src/lib/ostream-file.c

	ostream-file.c revision 0e88f0a214ea86055cdfd2ae4105afbb6aba8119
5a580c3a38ced62d4bcc95b8ac7c4f2935b5d294Timo Sirainen/*
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen   ostream-file.c : Output stream handling for files
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    Copyright (c) 2002 Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    Permission is hereby granted, free of charge, to any person obtaining
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    a copy of this software and associated documentation files (the
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen    "Software"), to deal in the Software without restriction, including
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen    without limitation the rights to use, copy, modify, merge, publish,
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    distribute, sublicense, and/or sell copies of the Software, and to
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    permit persons to whom the Software is furnished to do so, subject to
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    the following conditions:
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    The above copyright notice and this permission notice shall be
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    included in all copies or substantial portions of the Software.
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen*/
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen/* @UNSAFE: whole file */
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
4e8e7a93628b4ed60aaaa47c6f72c1433f21e81dTimo Sirainen#include "lib.h"
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen#include "alarm-hup.h"
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen#include "ioloop.h"
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen#include "file-set-size.h"
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen#include "write-full.h"
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#include "network.h"
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#include "sendfile-util.h"
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#include "istream.h"
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#include "istream-internal.h"
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#include "ostream-internal.h"
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#include <unistd.h>
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#include <sys/stat.h>
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#ifdef HAVE_SYS_UIO_H
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#  include <sys/uio.h>
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#endif
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen/* try to keep the buffer size within 4k..128k. ReiserFS may actually return
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen   128k as optimal size. */
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen#define DEFAULT_OPTIMAL_BLOCK_SIZE 4096
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen#define MAX_OPTIMAL_BLOCK_SIZE (128*1024)
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen#define IS_STREAM_EMPTY(fstream) \
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    ((fstream)->head == (fstream)->tail && !(fstream)->full)
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen#define MAX_SSIZE_T(size) \
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    ((size) < SSIZE_T_MAX ? (size_t)(size) : SSIZE_T_MAX)
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainenstruct file_ostream {
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    struct _ostream ostream;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    int fd;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    int priority;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    struct io *io;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    unsigned char *buffer; /* ring-buffer */
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    size_t buffer_size, max_buffer_size, optimal_block_size;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    size_t head, tail; /* first unsent/unused byte */
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    int timeout_msecs;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    void (*timeout_cb)(void *);
4e8e7a93628b4ed60aaaa47c6f72c1433f21e81dTimo Sirainen    void *timeout_context;
4e8e7a93628b4ed60aaaa47c6f72c1433f21e81dTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    unsigned int full:1; /* if head == tail, is buffer empty or full? */
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    unsigned int corked:1;
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    unsigned int no_socket_cork:1;
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    unsigned int no_sendfile:1;
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    unsigned int autoclose_fd:1;
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen};
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainenstatic void stream_closed(struct file_ostream *fstream)
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen{
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    if (fstream->autoclose_fd && fstream->fd != -1) {
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen        if (close(fstream->fd) < 0)
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen            i_error("file_ostream.close() failed: %m");
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen        fstream->fd = -1;
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    }
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    if (fstream->io != NULL) {
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen        io_remove(fstream->io);
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen        fstream->io = NULL;
86bdb644d147a73df85abce4325254d694217a5fTimo Sirainen    }
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    fstream->ostream.ostream.closed = TRUE;
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen}
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainenstatic void _close(struct _iostream *stream)
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen{
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    /* flush output before really closing it */
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    o_stream_flush(&fstream->ostream.ostream);
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    stream_closed(fstream);
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen}
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainenstatic void _destroy(struct _iostream *stream)
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen{
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    p_free(fstream->ostream.iostream.pool, fstream->buffer);
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen}
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainenstatic void _set_max_buffer_size(struct _iostream *stream, size_t max_size)
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen{
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    fstream->max_buffer_size = max_size;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen}
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainenstatic void _set_blocking(struct _iostream *stream, int timeout_msecs,
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen              void (*timeout_cb)(void *), void *context)
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen{
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    fstream->timeout_msecs = timeout_msecs;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    fstream->timeout_cb = timeout_cb;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    fstream->timeout_context = context;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    net_set_nonblock(fstream->fd, timeout_msecs == 0);
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    if (timeout_msecs != 0)
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen        alarm_hup_init();
a18e2525cb076066784967d6c8118a01dd38ac6bTimo Sirainen}
a18e2525cb076066784967d6c8118a01dd38ac6bTimo Sirainen
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainenstatic void _cork(struct _ostream *stream)
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen{
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
a18e2525cb076066784967d6c8118a01dd38ac6bTimo Sirainen
a18e2525cb076066784967d6c8118a01dd38ac6bTimo Sirainen    if (!fstream->corked) {
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen        if (!fstream->no_socket_cork) {
2eccb2637d0153bb7f9ad39a70f254cece74342cTimo Sirainen            if (net_set_cork(fstream->fd, TRUE) < 0)
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen                fstream->no_socket_cork = TRUE;
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen        }
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen        fstream->corked = TRUE;
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    }
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen}
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainenstatic void update_iovec(struct iovec *iov, unsigned int iov_size, size_t size)
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen{
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    while (size > 0) {
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen        i_assert(iov_size > 0);
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen        if ((size_t)iov->iov_len <= size) {
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen            size -= iov->iov_len;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen            iov->iov_base = NULL;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen            iov->iov_len = 0;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen        } else {
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen            iov->iov_base = (char *) iov->iov_base + size;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen            iov->iov_len -= size;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen            size = 0;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen        }
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen        iov++; iov_size--;
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    }
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen}
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainenstatic void update_buffer(struct file_ostream *fstream, size_t size)
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen{
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen    size_t used;
4e8e7a93628b4ed60aaaa47c6f72c1433f21e81dTimo Sirainen
7877db7b5daad125b6cb3e015574f33871c9a51bTimo Sirainen    if (IS_STREAM_EMPTY(fstream))
ae9691f7ef36d5272d72c90fa51393dfea5dd126Timo Sirainen        return;

