1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
|
/* syscalls.h
*
* A simpler stdio.h to aid in exercises within chapter 8
*/
/* Declarations */
int puts(char *);
long lseek(int fd, long offset, int origin);
/* workarounds for GNU/Linux */
#undef NULL
#define PERMS 0666
#define NULL 0
#define EOF (-1)
#define BUFSIZ 100
#define FOPEN_MAX 20
struct _flags {
unsigned int _READ : 1;
unsigned int _WRITE : 1;
unsigned int _UNBUF : 1;
unsigned int _EOF : 1;
unsigned int _ERR : 1;
} flags;
typedef struct _iobuf {
int cnt;
char *ptr;
char *base;
struct _flags flags;
int fd;
} FILE;
FILE _iob[FOPEN_MAX] = {
/* stdin is read-only */
{ 0, (char *) 0, (char *) 0, {1, 0, 0, 0, 0}, 0 },
/* stdout is write only */
{ 0, (char *) 0, (char *) 0, {0, 1, 0, 0, 0}, 1 },
/* stderr is written AND not buffered */
{ 0, (char *) 0, (char *) 0, {0, 1, 1, 0, 0}, 2 }
};
#define stdin (&_iob[0])
#define stdout (&_iob[1])
#define stderr (&_iob[2])
#define feof(p) (((p)->flags._EOF) != 0)
#define ferror(p) (((p)->flags._ERR) != 0)
#define fileno(p) ((p)->fd)
#define getc(p) (--(p)->cnt >= 0 ? (unsigned char) *(p)->ptr++ : _fillbuf(p))
#define putc(x,p) (--(p)->cnt >= 0 ? *(p)->ptr++ = (x) : _flushbuf((x),p))
#define getchar() getc(stdin)
#define putchar(x) putc((x), stdout)
int fempty(struct _flags flags) {
if (!flags._READ && !flags._WRITE && !flags._UNBUF && !flags._EOF && !flags._ERR) {
return 1;
} else {
return 0;
}
}
FILE * fopen(char *name, char *mode) {
int fd;
FILE *fp;
if (*mode != 'r' && *mode != 'w' && *mode != 'a') {
return NULL;
}
for (fp = _iob; fp < _iob + FOPEN_MAX; fp++) {
if (fp->flags._READ == 0 && fp->flags._WRITE == 0) {
break;
}
}
if (fp >= _iob + FOPEN_MAX) {
return NULL;
}
if (*mode == 'w') {
fd = creat(name, PERMS);
} else if (*mode == 'a') {
if ((fd = open(name, O_WRONLY, 0)) == -1) {
fd = creat(name, PERMS);
}
lseek(fd, 0L, 2);
} else {
fd = open(name, O_RDONLY, 0);
}
if (fd == -1) {
return NULL;
}
fp->fd = fd;
fp->cnt = 0;
if (*mode == 'r') {
fp->flags._READ = 1;
} else {
fp->flags._WRITE = 1;
}
return fp;
}
/* int _fillbuf(FILE *); */
int _fillbuf(FILE *fp) {
int bufsize;
if (fp->flags._READ == 0) {
return EOF;
}
bufsize = (fp->flags._UNBUF != 0) ? 1 : BUFSIZ;
if (fp->base == NULL) {
if ((fp->base = (char *) calloc(bufsize, sizeof (char))) == NULL) {
return EOF;
}
}
fp->ptr = fp->base;
fp->cnt = read(fp->fd, fp->ptr, bufsize);
if (--(fp)->cnt < 0) {
if (fp->cnt == -1) {
fp->flags._EOF = 1;
} else {
fp->flags._ERR = 1;
}
fp->cnt = 0;
return EOF;
}
return (unsigned char) *fp->ptr++;
}
int _cleanbuf(FILE *fp) {
int bufsize = (fp->flags._UNBUF != 0) ? 1 : BUFSIZ;
if (fp->base != NULL) {
free(fp->base);
}
fp->base = (char *) calloc(bufsize, sizeof (char));
if (fp->base == NULL) {
return EOF;
}
return 0;
}
/*
* write the buffer's contents to the file and reset the buffer
*
* Returns 0 on success, EOF on errors, with errno set.
*/
int _flushbuf(char c, FILE *fp) {
int bufsize = (fp->flags._UNBUF != 0) ? 1 : BUFSIZ;
if (fp->base == NULL) {
if (_cleanbuf(fp) != 0) {
errno = ENOMEM;
return EOF;
}
}
if (fp->flags._WRITE == 0) {
errno = EBADF;
return EOF;
}
int written = write(fp->fd, fp->base, bufsize);
if (errno > 0) {
fp->flags._ERR = 1;
strerror(errno);
return EOF;
}
if (_cleanbuf(fp) != 0) {
errno = ENOMEM;
return EOF;
}
fp->ptr = fp->base;
fp->cnt = bufsize;
if (c != NULL) {
putc(c,fp);
}
return 0;
}
int fflush(FILE *fp) {
if (fp == NULL) {
int i;
for (i=0; i < FOPEN_MAX; i++) {
/* maybe check flags and buffers? */
if (fp->flags._WRITE == 1) {
if (_flushbuf(NULL, &_iob[i]) == EOF) {
strerror(errno);
}
}
}
return 0;
}
if (fp->flags._WRITE == 1) {
if (_flushbuf(NULL, fp) == EOF) {
strerror(errno);
}
}
return 0;
}
int fclose(FILE *fp) {
struct _flags f = {0,0,0,0,0};
if (fp->flags._WRITE == 1) {
fflush(fp);
}
if (fp->base != NULL) {
free(fp->base);
fp->base = NULL;
fp->ptr = NULL;
}
fp->cnt = 0;
fp->flags = f;
close(fp->fd);
fp->fd = -1;
return 0;
}
int puts(char *s) {
int i;
for (i=0; s[i] != '\0' && s[i] != EOF; i++) {
putchar(s[i]);
}
putchar('\n');
return i;
}
|
