request.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 *
 * Things used to handle special requests (eg. manual feed) globally or on a per
 * page basis. Requests are passed through to the translator using the -R option.
 * The argument to -R can be "request", "request:page", or "request:page:file".
 * If page is omitted (as in the first form) or set to 0 request will be applied
 * to the global environment. In all other cases it applies only to the selected
 * page. If a file is given, page must be supplied, and the lookup is in that file
 * rather than *requestfile.
 *
 */

#include <stdio.h>

#include "gen.h"			/* general purpose definitions */
#include "request.h"			/* a few special definitions */
#include "path.h"			/* for the default request file */

Request	request[MAXREQUEST];		/* next page or global request */
int	nextreq = 0;			/* goes in request[nextreq] */
char	*requestfile = REQUESTFILE;	/* default lookup file */

/*****************************************************************************/

saverequest(want)

    char	*want;			/* grab code for this stuff */

{

    char	*page;			/* and save it for this page */
    char	*strtok();

/*
 *
 * Save the request until we get to appropriate page - don't even bother with
 * the lookup right now. Format of *want string is "request", "request:page", or
 * "request:page:file", and we assume we can change the string here as needed.
 * If page is omitted or given as 0 the request will be done globally. If *want
 * includes a file, request and page must also be given, and in that case *file
 * will be used for the lookup.
 *
 */

    if ( nextreq < MAXREQUEST )  {
	request[nextreq].want = strtok(want, ": ");
	if ( (page = strtok(NULL, ": ")) == NULL )
	    request[nextreq].page = 0;
	else request[nextreq].page = atoi(page);
	if ( (request[nextreq].file = strtok(NULL, ": ")) == NULL )
	    request[nextreq].file = requestfile;
	nextreq++;
    } else error(NON_FATAL, "too many requests - ignoring %s", want);

}   /* End of saverequest */

/*****************************************************************************/

writerequest(page, fp_out)

    int		page;			/* write everything for this page */
    FILE	*fp_out;		/* to this file */

{

    int		i;			/* loop index */

/*
 *
 * Writes out all the requests that have been saved for page. Page 0 refers to
 * the global environment and is done during initial setup.
 *
 */

    for ( i = 0; i < nextreq; i++ )
	if ( request[i].page == page )
	    dumprequest(request[i].want, request[i].file, fp_out);

}   /* End of writerequest */

/*****************************************************************************/

dumprequest(want, file, fp_out)

    char	*want;			/* look for this string */
    char	*file;			/* in this file */
    FILE	*fp_out;		/* and write the value out here */

{

    char	buf[100];		/* line buffer for reading *file */
    FILE	*fp_in;

/*
 *
 * Looks for *want in the request file and if it's found the associated value
 * is copied to the output file. Keywords (ie. the *want strings) begin an @ in
 * the first column of file, while the values (ie. the stuff that's copied to
 * the output file) starts on the next line and extends to the next keyword or
 * to the end of file.
 *
 */

    if ( (fp_in = fopen(file, "r")) != NULL )  {
	while ( fgets(buf, sizeof(buf), fp_in) != NULL )
	    if ( buf[0] == '@' && strncmp(want, &buf[1], strlen(want)) == 0 )
		while ( fgets(buf, sizeof(buf), fp_in) != NULL )
		    if ( buf[0] == '#' || buf[0] == '%' )
			continue;
		    else if ( buf[0] != '@' )
			fprintf(fp_out, "%s", buf);
		    else break;
	fclose(fp_in);
    }	/* End if */

}   /* End of dumprequest */

/*****************************************************************************/