lib/buffer.c

   1 /*
   2   FUSE: Filesystem in Userspace
   3   Copyright (C) 2010  Miklos Szeredi <miklos@szeredi.hu>
   4
   5   This program can be distributed under the terms of the GNU LGPLv2.
   6   See the file COPYING.LIB
   7 */
   8
   9 #define _GNU_SOURCE
  10
  11 #include "fuse_i.h"
  12 #include "fuse_lowlevel.h"
  13 #include <string.h>
  14 #include <unistd.h>
  15 #include <errno.h>
  16 #include <assert.h>
  17
  18 size_t fuse_buf_size(const struct fuse_bufvec *bufv)
  19 {
  20         size_t i;
  21         size_t size = 0;
  22
  23         for (i = 0; i < bufv->count; i++) {
  24                 if (bufv->buf[i].size == SIZE_MAX)
  25                         size = SIZE_MAX;
  26                 else
  27                         size += bufv->buf[i].size;
  28         }
  29
  30         return size;
  31 }
  32
  33 static size_t min_size(size_t s1, size_t s2)
  34 {
  35         return s1 < s2 ? s1 : s2;
  36 }
  37
  38 static ssize_t fuse_buf_write(const struct fuse_buf *dst, size_t dst_off,
  39                               const struct fuse_buf *src, size_t src_off,
  40                               size_t len)
  41 {
  42         ssize_t res = 0;
  43         size_t copied = 0;
  44
  45         while (len) {
  46                 if (dst->flags & FUSE_BUF_FD_SEEK) {
  47                         res = pwrite(dst->fd, src->mem + src_off, len,
  48                                      dst->pos + dst_off);
  49                 } else {
  50                         res = write(dst->fd, src->mem + src_off, len);
  51                 }
  52                 if (res == -1) {
  53                         if (!copied)
  54                                 return -errno;
  55                         break;
  56                 }
  57                 if (res == 0)
  58                         break;
  59
  60                 copied += res;
  61                 if (!(dst->flags & FUSE_BUF_FD_RETRY))
  62                         break;
  63
  64                 src_off += res;
  65                 dst_off += res;
  66                 len -= res;
  67         }
  68
  69         return copied;
  70 }
  71
  72 static ssize_t fuse_buf_read(const struct fuse_buf *dst, size_t dst_off,
  73                              const struct fuse_buf *src, size_t src_off,
  74                              size_t len)
  75 {
  76         ssize_t res = 0;
  77         size_t copied = 0;
  78
  79         while (len) {
  80                 if (src->flags & FUSE_BUF_FD_SEEK) {
  81                         res = pread(src->fd, dst->mem + dst_off, len,
  82                                      src->pos + src_off);
  83                 } else {
  84                         res = read(src->fd, dst->mem + dst_off, len);
  85                 }
  86                 if (res == -1) {
  87                         if (!copied)
  88                                 return -errno;
  89                         break;
  90                 }
  91                 if (res == 0)
  92                         break;
  93
  94                 copied += res;
  95                 if (!(src->flags & FUSE_BUF_FD_RETRY))
  96                         break;
  97
  98                 dst_off += res;
  99                 src_off += res;
 100                 len -= res;
 101         }
 102
 103         return copied;
 104 }
 105
 106 static ssize_t fuse_buf_fd_to_fd(const struct fuse_buf *dst, size_t dst_off,
 107                                  const struct fuse_buf *src, size_t src_off,
 108                                  size_t len)
 109 {
 110         char buf[4096];
 111         struct fuse_buf tmp = {
 112                 .size = sizeof(buf),
 113                 .flags = 0,
 114         };
 115         ssize_t res;
 116         size_t copied = 0;
 117
 118         tmp.mem = buf;
 119
 120         while (len) {
 121                 size_t this_len = min_size(tmp.size, len);
 122                 size_t read_len;
 123
 124                 res = fuse_buf_read(&tmp, 0, src, src_off, this_len);
 125                 if (res < 0) {
 126                         if (!copied)
 127                                 return res;
 128                         break;
 129                 }
 130                 if (res == 0)
 131                         break;
 132
 133                 read_len = res;
 134                 res = fuse_buf_write(dst, dst_off, &tmp, 0, read_len);
 135                 if (res < 0) {
 136                         if (!copied)
 137                                 return res;
 138                         break;
 139                 }
 140                 if (res == 0)
 141                         break;
 142
 143                 copied += res;
 144
 145                 if (res < this_len)
 146                         break;
 147
 148                 dst_off += res;
 149                 src_off += res;
 150                 len -= res;
 151         }
 152
 153         return copied;
 154 }
 155
 156 #ifdef HAVE_SPLICE
 157 static ssize_t fuse_buf_splice(const struct fuse_buf *dst, size_t dst_off,
 158                                const struct fuse_buf *src, size_t src_off,
 159                                size_t len, enum fuse_buf_copy_flags flags)
 160 {
 161         int splice_flags = 0;
 162         off_t *srcpos = NULL;
 163         off_t *dstpos = NULL;
 164         off_t srcpos_val;
 165         off_t dstpos_val;
 166         ssize_t res;
 167         size_t copied = 0;
 168
 169         if (flags & FUSE_BUF_SPLICE_MOVE)
 170                 splice_flags |= SPLICE_F_MOVE;
