file.c

四皇后问题

/*
	Little Smalltalk

		programs used by class File
		timothy a. budd 11/84
*/
/*
	The source code for the Little Smalltalk System may be freely
	copied provided that the source of all files is acknowledged
	and that this condition is copied with each file.

	The Little Smalltalk System is distributed without responsibility
	for the performance of the program and without any guarantee of
	maintenance.

	All questions concerning Little Smalltalk should be addressed to:

		Professor Tim Budd
		Department of Computer Science
		Oregon State University
		Corvallis, Oregon
		97331
		USA
*/
# include <stdio.h>
# include "object.h"
# include "file.h"
# include "string.h"
# include "number.h"
# include "primitive.h"

static mstruct *fr_file = 0;	/* free file list */

object *new_file()
{	struct file_struct *new;

	if (fr_file) {
		new = (struct file_struct *) fr_file;
		fr_file = fr_file->mlink;
		}
	else {
		new = structalloc(struct file_struct);
		}

	new->l_size = FILESIZE;
	new->l_ref_count = 0;
	new->file_mode = STRMODE;
	new->fp = NULL;
	return((object *) new);
}

free_file(phil)
struct file_struct *phil;
{
	if (! is_file(phil))
		cant_happen(8);
	if (phil->fp != NULL)
		fclose(phil->fp);
	((mstruct *) phil)->mlink = fr_file;
	fr_file = (mstruct *) phil;
}

file_err(message)
char *message;
{	object *errp;
	char buffer[150];

	sprintf(buffer,"File: %s", message);
	sassign(errp, new_str(buffer));
	primitive(ERRPRINT, 1, &errp);
	obj_dec(errp);
}

file_open(phil, name, type)
struct file_struct *phil;
char *name, *type;
{	char buffer[100];

	if (phil->fp != NULL)
		fclose(phil->fp);
	phil->fp = fopen(name, type);
	if (phil->fp == NULL) {
		sprintf(buffer,"can't open: %s\n", name);
		file_err(buffer);
		}
}

# define BUFLENGTH 250

object *file_read(phil)
struct file_struct *phil;
{	object *new;
	int c;
	char buffer[BUFLENGTH], *p;

	if (phil->fp == NULL) {
		file_err("attempt to read from unopened file");
		return(o_nil);
		}
	switch(phil->file_mode) {
		case CHARMODE:
			if (EOF == (c = fgetc(phil->fp)))
				new = o_nil;
			else
				new = new_char(c);
			break;
		case STRMODE:
			if (NULL == fgets(buffer, BUFLENGTH, phil->fp))
				new = o_nil;
			else {
				p = &buffer[strlen(buffer) - 1];
				if (*p == '\n') *p = '\0';
				new = new_str(buffer);
				}
			break;
		case INTMODE:
			if (EOF == (c = getw(phil->fp)))
				new = o_nil;
			else
				new = new_int(c);
			break;
		default:
			file_err("unknown mode");
			new = o_nil;
		}
	return(new);
}

file_write(phil, obj)
struct file_struct *phil;
object *obj;
{
	if (phil->fp == NULL) {
		file_err("attempt to write to unopened file");
		return;
		}
	switch(phil->file_mode) {
		case CHARMODE:
			if (! is_character(obj)) goto modeerr;
			fputc(int_value(obj), phil->fp);
			break;
		case STRMODE:
			if (! is_string(obj)) goto modeerr;
			fputs(string_value(obj), phil->fp);
			fputc('\n', phil->fp);
			break;
		case INTMODE:
			if (! is_integer(obj)) goto modeerr;
			putw(int_value(obj), phil->fp);
			break;
		}
	return;
modeerr:
	file_err("attempt to write object of wrong type for mode");
}