Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/fs/seq_file.c
Version:
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1 /* 2 * linux/fs/seq_file.c 3 * 4 * helper functions for making syntetic files from sequences of records. 5 * initial implementation -- AV, Oct 2001. 6 */ 7 8 #include <linux/fs.h> 9 #include <linux/seq_file.h> 10 #include <linux/slab.h> 11 12 #include <asm/uaccess.h> 13 14 /** 15 * seq_open - initialize sequential file 16 * @file: file we initialize 17 * @op: method table describing the sequence 18 * 19 * seq_open() sets @file, associating it with a sequence described 20 * by @op. @op->start() sets the iterator up and returns the first 21 * element of sequence. @op->stop() shuts it down. @op->next() 22 * returns the next element of sequence. @op->show() prints element 23 * into the buffer. In case of error ->start() and ->next() return 24 * ERR_PTR(error). In the end of sequence they return %NULL. ->show() 25 * returns 0 in case of success and negative number in case of error. 26 */ 27 int seq_open(struct file *file, struct seq_operations *op) 28 { 29 struct seq_file *p = kmalloc(sizeof(*p), GFP_KERNEL); 30 if (!p) 31 return -ENOMEM; 32 memset(p, 0, sizeof(*p)); 33 sema_init(&p->sem, 1); 34 p->op = op; 35 file->private_data = p; 36 return 0; 37 } 38 39 /** 40 * seq_read - ->read() method for sequential files. 41 * @file, @buf, @size, @ppos: see file_operations method 42 * 43 * Ready-made ->f_op->read() 44 */ 45 ssize_t seq_read(struct file *file, char *buf, size_t size, loff_t *ppos) 46 { 47 struct seq_file *m = (struct seq_file *)file->private_data; 48 size_t copied = 0; 49 loff_t pos; 50 size_t n; 51 void *p; 52 int err = 0; 53 54 if (ppos != &file->f_pos) 55 return -EPIPE; 56 57 down(&m->sem); 58 /* grab buffer if we didn't have one */ 59 if (!m->buf) { 60 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); 61 if (!m->buf) 62 goto Enomem; 63 } 64 /* if not empty - flush it first */ 65 if (m->count) { 66 n = min(m->count, size); 67 err = copy_to_user(buf, m->buf + m->from, n); 68 if (err) 69 goto Efault; 70 m->count -= n; 71 m->from += n; 72 size -= n; 73 buf += n; 74 copied += n; 75 if (!m->count) 76 m->index++; 77 if (!size) 78 goto Done; 79 } 80 /* we need at least one record in buffer */ 81 while (1) { 82 pos = m->index; 83 p = m->op->start(m, &pos); 84 err = PTR_ERR(p); 85 if (!p || IS_ERR(p)) 86 break; 87 err = m->op->show(m, p); 88 if (err) 89 break; 90 if (m->count < m->size) 91 goto Fill; 92 m->op->stop(m, p); 93 kfree(m->buf); 94 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); 95 if (!m->buf) 96 goto Enomem; 97 m->count = 0; 98 } 99 m->op->stop(m, p); 100 m->count = 0; 101 goto Done; 102 Fill: 103 /* they want more? let's try to get some more */ 104 while (m->count < size) { 105 size_t offs = m->count; 106 loff_t next = pos; 107 p = m->op->next(m, p, &next); 108 if (!p || IS_ERR(p)) { 109 err = PTR_ERR(p); 110 break; 111 } 112 err = m->op->show(m, p); 113 if (err || m->count == m->size) { 114 m->count = offs; 115 break; 116 } 117 pos = next; 118 } 119 m->op->stop(m, p); 120 n = min(m->count, size); 121 err = copy_to_user(buf, m->buf, n); 122 if (err) 123 goto Efault; 124 copied += n; 125 m->count -= n; 126 if (m->count) 127 m->from = n; 128 else 129 pos++; 130 m->index = pos; 131 Done: 132 if (!copied) 133 copied = err; 134 else 135 *ppos += copied; 136 up(&m->sem); 137 return copied; 138 Enomem: 139 err = -ENOMEM; 140 goto Done; 141 Efault: 142 err = -EFAULT; 143 goto Done; 144 } 145 146 static int traverse(struct