 171         if (flags & FUSE_BUF_SPLICE_NONBLOCK)
 172                 splice_flags |= SPLICE_F_NONBLOCK;
 173
 174         if (src->flags & FUSE_BUF_FD_SEEK) {
 175                 srcpos_val = src->pos + src_off;
 176                 srcpos = &srcpos_val;
 177         }
 178         if (dst->flags & FUSE_BUF_FD_SEEK) {
 179                 dstpos_val = dst->pos + dst_off;
 180                 dstpos = &dstpos_val;
 181         }
 182
 183         while (len) {
 184                 res = splice(src->fd, srcpos, dst->fd, dstpos, len,
 185                              splice_flags);
 186                 if (res == -1) {
 187                         if (copied)
 188                                 break;
 189
 190                         if (errno != EINVAL || (flags & FUSE_BUF_FORCE_SPLICE))
 191                                 return -errno;
 192
 193                         /* Maybe splice is not supported for this combination */
 194                         return fuse_buf_fd_to_fd(dst, dst_off, src, src_off,
 195                                                  len);
 196                 }
 197                 if (res == 0)
 198                         break;
 199
 200                 copied += res;
 201                 if (!(src->flags & FUSE_BUF_FD_RETRY) &&
 202                     !(dst->flags & FUSE_BUF_FD_RETRY)) {
 203                         break;
 204                 }
 205
 206                 len -= res;
 207         }
 208
 209         return copied;
 210 }
 211 #else
 212 static ssize_t fuse_buf_splice(const struct fuse_buf *dst, size_t dst_off,
 213                                const struct fuse_buf *src, size_t src_off,
 214                                size_t len, enum fuse_buf_copy_flags flags)
 215 {
 216         (void) flags;
 217
 218         return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
 219 }
 220 #endif
 221
 222
 223 static ssize_t fuse_buf_copy_one(const struct fuse_buf *dst, size_t dst_off,
 224                                  const struct fuse_buf *src, size_t src_off,
 225                                  size_t len, enum fuse_buf_copy_flags flags)
 226 {
 227         int src_is_fd = src->flags & FUSE_BUF_IS_FD;
 228         int dst_is_fd = dst->flags & FUSE_BUF_IS_FD;
 229
 230         if (!src_is_fd && !dst_is_fd) {
 231                 void *dstmem = dst->mem + dst_off;
 232                 void *srcmem = src->mem + src_off;
 233
 234                 if (dstmem != srcmem) {
 235                         if (dstmem + len <= srcmem || srcmem + len <= dstmem)
 236                                 memcpy(dstmem, srcmem, len);
 237                         else
 238                                 memmove(dstmem, srcmem, len);
 239                 }
 240
 241                 return len;
 242         } else if (!src_is_fd) {
 243                 return fuse_buf_write(dst, dst_off, src, src_off, len);
 244         } else if (!dst_is_fd) {
 245                 return fuse_buf_read(dst, dst_off, src, src_off, len);
 246         } else if (flags & FUSE_BUF_NO_SPLICE) {
 247                 return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
 248         } else {
 249                 return fuse_buf_splice(dst, dst_off, src, src_off, len, flags);
 250         }
 251 }
 252
 253 static const struct fuse_buf *fuse_bufvec_current(struct fuse_bufvec *bufv)
 254 {
 255         if (bufv->idx < bufv->count)
 256                 return &bufv->buf[bufv->idx];
 257         else
 258                 return NULL;
 259 }
 260
 261 static int fuse_bufvec_advance(struct fuse_bufvec *bufv, size_t len)
 262 {
 263         const struct fuse_buf *buf = fuse_bufvec_current(bufv);
 264
 265         bufv->off += len;
 266         assert(bufv->off <= buf->size);
 267         if (bufv->off == buf->size) {
 268                 assert(bufv->idx < bufv->count);
 269                 bufv->idx++;
 270                 if (bufv->idx == bufv->count)
 271                         return 0;
 272                 bufv->off = 0;
 273         }
 274         return 1;
 275 }
 276
 277 ssize_t fuse_buf_copy(struct fuse_bufvec *dstv, struct fuse_bufvec *srcv,
 278                       enum fuse_buf_copy_flags flags)
 279 {
 280         size_t copied = 0;
 281
 282         if (dstv == srcv)
 283                 return fuse_buf_size(dstv);
 284
 285         for (;;) {
 286                 const struct fuse_buf *src = fuse_bufvec_current(srcv);
 287                 const struct fuse_buf *dst = fuse_bufvec_current(dstv);
 288                 size_t src_len;
 289                 size_t dst_len;
 290                 size_t len;
 291                 ssize_t res;
 292
 293                 if (src == NULL || dst == NULL)
 294                         break;
 295
 296                 src_len = src->size - srcv->off;
 297                 dst_len = dst->size - dstv->off;
 298                 len = min_size(src_len, dst_len);
 299
 300                 res = fuse_buf_copy_one(dst, dstv->off, src, srcv->off, len, flags);
 301                 if (res < 0) {
 302                         if (!copied)
 303                                 return res;
 304                         break;
 305                 }
 306                 copied += res;
 307
 308                 if (!fuse_bufvec_advance(srcv, res) ||
 309                     !fuse_bufvec_advance(dstv, res))
 310                         break;
 311
 312                 if (res < len)
 313                         break;
 314         }
 315
 316         return copied;
 317 }