    if (fstream->head < fstream->tail) {
        /* ...HXXXT... */
        used = fstream->tail - fstream->head;
        fstream->head += I_MIN(used, size);
    } else {
        /* XXXT...HXXX */
        used = fstream->buffer_size - fstream->head;
        if (size > used) {
            size -= used;
            if (size < fstream->tail)
                fstream->head = size;
            else {
                /* whole buffer is sent */
                fstream->head = fstream->tail = 0;
            }
        } else {
            fstream->head += I_MIN(used, size);
        }

        fstream->full = FALSE;
    }

    if (fstream->head == fstream->tail)
        fstream->head = fstream->tail = 0;

    if (fstream->head == fstream->buffer_size)
        fstream->head = 0;
}

/* NOTE: modifies iov */
static ssize_t
o_stream_writev(struct file_ostream *fstream, struct iovec *iov, int iov_size)
{
    ssize_t ret;

    while (iov->iov_len == 0 && iov_size > 0) {
        iov++;
        iov_size--;
    }

    i_assert(iov_size > 0);

    if (iov_size == 1)
        ret = write(fstream->fd, iov->iov_base, iov->iov_len);
    else
        ret = writev(fstream->fd, iov, iov_size);

    if (ret < 0) {
        if (errno == EAGAIN || errno == EINTR)
            return 0;
        fstream->ostream.ostream.stream_errno = errno;
        stream_closed(fstream);
        return -1;
    }

    update_iovec(iov, iov_size, ret);
    update_buffer(fstream, ret);

    return ret;
}

/* returns how much of vector was used */
static int o_stream_fill_iovec(struct file_ostream *fstream,
                   struct iovec iov[2])
{
    if (IS_STREAM_EMPTY(fstream))
        return 0;

