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 static ssize_t fuse_buf_splice(const struct fuse_buf *dst, size_t dst_off,
 157                                const struct fuse_buf *src, size_t src_off,
 158                                size_t len, enum fuse_buf_copy_flags flags)
 159 {
 160         int splice_flags = 0;
 161         off_t *srcpos = NULL;
 162         off_t *dstpos = NULL;
 163         off_t srcpos_val;
 164         off_t dstpos_val;
 165         ssize_t res;
 166         size_t copied = 0;
 167
 168         if (flags & FUSE_BUF_SPLICE_MOVE)
 169                 splice_flags |= SPLICE_F_MOVE;
 170         if (flags & FUSE_BUF_SPLICE_NONBLOCK)
 171                 splice_flags |= SPLICE_F_NONBLOCK;
 172
 173         if (src->flags & FUSE_BUF_FD_SEEK) {
 174                 srcpos_val = src->pos + src_off;
 175                 srcpos = &srcpos_val;
 176         }
 177         if (dst->flags & FUSE_BUF_FD_SEEK) {
 178                 dstpos_val = dst->pos + dst_off;
 179                 dstpos = &dstpos_val;
 180         }
 181
 182         while (len) {
 183                 res = splice(src->fd, srcpos, dst->fd, dstpos, len,
 184                              splice_flags);
 185                 if (res == -1) {
 186                         if (copied)
 187                                 break;
 188
 189                         if (errno != EINVAL || (flags & FUSE_BUF_FORCE_SPLICE))
 190                                 return -errno;
 191
 192                         /* Maybe splice is not supported for this combination */
 193                         return fuse_buf_fd_to_fd(dst, dst_off, src, src_off,
 194                                                  len);
 195                 }
 196                 if (res == 0)
 197                         break;
 198
 199                 copied += res;
 200                 if (!(src->flags & FUSE_BUF_FD_RETRY) &&
 201                     !(dst->flags & FUSE_BUF_FD_RETRY)) {
 202                         break;
 203                 }
 204
 205                 len -= res;
 206         }
 207
 208         return copied;
 209 }
 210
 211
 212 static ssize_t fuse_buf_copy_one(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         int src_is_fd = src->flags & FUSE_BUF_IS_FD;
 217         int dst_is_fd = dst->flags & FUSE_BUF_IS_FD;
 218
 219         if (!src_is_fd && !dst_is_fd) {
 220                 void *dstmem = dst->mem + dst_off;
 221                 void *srcmem = src->mem + src_off;
 222
 223                 if (dstmem != srcmem) {
 224                         if (dstmem + len <= srcmem || srcmem + len <= dstmem)
 225                                 memcpy(dstmem, srcmem, len);
 226                         else
 227                                 memmove(dstmem, srcmem, len);
 228                 }
 229
 230                 return len;
 231         } else if (!src_is_fd) {
 232                 return fuse_buf_write(dst, dst_off, src, src_off, len);
 233         } else if (!dst_is_fd) {
 234                 return fuse_buf_read(dst, dst_off, src, src_off, len);
 235         } else if (flags & FUSE_BUF_NO_SPLICE) {
 236                 return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
 237         } else {
 238                 return fuse_buf_splice(dst, dst_off, src, src_off, len, flags);
 239         }
 240 }
 241
 242 static const struct fuse_buf *fuse_bufvec_current(struct fuse_bufvec *bufv)
 243 {
 244         if (bufv->idx < bufv->count)
 245                 return &bufv->buf[bufv->idx];
 246         else
 247                 return NULL;
 248 }
 249
 250 static int fuse_bufvec_advance(struct fuse_bufvec *bufv, size_t len)
 251 {
 252         const struct fuse_buf *buf = fuse_bufvec_current(bufv);
 253
 254         bufv->off += len;
 255         assert(bufv->off <= buf->size);
 256         if (bufv->off == buf->size) {
 257                 assert(bufv->idx < bufv->count);
 258                 bufv->idx++;
 259                 if (bufv->idx == bufv->count)
 260                         return 0;
 261                 bufv->off = 0;
 262         }
 263         return 1;
 264 }
 265
 266 ssize_t fuse_buf_copy(struct fuse_bufvec *dstv, struct fuse_bufvec *srcv,
 267                       enum fuse_buf_copy_flags flags)
 268 {
 269         size_t copied = 0;
 270
 271         if (dstv == srcv)
 272                 return fuse_buf_size(dstv);
 273
 274         for (;;) {
 275                 const struct fuse_buf *src = fuse_bufvec_current(srcv);
 276                 const struct fuse_buf *dst = fuse_bufvec_current(dstv);
 277                 size_t src_len;
 278                 size_t dst_len;
 279                 size_t len;
 280                 ssize_t res;
 281
 282                 if (src == NULL || dst == NULL)
 283                         break;
 284
 285                 src_len = src->size - srcv->off;
 286                 dst_len = dst->size - dstv->off;
 287                 len = min_size(src_len, dst_len);
 288
 289                 res = fuse_buf_copy_one(dst, dstv->off, src, srcv->off, len, flags);
 290                 if (res < 0) {
 291                         if (!copied)
 292                                 return res;
 293                         break;
 294                 }
 295                 copied += res;
 296
 297                 if (!fuse_bufvec_advance(srcv, res) ||
 298                     !fuse_bufvec_advance(dstv, res))
 299                         break;
 300
 301                 if (res < len)
 302                         break;
 303         }
 304
 305         return copied;
 306 }