mirror of https://gitee.com/openkylin/qemu.git
352 lines
8.0 KiB
C
352 lines
8.0 KiB
C
/*
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* FUSE: Filesystem in Userspace
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* Copyright (C) 2010 Miklos Szeredi <miklos@szeredi.hu>
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*
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* Functions for dealing with `struct fuse_buf` and `struct
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* fuse_bufvec`.
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*
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* This program can be distributed under the terms of the GNU LGPLv2.
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* See the file COPYING.LIB
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*/
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#include "qemu/osdep.h"
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#include "fuse_i.h"
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#include "fuse_lowlevel.h"
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#include <assert.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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size_t fuse_buf_size(const struct fuse_bufvec *bufv)
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{
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size_t i;
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size_t size = 0;
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for (i = 0; i < bufv->count; i++) {
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if (bufv->buf[i].size == SIZE_MAX) {
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size = SIZE_MAX;
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} else {
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size += bufv->buf[i].size;
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}
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}
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return size;
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}
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static ssize_t fuse_buf_writev(struct fuse_buf *out_buf,
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struct fuse_bufvec *in_buf)
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{
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ssize_t res, i, j;
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size_t iovcnt = in_buf->count;
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struct iovec *iov;
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int fd = out_buf->fd;
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iov = calloc(iovcnt, sizeof(struct iovec));
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if (!iov) {
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return -ENOMEM;
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}
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for (i = 0, j = 0; i < iovcnt; i++) {
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/* Skip the buf with 0 size */
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if (in_buf->buf[i].size) {
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iov[j].iov_base = in_buf->buf[i].mem;
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iov[j].iov_len = in_buf->buf[i].size;
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j++;
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}
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}
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if (out_buf->flags & FUSE_BUF_FD_SEEK) {
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res = pwritev(fd, iov, iovcnt, out_buf->pos);
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} else {
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res = writev(fd, iov, iovcnt);
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}
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if (res == -1) {
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res = -errno;
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}
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free(iov);
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return res;
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}
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static size_t min_size(size_t s1, size_t s2)
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{
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return s1 < s2 ? s1 : s2;
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}
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static ssize_t fuse_buf_write(const struct fuse_buf *dst, size_t dst_off,
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const struct fuse_buf *src, size_t src_off,
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size_t len)
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{
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ssize_t res = 0;
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size_t copied = 0;
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while (len) {
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if (dst->flags & FUSE_BUF_FD_SEEK) {
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res = pwrite(dst->fd, (char *)src->mem + src_off, len,
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dst->pos + dst_off);
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} else {
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res = write(dst->fd, (char *)src->mem + src_off, len);
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}
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if (res == -1) {
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if (!copied) {
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return -errno;
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}
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break;
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}
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if (res == 0) {
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break;
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}
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copied += res;
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if (!(dst->flags & FUSE_BUF_FD_RETRY)) {
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break;
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}
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src_off += res;
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dst_off += res;
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len -= res;
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}
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return copied;
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}
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static ssize_t fuse_buf_read(const struct fuse_buf *dst, size_t dst_off,
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const struct fuse_buf *src, size_t src_off,
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size_t len)
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{
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ssize_t res = 0;
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size_t copied = 0;
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while (len) {
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if (src->flags & FUSE_BUF_FD_SEEK) {
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res = pread(src->fd, (char *)dst->mem + dst_off, len,
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src->pos + src_off);
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} else {
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res = read(src->fd, (char *)dst->mem + dst_off, len);
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}
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if (res == -1) {
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if (!copied) {
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return -errno;
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}
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break;
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}
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if (res == 0) {
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break;
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}
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copied += res;
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if (!(src->flags & FUSE_BUF_FD_RETRY)) {
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break;
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}
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dst_off += res;
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src_off += res;
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len -= res;
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}
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return copied;
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}
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static ssize_t fuse_buf_fd_to_fd(const struct fuse_buf *dst, size_t dst_off,
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const struct fuse_buf *src, size_t src_off,
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size_t len)
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{
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char buf[4096];
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struct fuse_buf tmp = {
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.size = sizeof(buf),
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.flags = 0,
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};
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ssize_t res;
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size_t copied = 0;
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tmp.mem = buf;
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while (len) {
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size_t this_len = min_size(tmp.size, len);
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size_t read_len;
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res = fuse_buf_read(&tmp, 0, src, src_off, this_len);
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if (res < 0) {
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if (!copied) {
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return res;
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}
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break;
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}
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if (res == 0) {
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break;
