String Manipulation Module for C02

These functions are not part of the standard C and C++ string libraries. 
They are included because they are more efficient than equivalent C02 code.


  #include <stddef.h02>
  #include <ctype.h02>
  #include <string.h02>
  
The following functions are defined:

  n = strapd(c, s);   Appends character c to string s.
  
                      Returns the new length of the string.
                      
                      Note: Calls strlen(), then writes c into the end
                      position and a 0 byte into the following position.

  n = straps(s);      Appends a space to string s.
                      
                      Returns the new length of the string.
                      
                      Note: Executes strspd with arguments ' ' and s.
                     
  n = strppd(c, s);   Prepends character c to string s.
  
                      Returns the new length of the string.
                      
                      Note: Calls strlen(), shifts the entire string one
                      character to the right and writes c to position 0.

  n = strpps(s);      Prepends a space to string s.
                      
                      Returns the new length of the string.
                      
                      Note: Executes strppd with arguments ' ' and s.
                     
  n = strpad(v,s);    Right pads string s with spaces to length v.
                      
                      If v is less than the current length of the
                      string. the string is not changed.
                      
                      Returns the new length of the string.
                      
                      Note: Calls strlen(), and if the result is less
                      than v, appends the appropriate number of spaces.
                                           
  n = strlwr(s);      Converts letters in string s to lowercase.
                      
                      Returns the length of the string.
                      
                      Note: Sets srcptr to &s, then iterates through 
                      the string, calling tolowr() on each character,
                      
  n = strupr(s);      Converts letters in string s to uppercase.
                      
                      Returns the length of the string.
                      
                      Note: Sets srcptr to &s, then iterates through 
                      the string, calling touppr() on each character,

Note: This module expects the following functions to be defined

  setdst(s);         Set destination pointer
  setsrc(s);         Set source pointer and initialize index

along with the zero page variable pairs
  
  srcptr              Source String Pointer 
  dstptr              Destination String Pointer