile</font>::<font color="#008800">ReadString</font>()
and then convert the resulting string into the desired type.

<p>
So how do we use this cGenesis class to load in and make use of
the initialization file by the same name?  For that, you'll need to read
about the cConfig class in the next document.