buffer.c
/*
FUSE: Filesystem in Userspace
Copyright (C) 2010 Miklos Szeredi <miklos@szeredi.hu>
Functions for dealing with `struct fuse_buf` and `struct
fuse_bufvec`.
This program can be distributed under the terms of the GNU LGPLv2.
See the file COPYING.LIB
*/
#define _GNU_SOURCE
#include "config.h"
#include "fuse_i.h"
#include "fuse_lowlevel.h"
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <assert.h>
size_t fuse_buf_size(const struct fuse_bufvec *bufv)
{
size_t i;
size_t size = 0;
for (i = 0; i < bufv->count; i++) {
if (bufv->buf[i].size == SIZE_MAX)
size = SIZE_MAX;
else
size += bufv->buf[i].size;
}
return size;
}
static size_t min_size(size_t s1, size_t s2)
{
return s1 < s2 ? s1 : s2;
}
static ssize_t fuse_buf_write(const struct fuse_buf *dst, size_t dst_off,
const struct fuse_buf *src, size_t src_off,
size_t len)
{
ssize_t res = 0;
size_t copied = 0;
while (len) {
if (dst->flags & FUSE_BUF_FD_SEEK) {
res = pwrite(dst->fd, src->mem + src_off, len,
dst->pos + dst_off);
} else {
res = write(dst->fd, src->mem + src_off, len);
}
if (res == -1) {
if (!copied)
return -errno;
break;
}
if (res == 0)
break;
copied += res;
if (!(dst->flags & FUSE_BUF_FD_RETRY))
break;
src_off += res;
dst_off += res;
len -= res;
}
return copied;
}
static ssize_t fuse_buf_read(const struct fuse_buf *dst, size_t dst_off,
const struct fuse_buf *src, size_t src_off,
size_t len)
{
ssize_t res = 0;
size_t copied = 0;
while (len) {
if (src->flags & FUSE_BUF_FD_SEEK) {
res = pread(src->fd, dst->mem + dst_off, len,
src->pos + src_off);
} else {
res = read(src->fd, dst->mem + dst_off, len);
}
if (res == -1) {
if (!copied)
return -errno;
break;
}
if (res == 0)
break;
copied += res;
if (!(src->flags & FUSE_BUF_FD_RETRY))
break;
dst_off += res;
src_off += res;
len -= res;
}
return copied;
}
static ssize_t fuse_buf_fd_to_fd(const struct fuse_buf *dst, size_t dst_off,
const struct fuse_buf *src, size_t src_off,
size_t len)
{
char buf[4096];
struct fuse_buf tmp = {
.size = sizeof(buf),
.flags = 0,
};
ssize_t res;
size_t copied = 0;
tmp.mem = buf;
while (len) {
size_t this_len = min_size(tmp.size, len);
size_t read_len;
res = fuse_buf_read(&tmp, 0, src, src_off, this_len);
if (res < 0) {
if (!copied)
return res;
break;
}
if (res == 0)
break;
read_len = res;
res = fuse_buf_write(dst, dst_off, &tmp, 0, read_len);
if (res < 0) {
if (!copied)
return res;
break;
}
if (res == 0)
break;
copied += res;
if (res < this_len)
break;
dst_off += res;
src_off += res;
len -= res;
}
return copied;
}
#ifdef HAVE_SPLICE
static ssize_t fuse_buf_splice(const struct fuse_buf *dst, size_t dst_off,
const struct fuse_buf *src, size_t src_off,
size_t len, enum fuse_buf_copy_flags flags)
{
int splice_flags = 0;
off_t *srcpos = NULL;
off_t *dstpos = NULL;
off_t srcpos_val;
off_t dstpos_val;
ssize_t res;
size_t copied = 0;
if (flags & FUSE_BUF_SPLICE_MOVE)
splice_flags |= SPLICE_F_MOVE;
if (flags & FUSE_BUF_SPLICE_NONBLOCK)
splice_flags |= SPLICE_F_NONBLOCK;
if (src->flags & FUSE_BUF_FD_SEEK) {
srcpos_val = src->pos + src_off;
srcpos = &srcpos_val;
}
if (dst->flags & FUSE_BUF_FD_SEEK) {
dstpos_val = dst->pos + dst_off;
dstpos = &dstpos_val;
}
while (len) {
res = splice(src->fd, srcpos, dst->fd, dstpos, len,
splice_flags);
if (res == -1) {
if (copied)
break;
if (errno != EINVAL || (flags & FUSE_BUF_FORCE_SPLICE))
return -errno;
/* Maybe splice is not supported for this combination */
return fuse_buf_fd_to_fd(dst, dst_off, src, src_off,
len);
}
if (res == 0)
break;
copied += res;
if (!(src->flags & FUSE_BUF_FD_RETRY) &&
!(dst->flags & FUSE_BUF_FD_RETRY)) {
break;
}
len -= res;
}
return copied;
}
#else
