ngx_chain_t *
ngx_freebsd_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
{
    int              rc, flags;
    u_char          *prev;
    off_t            size, send, prev_send, aligned, sent, fprev;
    size_t           header_size, file_size;
    ngx_uint_t       eintr, eagain, complete;
    ngx_err_t        err;
    ngx_buf_t       *file;
    ngx_array_t      header, trailer;
    ngx_event_t     *wev;
    ngx_chain_t     *cl;
    struct sf_hdtr   hdtr;
    struct iovec    *iov, headers[NGX_HEADERS], trailers[NGX_TRAILERS];

    wev = c->write;

    if (!wev->ready) {
        return in;
    }

#if (NGX_HAVE_KQUEUE)

    if ((ngx_event_flags & NGX_USE_KQUEUE_EVENT) && wev->pending_eof) {
        (void) ngx_connection_error(c, wev->kq_errno,
                               "kevent() reported about an closed connection");
        wev->error = 1;
        return NGX_CHAIN_ERROR;
    }

#endif

    /* the maximum limit size is the maximum size_t value - the page size */

    if (limit == 0 || limit > (off_t) (NGX_MAX_SIZE_T_VALUE - ngx_pagesize)) {
        limit = NGX_MAX_SIZE_T_VALUE - ngx_pagesize;
    }

    send = 0;
    eagain = 0;
    flags = 0;

    header.elts = headers;
    header.size = sizeof(struct iovec);
    header.nalloc = NGX_HEADERS;
    header.pool = c->pool;

    trailer.elts = trailers;
    trailer.size = sizeof(struct iovec);
    trailer.nalloc = NGX_TRAILERS;
    trailer.pool = c->pool;

    for ( ;; ) {
        file = NULL;
        file_size = 0;
        header_size = 0;
        eintr = 0;
        complete = 0;
        prev_send = send;

        header.nelts = 0;
        trailer.nelts = 0;

        /* create the header iovec and coalesce the neighbouring bufs */

        prev = NULL;
        iov = NULL;

        for (cl = in; cl && send < limit; cl = cl->next) {

            if (ngx_buf_special(cl->buf)) {
                continue;
            }

            if (!ngx_buf_in_memory_only(cl->buf)) {
                break;
            }

            size = cl->buf->last - cl->buf->pos;

            if (send + size > limit) {
                size = limit - send;
            }

            if (prev == cl->buf->pos) {
                iov->iov_len += (size_t) size;

            } else {
                if (header.nelts >= IOV_MAX){
                    break;
                }

                iov = ngx_array_push(&header);
                if (iov == NULL) {
                    return NGX_CHAIN_ERROR;
                }

                iov->iov_base = (void *) cl->buf->pos;
                iov->iov_len = (size_t) size;
            }

            prev = cl->buf->pos + (size_t) size;
            header_size += (size_t) size;
            send += size;
        }


        if (cl && cl->buf->in_file && send < limit) {
            file = cl->buf;

            /* coalesce the neighbouring file bufs */

            do {
                size = cl->buf->file_last - cl->buf->file_pos;

                if (send + size > limit) {
                    size = limit - send;

                    aligned = (cl->buf->file_pos + size + ngx_pagesize - 1)
                               & ~((off_t) ngx_pagesize - 1);

                    if (aligned <= cl->buf->file_last) {
                        size = aligned - cl->buf->file_pos;
                    }
                }

                file_size += (size_t) size;
                send += size;
                fprev = cl->buf->file_pos + size;
                cl = cl->next;

            } while (cl
                     && cl->buf->in_file
                     && send < limit
                     && file->file->fd == cl->buf->file->fd
                     && fprev == cl->buf->file_pos);
        }


        if (file) {

            /* create the trailer iovec and coalesce the neighbouring bufs */

            prev = NULL;
            iov = NULL;

            while (cl && send < limit) {

                if (ngx_buf_special(cl->buf)) {
                    cl = cl->next;
                    continue;
                }

                if (!ngx_buf_in_memory_only(cl->buf)) {
                    break;
                }

                size = cl->buf->last - cl->buf->pos;

                if (send + size > limit) {
                    size = limit - send;
                }

                if (prev == cl->buf->pos) {
                    iov->iov_len += (size_t) size;

