-
Notifications
You must be signed in to change notification settings - Fork 0
/
FileOperations.cpp
341 lines (285 loc) · 7.32 KB
/
FileOperations.cpp
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
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
/*
* FileOperations.cpp
*
* Created on: 12-Aug-2014
* Author: bharathkumar
*/
#include "FileOperations.h"
#include <stdio.h>
#include <memory.h>
#include <string.h>
#include <stdlib.h>
//////////////////////////////////////////////
// Initialization functions
//////////////////////////////////////////////
CVFS* getVFS(){
static CVFS *vfs = 0;
if(vfs==NULL){
vfs = new CVFS();
}
return vfs;
}
void initVFS(int vfs_size){
CVFS* fs = getVFS();
fs->disk = malloc(vfs_size);
fs->disk_size = vfs_size;
fs->myft = NULL;
fs->free = new BLOCK();
fs->free->size = vfs_size;
fs->free->offset = 0;
fs->free->next = fs->free->prev = NULL;
}
/////////////////////////////////////////////
// VFS API Functions
/////////////////////////////////////////////
int createFile(const char* fileName){
CVFS *vfs = getVFS();
FT *trav = new FT();
//add new entry to the file table
trav->next = vfs->myft;
trav->name = (char*)fileName;
trav->data = NULL;
trav->size = 0;
vfs->myft = trav;
return SUCCESS;
}
int writeFile(const char* fileName,const void* buffer,int buffersize,int offset){
CVFS *vfs = getVFS();
FT *trav = vfs->myft;
if(buffersize > vfs->disk_size)
return NOMEM;
while(trav != NULL){
//search the file
if(strcmp(trav->name,fileName)==0){
BLOCK *prev=NULL,*move=trav->data;
if((offset && trav->size<=offset) || offset<-1)
return NOTDEF;
//traverse till end
if(offset==-1){
if(move != NULL) {
while(move->next != NULL){
move = move->next;
}
prev = move;
move = move->next;
}
offset = 0;
}
if(offset>0){
//traverse till the data block which has specified offset
while(offset>=move->size){
offset -= move->size;
prev = move;
move = move->next;
}
//write form offset to end of block or end of buffer
memcpy((void*)((char*)vfs->disk + move->offset + offset),buffer,min(buffersize,move->size-offset));
//printf("written data:%s - to offset %d till %d characters\n",(char*)buffer,move->offset+offset,min(buffersize,move->size-offset));
buffer = (char*)buffer + min(buffersize,move->size-offset);
buffersize -= move->size-offset;
offset = 0;
prev = move;
move = move->next;
}
while(buffersize>0){
//allocate a new block when the next block is NULL for write
if(move==NULL){
if(prev==NULL)
move = trav->data = get_block(buffersize);
else{
prev->next = get_block(buffersize);
prev->next->prev = prev;
move = prev->next;
}
trav->size += move->size;
}
//write the buffer to disk
memcpy((void*)((char*)vfs->disk + move->offset),buffer,min(buffersize,move->size));
//printf("written data:%s - to offset %d till %d characters\n",(char*)buffer,move->offset,min(buffersize,move->size));
buffersize -= move->size;
//move buffer pointer
buffer = (char*)buffer + move->size;
prev = move;
move = move->next;
}
return SUCCESS;
}
trav = trav->next;
}
return NOTFOUND;
}
int readFile(const char* fileName,void* buffer,int buffersize,int offset){
CVFS *vfs = getVFS();
FT *trav = vfs->myft;
int bytes_read = 0;
//traverse till the required file
while(trav!=NULL){
if(strcmp(fileName,trav->name)==0){
BLOCK* move = trav->data;
//traverse all data blocks of the file
while(move != NULL && buffersize>0){
while(offset>=move->size){
offset -= move->size;
move = move->next;
}
//copy the data in the data block to buffer
memcpy(buffer,(void*)((char*)vfs->disk + move->offset + offset),min(buffersize,move->size-offset));