    if (fstream->head < fstream->tail) {
        iov[0].iov_base = fstream->buffer + fstream->head;
        iov[0].iov_len = fstream->tail - fstream->head;
        return 1;
    } else {
        iov[0].iov_base = fstream->buffer + fstream->head;
        iov[0].iov_len = fstream->buffer_size - fstream->head;
        if (fstream->tail == 0)
            return 1;
        else {
            iov[1].iov_base = fstream->buffer;
            iov[1].iov_len = fstream->tail;
            return 2;
        }
    }
}

static int o_stream_send_blocking(struct file_ostream *fstream,
                  const void *data, size_t size)
{
    time_t timeout_time;
    struct iovec iov[3];
    int iov_len, first;

    iov_len = o_stream_fill_iovec(fstream, iov);
    if (size > 0) {
        iov[iov_len].iov_base = (void *) data;
        iov[iov_len].iov_len = size;
        iov_len++;
    }

    first = TRUE;

    timeout_time = GET_TIMEOUT_TIME(fstream);
    while (iov[iov_len-1].iov_len != 0) {
        if (first)
            first = FALSE;
        else if (timeout_time > 0 && time(NULL) > timeout_time) {
            /* timeouted */
            if (fstream->timeout_cb != NULL)
                fstream->timeout_cb(fstream->timeout_context);
            fstream->ostream.ostream.stream_errno = EAGAIN;
            return -1;
        }

        if (o_stream_writev(fstream, iov, iov_len) < 0)
            return -1;
    }

        return 1;
}

static int buffer_flush(struct file_ostream *fstream)
{
    struct iovec iov[2];
    int iov_len;

    if (!IS_STREAM_EMPTY(fstream)) {
        iov_len = o_stream_fill_iovec(fstream, iov);
        if (o_stream_writev(fstream, iov, iov_len) < 0)
            return -1;

        if (!IS_STREAM_EMPTY(fstream)) {
            if (o_stream_send_blocking(fstream, NULL, 0) < 0)
                return -1;
        }
    }

    return 1;
}

static int _flush(struct _ostream *stream)
{
    struct file_ostream *fstream = (struct file_ostream *) stream;
    int ret;

    ret = buffer_flush(fstream);

    if (fstream->corked) {
        /* remove cork */
        if (!fstream->no_socket_cork) {
            if (net_set_cork(fstream->fd, FALSE) < 0)
                i_error("net_set_cork() failed: %m");
        }
        fstream->corked = FALSE;
    }

    return ret;
}

static size_t get_unused_space(struct file_ostream *fstream)
{
    if (fstream->head > fstream->tail) {
        /* XXXT...HXXX */
        return fstream->head - fstream->tail;
    } else if (fstream->head < fstream->tail) {
        /* ...HXXXT... */
        return (fstream->buffer_size - fstream->tail) + fstream->head;
    } else {
        /* either fully unused or fully used */
        return fstream->full ? 0 : fstream->buffer_size;
    }
}

static int _have_space(struct _ostream *stream, size_t size)
{
    struct file_ostream *fstream = (struct file_ostream *) stream;
    size_t unused;

    unused = get_unused_space(fstream);
    if (size <= unused)
        return 1;

    if (fstream->max_buffer_size == 0)
        return 1;

    unused += (fstream->max_buffer_size - fstream->buffer_size);
    return size <= unused ? 1 : 0;
}

static int _seek(struct _ostream *stream, uoff_t offset)
{
    struct file_ostream *fstream = (struct file_ostream *) stream;
    off_t ret;

    if (offset > OFF_T_MAX) {
        stream->ostream.stream_errno = EINVAL;
        return -1;
    }

    if (buffer_flush(fstream) < 0)
        return -1;

    ret = lseek(fstream->fd, (off_t)offset, SEEK_SET);
    if (ret < 0) {
        stream->ostream.stream_errno = errno;
        return -1;
    }