                } else {
                    if (trailer.nelts >= IOV_MAX){
                        break;
                    }

                    iov = ngx_array_push(&trailer);
                    if (iov == NULL) {
                        return NGX_CHAIN_ERROR;
                    }

                    iov->iov_base = (void *) cl->buf->pos;
                    iov->iov_len = (size_t) size;
                }

                prev = cl->buf->pos + (size_t) size;
                send += size;
                cl = cl->next;
            }
        }

        if (file) {

            if (ngx_freebsd_use_tcp_nopush
                && c->tcp_nopush == NGX_TCP_NOPUSH_UNSET)
            {
                if (ngx_tcp_nopush(c->fd) == NGX_ERROR) {
                    err = ngx_socket_errno;

                    /*
                     * there is a tiny chance to be interrupted, however,
                     * we continue a processing without the TCP_NOPUSH
                     */

                    if (err != NGX_EINTR) {
                        wev->error = 1;
                        (void) ngx_connection_error(c, err,
                                                    ngx_tcp_nopush_n " failed");
                        return NGX_CHAIN_ERROR;
                    }

                } else {
                    c->tcp_nopush = NGX_TCP_NOPUSH_SET;

                    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
                                   "tcp_nopush");
                }
            }

            /*
             * sendfile() does unneeded work if sf_hdtr's count is 0,
             * but corresponding pointer is not NULL
             */

            hdtr.headers = header.nelts ? (struct iovec *) header.elts: NULL;
            hdtr.hdr_cnt = header.nelts;
            hdtr.trailers = trailer.nelts ? (struct iovec *) trailer.elts: NULL;
            hdtr.trl_cnt = trailer.nelts;

            /*
             * the "nbytes bug" of the old sendfile() syscall:
             * http://bugs.freebsd.org/33771
             */

            if (!ngx_freebsd_sendfile_nbytes_bug) {
                header_size = 0;
            }

            sent = 0;

#if (NGX_HAVE_AIO_SENDFILE)
            flags = c->aio_sendfile ? SF_NODISKIO : 0;
#endif

            rc = sendfile(file->file->fd, c->fd, file->file_pos,
                          file_size + header_size, &hdtr, &sent, flags);

            if (rc == -1) {
                err = ngx_errno;

                switch (err) {
                case NGX_EAGAIN:
                    eagain = 1;
                    break;

                case NGX_EINTR:
                    eintr = 1;
                    break;

#if (NGX_HAVE_AIO_SENDFILE)
                case NGX_EBUSY:
                    c->busy_sendfile = file;
                    break;
#endif

                default:
                    wev->error = 1;
                    (void) ngx_connection_error(c, err, "sendfile() failed");
                    return NGX_CHAIN_ERROR;
                }

                ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, err,
                               "sendfile() sent only %O bytes", sent);

            /*
             * sendfile() in FreeBSD 3.x-4.x may return value >= 0
             * on success, although only 0 is documented
             */

            } else if (rc >= 0 && sent == 0) {

                /*
                 * if rc is OK and sent equal to zero, then someone
                 * has truncated the file, so the offset became beyond
                 * the end of the file
                 */

                ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                         "sendfile() reported that \"%s\" was truncated at %O",
                         file->file->name.data, file->file_pos);

                return NGX_CHAIN_ERROR;
            }

            ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0,
                           "sendfile: %d, @%O %O:%uz",
                           rc, file->file_pos, sent, file_size + header_size);

        } else {
            rc = writev(c->fd, header.elts, header.nelts);

            ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
                           "writev: %d of %uz", rc, header_size);

            if (rc == -1) {
                err = ngx_errno;

                switch (err) {
                case NGX_EAGAIN:
                    break;

                case NGX_EINTR:
                    eintr = 1;
                    break;

                default:
                    wev->error = 1;
                    ngx_connection_error(c, err, "writev() failed");
                    return NGX_CHAIN_ERROR;
                }

                ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, err,
                               "writev() not ready");
            }

            sent = rc > 0 ? rc : 0;
        }

        if (send - prev_send == sent) {
            complete = 1;
        }

        c->sent += sent;

        for ( /* void */ ; in; in = in->next) {

            if (ngx_buf_special(in->buf)) {
                continue;
            }

            if (sent == 0) {
                break;
            }

            size = ngx_buf_size(in->buf);

            if (sent >= size) {
                sent -= size;

                if (ngx_buf_in_memory(in->buf)) {
                    in->buf->pos = in->buf->last;
                }

                if (in->buf->in_file) {
                    in->buf->file_pos = in->buf->file_last;
                }

                continue;
            }

            if (ngx_buf_in_memory(in->buf)) {
                in->buf->pos += (size_t) sent;
            }

            if (in->buf->in_file) {
                in->buf->file_pos += sent;
            }

            break;
        }

#if (NGX_HAVE_AIO_SENDFILE)
        if (c->busy_sendfile) {
            return in;
        }
#endif

        if (eagain) {

            /*
             * sendfile() may return EAGAIN, even if it has sent a whole file
             * part, it indicates that the successive sendfile() call would
             * return EAGAIN right away and would not send anything.
             * We use it as a hint.
             */

            wev->ready = 0;
            return in;
        }

        if (eintr) {
            continue;
        }

        if (!complete) {
            wev->ready = 0;
            return in;
        }

        if (send >= limit || in == NULL) {
            return in;
        }
    }
}
ngx_chain_t *
ngx_freebsd_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
{
    int              rc, flags;
    off_t            send, prev_send, sent;
    size_t           file_size;
    ssize_t          n;
    ngx_uint_t       eintr, eagain;
    ngx_err_t        err;
    ngx_buf_t       *file;
    ngx_event_t     *wev;
    ngx_chain_t     *cl;
    ngx_iovec_t      header, trailer;
    struct sf_hdtr   hdtr;
    struct iovec     headers[NGX_IOVS_PREALLOCATE];
    struct iovec     trailers[NGX_IOVS_PREALLOCATE];

    wev = c->write;

    if (!wev->ready) {
        return in;
    }

#if (NGX_HAVE_KQUEUE)

    if ((ngx_event_flags & NGX_USE_KQUEUE_EVENT) && wev->pending_eof) {
        (void) ngx_connection_error(c, wev->kq_errno,
                               "kevent() reported about an closed connection");
        wev->error = 1;
        return NGX_CHAIN_ERROR;
    }

#endif

    /* the maximum limit size is the maximum size_t value - the page size */

    if (limit == 0 || limit > (off_t) (NGX_MAX_SIZE_T_VALUE - ngx_pagesize)) {
        limit = NGX_MAX_SIZE_T_VALUE - ngx_pagesize;
    }

    send = 0;
    eagain = 0;
    flags = 0;

    header.iovs = headers;
    header.nalloc = NGX_IOVS_PREALLOCATE;

    trailer.iovs = trailers;
    trailer.nalloc = NGX_IOVS_PREALLOCATE;

    for ( ;; ) {
        eintr = 0;
        prev_send = send;

        /* create the header iovec and coalesce the neighbouring bufs */

        cl = ngx_output_chain_to_iovec(&header, in, limit - send, c->log);

        if (cl == NGX_CHAIN_ERROR) {
            return NGX_CHAIN_ERROR;
        }

        send += header.size;

        if (cl && cl->buf->in_file && send < limit) {
            file = cl->buf;

            /* coalesce the neighbouring file bufs */

            file_size = (size_t) ngx_chain_coalesce_file(&cl, limit - send);

            send += file_size;

            /* create the trailer iovec and coalesce the neighbouring bufs */

            cl = ngx_output_chain_to_iovec(&trailer, cl, limit - send, c->log);

            if (cl == NGX_CHAIN_ERROR) {
                return NGX_CHAIN_ERROR;
            }

            send += trailer.size;

            if (ngx_freebsd_use_tcp_nopush
                && c->tcp_nopush == NGX_TCP_NOPUSH_UNSET)
            {
                if (ngx_tcp_nopush(c->fd) == NGX_ERROR) {
                    err = ngx_socket_errno;

                    /*
                     * there is a tiny chance to be interrupted, however,
                     * we continue a processing without the TCP_NOPUSH
                     */

                    if (err != NGX_EINTR) {
                        wev->error = 1;
                        (void) ngx_connection_error(c, err,
                                                    ngx_tcp_nopush_n " failed");
                        return NGX_CHAIN_ERROR;
                    }

