src/lib/ostream-file.c

	ostream-file.c revision 007d354a674fb3ddf49db160cf050cf61270a1a0
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen/*
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen   ostream-file.c : Output stream handling for files
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    Copyright (c) 2002 Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    Permission is hereby granted, free of charge, to any person obtaining
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    a copy of this software and associated documentation files (the
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    "Software"), to deal in the Software without restriction, including
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    without limitation the rights to use, copy, modify, merge, publish,
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    distribute, sublicense, and/or sell copies of the Software, and to
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    permit persons to whom the Software is furnished to do so, subject to
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    the following conditions:
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    The above copyright notice and this permission notice shall be
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    included in all copies or substantial portions of the Software.
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen*/
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen/* @UNSAFE: whole file */
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "lib.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "alarm-hup.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "ioloop.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "file-set-size.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "write-full.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "network.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "sendfile-util.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "istream.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "istream-internal.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include "ostream-internal.h"
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include <unistd.h>
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#include <sys/stat.h>
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#ifdef HAVE_SYS_UIO_H
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#  include <sys/uio.h>
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#endif
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen/* try to keep the buffer size within 4k..128k. ReiserFS may actually return
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen   128k as optimal size. */
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#define DEFAULT_OPTIMAL_BLOCK_SIZE 4096
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#define MAX_OPTIMAL_BLOCK_SIZE (128*1024)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#define IS_STREAM_EMPTY(fstream) \
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    ((fstream)->head == (fstream)->tail && !(fstream)->full)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen#define MAX_SSIZE_T(size) \
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    ((size) < SSIZE_T_MAX ? (size_t)(size) : SSIZE_T_MAX)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainenstruct file_ostream {
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    struct _ostream ostream;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    int fd;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    struct io *io;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    unsigned char *buffer; /* ring-buffer */
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    size_t buffer_size, max_buffer_size, optimal_block_size;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    size_t head, tail; /* first unsent/unused byte */
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    int timeout_msecs;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    void (*timeout_cb)(void *);
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    void *timeout_context;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    unsigned int full:1; /* if head == tail, is buffer empty or full? */
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    unsigned int file:1;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    unsigned int corked:1;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    unsigned int no_socket_cork:1;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    unsigned int no_sendfile:1;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    unsigned int autoclose_fd:1;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen};
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainenstatic void stream_closed(struct file_ostream *fstream)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen{
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    if (fstream->autoclose_fd && fstream->fd != -1) {
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen        if (close(fstream->fd) < 0)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen            i_error("file_ostream.close() failed: %m");
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen        fstream->fd = -1;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    }
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    if (fstream->io != NULL) {
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen        io_remove(fstream->io);
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen        fstream->io = NULL;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    }
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    fstream->ostream.ostream.closed = TRUE;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen}
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainenstatic void _close(struct _iostream *stream)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen{
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    /* flush output before really closing it */
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    o_stream_flush(&fstream->ostream.ostream);
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    stream_closed(fstream);
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen}
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainenstatic void _destroy(struct _iostream *stream)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen{
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    p_free(fstream->ostream.iostream.pool, fstream->buffer);
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen}
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainenstatic void _set_max_buffer_size(struct _iostream *stream, size_t max_size)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen{
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    fstream->max_buffer_size = max_size;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen}
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainenstatic void _set_blocking(struct _iostream *stream, int timeout_msecs,
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen              void (*timeout_cb)(void *), void *context)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen{
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    struct file_ostream *fstream = (struct file_ostream *) stream;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    fstream->timeout_msecs = timeout_msecs;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    fstream->timeout_cb = timeout_cb;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    fstream->timeout_context = context;
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    if (!fstream->file)
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen        net_set_nonblock(fstream->fd, timeout_msecs == 0);
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen
8871c97974dd4e682c7b8d5cff0bbc5b024f56f2Timo Sirainen    if (timeout_msecs != 0)
        alarm_hup_init();
}

static void _cork(struct _ostream *stream)
{
    struct file_ostream *fstream = (struct file_ostream *) stream;

    if (!fstream->corked) {
        if (!fstream->no_socket_cork) {
            if (net_set_cork(fstream->fd, TRUE) < 0)
                fstream->no_socket_cork = TRUE;
        }
        fstream->corked = TRUE;
    }
}

static void update_iovec(struct iovec *iov, unsigned int iov_size, size_t size)
{
    while (size > 0) {
        i_assert(iov_size > 0);

        if ((size_t)iov->iov_len <= size) {
            size -= iov->iov_len;
            iov->iov_base = NULL;
            iov->iov_len = 0;
        } else {
            iov->iov_base = (char *) iov->iov_base + size;
            iov->iov_len -= size;
            size = 0;
        }
        iov++; iov_size--;
    }
}

static void update_buffer(struct file_ostream *fstream, size_t size)
{
    size_t used;

    if (IS_STREAM_EMPTY(fstream))
        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->file) {
        fstream->io = io_add(fstream->fd, 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 hflushing 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 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->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) {
            if ((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);
            }

            if (S_ISREG(st.st_mode)) {
                fstream->no_socket_cork = TRUE;
                fstream->file = TRUE;

                o_stream_set_blocking(ostream, 60000, 0, NULL);
            }
        }
#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
    } else {
        if (net_getsockname(fd, NULL, NULL) < 0) {
            fstream->no_sendfile = TRUE;
            fstream->no_socket_cork = TRUE;
        }
    }
    return ostream;
}