1 /*
2 * linux/fs/file_dev.c
3 *
4 * (C) 1991 Linus Torvalds
5 */
6
7 #include <errno.h>
8 #include <fcntl.h>
9
10 #include <linux/sched.h>
11 #include <linux/kernel.h>
12 #include <asm/segment.h>
13
14 #define MIN(a,b) (((a)<(b))?(a):(b))
15 #define MAX(a,b) (((a)>(b))?(a):(b))
16
17 int file_read(struct m_inode * inode, struct file * filp, char * buf, int count)
18 {
19 int left,chars,nr;
20 struct buffer_head * bh;
21
22 if ((left=count)<=0)
23 return 0;
24 while (left) {
25 if (nr = bmap(inode,(filp->f_pos)/BLOCK_SIZE)) {
26 if (!(bh=bread(inode->i_dev,nr)))
27 break;
28 } else
29 bh = NULL;
30 nr = filp->f_pos % BLOCK_SIZE;
31 chars = MIN( BLOCK_SIZE-nr , left );
32 filp->f_pos += chars;
33 left -= chars;
34 if (bh) {
35 char * p = nr + bh->b_data;
36 while (chars-->0)
37 put_fs_byte(*(p++),buf++);
38 brelse(bh);
39 } else {
40 while (chars-->0)
41 put_fs_byte(0,buf++);
42 }
43 }
44 inode->i_atime = CURRENT_TIME;
45 return (count-left)?(count-left):-ERROR;
46 }
47
48 int file_write(struct m_inode * inode, struct file * filp, char * buf, int count)
49 {
50 off_t pos;
51 int block,c;
52 struct buffer_head * bh;
53 char * p;
54 int i=0;
55
56 /*
57 * ok, append may not work when many processes are writing at the same time
58 * but so what. That way leads to madness anyway.
59 */
60 if (filp->f_flags & O_APPEND)
61 pos = inode->i_size;
62 else
63 pos = filp->f_pos;
64 while (i<count) {
65 if (!(block = create_block(inode,pos/BLOCK_SIZE)))
66 break;
67 if (!(bh=bread(inode->i_dev,block)))
68 break;
69 c = pos % BLOCK_SIZE;
70 p = c + bh->b_data;
71 bh->b_dirt = 1;
72 c = BLOCK_SIZE-c;
73 if (c > count-i) c = count-i;
74 pos += c;
75 if (pos > inode->i_size) {
76 inode->i_size = pos;
77 inode->i_dirt = 1;
78 }
79 i += c;
80 while (c-->0)
81 *(p++) = get_fs_byte(buf++);
82 brelse(bh);
83 }
84 inode->i_mtime = CURRENT_TIME;
85 if (!(filp->f_flags & O_APPEND)) {
86 filp->f_pos = pos;
87 inode->i_ctime = CURRENT_TIME;
88 }
89 return (i?i:-1);
90 }
91
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