                } else {
                    c->tcp_nopush = NGX_TCP_NOPUSH_SET;

                    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
                                   "tcp_nopush");
                }
            }

            /*
             * sendfile() does unneeded work if sf_hdtr's count is 0,
             * but corresponding pointer is not NULL
             */

            hdtr.headers = header.count ? header.iovs : NULL;
            hdtr.hdr_cnt = header.count;
            hdtr.trailers = trailer.count ? trailer.iovs : NULL;
            hdtr.trl_cnt = trailer.count;

            /*
             * the "nbytes bug" of the old sendfile() syscall:
             * http://bugs.freebsd.org/33771
             */

            if (!ngx_freebsd_sendfile_nbytes_bug) {
                header.size = 0;
            }

            sent = 0;

#if (NGX_HAVE_AIO_SENDFILE)
            flags = c->aio_sendfile ? SF_NODISKIO : 0;
#endif

            rc = sendfile(file->file->fd, c->fd, file->file_pos,
                          file_size + header.size, &hdtr, &sent, flags);

            if (rc == -1) {
                err = ngx_errno;

                switch (err) {
                case NGX_EAGAIN:
                    eagain = 1;
                    break;

                case NGX_EINTR:
                    eintr = 1;
                    break;

#if (NGX_HAVE_AIO_SENDFILE)
                case NGX_EBUSY:
                    c->busy_sendfile = file;
                    break;
#endif

                default:
                    wev->error = 1;
                    (void) ngx_connection_error(c, err, "sendfile() failed");
                    return NGX_CHAIN_ERROR;
                }

                ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, err,
                               "sendfile() sent only %O bytes", sent);

            /*
             * sendfile() in FreeBSD 3.x-4.x may return value >= 0
             * on success, although only 0 is documented
             */

            } else if (rc >= 0 && sent == 0) {

                /*
                 * if rc is OK and sent equal to zero, then someone
                 * has truncated the file, so the offset became beyond
                 * the end of the file
                 */

                ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                         "sendfile() reported that \"%s\" was truncated at %O",
                         file->file->name.data, file->file_pos);

                return NGX_CHAIN_ERROR;
            }

            ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0,
                           "sendfile: %d, @%O %O:%uz",
                           rc, file->file_pos, sent, file_size + header.size);

        } else {
            n = ngx_writev(c, &header);

            if (n == NGX_ERROR) {
                return NGX_CHAIN_ERROR;
            }

            sent = (n == NGX_AGAIN) ? 0 : n;
        }

        c->sent += sent;

        in = ngx_chain_update_sent(in, sent);

#if (NGX_HAVE_AIO_SENDFILE)
        if (c->busy_sendfile) {
            return in;
        }
#endif

        if (eagain) {

            /*
             * sendfile() may return EAGAIN, even if it has sent a whole file
             * part, it indicates that the successive sendfile() call would
             * return EAGAIN right away and would not send anything.
             * We use it as a hint.
             */

            wev->ready = 0;
            return in;
        }

        if (eintr) {
            send = prev_send + sent;
            continue;
        }

        if (send - prev_send != sent) {
            wev->ready = 0;
            return in;
        }

        if (send >= limit || in == NULL) {
            return in;
        }
    }
}
예제 #3
0
ngx_chain_t *
ngx_linux_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
{
    int            rc, tcp_nodelay;
    off_t          size, send, prev_send, aligned, sent, fprev;
    u_char        *prev;
    size_t         file_size;
    ngx_err_t      err;
    ngx_buf_t     *file;
    ngx_uint_t     eintr, complete;
    ngx_array_t    header;
    ngx_event_t   *wev;
    ngx_chain_t   *cl;
    struct iovec  *iov, headers[NGX_HEADERS];
#if (NGX_HAVE_SENDFILE64)
    off_t          offset;
#else
    int32_t        offset;
#endif

    wev = c->write;

    if (!wev->ready) {
        return in;
    }


    /* the maximum limit size is 2G-1 - the page size */

    if (limit == 0 || limit > (off_t) (NGX_SENDFILE_LIMIT - ngx_pagesize)) {
        limit = NGX_SENDFILE_LIMIT - ngx_pagesize;
    }


    send = 0;

    header.elts = headers;
    header.size = sizeof(struct iovec);
    header.nalloc = NGX_HEADERS;
    header.pool = c->pool;

    for ( ;; ) {
        file = NULL;
        file_size = 0;
        eintr = 0;
        complete = 0;
        prev_send = send;

        header.nelts = 0;

        prev = NULL;
        iov = NULL;

