src/lib/istream.c

	istream.c revision c28f6aa0b70af4811c9ace9114fe827c2f503455
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen/* Copyright (c) 2002-2011 Dovecot authors, see the included COPYING file */
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen#include "lib.h"
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen#include "ioloop.h"
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen#include "str.h"
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen#include "istream-private.h"
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainenvoid i_stream_set_name(struct istream *stream, const char *name)
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen{
6d2b3ce2c6ef62334985ece4f0ab8b154e0e9560Timo Sirainen    i_free(stream->real_stream->iostream.name);
c6335901c67a4c9365319190a111a2168f3b06f5Timo Sirainen    stream->real_stream->iostream.name = i_strdup(name);
c6335901c67a4c9365319190a111a2168f3b06f5Timo Sirainen}
c6335901c67a4c9365319190a111a2168f3b06f5Timo Sirainen
01230de017cd273de41143d88e9c18df1243ae8aTimo Sirainenconst char *i_stream_get_name(struct istream *stream)
01230de017cd273de41143d88e9c18df1243ae8aTimo Sirainen{
047c00cd3f7f403672f81569413669238df8c15aTimo Sirainen    while (stream->real_stream->iostream.name == NULL) {
047c00cd3f7f403672f81569413669238df8c15aTimo Sirainen        stream = stream->real_stream->parent;
047c00cd3f7f403672f81569413669238df8c15aTimo Sirainen        if (stream == NULL)
047c00cd3f7f403672f81569413669238df8c15aTimo Sirainen            return "";
cf0ad1a0bddb0787f3d7b408a96d721a8b2a98a3Timo Sirainen    }
cf0ad1a0bddb0787f3d7b408a96d721a8b2a98a3Timo Sirainen    return stream->real_stream->iostream.name;
cf0ad1a0bddb0787f3d7b408a96d721a8b2a98a3Timo Sirainen}
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainenvoid i_stream_destroy(struct istream **stream)
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen{
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    i_stream_close(*stream);
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    i_stream_unref(stream);
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen}
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainenvoid i_stream_ref(struct istream *stream)
7487ff578435377bbeefffdbfb78ca09ed1292dfTimo Sirainen{
89237470342ea6d4bbdf4cff9764037cfb3f6f45Timo Sirainen    io_stream_ref(&stream->real_stream->iostream);
89237470342ea6d4bbdf4cff9764037cfb3f6f45Timo Sirainen}
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainenvoid i_stream_unref(struct istream **stream)
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen{
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    struct istream_private *_stream = (*stream)->real_stream;
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen
4d4d6d4745682790c20d759ba93dbea46b812c5dTimo Sirainen    if (_stream->iostream.refcount == 1) {
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen        if (_stream->line_str != NULL)
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen            str_free(&_stream->line_str);
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    }
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    io_stream_unref(&(*stream)->real_stream->iostream);
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    *stream = NULL;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen}
a3fe8c0c54d87822f4b4f8f0d10caac611861b2bTimo Sirainen
578ef2538ccf42e2a48234c24a8b709397101d88Timo Sirainen#undef i_stream_set_destroy_callback
578ef2538ccf42e2a48234c24a8b709397101d88Timo Sirainenvoid i_stream_set_destroy_callback(struct istream *stream,
578ef2538ccf42e2a48234c24a8b709397101d88Timo Sirainen                   istream_callback_t *callback, void *context)
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen{
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    struct iostream_private *iostream = &stream->real_stream->iostream;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    iostream->destroy_callback = callback;
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    iostream->destroy_context = context;
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen}
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainenvoid i_stream_unset_destroy_callback(struct istream *stream)
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen{
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    struct iostream_private *iostream = &stream->real_stream->iostream;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
e0740628f6ca05f4bc79a9d8a90b650f4d38d4d0Timo Sirainen    iostream->destroy_callback = NULL;
e0740628f6ca05f4bc79a9d8a90b650f4d38d4d0Timo Sirainen    iostream->destroy_context = NULL;
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen}
3f603ef00e35fca21605afa0ad8d76e94fee2b96Timo Sirainen
3f603ef00e35fca21605afa0ad8d76e94fee2b96Timo Sirainenint i_stream_get_fd(struct istream *stream)
3f603ef00e35fca21605afa0ad8d76e94fee2b96Timo Sirainen{
3f603ef00e35fca21605afa0ad8d76e94fee2b96Timo Sirainen    struct istream_private *_stream = stream->real_stream;
86791365b10f45982c88e70f2eb94fd6c3fea151Timo Sirainen
86791365b10f45982c88e70f2eb94fd6c3fea151Timo Sirainen    return _stream->fd;
86791365b10f45982c88e70f2eb94fd6c3fea151Timo Sirainen}
86791365b10f45982c88e70f2eb94fd6c3fea151Timo Sirainen
86791365b10f45982c88e70f2eb94fd6c3fea151Timo Sirainenvoid i_stream_close(struct istream *stream)
6fdfa4d4cf14d1d7764d7faa8258f112e39c8dbeTimo Sirainen{
6fdfa4d4cf14d1d7764d7faa8258f112e39c8dbeTimo Sirainen    io_stream_close(&stream->real_stream->iostream);
6fdfa4d4cf14d1d7764d7faa8258f112e39c8dbeTimo Sirainen    stream->closed = TRUE;
6fdfa4d4cf14d1d7764d7faa8258f112e39c8dbeTimo Sirainen
6fdfa4d4cf14d1d7764d7faa8258f112e39c8dbeTimo Sirainen    if (stream->stream_errno == 0)
3f603ef00e35fca21605afa0ad8d76e94fee2b96Timo Sirainen        stream->stream_errno = ENOENT;
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen}
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainenvoid i_stream_set_init_buffer_size(struct istream *stream, size_t size)
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen{
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    stream->real_stream->init_buffer_size = size;
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen}
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainenvoid i_stream_set_max_buffer_size(struct istream *stream, size_t max_size)
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen{
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    io_stream_set_max_buffer_size(&stream->real_stream->iostream, max_size);
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen}
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainensize_t i_stream_get_max_buffer_size(struct istream *stream)
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen{
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    return stream->real_stream->max_buffer_size;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen}
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainenvoid i_stream_set_return_partial_line(struct istream *stream, bool set)
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen{
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    stream->real_stream->return_nolf_line = set;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen}
b2d562f9c7fd13f9a16e9b3bcee904630b80b1feTimo Sirainen
b2d562f9c7fd13f9a16e9b3bcee904630b80b1feTimo Sirainenstatic void i_stream_update(struct istream_private *stream)
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen{
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    if (stream->parent == NULL)
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen        stream->access_counter++;
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen    else {
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen        stream->access_counter =
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen            stream->parent->real_stream->access_counter;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen        stream->parent_expected_offset = stream->parent->v_offset;
6c2ce1d5bf17b21e804a079eb0f973b7ab83e0d8Timo Sirainen    }
6c2ce1d5bf17b21e804a079eb0f973b7ab83e0d8Timo Sirainen}
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainenssize_t i_stream_read(struct istream *stream)
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen{
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    struct istream_private *_stream = stream->real_stream;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    size_t old_size;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen    ssize_t ret;
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen
    if (unlikely(stream->closed))
        return -1;

