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
|
/*
* Buffer read/write module
*/
#include "sysincludes.h"
#include "msdos.h"
#include "mtools.h"
#include "buffer.h"
typedef struct Buffer_t {
Class_t *Class;
int refs;
Stream_t *Next;
Stream_t *Buffer;
size_t size; /* size of read/write buffer */
int dirty; /* is the buffer dirty? */
int grain;
int grain2;
int ever_dirty; /* was the buffer ever dirty? */
int dirty_pos;
int dirty_end;
off_t current; /* first sector in buffer */
size_t cur_size; /* the current size */
char *buf; /* disk read/write buffer */
} Buffer_t;
/*
* Flush a dirty buffer to disk. Resets Buffer->dirty to zero.
* All errors are fatal.
*/
static int _buf_flush(Buffer_t *Buffer)
{
int ret;
if (!Buffer->Next || !Buffer->dirty)
return 0;
if(Buffer->current < 0L) {
fprintf(stderr,"Should not happen\n");
return 0;
}
ret = force_write(Buffer->Next,
Buffer->buf + Buffer->dirty_pos,
Buffer->current + Buffer->dirty_pos,
Buffer->dirty_end - Buffer->dirty_pos);
if(ret != Buffer->dirty_end - Buffer->dirty_pos) {
if(ret < 0)
perror("buffer_flush: write");
else
fprintf(stderr,"buffer_flush: short write\n");
return -1;
}
Buffer->dirty = 0;
return 0;
}
static void invalidate_buffer(Buffer_t *Buffer, off_t start)
{
_buf_flush(Buffer);
Buffer->current = start - start % Buffer->grain;
Buffer->cur_size = 0;
}
static int buf_read(Stream_t *Stream, char *buf, off_t start, size_t len)
{
int length, offset;
char *disk_ptr;
int ret;
DeclareThis(Buffer_t);
if(!len)
return 0;
/* a "cache" miss, load buffer */
if (start < This->current || start >= This->current + This->cur_size) {
invalidate_buffer(This, start);
/* always load aligned */
length = This->size - (This->current % This->grain2);
/* read it! */
ret=This->Next->Class->read(This->Next,
This->buf,
This->current,
length);
if ( ret < 0 )
return ret;
This->cur_size = ret;
}
offset = start - This->current;
disk_ptr = This->buf + offset;
maximize(&len, This->cur_size - offset);
memcpy(buf, disk_ptr, len);
return len;
}
static int buf_write(Stream_t *Stream, char *buf, off_t start, size_t len)
{
char *disk_ptr;
DeclareThis(Buffer_t);
int offset, ret;
if(!len)
return 0;
This->ever_dirty = 1;
/* a cache miss... */
if (start < This->current ||
start >= This->current + This->size ||
start > This->current + This->cur_size ||
(start == This->current + This->cur_size &&
(len < This->grain || !(start % This->grain2)))) {
invalidate_buffer(This, start);
if(start % This->grain || len < This->grain) {
/* read it! */
ret=This->Next->Class->read(This->Next,
This->buf,
This->current,
This->grain);
if ( ret < 0 )
return ret;
This->cur_size = ret;
/* for dosemu. Autoextend size */
if(!This->cur_size) {
memset(This->buf, 0, This->grain);
This->cur_size = This->grain;
}
}
}
maximize(&len,This->size - (start % This->size));
offset = start - This->current;
if(len + offset > This->cur_size) {
/* enforce aligned writes */
len -= (len + offset ) % This->grain;
This->cur_size = len + offset;
}
disk_ptr = This->buf + offset;
memcpy(disk_ptr, buf, len);
if(!This->dirty || disk_ptr - This->buf < This->dirty_pos){
This->dirty_pos = disk_ptr - This->buf;
This->dirty_pos -= This->dirty_pos % This->grain;
}
if(!This->dirty || disk_ptr - This->buf + len > This->dirty_end){
This->dirty_end = disk_ptr - This->buf + len;
This->dirty_end += This->grain - 1;
This->dirty_end -= This->dirty_end % This->grain;
}
This->dirty = 1;
return len;
}
static int buf_flush(Stream_t *Stream)
{
int ret;
DeclareThis(Buffer_t);
if (!This->ever_dirty)
return 0;
ret = _buf_flush(This);
This->ever_dirty = 0;
return ret;
}
static Class_t BufferClass = {
buf_read,
buf_write,
buf_flush,
0, /* buf_free */
0, /* set_geom */
get_data_pass_through, /* get_data */
};
Stream_t *buf_init(Stream_t *Next, int size, int grain, int grain2)
{
Buffer_t *Buffer;
Stream_t *Stream;
if(Next->Buffer){
Next->refs--;
Next->Buffer->refs++;
return Next->Buffer;
}
Stream = (Stream_t *) malloc (sizeof(Buffer_t));
Buffer = (Buffer_t *) Stream;
Buffer->buf = malloc(size);
Buffer->size = size;
Buffer->grain = grain;
Buffer->grain2 = grain2;
Buffer->cur_size = 0; /* buffer currently empty */
Buffer->dirty = 0;
Buffer->ever_dirty = 0;
if ( !Buffer->buf){
Free(Stream);
return 0;
}
Buffer->Next = Next;
Buffer->Class = &BufferClass;
Buffer->refs = 1;
Buffer->Buffer = 0;
Buffer->Next->Buffer = (Stream_t *) Buffer;
return Stream;
}
|
