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glib/gio/gmemoryoutputstream.c
Ryan Lortie fdc5cd8d9f Change semantics of seek on memory output stream 
It is our intention that memory output streams should operate in two
distinct modes, depending on if a realloc function was provided or not.

In the case that we have a realloc function (resizable mode), we want
the stream to behave as if it were a file that started out empty.  In
the case that we don't have a realloc function (fixed-sized mode), we
want the stream to behave as a block device would.

To this end, we introduce two changes in functionality:

 - seeking to SEEK_END on a resizable stream will now seek to the end of
   the valid data region, not to the end of the allocated memory (which
   is really just an implementation detail)

 - seeks past the end of the allocated memory size are now permitted,
   but only on resizable streams.  The next write will grow the buffer
   (inserting zeros between).

Some tweaks to testcases were required in order not to break the build,
which indicates that this is an API break, but it seems unlikely that
anyone will be effected by these changes 'in the real world'.

Updates to documentation and further testcases are in following commits.

Based on a patch from Maciej Piechotka <uzytkownik2@gmail.com>.

https://bugzilla.gnome.org/show_bug.cgi?id=684842
2013-10-23 11:31:27 -04:00

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/* GIO - GLib Input, Output and Streaming Library
*
* Copyright (C) 2006-2007 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*
* Authors:
* Christian Kellner <gicmo@gnome.org>
* Krzysztof Kosiński <tweenk.pl@gmail.com>
*/
#include "config.h"
#include "gmemoryoutputstream.h"
#include "goutputstream.h"
#include "gpollableoutputstream.h"
#include "gseekable.h"
#include "gtask.h"
#include "gioerror.h"
#include "string.h"
#include "glibintl.h"
/**
* SECTION:gmemoryoutputstream
* @short_description: Streaming output operations on memory chunks
* @include: gio/gio.h
* @see_also: #GMemoryInputStream
*
* #GMemoryOutputStream is a class for using arbitrary
* memory chunks as output for GIO streaming output operations.
*
* As of GLib 2.34, #GMemoryOutputStream implements
* #GPollableOutputStream.
*/
#define MIN_ARRAY_SIZE 16
enum {
PROP_0,
PROP_DATA,
PROP_SIZE,
PROP_DATA_SIZE,
PROP_REALLOC_FUNCTION,
PROP_DESTROY_FUNCTION
};
struct _GMemoryOutputStreamPrivate {
gpointer data; /* Write buffer */
gsize len; /* Current length of the data buffer. Can change with resizing. */
gsize valid_len; /* The part of data that has been written to */
gsize pos; /* Current position in the stream. Distinct from valid_len,
because the stream is seekable. */
GReallocFunc realloc_fn;
GDestroyNotify destroy;
};
static void g_memory_output_stream_set_property (GObject *object,
guint prop_id,
const GValue *value,
GParamSpec *pspec);
static void g_memory_output_stream_get_property (GObject *object,
guint prop_id,
GValue *value,
GParamSpec *pspec);
static void g_memory_output_stream_finalize (GObject *object);
static gssize g_memory_output_stream_write (GOutputStream *stream,
const void *buffer,
gsize count,
GCancellable *cancellable,
GError **error);
static gboolean g_memory_output_stream_close (GOutputStream *stream,
GCancellable *cancellable,
GError **error);
static void g_memory_output_stream_close_async (GOutputStream *stream,
int io_priority,
GCancellable *cancellable,
GAsyncReadyCallback callback,
gpointer data);
static gboolean g_memory_output_stream_close_finish (GOutputStream *stream,
GAsyncResult *result,
GError **error);
static void g_memory_output_stream_seekable_iface_init (GSeekableIface *iface);
