9.3.2 sic_syntax.c

back: sic_repl.c
forward: sic_builtin.c
 
fastback: sic_builtin.c
up: a sample shell application
fastforward: introducing gnu libtool
top: autoconf, automake, and libtool
contents: table of contents
index: index
about: about this document

9.3.2 `sic_syntax.c'

The syntax of the commands in the shell I am writing is defined by a set of syntax handlers which are loaded into `libsic' at startup. I can get the C preprocessor to do most of the repetitive code for me, and just fill in the function bodies:

 
 #if HAVE_CONFIG_H #  include <sic/config.h> #endif #include "sic.h" /* List of builtin syntax. */ #define syntax_functions                \         SYNTAX(escape,  "\")           \         SYNTAX(space,   " \f\n\r\t\v")  \         SYNTAX(comment, "#")            \         SYNTAX(string,  "\"")           \         SYNTAX(endcmd,  ";")            \         SYNTAX(endstr,  "") /* Prototype Generator. */ #define SIC_SYNTAX(name)                \         int name (Sic *sic, BufferIn *in, BufferOut *out) #define SYNTAX(name, string)            \         extern SIC_SYNTAX (CONC (syntax_, name)); syntax_functions #undef SYNTAX /* Syntax handler mappings. */ Syntax syntax_table[] = { #define SYNTAX(name, string)            \         { CONC (syntax_, name), string },   syntax_functions #undef SYNTAX      { NULL, NULL } }; 

This code writes the prototypes for the syntax handler functions, and creates a table which associates each with one or more characters that might occur in the input stream. The advantage of writing the code this way is that when I want to add a new syntax handler later, it is a simple matter of adding a new row to the syntax_functions macro, and writing the function itself.


This document was generated by Gary V. Vaughan on May, 24 2001 using texi2html


GNU Autoconf, Automake and Libtool
GNU Autoconf, Automake, and Libtool
ISBN: 1578701902
EAN: 2147483647
Year: 2002
Pages: 290

Similar book on Amazon

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net