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DEFINITIONS
This source file includes following definitions.
- fileinit
- filealloc
- filedup
- fileclose
- filestat
- fileread
- filewrite
1 //
2 // File descriptors
3 //
4
5 #include "types.h"
6 #include "defs.h"
7 #include "param.h"
8 #include "fs.h"
9 #include "file.h"
10 #include "spinlock.h"
11
12 struct devsw devsw[NDEV];
13 struct {
14 struct spinlock lock;
15 struct file file[NFILE];
16 } ftable;
17
18 void
19 fileinit(void)
20 {
21 initlock(&ftable.lock, "ftable");
22 }
23
24 // Allocate a file structure.
25 struct file*
26 filealloc(void)
27 {
28 struct file *f;
29
30 acquire(&ftable.lock);
31 for(f = ftable.file; f < ftable.file + NFILE; f++){
32 if(f->ref == 0){
33 f->ref = 1;
34 release(&ftable.lock);
35 return f;
36 }
37 }
38 release(&ftable.lock);
39 return 0;
40 }
41
42 // Increment ref count for file f.
43 struct file*
44 filedup(struct file *f)
45 {
46 acquire(&ftable.lock);
47 if(f->ref < 1)
48 panic("filedup");
49 f->ref++;
50 release(&ftable.lock);
51 return f;
52 }
53
54 // Close file f. (Decrement ref count, close when reaches 0.)
55 void
56 fileclose(struct file *f)
57 {
58 struct file ff;
59
60 acquire(&ftable.lock);
61 if(f->ref < 1)
62 panic("fileclose");
63 if(--f->ref > 0){
64 release(&ftable.lock);
65 return;
66 }
67 ff = *f;
68 f->ref = 0;
69 f->type = FD_NONE;
70 release(&ftable.lock);
71
72 if(ff.type == FD_PIPE)
73 pipeclose(ff.pipe, ff.writable);
74 else if(ff.type == FD_INODE){
75 begin_op();
76 iput(ff.ip);
77 end_op();
78 }
79 }
80
81 // Get metadata about file f.
82 int
83 filestat(struct file *f, struct stat *st)
84 {
85 if(f->type == FD_INODE){
86 ilock(f->ip);
87 stati(f->ip, st);
88 iunlock(f->ip);
89 return 0;
90 }
91 return -1;
92 }
93
94 // Read from file f.
95 int
96 fileread(struct file *f, char *addr, int n)
97 {
98 int r;
99
100 if(f->readable == 0)
101 return -1;
102 if(f->type == FD_PIPE)
103 return piperead(f->pipe, addr, n);
104 if(f->type == FD_INODE){
105 ilock(f->ip);
106 if((r = readi(f->ip, addr, f->off, n)) > 0)
107 f->off += r;
108 iunlock(f->ip);
109 return r;
110 }
111 panic("fileread");
112 }
113
114 //PAGEBREAK!
115 // Write to file f.
116 int
117 filewrite(struct file *f, char *addr, int n)
118 {
119 int r;
120
121 if(f->writable == 0)
122 return -1;
123 if(f->type == FD_PIPE)
124 return pipewrite(f->pipe, addr, n);
125 if(f->type == FD_INODE){
126 // write a few blocks at a time to avoid exceeding
127 // the maximum log transaction size, including
128 // i-node, indirect block, allocation blocks,
129 // and 2 blocks of slop for non-aligned writes.
130 // this really belongs lower down, since writei()
131 // might be writing a device like the console.
132 int max = ((LOGSIZE-1-1-2) / 2) * 512;
133 int i = 0;
134 while(i < n){
135 int n1 = n - i;
136 if(n1 > max)
137 n1 = max;
138
139 begin_op();
140 ilock(f->ip);
141 if ((r = writei(f->ip, addr + i, f->off, n1)) > 0)
142 f->off += r;
143 iunlock(f->ip);
144 end_op();
145
146 if(r < 0)
147 break;
148 if(r != n1)
149 panic("short filewrite");
150 i += r;
151 }
152 return i == n ? n : -1;
153 }
154 panic("filewrite");
155 }
156