        /* create the iovec and coalesce the neighbouring bufs */

        for (cl = in;
             cl && header.nelts < IOV_MAX && send < limit;
             cl = cl->next)
        {
            if (ngx_buf_special(cl->buf)) {
                continue;
            }

#if 1
            if (!ngx_buf_in_memory(cl->buf) && !cl->buf->in_file) {
                ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                              "zero size buf in sendfile "
                              "t:%d r:%d f:%d %p %p-%p %p %O-%O",
                              cl->buf->temporary,
                              cl->buf->recycled,
                              cl->buf->in_file,
                              cl->buf->start,
                              cl->buf->pos,
                              cl->buf->last,
                              cl->buf->file,
                              cl->buf->file_pos,
                              cl->buf->file_last);

                ngx_debug_point();

                return NGX_CHAIN_ERROR;
            }
#endif

            if (!ngx_buf_in_memory_only(cl->buf)) {
                break;
            }

            size = cl->buf->last - cl->buf->pos;

            if (send + size > limit) {
                size = limit - send;
            }

            if (prev == cl->buf->pos) {
                iov->iov_len += (size_t) size;

            } else {
                iov = ngx_array_push(&header);
                if (iov == NULL) {
                    return NGX_CHAIN_ERROR;
                }

                iov->iov_base = (void *) cl->buf->pos;
                iov->iov_len = (size_t) size;
            }

            prev = cl->buf->pos + (size_t) size;
            send += size;
        }

        /* set TCP_CORK if there is a header before a file */

        if (c->tcp_nopush == NGX_TCP_NOPUSH_UNSET
            && header.nelts != 0
            && cl
            && cl->buf->in_file)
        {
            /* the TCP_CORK and TCP_NODELAY are mutually exclusive */

            if (c->tcp_nodelay == NGX_TCP_NODELAY_SET) {

                tcp_nodelay = 0;

                if (setsockopt(c->fd, IPPROTO_TCP, TCP_NODELAY,
                               (const void *) &tcp_nodelay, sizeof(int)) == -1)
                {
                    err = ngx_errno;

                    /*
                     * there is a tiny chance to be interrupted, however,
                     * we continue a processing with the TCP_NODELAY
                     * and without the TCP_CORK
                     */

                    if (err != NGX_EINTR) {
                        wev->error = 1;
                        ngx_connection_error(c, err,
                                             "setsockopt(TCP_NODELAY) failed");
                        return NGX_CHAIN_ERROR;
                    }

                } else {
                    c->tcp_nodelay = NGX_TCP_NODELAY_UNSET;

                    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                                   "no tcp_nodelay");
                }
            }

            if (c->tcp_nodelay == NGX_TCP_NODELAY_UNSET) {

                if (ngx_tcp_nopush(c->fd) == NGX_ERROR) {
                    err = ngx_errno;

                    /*
                     * there is a tiny chance to be interrupted, however,
                     * we continue a processing without the TCP_CORK
                     */

                    if (err != NGX_EINTR) {
                        wev->error = 1;
                        ngx_connection_error(c, err,
                                             ngx_tcp_nopush_n " failed");
                        return NGX_CHAIN_ERROR;
                    }

                } else {
                    c->tcp_nopush = NGX_TCP_NOPUSH_SET;

                    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
                                   "tcp_nopush");
                }
            }
        }

        /* get the file buf */

        if (header.nelts == 0 && cl && cl->buf->in_file && send < limit) {
            file = cl->buf;