//increment the buffer point
buffer = (char*)buffer + min(move->size-offset,buffersize);
bytes_read += min(move->size-offset,buffersize);
buffersize -= min(move->size-offset,buffersize);
offset = 0;
move = move->next;
}
return bytes_read;
}
trav = trav->next;
}
return -1;
}
int renameFile(const char* oldName,const char* newName){
CVFS *vfs=getVFS();
FT *trav = vfs->myft;
//traverse till the required file
while(trav!=NULL){
if(strcmp(trav->name,oldName)==0){
//rename and return success
trav->name = (char*)newName;
return SUCCESS;
}
trav = trav->next;
}
return NOTFOUND;
}
int deleteFile(const char* fileName){
CVFS *vfs=getVFS();
FT *trav = vfs->myft;
FT *prev = NULL;
//traverse till the required file
while(trav!=NULL){
if(strcmp(trav->name,fileName)==0){
BLOCK *del = trav->data,*next;
//add data block of the file to free data blocks
while(del!=NULL){
next = del->next;
add_to_free(del);
del = next;
}
if(prev == NULL)
vfs->myft = trav->next;
else
prev->next = trav->next;
//printf("root %d %d\n",vfs->free->offset,vfs->free->size);
del = vfs->free;
//combine adjacent data blocks in the free to overcome fragmentation of data blocks in free
while(del->next != NULL){
if(del->offset+del->size == del->next->offset){
del->size += del->next->size;
next = del->next;
del->next = del->next->next;
free(next);
}
del = del->next;
if(del==NULL)
break;
}
//free the data entry
free(trav);
return SUCCESS;
}
prev = trav;
trav = trav->next;
}
return NOTFOUND;
}
BLOCK* get_block(int block_size){
CVFS* vfs = getVFS();
BLOCK *ret = vfs->free,*suit;
int max = 0;
//return the data block of specified size
//or greatest block smaller than specified block
while(ret!=NULL){
if(ret->size>block_size){
BLOCK* found = new BLOCK();
found->offset =ret->offset;
found->size = block_size;
found->next = NULL;
found->prev = NULL;
ret->offset = ret->offset+block_size;
ret->size-=block_size;
return found;
}
if(ret->size==block_size){
ret->prev->next = ret->next;
ret->next->prev = ret->prev;
return ret;
}
if(ret->size>max){
max = ret->size;
suit = ret;
}
}
return suit;
}
//list all files in the file table
void listFiles(){
CVFS *vfs = getVFS();
FT* trav = vfs->myft;
while(trav!=NULL){
printf("%s\n",trav->name);
trav = trav->next;
}
}
// find minimum
int min(int a,int b){
return a<=b?a:b;
}
//add blocks to free blocks in the disk
void add_to_free(BLOCK* add){
CVFS *vfs = getVFS();
BLOCK *move = vfs->free,*prev=NULL;
while(move != NULL){
if(move->offset == add->offset+add->size){
move->offset=add->offset;
move->size += add->size;
//printf("adding block offset %d:size %d to start of move\n",add->offset,add->size);
return;
}
if(move->offset+move->size == add->offset){
move->size += add->size;
//printf("adding block offset %d:size %d to end of move\n",add->offset,add->size);
return;
}
if(move->offset>add->offset+add->size){
if(prev==NULL){
add->next = vfs->free;
add->prev = NULL;
vfs->free->prev = add;
vfs->free = add;
return;
}
add->next = move;
add->prev = prev;
move->prev = add;
prev->next = add;
return;
//adding the block in the position such the next node starts after present block in lexicographical order
}
prev = move;
move = move->next;
}
if(prev==NULL){
vfs->free = add;
}
prev->next = add;
//printf("adding block offset %d:size %d at end\n",add->offset,add->size);
}
//list free blocks in the disk
void list_free_blocks(){
CVFS* vfs = getVFS();
BLOCK *move = vfs->free;
while(move != NULL){
printf("offset %d : size %d\n",move->offset,move->size);
move = move->next;
}
}