static goffset g_memory_output_stream_tell (GSeekable *seekable);
static gboolean g_memory_output_stream_can_seek (GSeekable *seekable);
static gboolean g_memory_output_stream_seek (GSeekable *seekable,
goffset offset,
GSeekType type,
GCancellable *cancellable,
GError **error);
static gboolean g_memory_output_stream_can_truncate (GSeekable *seekable);
static gboolean g_memory_output_stream_truncate (GSeekable *seekable,
goffset offset,
GCancellable *cancellable,
GError **error);
static gboolean g_memory_output_stream_is_writable (GPollableOutputStream *stream);
static GSource *g_memory_output_stream_create_source (GPollableOutputStream *stream,
GCancellable *cancellable);
static void g_memory_output_stream_pollable_iface_init (GPollableOutputStreamInterface *iface);
G_DEFINE_TYPE_WITH_CODE (GMemoryOutputStream, g_memory_output_stream, G_TYPE_OUTPUT_STREAM,
G_ADD_PRIVATE (GMemoryOutputStream)
G_IMPLEMENT_INTERFACE (G_TYPE_SEEKABLE,
g_memory_output_stream_seekable_iface_init);
G_IMPLEMENT_INTERFACE (G_TYPE_POLLABLE_OUTPUT_STREAM,
g_memory_output_stream_pollable_iface_init))
static void
g_memory_output_stream_class_init (GMemoryOutputStreamClass *klass)
{
GOutputStreamClass *ostream_class;
GObjectClass *gobject_class;
gobject_class = G_OBJECT_CLASS (klass);
gobject_class->set_property = g_memory_output_stream_set_property;
gobject_class->get_property = g_memory_output_stream_get_property;
gobject_class->finalize = g_memory_output_stream_finalize;
ostream_class = G_OUTPUT_STREAM_CLASS (klass);
ostream_class->write_fn = g_memory_output_stream_write;
ostream_class->close_fn = g_memory_output_stream_close;
ostream_class->close_async = g_memory_output_stream_close_async;
ostream_class->close_finish = g_memory_output_stream_close_finish;
/**
* GMemoryOutputStream:data:
*
* Pointer to buffer where data will be written.
*
* Since: 2.24
**/
g_object_class_install_property (gobject_class,
PROP_DATA,
g_param_spec_pointer ("data",
P_("Data Buffer"),
P_("Pointer to buffer where data will be written."),
G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
G_PARAM_STATIC_STRINGS));
/**
* GMemoryOutputStream:size:
*
* Current size of the data buffer.
*
* Since: 2.24
**/
g_object_class_install_property (gobject_class,
PROP_SIZE,
g_param_spec_ulong ("size",
P_("Data Buffer Size"),
P_("Current size of the data buffer."),
0, G_MAXULONG, 0,
G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
G_PARAM_STATIC_STRINGS));
/**
* GMemoryOutputStream:data-size:
*
* Size of data written to the buffer.
*
* Since: 2.24
**/
g_object_class_install_property (gobject_class,
PROP_DATA_SIZE,
g_param_spec_ulong ("data-size",
P_("Data Size"),
P_("Size of data written to the buffer."),
0, G_MAXULONG, 0,
G_PARAM_READABLE |
G_PARAM_STATIC_STRINGS));
/**
* GMemoryOutputStream:realloc-function: (skip)
*
* Function with realloc semantics called to enlarge the buffer.
*
* Since: 2.24
**/
g_object_class_install_property (gobject_class,
PROP_REALLOC_FUNCTION,
g_param_spec_pointer ("realloc-function",
P_("Memory Reallocation Function"),
P_("Function with realloc semantics called to enlarge the buffer."),
G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
G_PARAM_STATIC_STRINGS));
/**
* GMemoryOutputStream:destroy-function: (skip)
*
* Function called with the buffer as argument when the stream is destroyed.
*
* Since: 2.24
**/
g_object_class_install_property (gobject_class,
PROP_DESTROY_FUNCTION,
g_param_spec_pointer ("destroy-function",
P_("Destroy Notification Function"),
P_("Function called with the buffer as argument when the stream is destroyed."),
G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
G_PARAM_STATIC_STRINGS));
}
static void