    stream->eof = FALSE;
    stream->stream_errno = 0;

    if (_stream->parent != NULL)
        i_stream_seek(_stream->parent, _stream->parent_expected_offset);

    old_size = _stream->pos - _stream->skip;
    ret = _stream->read(_stream);
    switch (ret) {
    case -2:
        i_assert(_stream->skip != _stream->pos);
        break;
    case -1:
        if (stream->stream_errno != 0) {
            /* error handling should be easier if we now just
               assume the stream is now at EOF */
            stream->eof = TRUE;
        } else {
            i_assert(stream->eof);
        }
        break;
    case 0:
        i_assert(!stream->blocking);
        break;
    default:
        i_assert(ret > 0);
        i_assert(_stream->skip < _stream->pos);
        i_assert((size_t)ret+old_size == _stream->pos - _stream->skip);
        break;
    }

    i_stream_update(_stream);
    return ret;
}

ssize_t i_stream_read_copy_from_parent(struct istream *istream)
{
    struct istream_private *stream = istream->real_stream;
    size_t pos;
    ssize_t ret;

    stream->pos -= stream->skip;
    stream->skip = 0;

    stream->buffer = i_stream_get_data(stream->parent, &pos);
    if (pos > stream->pos)
        ret = 0;
    else do {
        if ((ret = i_stream_read(stream->parent)) == -2)
            return -2;