static ssize_t fuse_buf_splice(const struct fuse_buf *dst, size_t dst_off,
const struct fuse_buf *src, size_t src_off,
size_t len, enum fuse_buf_copy_flags flags)
{
(void) flags;
return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
}
#endif
static ssize_t fuse_buf_copy_one(const struct fuse_buf *dst, size_t dst_off,
const struct fuse_buf *src, size_t src_off,
size_t len, enum fuse_buf_copy_flags flags)
{
int src_is_fd = src->flags & FUSE_BUF_IS_FD;
int dst_is_fd = dst->flags & FUSE_BUF_IS_FD;
if (!src_is_fd && !dst_is_fd) {
void *dstmem = dst->mem + dst_off;
void *srcmem = src->mem + src_off;
if (dstmem != srcmem) {
if (dstmem + len <= srcmem || srcmem + len <= dstmem)
memcpy(dstmem, srcmem, len);
else
memmove(dstmem, srcmem, len);
}
return len;
} else if (!src_is_fd) {
return fuse_buf_write(dst, dst_off, src, src_off, len);
} else if (!dst_is_fd) {
return fuse_buf_read(dst, dst_off, src, src_off, len);
} else if (flags & FUSE_BUF_NO_SPLICE) {
return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
} else {
return fuse_buf_splice(dst, dst_off, src, src_off, len, flags);
}
}
static const struct fuse_buf *fuse_bufvec_current(struct fuse_bufvec *bufv)
{
if (bufv->idx < bufv->count)
return &bufv->buf[bufv->idx];
else
return NULL;
}
static int fuse_bufvec_advance(struct fuse_bufvec *bufv, size_t len)
{
const struct fuse_buf *buf = fuse_bufvec_current(bufv);
bufv->off += len;
assert(bufv->off <= buf->size);
if (bufv->off == buf->size) {
assert(bufv->idx < bufv->count);
bufv->idx++;
if (bufv->idx == bufv->count)
return 0;
bufv->off = 0;
}
return 1;
}
ssize_t fuse_buf_copy(struct fuse_bufvec *dstv, struct fuse_bufvec *srcv,
enum fuse_buf_copy_flags flags)
{
size_t copied = 0;
if (dstv == srcv)
return fuse_buf_size(dstv);
for (;;) {
const struct fuse_buf *src = fuse_bufvec_current(srcv);
const struct fuse_buf *dst = fuse_bufvec_current(dstv);
size_t src_len;
size_t dst_len;
size_t len;
ssize_t res;
if (src == NULL || dst == NULL)
break;
src_len = src->size - srcv->off;
dst_len = dst->size - dstv->off;
len = min_size(src_len, dst_len);
res = fuse_buf_copy_one(dst, dstv->off, src, srcv->off, len, flags);
if (res < 0) {
if (!copied)
return res;
break;
}
copied += res;
if (!fuse_bufvec_advance(srcv, res) ||
!fuse_bufvec_advance(dstv, res))
break;
if (res < len)
break;
}
return copied;
}
fuse_bufvec::off
size_t off
Definition: fuse_common.h:679
FUSE_BUF_IS_FD
Definition: fuse_common.h:555
FUSE_BUF_FORCE_SPLICE
Definition: fuse_common.h:597
FUSE_BUF_SPLICE_MOVE
Definition: fuse_common.h:606
FUSE_BUF_FD_RETRY
Definition: fuse_common.h:573
fuse_buf::pos
off_t pos
Definition: fuse_common.h:654
fuse_bufvec
Definition: fuse_common.h:665
fuse_bufvec::idx
size_t idx
Definition: fuse_common.h:674
fuse_bufvec::count
size_t count
Definition: fuse_common.h:669
fuse_buf::flags
enum fuse_buf_flags flags
Definition: fuse_common.h:633
FUSE_BUF_NO_SPLICE
Definition: fuse_common.h:589
fuse_buf::mem
void * mem
Definition: fuse_common.h:640
fuse_lowlevel.h
FUSE_BUF_SPLICE_NONBLOCK
Definition: fuse_common.h:615
fuse_bufvec::buf
struct fuse_buf buf[1]
Definition: fuse_common.h:684
FUSE_BUF_FD_SEEK
Definition: fuse_common.h:564
fuse_buf_size
size_t fuse_buf_size(const struct fuse_bufvec *bufv)
Definition: buffer.c:22
fuse_buf_copy
ssize_t fuse_buf_copy(struct fuse_bufvec *dst, struct fuse_bufvec *src, enum fuse_buf_copy_flags flags)
Definition: buffer.c:281
fuse_buf::size
size_t size
Definition: fuse_common.h:628
fuse_buf_copy_flags
fuse_buf_copy_flags
Definition: fuse_common.h:579
fuse_buf::fd
int fd
Definition: fuse_common.h:647
fuse_buf
Definition: fuse_common.h:624