            /* coalesce the neighbouring file bufs */

            do {
                size = cl->buf->file_last - cl->buf->file_pos;

                if (send + size > limit) {
                    size = limit - send;

                    aligned = (cl->buf->file_pos + size + ngx_pagesize - 1)
                               & ~((off_t) ngx_pagesize - 1);

                    if (aligned <= cl->buf->file_last) {
                        size = aligned - cl->buf->file_pos;
                    }
                }

                file_size += (size_t) size;
                send += size;
                fprev = cl->buf->file_pos + size;
                cl = cl->next;

            } while (cl
                     && cl->buf->in_file
                     && send < limit
                     && file->file->fd == cl->buf->file->fd
                     && fprev == cl->buf->file_pos);
        }

        if (file) {
#if 1
            if (file_size == 0) {
                ngx_debug_point();
                return NGX_CHAIN_ERROR;
            }
#endif
#if (NGX_HAVE_SENDFILE64)
            offset = file->file_pos;
#else
            offset = (int32_t) file->file_pos;
#endif

            ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
                           "sendfile: @%O %uz", file->file_pos, file_size);

            rc = sendfile(c->fd, file->file->fd, &offset, file_size);

            if (rc == -1) {
                err = ngx_errno;

                switch (err) {
                case NGX_EAGAIN:
                    break;

                case NGX_EINTR:
                    eintr = 1;
                    break;

                default:
                    wev->error = 1;
                    ngx_connection_error(c, err, "sendfile() failed");
                    return NGX_CHAIN_ERROR;
                }

                ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, err,
                               "sendfile() is not ready");
            }

            sent = rc > 0 ? rc : 0;

            ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0,
                           "sendfile: %d, @%O %O:%uz",
                           rc, file->file_pos, sent, file_size);

        } else {
            rc = writev(c->fd, header.elts, header.nelts);

            if (rc == -1) {
                err = ngx_errno;

                switch (err) {
                case NGX_EAGAIN:
                    break;

                case NGX_EINTR:
                    eintr = 1;
                    break;

                default:
                    wev->error = 1;
                    ngx_connection_error(c, err, "writev() failed");
                    return NGX_CHAIN_ERROR;
                }

                ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, err,
                               "writev() not ready");
            }

            sent = rc > 0 ? rc : 0;

            ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0, "writev: %O", sent);
        }

        if (send - prev_send == sent) {
            complete = 1;
        }

        c->sent += sent;

        for (cl = in; cl; cl = cl->next) {

            if (ngx_buf_special(cl->buf)) {
                continue;
            }

            if (sent == 0) {
                break;
            }

            size = ngx_buf_size(cl->buf);

            if (sent >= size) {
                sent -= size;

                if (ngx_buf_in_memory(cl->buf)) {
                    cl->buf->pos = cl->buf->last;
                }

                if (cl->buf->in_file) {
                    cl->buf->file_pos = cl->buf->file_last;
                }

                continue;
            }

            if (ngx_buf_in_memory(cl->buf)) {
                cl->buf->pos += (size_t) sent;
            }

            if (cl->buf->in_file) {
                cl->buf->file_pos += sent;
            }

            break;
        }

        if (eintr) {
            continue;
        }

        if (!complete) {
            wev->ready = 0;
            return cl;
        }

        if (send >= limit || cl == NULL) {
            return cl;
        }

        in = cl;
    }
}
//遍历r->out上的每一个缓存块,根据缓存块里的数据类型调用不同的系统接口函数将数据写出到客户端。
ngx_chain_t *
ngx_linux_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
{
    int            tcp_nodelay;
    off_t          send, prev_send;
    size_t         file_size, sent;
    ssize_t        n;
    ngx_err_t      err;
    ngx_buf_t     *file;
    ngx_event_t   *wev;
    ngx_chain_t   *cl;
    ngx_iovec_t    header;
    struct iovec   headers[NGX_IOVS_PREALLOCATE];
#if (NGX_THREADS)
    ngx_int_t      rc;
    ngx_uint_t     thread_handled, thread_complete;
#endif

    wev = c->write;

    if (!wev->ready) {
        return in;
    }


    /* the maximum limit size is 2G-1 - the page size */

    if (limit == 0 || limit > (off_t) (NGX_SENDFILE_MAXSIZE - ngx_pagesize)) {
        limit = NGX_SENDFILE_MAXSIZE - ngx_pagesize;
    }


    send = 0;

    header.iovs = headers;
    header.nalloc = NGX_IOVS_PREALLOCATE;

    for ( ;; ) {
        prev_send = send;
#if (NGX_THREADS)
        thread_handled = 0;
        thread_complete = 0;
#endif

