ssize_t
ngx_write_chain_to_file(ngx_file_t *file, ngx_chain_t *cl, off_t offset,
ngx_pool_t *pool)
{
ssize_t total, n;
ngx_iovec_t vec;
struct iovec iovs[NGX_IOVS_PREALLOCATE];
/* use pwrite() if there is the only buf in a chain */
if (cl->next == NULL) {
return ngx_write_file(file, cl->buf->pos,
(size_t) (cl->buf->last - cl->buf->pos),
offset);
}
total = 0;
vec.iovs = iovs;
vec.nalloc = NGX_IOVS_PREALLOCATE;
do {
/* create the iovec and coalesce the neighbouring bufs */
cl = ngx_chain_to_iovec(&vec, cl);
/* use pwrite() if there is the only iovec buffer */
if (vec.count == 1) {
n = ngx_write_file(file, (u_char *) iovs[0].iov_base,
iovs[0].iov_len, offset);
if (n == NGX_ERROR) {
return n;
}
return total + n;
}
n = ngx_writev_file(file, &vec, offset);
if (n == NGX_ERROR) {
return n;
}
offset += n;
total += n;
} while (cl);
return total;
}
ssize_t
ngx_write_chain_to_file(ngx_file_t *file, ngx_chain_t *cl, off_t offset,
ngx_pool_t *pool)
{
u_char *prev;
size_t size;
ssize_t total, n;
ngx_array_t vec;
struct iovec *iov, iovs[NGX_IOVS];
/* use pwrite() if there is the only buf in a chain */
if (cl->next == NULL) {
return ngx_write_file(file, cl->buf->pos,
(size_t) (cl->buf->last - cl->buf->pos),
offset);
}
total = 0;
vec.elts = iovs;
vec.size = sizeof(struct iovec);
vec.nalloc = NGX_IOVS;
vec.pool = pool;
do {
prev = NULL;
iov = NULL;
size = 0;
vec.nelts = 0;
/* create the iovec and coalesce the neighbouring bufs */
while (cl && vec.nelts < IOV_MAX) {
if (prev == cl->buf->pos) {
iov->iov_len += cl->buf->last - cl->buf->pos;
} else {
iov = ngx_array_push(&vec);
if (iov == NULL) {
return NGX_ERROR;
}
iov->iov_base = (void *) cl->buf->pos;
iov->iov_len = cl->buf->last - cl->buf->pos;
}
size += cl->buf->last - cl->buf->pos;
prev = cl->buf->last;
cl = cl->next;
}
/* use pwrite() if there is the only iovec buffer */
if (vec.nelts == 1) {
iov = vec.elts;
n = ngx_write_file(file, (u_char *) iov[0].iov_base,
iov[0].iov_len, offset);
if (n == NGX_ERROR) {
return n;
}
return total + n;
}
n = ngx_writev_file(file, &vec, size, offset);
if (n == NGX_ERROR) {
return n;
}
offset += n;
total += n;
} while (cl);
return total;
}