    if (ret != (off_t)offset) {
        stream->ostream.stream_errno = EINVAL;
        return -1;
    }

    stream->ostream.stream_errno = 0;
    stream->ostream.offset = offset;
    return 1;
}

static void o_stream_grow_buffer(struct file_ostream *fstream, size_t bytes)
{
    size_t size, head_size;

    size = nearest_power(fstream->buffer_size + bytes);
    if (fstream->max_buffer_size != 0) {
        if (size > fstream->max_buffer_size) {
            /* limit the size */
            size = fstream->max_buffer_size;
        } else if (fstream->corked) {
            /* use the largest possible buffer with corking */
            size = fstream->max_buffer_size;
        }
    }

    if (size == fstream->buffer_size)
        return;

    fstream->buffer = p_realloc(fstream->ostream.iostream.pool,
                    fstream->buffer,
                    fstream->buffer_size, size);

    if (fstream->tail <= fstream->head && !IS_STREAM_EMPTY(fstream)) {
        head_size = I_MIN(fstream->head, size - fstream->buffer_size);
        memcpy(fstream->buffer + fstream->buffer_size, fstream->buffer,
               head_size);

        if (head_size == fstream->head)
            fstream->tail = fstream->buffer_size + head_size;
        else {
            memmove(fstream->buffer, fstream->buffer + head_size,
                fstream->head - head_size);
            fstream->tail = fstream->head - head_size;
        }
    }

    fstream->full = FALSE;
    fstream->buffer_size = size;
}

static void stream_send_io(void *context)
{
    struct file_ostream *fstream = context;
    struct iovec iov[2];
    int iov_len;

    iov_len = o_stream_fill_iovec(fstream, iov);

    if (iov_len == 0 || o_stream_writev(fstream, iov, iov_len) < 0 ||
        iov[iov_len-1].iov_len == 0) {
        /* error / all sent */
        if (fstream->io != NULL) {
            io_remove(fstream->io);
            fstream->io = NULL;
        }
    }
}

static size_t o_stream_add(struct file_ostream *fstream,
               const void *data, size_t size)
{
    size_t unused, sent;
    int i;

    unused = get_unused_space(fstream);
    if (unused < size)
        o_stream_grow_buffer(fstream, size-unused);

    sent = 0;
    for (i = 0; i < 2 && sent < size && !fstream->full; i++) {
        unused = fstream->tail >= fstream->head ?
            fstream->buffer_size - fstream->tail :
            fstream->head - fstream->tail;

        if (unused > size-sent)
            unused = size-sent;
        memcpy(fstream->buffer + fstream->tail, data, unused);
        sent += unused;

        fstream->tail += unused;
        if (fstream->tail == fstream->buffer_size)
            fstream->tail = 0;

        if (fstream->head == fstream->tail)
            fstream->full = TRUE;
    }

    if (sent != 0 && fstream->io == NULL && !fstream->corked) {
        fstream->io = io_add_priority(fstream->fd, fstream->priority,
                          IO_WRITE, stream_send_io,
                          fstream);
    }

    i_assert(!STREAM_IS_BLOCKING(fstream) || sent == size);
    return sent;
}

static ssize_t _send(struct _ostream *stream, const void *data, size_t size)
{
    struct file_ostream *fstream = (struct file_ostream *) stream;
    struct iovec iov;
    ssize_t ret = 0;

    i_assert(size <= SSIZE_T_MAX);

    stream->ostream.stream_errno = 0;