        stream->istream.stream_errno = stream->parent->stream_errno;
        stream->istream.eof = stream->parent->eof;
        stream->buffer = i_stream_get_data(stream->parent, &pos);
        /* check again, in case the parent stream had been seeked
           backwards and the previous read() didn't get us far
           enough. */
    } while (pos <= stream->pos && ret > 0);

    ret = pos > stream->pos ? (ssize_t)(pos - stream->pos) :
        (ret == 0 ? 0 : -1);
    stream->pos = pos;
    i_assert(ret != -1 || stream->istream.eof ||
         stream->istream.stream_errno != 0);
    return ret;
}

void i_stream_skip(struct istream *stream, uoff_t count)
{
    struct istream_private *_stream = stream->real_stream;
    size_t data_size;

    data_size = _stream->pos - _stream->skip;
    if (count <= data_size) {
        /* within buffer */
        stream->v_offset += count;
        _stream->skip += count;
        return;
    }

    /* have to seek forward */
    count -= data_size;
    _stream->skip = _stream->pos;
    stream->v_offset += data_size;

    if (unlikely(stream->closed))
        return;

    stream->stream_errno = 0;
    _stream->seek(_stream, stream->v_offset + count, FALSE);
}

static bool i_stream_can_optimize_seek(struct istream_private *stream)
{
    if (stream->parent == NULL)
        return TRUE;

    /* use the fast route only if the parent stream hasn't been changed */
    if (stream->access_counter !=
        stream->parent->real_stream->access_counter)
        return FALSE;

    return i_stream_can_optimize_seek(stream->parent->real_stream);
}

void i_stream_seek(struct istream *stream, uoff_t v_offset)
{
    struct istream_private *_stream = stream->real_stream;

    if (v_offset >= stream->v_offset &&
        i_stream_can_optimize_seek(_stream))
        i_stream_skip(stream, v_offset - stream->v_offset);
    else {
        if (unlikely(stream->closed))
            return;

        stream->eof = FALSE;
        _stream->seek(_stream, v_offset, FALSE);
    }
    i_stream_update(_stream);
}

void i_stream_seek_mark(struct istream *stream, uoff_t v_offset)
{
    struct istream_private *_stream = stream->real_stream;

    if (unlikely(stream->closed))
        return;

    stream->eof = FALSE;
    _stream->seek(_stream, v_offset, TRUE);
    i_stream_update(_stream);
}

void i_stream_sync(struct istream *stream)
{
    struct istream_private *_stream = stream->real_stream;

    if (unlikely(stream->closed))
        return;

    if (_stream->sync != NULL) {
        _stream->sync(_stream);
        i_stream_update(_stream);
    }
}

const struct stat *i_stream_stat(struct istream *stream, bool exact)
{
    struct istream_private *_stream = stream->real_stream;

    if (unlikely(stream->closed))
        return NULL;

    return _stream->stat(_stream, exact);
}

int i_stream_get_size(struct istream *stream, bool exact, uoff_t *size_r)
{
    struct istream_private *_stream = stream->real_stream;

    if (unlikely(stream->closed))
        return -1;

    return _stream->get_size(_stream, exact, size_r);
}

bool i_stream_have_bytes_left(const struct istream *stream)
{
    const struct istream_private *_stream = stream->real_stream;

    return !stream->eof || _stream->skip != _stream->pos;
}

bool i_stream_is_eof(struct istream *stream)
{
    const struct istream_private *_stream = stream->real_stream;

    if (_stream->skip == _stream->pos)
        (void)i_stream_read(stream);
    return !i_stream_have_bytes_left(stream);
}

uoff_t i_stream_get_absolute_offset(struct istream *stream)
{
    return stream->real_stream->abs_start_offset + stream->v_offset;
}

static char *i_stream_next_line_finish(struct istream_private *stream, size_t i)
{
    char *ret;
    size_t end;

    if (i > 0 && stream->buffer[i-1] == '\r')
        end = i - 1;
    else
        end = i;

    if (stream->w_buffer != NULL) {
        /* modify the buffer directly */
        stream->w_buffer[end] = '\0';
        ret = (char *)stream->w_buffer + stream->skip;
    } else {
        /* use a temporary string to return it */
        if (stream->line_str == NULL)
            stream->line_str = str_new(default_pool, 256);
        str_truncate(stream->line_str, 0);
        str_append_n(stream->line_str, stream->buffer + stream->skip,
                 end - stream->skip);
        ret = str_c_modifiable(stream->line_str);
    }