        /* create the iovec and coalesce the neighbouring bufs */

        cl = ngx_output_chain_to_iovec(&header, in, limit - send, c->log);

        if (cl == NGX_CHAIN_ERROR) {
            return NGX_CHAIN_ERROR;
        }

        send += header.size;

        /* set TCP_CORK if there is a header before a file */

        if (c->tcp_nopush == NGX_TCP_NOPUSH_UNSET
            && header.count != 0
            && cl
            && cl->buf->in_file)
        {
            /* the TCP_CORK and TCP_NODELAY are mutually exclusive */

            if (c->tcp_nodelay == NGX_TCP_NODELAY_SET) {

                tcp_nodelay = 0;

                if (setsockopt(c->fd, IPPROTO_TCP, TCP_NODELAY,
                               (const void *) &tcp_nodelay, sizeof(int)) == -1)
                {
                    err = ngx_socket_errno;

                    /*
                     * there is a tiny chance to be interrupted, however,
                     * we continue a processing with the TCP_NODELAY
                     * and without the TCP_CORK
                     */

                    if (err != NGX_EINTR) {
                        wev->error = 1;
                        ngx_connection_error(c, err,
                                             "setsockopt(TCP_NODELAY) failed");
                        return NGX_CHAIN_ERROR;
                    }

                } else {
                    c->tcp_nodelay = NGX_TCP_NODELAY_UNSET;

                    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
                                   "no tcp_nodelay");
                }
            }

            if (c->tcp_nodelay == NGX_TCP_NODELAY_UNSET) {

                if (ngx_tcp_nopush(c->fd) == NGX_ERROR) {
                    err = ngx_socket_errno;

                    /*
                     * there is a tiny chance to be interrupted, however,
                     * we continue a processing without the TCP_CORK
                     */

                    if (err != NGX_EINTR) {
                        wev->error = 1;
                        ngx_connection_error(c, err,
                                             ngx_tcp_nopush_n " failed");
                        return NGX_CHAIN_ERROR;
                    }

                } else {
                    c->tcp_nopush = NGX_TCP_NOPUSH_SET;

                    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
                                   "tcp_nopush");
                }
            }
        }

        /* get the file buf */

        if (header.count == 0 && cl && cl->buf->in_file && send < limit) {
            file = cl->buf;

            /* coalesce the neighbouring file bufs */

            file_size = (size_t) ngx_chain_coalesce_file(&cl, limit - send);

            send += file_size;
#if 1
            if (file_size == 0) 
			{
                ngx_debug_point();
                return NGX_CHAIN_ERROR;
            }
#endif

#if (NGX_THREADS)
            if (file->file->thread_handler) {
                rc = ngx_linux_sendfile_thread(c, file, file_size, &sent);

                switch (rc) {
                case NGX_OK:
                    thread_handled = 1;
                    break;

                case NGX_DONE:
                    thread_complete = 1;
                    break;

                case NGX_AGAIN:
                    break;

                default: /* NGX_ERROR */
                    return NGX_CHAIN_ERROR;
                }

            } else
#endif
            {
                n = ngx_linux_sendfile(c, file, file_size);

                if (n == NGX_ERROR) {
                    return NGX_CHAIN_ERROR;
                }

                sent = (n == NGX_AGAIN) ? 0 : n;
            }

        } else {
            n = ngx_writev(c, &header);

            if (n == NGX_ERROR) {
                return NGX_CHAIN_ERROR;
            }

            sent = (n == NGX_AGAIN) ? 0 : n;
        }

        c->sent += sent;

        in = ngx_chain_update_sent(in, sent);

        if ((size_t) (send - prev_send) != sent) {
#if (NGX_THREADS)
            if (thread_handled) {
                return in;
            }

            if (thread_complete) {
                send = prev_send + sent;
                continue;
            }
#endif
            wev->ready = 0;
            return in;
        }

        if (send >= limit || in == NULL) {
            return in;
        }
    }
}