    /* never try sending immediately if fd is blocking,
       so we don't need to deal with timeout issues here */
    if (IS_STREAM_EMPTY(fstream) && !STREAM_IS_BLOCKING(fstream) &&
        (!fstream->corked || !_have_space(stream, size))) {
        iov.iov_base = (void *) data;
        iov.iov_len = size;

        ret = o_stream_writev(fstream, &iov, 1);
        if (ret > 0)
            stream->ostream.offset += ret;

        if (ret < 0 || (size_t)ret == size)
            return ret;

        data = (const char *) data + ret;
        size -= ret;
    }

    if (!_have_space(stream, size) && STREAM_IS_BLOCKING(fstream)) {
        /* send it blocking */
        if (o_stream_send_blocking(fstream, data, size) < 0)
            return -1;
        ret += (ssize_t)size;
    } else {
        /* buffer it, at least partly */
        ret += (ssize_t)o_stream_add(fstream, data, size);
    }

    stream->ostream.offset += ret;
    return ret;
}

static off_t io_stream_sendfile(struct _ostream *outstream,
                struct istream *instream, int in_fd)
{
    struct file_ostream *foutstream = (struct file_ostream *) outstream;
    time_t timeout_time;
    uoff_t start_offset;
    uoff_t offset, send_size, v_offset;
    ssize_t ret;
    int first;

    /* set timeout time before flushing existing buffer which may block */
    timeout_time = GET_TIMEOUT_TIME(foutstream);
        start_offset = instream->v_offset;

    /* flush out any data in buffer */
    if (buffer_flush(foutstream) < 0)
        return -1;

    v_offset = instream->v_offset;

    first = TRUE;
    do {
        if (first)
            first = FALSE;
        else if (timeout_time > 0 && time(NULL) > timeout_time) {
            /* timeouted */
            if (foutstream->timeout_cb != NULL) {
                foutstream->timeout_cb(
                    foutstream->timeout_context);
            }
            outstream->ostream.stream_errno = EAGAIN;
            ret = -1;
            break;
        }

        offset = instream->start_offset + v_offset;
        send_size = instream->v_limit - v_offset;

        ret = safe_sendfile(foutstream->fd, in_fd, &offset,
                    MAX_SSIZE_T(send_size));
        if (ret < 0) {
            if (errno != EINTR && errno != EAGAIN) {
                outstream->ostream.stream_errno = errno;
                if (errno != EINVAL) {
                    /* close only if error wasn't because
                       sendfile() isn't supported */
                    stream_closed(foutstream);
                }
                break;
            }

            ret = 0;
            if (!STREAM_IS_BLOCKING(foutstream)) {
                /* don't block */
                break;
            }
        }

        v_offset += ret;
        outstream->ostream.offset += ret;
    } while ((uoff_t)ret != send_size);

    i_stream_seek(instream, v_offset);
    return ret < 0 ? -1 : (off_t)(instream->v_offset - start_offset);
}

static off_t io_stream_copy(struct _ostream *outstream,
                struct istream *instream, int overlapping)
{
    struct file_ostream *foutstream = (struct file_ostream *) outstream;
    time_t timeout_time;
    uoff_t start_offset;
    struct iovec iov[3];
    int iov_len;
    const unsigned char *data;
    size_t size, skip_size;
    ssize_t ret;
    int pos;

    timeout_time = GET_TIMEOUT_TIME(foutstream);
    iov_len = o_stream_fill_iovec(foutstream, iov);

        skip_size = 0;
    for (pos = 0; pos < iov_len; pos++)
        skip_size += iov[pos].iov_len;

    i_assert(!overlapping || iov_len == 0);

        start_offset = instream->v_offset;
    for (;;) {
        if (overlapping)
            i_stream_seek(instream, instream->v_offset);
        (void)i_stream_read_data(instream, &data, &size,
                     foutstream->optimal_block_size-1);

        if (size == 0) {
            /* all sent */
            break;
        }

        pos = iov_len++;
        iov[pos].iov_base = (void *) data;
        iov[pos].iov_len = size;

        if (overlapping) {
            if (o_stream_seek(&outstream->ostream,
                      outstream->ostream.offset) < 0)
                return -1;
        }

        ret = o_stream_writev(foutstream, iov, iov_len);
        if (ret < 0) {
            /* error */
            return -1;
        }

        if (ret == 0 && !STREAM_IS_BLOCKING(foutstream)) {
            /* don't block */
            break;
        }