    if (i < stream->pos)
        i++;
    stream->istream.v_offset += i - stream->skip;
    stream->skip = i;
    return ret;
}

static char *i_stream_last_line(struct istream_private *_stream)
{
    if (_stream->istream.eof && _stream->skip != _stream->pos &&
        _stream->return_nolf_line) {
        /* the last line is missing LF and we want to return it. */
        return i_stream_next_line_finish(_stream, _stream->pos);
    }
    return NULL;
}

char *i_stream_next_line(struct istream *stream)
{
    struct istream_private *_stream = stream->real_stream;
    const unsigned char *pos;

    if (_stream->skip >= _stream->pos) {
        stream->stream_errno = 0;
        return NULL;
    }

    pos = memchr(_stream->buffer + _stream->skip, '\n',
             _stream->pos - _stream->skip);
    if (pos != NULL) {
        return i_stream_next_line_finish(_stream,
                         pos - _stream->buffer);
    } else {
        return i_stream_last_line(_stream);
    }
}

char *i_stream_read_next_line(struct istream *stream)
{
    char *line;

    for (;;) {
        line = i_stream_next_line(stream);
        if (line != NULL)
            break;

        if (i_stream_read(stream) <= 0)
            return i_stream_last_line(stream->real_stream);
    }
    return line;
}

const unsigned char *
i_stream_get_data(const struct istream *stream, size_t *size_r)
{
    const struct istream_private *_stream = stream->real_stream;

    if (_stream->skip >= _stream->pos) {
        *size_r = 0;
        return NULL;
    }

        *size_r = _stream->pos - _stream->skip;
        return _stream->buffer + _stream->skip;
}

unsigned char *i_stream_get_modifiable_data(const struct istream *stream,
                        size_t *size_r)
{
    const struct istream_private *_stream = stream->real_stream;

    if (_stream->skip >= _stream->pos || _stream->w_buffer == NULL) {
        *size_r = 0;
        return NULL;
    }

        *size_r = _stream->pos - _stream->skip;
        return _stream->w_buffer + _stream->skip;
}

int i_stream_read_data(struct istream *stream, const unsigned char **data_r,
               size_t *size_r, size_t threshold)
{
    ssize_t ret = 0;
    bool read_more = FALSE;

    do {
        *data_r = i_stream_get_data(stream, size_r);
        if (*size_r > threshold)
            return 1;

        /* we need more data */
        ret = i_stream_read(stream);
        if (ret > 0)
            read_more = TRUE;
    } while (ret > 0);

    *data_r = i_stream_get_data(stream, size_r);
    if (ret == -2)
        return -2;

    if (ret == 0) {
        /* need to read more */
        i_assert(!stream->blocking);
        return 0;
    }
    if (stream->eof) {
        if (read_more) {
            /* we read at least some new data */
            return 0;
        }
    } else {
        i_assert(stream->stream_errno != 0);
    }
    return -1;
}

void i_stream_compress(struct istream_private *stream)
{
    memmove(stream->w_buffer, stream->w_buffer + stream->skip,
        stream->pos - stream->skip);
    stream->pos -= stream->skip;

    stream->skip = 0;
}

void i_stream_grow_buffer(struct istream_private *stream, size_t bytes)
{
    size_t old_size;

    old_size = stream->buffer_size;

    stream->buffer_size = stream->pos + bytes;
    if (stream->buffer_size <= stream->init_buffer_size)
        stream->buffer_size = stream->init_buffer_size;
    else
        stream->buffer_size = nearest_power(stream->buffer_size);

    if (stream->max_buffer_size > 0 &&
        stream->buffer_size > stream->max_buffer_size)
        stream->buffer_size = stream->max_buffer_size;

    if (stream->buffer_size <= old_size)
        stream->buffer_size = old_size;
    else {
        stream->w_buffer = i_realloc(stream->w_buffer, old_size,
                         stream->buffer_size);
        stream->buffer = stream->w_buffer;
    }
}

bool i_stream_get_buffer_space(struct istream_private *stream,
                   size_t wanted_size, size_t *size_r)
{
    i_assert(wanted_size > 0);