seq_file *m, loff_t offset) 147 { 148 loff_t pos = 0; 149 int error = 0; 150 void *p; 151 152 m->index = 0; 153 m->count = m->from = 0; 154 if (!offset) 155 return 0; 156 if (!m->buf) { 157 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); 158 if (!m->buf) 159 return -ENOMEM; 160 } 161 p = m->op->start(m, &m->index); 162 while (p) { 163 error = PTR_ERR(p); 164 if (IS_ERR(p)) 165 break; 166 error = m->op->show(m, p); 167 if (error) 168 break; 169 if (m->count == m->size) 170 goto Eoverflow; 171 if (pos + m->count > offset) { 172 m->from = offset - pos; 173 m->count -= m->from; 174 break; 175 } 176 pos += m->count; 177 m->count = 0; 178 if (pos == offset) { 179 m->index++; 180 break; 181 } 182 p = m->op->next(m, p, &m->index); 183 } 184 m->op->stop(m, p); 185 return error; 186 187 Eoverflow: 188 m->op->stop(m, p); 189 kfree(m->buf); 190 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); 191 return !m->buf ? -ENOMEM : -EAGAIN; 192 } 193 194 /** 195 * seq_lseek - ->llseek() method for sequential files. 196 * @file, @offset, @origin: see file_operations method 197 * 198 * Ready-made ->f_op->llseek() 199 */ 200 loff_t seq_lseek(struct file *file, loff_t offset, int origin) 201 { 202 struct seq_file *m = (struct seq_file *)file->private_data; 203 long long retval = -EINVAL; 204 205 down(&m->sem); 206 switch (origin) { 207 case 1: 208 offset += file->f_pos; 209 case 0: 210 if (offset < 0) 211 break; 212 retval = offset; 213 if (offset != file->f_pos) { 214 while ((retval=traverse(m, offset)) == -EAGAIN) 215 ; 216 if (retval) { 217 /* with extreme perjudice... */ 218 file->f_pos = 0; 219 m->index = 0; 220 m->count = 0; 221 } else { 222 retval = file->f_pos = offset; 223 } 224 } 225 } 226 up(&m->sem); 227 return retval; 228 } 229 230 /** 231 * seq_release - free the structures associated with sequential file. 232 * @file: file in question 233 * @inode: file->f_dentry->d_inode 234 * 235 * Frees the structures associated with sequential file; can be used 236 * as ->f_op->release() if you don't have private data to destroy. 237 */ 238 int seq_release(struct inode *inode, struct file *file) 239 { 240 struct seq_file *m = (struct seq_file *)file->private_data; 241 kfree(m->buf); 242 kfree(m); 243 return 0; 244 } 245 246 /** 247 * seq_escape - print string into buffer, escaping some characters 248 * @m: target buffer 249 * @s: string 250 * @esc: set of characters that need escaping 251 * 252 * Puts string into buffer, replacing each occurence of character from 253 * @esc with usual octal escape. Returns 0 in case of success, -1 - in 254 * case of overflow. 255 */ 256 int seq_escape(struct seq_file *m, const char *s, const char *esc) 257 { 258 char *end = m->buf + m->size; 259 char *p; 260 char c; 261 262 for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) { 263 if (!strchr(esc, c)) { 264 *p++ = c; 265 continue; 266 } 267 if (p + 3 < end) { 268 *p++ = '\\'; 269 *p++ = '' + ((c & 0300) >> 6); 270 *p++ = '' + ((c & 070) >> 3); 271 *p++ = '' + (c & 07); 272 continue; 273 } 274 m->count = m->size; 275 return -1; 276 } 277 m->count = p - m->buf; 278 return 0; 279 } 280 281 int seq_printf(struct seq_file *m, const char *f, ...) 282 { 283 va_list args; 284 int len; 285 286 if (m->count < m->size) { 287 va_start(args, f); 288 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args); 289 va_end(args); 290 if (m->count + len < m->size) { 291 m->count += len; 292 return 0; 293 } 294 } 295 m->count = m->size; 296 return -1; 297 }
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