        if (skip_size > 0) {
            if ((size_t)ret < skip_size) {
                skip_size -= ret;
                ret = 0;
            } else {
                ret -= skip_size;
                skip_size = 0;
            }
        }
        outstream->ostream.offset += ret;

        if (timeout_time > 0 && time(NULL) > timeout_time) {
            /* timeouted */
            if (foutstream->timeout_cb != NULL) {
                foutstream->timeout_cb(
                    foutstream->timeout_context);
            }
            outstream->ostream.stream_errno = EAGAIN;
            return -1;
        }

        i_stream_skip(instream, size - iov[pos].iov_len);
        iov_len--;

        /* if we already sent the iov[0] and iov[1], we
           can just remove them from future calls */
        while (iov_len > 0 && iov[0].iov_len == 0) {
            iov[0] = iov[1];
            if (iov_len > 1) iov[1] = iov[2];
            iov_len--;
        }
    }

    return (off_t) (instream->v_offset - start_offset);
}

static off_t io_stream_copy_backwards(struct _ostream *outstream,
                      struct istream *instream)
{
    struct file_ostream *foutstream = (struct file_ostream *) outstream;
    time_t timeout_time;
    uoff_t in_start_offset, in_offset, out_offset;
    const unsigned char *data;
    size_t buffer_size, size, read_size;
    ssize_t ret;

    i_assert(IS_STREAM_EMPTY(foutstream));

    timeout_time = GET_TIMEOUT_TIME(foutstream);

    /* figure out optimal buffer size */
    buffer_size = instream->real_stream->buffer_size;
    if (buffer_size == 0 || buffer_size > foutstream->buffer_size) {
        if (foutstream->optimal_block_size > foutstream->buffer_size) {
            o_stream_grow_buffer(foutstream,
                         foutstream->optimal_block_size -
                         foutstream->buffer_size);
        }

        buffer_size = foutstream->buffer_size;
    }

    in_start_offset = instream->v_offset;
    in_offset = instream->v_limit;
    out_offset = outstream->ostream.offset +
        (instream->v_limit - instream->v_offset);

    i_assert(out_offset <= instream->start_offset + instream->v_size);

    while (in_offset > in_start_offset) {
        if (in_offset - in_start_offset <= buffer_size)
            read_size = in_offset - in_start_offset;
        else
            read_size = buffer_size;
        in_offset -= read_size;
        out_offset -= read_size;

        for (;;) {
            i_assert(in_offset <= instream->v_limit);

            i_stream_seek(instream, in_offset);
            read_size = instream->v_limit - in_offset;

            (void)i_stream_read_data(instream, &data, &size,
                         read_size-1);
            if (size == read_size) {
                if (instream->mmaped) {
                    /* we'll have to write it through
                       buffer of the file gets corrupted */
                    i_assert(size <=
                         foutstream->buffer_size);
                    memcpy(foutstream->buffer, data, size);
                    data = foutstream->buffer;
                }
                break;
            }

            i_assert(size < read_size);
            if (size < read_size) {
                /* buffer too large probably,
                   try with smaller */
                read_size -= size;
                in_offset += read_size;
                out_offset += read_size;
                buffer_size -= read_size;
            }
        }

        if (o_stream_seek(&outstream->ostream, out_offset) < 0)
            return -1;

        ret = write_full(foutstream->fd, data, size);
        if (ret < 0) {
            /* error */
            outstream->ostream.stream_errno = errno;
            return -1;
        }

        if (timeout_time > 0 && time(NULL) > timeout_time) {
            /* timeouted */
            if (foutstream->timeout_cb != NULL) {
                foutstream->timeout_cb(
                    foutstream->timeout_context);
            }
            outstream->ostream.stream_errno = EAGAIN;
            return -1;
        }

        i_stream_set_read_limit(instream, in_offset);
    }

    return (off_t) (instream->v_limit - in_start_offset);
}

static off_t _send_istream(struct _ostream *outstream, struct istream *instream)
{
    struct file_ostream *foutstream = (struct file_ostream *) outstream;
    uoff_t old_limit;
    off_t ret;
    int in_fd, overlapping;

