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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:

#  include <config.h>

#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));
#undef SYNTAX

/* Syntax handler mappings. */
Syntax syntax_table[] = {

#define SYNTAX(name, string)            \
        { CONC (syntax_, name), string },
#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 February, 8 2006 using texi2html