in_file.c

linux下的Ｃ语言开发

/********************************************************
 * infile module.					*
 *	Handles opening, reading and display of 	*
 *	data from the input file.			*
 *							*
 * Functions:						*
 *	in_open -- opens the input file.		*
 *	in_close -- close the input file		*
 *	read_char   -- Read the next character.		*
 *	in_char_char -- return the current character	*
 *	in_next_char -- return the next character	*
 *	in_flush -- Send line to the screen.		*
 ********************************************************/
#include <stdio.h>
#include <errno.h>

#include "in_file.h"

#define LINE_MAX 500	/* Longest possible line */

struct input_file {
    FILE *file;		/* File we are reading */
    char line[LINE_MAX];/* Current line */
    char *char_ptr;	/* Current character on the line */

    int cur_char;	/* Current character (can be EOF) */
    int next_char;	/* Next character (can be EOF) */
};

/* Input file that we are reading */
static struct input_file in_file = {
    NULL,		/* file */
    "",			/* line */
    NULL,		/* char_ptr */
    '\0',		/* cur_char */
    '\0'		/* next_char */
};


/********************************************************
 * in_open -- open the input file			*
 *							*
 * Parameters						*
 *	name -- name of disk file to use for input	*
 *							*
 * Returns						*
 *	0 -- Open succeeded.				*
 *	non-zero -- Open failed.			*
 ********************************************************/
int in_open(const char name[])
{
   in_file.file = fopen(name, "r");
   if (in_file.file == NULL)
       return (errno);

    /*
     * Initialize the input file and read the first 2 
     * characters.
     */
    in_file.cur_char = fgetc(in_file.file);
    in_file.next_char = fgetc(in_file.file);
    in_file.char_ptr = in_file.line;
    return (0);
}

/********************************************************
 * in_close -- close the input file.			*
 ********************************************************/
void in_close(void) 
{
    if (in_file.file != NULL) {
	fclose(in_file.file);
	in_file.file = NULL;
    }
}

/********************************************************
 * in_cur_char -- Get the current input character	*
 *							*
 * Returns						*
 *	current character.				*
 ********************************************************/
int in_cur_char(void) 
{
   return (in_file.cur_char);
}

/********************************************************
 * in_next_char -- Peek ahead one character		*
 *							*
 * Returns						*
 *	next character.					*
 ********************************************************/
int in_next_char(void)
{
   return (in_file.next_char);
}

/********************************************************
 * in_flush -- flush the buffered input line to the	*
 *		screen.					*
 ********************************************************/
void in_flush(void)
{
    *in_file.char_ptr = '\0';		/* End the line */
    fputs(in_file.line, stdout);	/* Send the line */
    in_file.char_ptr = in_file.line;	/* Reset the line */
}

/********************************************************
 * in_read_char -- read the next character from the 	*
 *	input file					*
 ********************************************************/
void in_read_char(void)
{
    *in_file.char_ptr = in_file.cur_char;
    ++in_file.char_ptr;

    in_file.cur_char = in_file.next_char;
    in_file.next_char = fgetc(in_file.file);
};