    if (wanted_size > stream->buffer_size - stream->pos) {
        if (stream->skip > 0) {
            /* remove the unused bytes from beginning of buffer */
                        i_stream_compress(stream);
        } else if (stream->max_buffer_size == 0 ||
               stream->buffer_size < stream->max_buffer_size) {
            /* buffer is full - grow it */
            i_stream_grow_buffer(stream, I_STREAM_MIN_SIZE);
        }
    }

    if (size_r != NULL)
        *size_r = stream->buffer_size - stream->pos;
    return stream->pos != stream->buffer_size;
}

bool i_stream_add_data(struct istream *_stream, const unsigned char *data,
               size_t size)
{
    struct istream_private *stream = _stream->real_stream;
    size_t size2;

    (void)i_stream_get_buffer_space(stream, size, &size2);
    if (size > size2)
        return FALSE;

    memcpy(stream->w_buffer + stream->pos, data, size);
    stream->pos += size;
    return TRUE;
}

static void
i_stream_default_set_max_buffer_size(struct iostream_private *stream,
                     size_t max_size)
{
    struct istream_private *_stream = (struct istream_private *)stream;

    _stream->max_buffer_size = max_size;
    if (_stream->parent != NULL)
        i_stream_set_max_buffer_size(_stream->parent, max_size);
}

static void i_stream_default_destroy(struct iostream_private *stream)
{
    struct istream_private *_stream = (struct istream_private *)stream;

    i_free(_stream->w_buffer);
    if (_stream->parent != NULL)
        i_stream_unref(&_stream->parent);
}

void i_stream_default_seek(struct istream_private *stream,
               uoff_t v_offset, bool mark ATTR_UNUSED)
{
    size_t available;

    if (stream->istream.v_offset > v_offset)
        i_panic("stream doesn't support seeking backwards");

    while (stream->istream.v_offset < v_offset) {
        (void)i_stream_read(&stream->istream);

        available = stream->pos - stream->skip;
        if (available == 0) {
            stream->istream.stream_errno = ESPIPE;
            return;
        }
        if (available <= v_offset - stream->istream.v_offset)
            i_stream_skip(&stream->istream, available);
        else {
            i_stream_skip(&stream->istream,
                      v_offset - stream->istream.v_offset);
        }
    }
}

static const struct stat *
i_stream_default_stat(struct istream_private *stream, bool exact ATTR_UNUSED)
{
    return &stream->statbuf;
}

static int
i_stream_default_get_size(struct istream_private *stream,
              bool exact, uoff_t *size_r)
{
    const struct stat *st;

    st = stream->stat(stream, exact);
    if (st == NULL)
        return -1;
    if (st->st_size == -1)
        return 0;

    *size_r = st->st_size;
    return 1;
}

struct istream *
i_stream_create(struct istream_private *_stream, struct istream *parent, int fd)
{
    _stream->fd = fd;
    if (parent != NULL) {
        _stream->access_counter = parent->real_stream->access_counter;
        _stream->parent = parent;
        _stream->parent_start_offset = parent->v_offset;
        _stream->parent_expected_offset = parent->v_offset;
        _stream->abs_start_offset = parent->v_offset +
            parent->real_stream->abs_start_offset;
        i_stream_ref(parent);
    }
    _stream->istream.real_stream = _stream;

    if (_stream->iostream.destroy == NULL)
        _stream->iostream.destroy = i_stream_default_destroy;
    if (_stream->seek == NULL) {
        i_assert(!_stream->istream.seekable);
        _stream->seek = i_stream_default_seek;
    }
    if (_stream->stat == NULL)
        _stream->stat = i_stream_default_stat;
    if (_stream->get_size == NULL)
        _stream->get_size = i_stream_default_get_size;
    if (_stream->iostream.set_max_buffer_size == NULL) {
        _stream->iostream.set_max_buffer_size =
            i_stream_default_set_max_buffer_size;
    }
    if (_stream->init_buffer_size == 0)
        _stream->init_buffer_size = I_STREAM_MIN_SIZE;

    memset(&_stream->statbuf, 0, sizeof(_stream->statbuf));
    _stream->statbuf.st_size = -1;
    _stream->statbuf.st_atime =
        _stream->statbuf.st_mtime =
        _stream->statbuf.st_ctime = ioloop_time;

    io_stream_init(&_stream->iostream);
    return &_stream->istream;
}