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}
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read_len = res;
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res = fuse_buf_write(dst, dst_off, &tmp, 0, read_len);
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if (res < 0) {
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if (!copied) {
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return res;
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}
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break;
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}
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if (res == 0) {
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break;
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}
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copied += res;
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if (res < this_len) {
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break;
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}
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dst_off += res;
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src_off += res;
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len -= res;
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}
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return copied;
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}
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static ssize_t fuse_buf_copy_one(const struct fuse_buf *dst, size_t dst_off,
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const struct fuse_buf *src, size_t src_off,
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size_t len)
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{
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int src_is_fd = src->flags & FUSE_BUF_IS_FD;
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int dst_is_fd = dst->flags & FUSE_BUF_IS_FD;
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if (!src_is_fd && !dst_is_fd) {
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char *dstmem = (char *)dst->mem + dst_off;
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char *srcmem = (char *)src->mem + src_off;
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if (dstmem != srcmem) {
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if (dstmem + len <= srcmem || srcmem + len <= dstmem) {
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memcpy(dstmem, srcmem, len);
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} else {
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memmove(dstmem, srcmem, len);
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}
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}
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return len;
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} else if (!src_is_fd) {
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return fuse_buf_write(dst, dst_off, src, src_off, len);
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} else if (!dst_is_fd) {
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return fuse_buf_read(dst, dst_off, src, src_off, len);
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} else {
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return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
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}
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}
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static const struct fuse_buf *fuse_bufvec_current(struct fuse_bufvec *bufv)
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{
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if (bufv->idx < bufv->count) {
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return &bufv->buf[bufv->idx];
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} else {
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return NULL;
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}
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}
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static int fuse_bufvec_advance(struct fuse_bufvec *bufv, size_t len)
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{
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const struct fuse_buf *buf = fuse_bufvec_current(bufv);
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bufv->off += len;
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assert(bufv->off <= buf->size);
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if (bufv->off == buf->size) {
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assert(bufv->idx < bufv->count);
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bufv->idx++;
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if (bufv->idx == bufv->count) {
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return 0;
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}
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bufv->off = 0;
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}
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return 1;
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}
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ssize_t fuse_buf_copy(struct fuse_bufvec *dstv, struct fuse_bufvec *srcv)
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{
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size_t copied = 0, i;
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if (dstv == srcv) {
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return fuse_buf_size(dstv);
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}
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/*
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* use writev to improve bandwidth when all the
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* src buffers already mapped by the daemon
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* process
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*/
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for (i = 0; i < srcv->count; i++) {
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if (srcv->buf[i].flags & FUSE_BUF_IS_FD) {
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break;
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}
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}
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if ((i == srcv->count) && (dstv->count == 1) &&
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(dstv->idx == 0) &&
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(dstv->buf[0].flags & FUSE_BUF_IS_FD)) {
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dstv->buf[0].pos += dstv->off;
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return fuse_buf_writev(&dstv->buf[0], srcv);
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}
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for (;;) {
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const struct fuse_buf *src = fuse_bufvec_current(srcv);
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const struct fuse_buf *dst = fuse_bufvec_current(dstv);
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size_t src_len;
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size_t dst_len;
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size_t len;
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ssize_t res;
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if (src == NULL || dst == NULL) {
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break;
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}
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src_len = src->size - srcv->off;
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dst_len = dst->size - dstv->off;
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len = min_size(src_len, dst_len);
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res = fuse_buf_copy_one(dst, dstv->off, src, srcv->off, len);
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if (res < 0) {
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if (!copied) {
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return res;
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}
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break;
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}
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copied += res;
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if (!fuse_bufvec_advance(srcv, res) ||
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!fuse_bufvec_advance(dstv, res)) {
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break;
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}
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if (res < len) {
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break;
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}
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}
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return copied;
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}
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void *fuse_mbuf_iter_advance(struct fuse_mbuf_iter *iter, size_t len)
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{
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void *ptr;
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if (len > iter->size - iter->pos) {
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return NULL;
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}
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ptr = iter->mem + iter->pos;
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iter->pos += len;
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return ptr;
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}
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const char *fuse_mbuf_iter_advance_str(struct fuse_mbuf_iter *iter)
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{
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const char *str = iter->mem + iter->pos;
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size_t remaining = iter->size - iter->pos;
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size_t i;
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for (i = 0; i < remaining; i++) {
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if (str[i] == '\0') {
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iter->pos += i + 1;
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return str;
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}
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}
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return NULL;
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}
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