CS318 - Pintos
Pintos source browser for JHU CS318 course
file.c
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1 #include "filesys/file.h"
2 #include <debug.h>
3 #include "filesys/inode.h"
4 #include "threads/malloc.h"
5 
6 /** An open file. */
7 struct file
8  {
9  struct inode *inode; /**< File's inode. */
10  off_t pos; /**< Current position. */
11  bool deny_write; /**< Has file_deny_write() been called? */
12  };
13 
14 /** Opens a file for the given INODE, of which it takes ownership,
15  and returns the new file. Returns a null pointer if an
16  allocation fails or if INODE is null. */
17 struct file *
18 file_open (struct inode *inode)
19 {
20  struct file *file = calloc (1, sizeof *file);
21  if (inode != NULL && file != NULL)
22  {
23  file->inode = inode;
24  file->pos = 0;
25  file->deny_write = false;
26  return file;
27  }
28  else
29  {
30  inode_close (inode);
31  free (file);
32  return NULL;
33  }
34 }
35 
36 /** Opens and returns a new file for the same inode as FILE.
37  Returns a null pointer if unsuccessful. */
38 struct file *
39 file_reopen (struct file *file)
40 {
41  return file_open (inode_reopen (file->inode));
42 }
43 
44 /** Closes FILE. */
45 void
46 file_close (struct file *file)
47 {
48  if (file != NULL)
49  {
50  file_allow_write (file);
51  inode_close (file->inode);
52  free (file);
53  }
54 }
55 
56 /** Returns the inode encapsulated by FILE. */
57 struct inode *
58 file_get_inode (struct file *file)
59 {
60  return file->inode;
61 }
62 
63 /** Reads SIZE bytes from FILE into BUFFER,
64  starting at the file's current position.
65  Returns the number of bytes actually read,
66  which may be less than SIZE if end of file is reached.
67  Advances FILE's position by the number of bytes read. */
68 off_t
69 file_read (struct file *file, void *buffer, off_t size)
70 {
71  off_t bytes_read = inode_read_at (file->inode, buffer, size, file->pos);
72  file->pos += bytes_read;
73  return bytes_read;
74 }
75 
76 /** Reads SIZE bytes from FILE into BUFFER,
77  starting at offset FILE_OFS in the file.
78  Returns the number of bytes actually read,
79  which may be less than SIZE if end of file is reached.
80  The file's current position is unaffected. */
81 off_t
82 file_read_at (struct file *file, void *buffer, off_t size, off_t file_ofs)
83 {
84  return inode_read_at (file->inode, buffer, size, file_ofs);
85 }
86 
87 /** Writes SIZE bytes from BUFFER into FILE,
88  starting at the file's current position.
89  Returns the number of bytes actually written,
90  which may be less than SIZE if end of file is reached.
91  (Normally we'd grow the file in that case, but file growth is
92  not yet implemented.)
93  Advances FILE's position by the number of bytes read. */
94 off_t
95 file_write (struct file *file, const void *buffer, off_t size)
96 {
97  off_t bytes_written = inode_write_at (file->inode, buffer, size, file->pos);
98  file->pos += bytes_written;
99  return bytes_written;
100 }
101 
102 /** Writes SIZE bytes from BUFFER into FILE,
103  starting at offset FILE_OFS in the file.
104  Returns the number of bytes actually written,
105  which may be less than SIZE if end of file is reached.
106  (Normally we'd grow the file in that case, but file growth is
107  not yet implemented.)
108  The file's current position is unaffected. */
109 off_t
110 file_write_at (struct file *file, const void *buffer, off_t size,
111  off_t file_ofs)
112 {
113  return inode_write_at (file->inode, buffer, size, file_ofs);
114 }
115 
116 /** Prevents write operations on FILE's underlying inode
117  until file_allow_write() is called or FILE is closed. */
118 void
119 file_deny_write (struct file *file)
120 {
121  ASSERT (file != NULL);
122  if (!file->deny_write)
123  {
124  file->deny_write = true;
125  inode_deny_write (file->inode);
126  }
127 }
128 
129 /** Re-enables write operations on FILE's underlying inode.