    i_assert(instream->v_limit <= OFF_T_MAX);
    i_assert(instream->v_offset <= instream->v_limit);

    outstream->ostream.stream_errno = 0;

    if (instream->v_offset == instream->v_limit)
        return 0;

    in_fd = i_stream_get_fd(instream);
    if (in_fd != foutstream->fd)
        overlapping = 0;
    else {
        /* copying data within same fd. we'll have to be careful with
           seeks and overlapping writes. */
        ret = (off_t)outstream->ostream.offset -
            (off_t)(instream->start_offset + instream->v_offset);
        if (ret == 0) {
            /* copying data over itself. we don't really
               need to do that, just fake it. */
            return instream->v_limit - instream->v_offset;
        }
        overlapping = ret < 0 ? -1 : 1;

        if (o_stream_seek(&outstream->ostream,
                  outstream->ostream.offset) < 0)
            return -1;
    }

    if (!foutstream->no_sendfile && in_fd != -1 && overlapping <= 0) {
        ret = io_stream_sendfile(outstream, instream, in_fd);
        if (ret >= 0 || outstream->ostream.stream_errno != EINVAL)
            return ret;

        /* sendfile() not supported (with this fd), fallback to
           regular sending. */
        outstream->ostream.stream_errno = 0;
        foutstream->no_sendfile = TRUE;
    }

    if (overlapping <= 0)
        return io_stream_copy(outstream, instream, overlapping);
    else {
        old_limit = instream->v_limit;
        ret = io_stream_copy_backwards(outstream, instream);
        i_stream_set_read_limit(instream, old_limit);
        return ret;
    }
}

struct ostream *
o_stream_create_file(int fd, pool_t pool, size_t max_buffer_size,
             int priority, int autoclose_fd)
{
    struct file_ostream *fstream;
    struct ostream *ostream;
    struct stat st;
    off_t offset;

    fstream = p_new(pool, struct file_ostream, 1);
    fstream->fd = fd;
    fstream->priority = priority;
    fstream->max_buffer_size = max_buffer_size;
    fstream->autoclose_fd = autoclose_fd;
    fstream->optimal_block_size = DEFAULT_OPTIMAL_BLOCK_SIZE;

    fstream->ostream.iostream.close = _close;
    fstream->ostream.iostream.destroy = _destroy;
    fstream->ostream.iostream.set_max_buffer_size = _set_max_buffer_size;
    fstream->ostream.iostream.set_blocking = _set_blocking;

    fstream->ostream.cork = _cork;
    fstream->ostream.flush = _flush;
    fstream->ostream.have_space = _have_space;
    fstream->ostream.seek = _seek;
    fstream->ostream.send = _send;
    fstream->ostream.send_istream = _send_istream;

    ostream = _o_stream_create(&fstream->ostream, pool);

    offset = lseek(fd, 0, SEEK_CUR);
    if (offset >= 0) {
        ostream->offset = offset;

        if (fstat(fd, &st) == 0 &&
            (uoff_t)st.st_blksize > fstream->optimal_block_size) {
            /* use the optimal block size, but with a
               reasonable limit */
            fstream->optimal_block_size =
                I_MIN(st.st_blksize, MAX_OPTIMAL_BLOCK_SIZE);
        }
#ifndef HAVE_LINUX_SENDFILE
        /* only Linux supports sendfile() with non-sockets. Other
           systems fail more or less gracefully if it's tried, so
           don't bother to even try with them. */
        fstream->no_sendfile = TRUE;
#endif
        fstream->no_socket_cork = FALSE;
    } else {
        if (net_getsockname(fd, NULL, NULL) < 0) {
            fstream->no_sendfile = TRUE;
            fstream->no_socket_cork = FALSE;
        }
    }
    return ostream;
}