130  (Writes might still be denied by some other file that has the
131  same inode open.) */
132 void
133 file_allow_write (struct file *file)
134 {
135  ASSERT (file != NULL);
136  if (file->deny_write)
137  {
138  file->deny_write = false;
139  inode_allow_write (file->inode);
140  }
141 }
142 
143 /** Returns the size of FILE in bytes. */
144 off_t
145 file_length (struct file *file)
146 {
147  ASSERT (file != NULL);
148  return inode_length (file->inode);
149 }
150 
151 /** Sets the current position in FILE to NEW_POS bytes from the
152  start of the file. */
153 void
154 file_seek (struct file *file, off_t new_pos)
155 {
156  ASSERT (file != NULL);
157  ASSERT (new_pos >= 0);
158  file->pos = new_pos;
159 }
160 
161 /** Returns the current position in FILE as a byte offset from the
162  start of the file. */
163 off_t
164 file_tell (struct file *file)
165 {
166  ASSERT (file != NULL);
167  return file->pos;
168 }
file_deny_write
void file_deny_write(struct file *file)
Prevents write operations on FILE's underlying inode until file_allow_write() is called or FILE is cl...
Definition: file.c:119
file_allow_write
void file_allow_write(struct file *file)
Re-enables write operations on FILE's underlying inode.
Definition: file.c:133
NULL
#define NULL
Definition: stddef.h:4
file_close
void file_close(struct file *file)
Closes FILE.
Definition: file.c:46
file
An open file.
Definition: file.c:7
off_t
int32_t off_t
An offset within a file.
Definition: off_t.h:9
file_reopen
struct file * file_reopen(struct file *file)
Opens and returns a new file for the same inode as FILE.
Definition: file.c:39
file::pos
off_t pos
Current position.
Definition: file.c:10
free
void free(void *p)
Frees block P, which must have been previously allocated with malloc(), calloc(), or realloc().
Definition: malloc.c:219
inode_deny_write
void inode_deny_write(struct inode *inode)
Disables writes to INODE.
Definition: inode.c:323
inode_write_at
off_t inode_write_at(struct inode *inode, const void *buffer_, off_t size, off_t offset)
Writes SIZE bytes from BUFFER into INODE, starting at OFFSET.
Definition: inode.c:258
file_read
off_t file_read(struct file *file, void *buffer, off_t size)
Reads SIZE bytes from FILE into BUFFER, starting at the file's current position.
Definition: file.c:69
buffer
static struct intq buffer
Stores keys from the keyboard and serial port.
Definition: input.c:7
inode
In-memory inode.
Definition: inode.c:32
file_tell
off_t file_tell(struct file *file)
Returns the current position in FILE as a byte offset from the start of the file.
Definition: file.c:164
file::deny_write
bool deny_write
Has file_deny_write() been called?
Definition: file.c:11
file_open
struct file * file_open(struct inode *inode)
Opens a file for the given INODE, of which it takes ownership, and returns the new file.
Definition: file.c:18
file_write
off_t file_write(struct file *file, const void *buffer, off_t size)
Writes SIZE bytes from BUFFER into FILE, starting at the file's current position.
Definition: file.c:95
malloc.h
file_length
off_t file_length(struct file *file)
Returns the size of FILE in bytes.
Definition: file.c:145
calloc
void * calloc(size_t a, size_t b)
Allocates and return A times B bytes initialized to zeroes.
Definition: malloc.c:159
ASSERT
#define ASSERT(CONDITION)
This is outside the header guard so that debug.h may be included multiple times with different settin...
Definition: debug.h:31
inode_length
off_t inode_length(const struct inode *inode)
Returns the length, in bytes, of INODE's data.
Definition: inode.c:342
file_write_at
off_t file_write_at(struct file *file, const void *buffer, off_t size, off_t file_ofs)
Writes SIZE bytes from BUFFER into FILE, starting at offset FILE_OFS in the file.
Definition: file.c:110
file_seek
void file_seek(struct file *file, off_t new_pos)
Sets the current position in FILE to NEW_POS bytes from the start of the file.
Definition: file.c:154
inode_allow_write
void inode_allow_write(struct inode *inode)
Re-enables writes to INODE.
Definition: inode.c:333
file_read_at
off_t file_read_at(struct file *file, void *buffer, off_t size, off_t file_ofs)
Reads SIZE bytes from FILE into BUFFER, starting at offset FILE_OFS in the file.
Definition: file.c:82
file::inode
struct inode * inode
File's inode.
Definition: file.c:9
file.h
inode_read_at
off_t inode_read_at(struct inode *inode, void *buffer_, off_t size, off_t offset)
Reads SIZE bytes from INODE into BUFFER, starting at position OFFSET.
Definition: inode.c:201
inode_reopen
struct inode * inode_reopen(struct inode *inode)
Reopens and returns INODE.
Definition: inode.c:146
file_get_inode
struct inode * file_get_inode(struct file *file)
Returns the inode encapsulated by FILE.
Definition: file.c:58
debug.h
inode_close
void inode_close(struct inode *inode)
Closes INODE and writes it to disk.
Definition: inode.c:164
inode.h
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