g_memory_output_stream_pollable_iface_init (GPollableOutputStreamInterface *iface)
{
iface->is_writable = g_memory_output_stream_is_writable;
iface->create_source = g_memory_output_stream_create_source;
}
static void
g_memory_output_stream_set_property (GObject *object,
guint prop_id,
const GValue *value,
GParamSpec *pspec)
{
GMemoryOutputStream *stream;
GMemoryOutputStreamPrivate *priv;
stream = G_MEMORY_OUTPUT_STREAM (object);
priv = stream->priv;
switch (prop_id)
{
case PROP_DATA:
priv->data = g_value_get_pointer (value);
break;
case PROP_SIZE:
priv->len = g_value_get_ulong (value);
break;
case PROP_REALLOC_FUNCTION:
priv->realloc_fn = g_value_get_pointer (value);
break;
case PROP_DESTROY_FUNCTION:
priv->destroy = g_value_get_pointer (value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
g_memory_output_stream_get_property (GObject *object,
guint prop_id,
GValue *value,
GParamSpec *pspec)
{
GMemoryOutputStream *stream;
GMemoryOutputStreamPrivate *priv;
stream = G_MEMORY_OUTPUT_STREAM (object);
priv = stream->priv;
switch (prop_id)
{
case PROP_DATA:
g_value_set_pointer (value, priv->data);
break;
case PROP_SIZE:
g_value_set_ulong (value, priv->len);
break;
case PROP_DATA_SIZE:
g_value_set_ulong (value, priv->valid_len);
break;
case PROP_REALLOC_FUNCTION:
g_value_set_pointer (value, priv->realloc_fn);
break;
case PROP_DESTROY_FUNCTION:
g_value_set_pointer (value, priv->destroy);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
g_memory_output_stream_finalize (GObject *object)
{
GMemoryOutputStream *stream;
GMemoryOutputStreamPrivate *priv;
stream = G_MEMORY_OUTPUT_STREAM (object);
priv = stream->priv;
if (priv->destroy)
priv->destroy (priv->data);
G_OBJECT_CLASS (g_memory_output_stream_parent_class)->finalize (object);
}
static void
g_memory_output_stream_seekable_iface_init (GSeekableIface *iface)
{
iface->tell = g_memory_output_stream_tell;
iface->can_seek = g_memory_output_stream_can_seek;
iface->seek = g_memory_output_stream_seek;
iface->can_truncate = g_memory_output_stream_can_truncate;
iface->truncate_fn = g_memory_output_stream_truncate;
}
static void
g_memory_output_stream_init (GMemoryOutputStream *stream)
{
stream->priv = g_memory_output_stream_get_instance_private (stream);
stream->priv->pos = 0;
stream->priv->valid_len = 0;
}
/**
* g_memory_output_stream_new: (skip)
* @data: (allow-none): pointer to a chunk of memory to use, or %NULL
* @size: the size of @data
* @realloc_function: (allow-none): a function with realloc() semantics (like g_realloc())
* to be called when @data needs to be grown, or %NULL
* @destroy_function: (allow-none): a function to be called on @data when the stream is
* finalized, or %NULL
*
* Creates a new #GMemoryOutputStream.
*
* If @data is non-%NULL, the stream will use that for its internal storage.
* If @realloc_fn is non-%NULL, it will be used for resizing the internal
* storage when necessary. To construct a fixed-size output stream,
* pass %NULL as @realloc_fn.
*
* |[
* /&ast; a stream that can grow &ast;/
* stream = g_memory_output_stream_new (NULL, 0, realloc, free);
*
* /&ast; another stream that can grow &ast;/
* stream2 = g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
*
* /&ast; a fixed-size stream &ast;/
* data = malloc (200);
* stream3 = g_memory_output_stream_new (data, 200, NULL, free);
* ]|
*
* Return value: A newly created #GMemoryOutputStream object.
**/
GOutputStream *
g_memory_output_stream_new (gpointer data,
gsize size,
GReallocFunc realloc_function,
GDestroyNotify destroy_function)
{
GOutputStream *stream;
stream = g_object_new (G_TYPE_MEMORY_OUTPUT_STREAM,
"data", data,
"size", size,
"realloc-function", realloc_function,
"destroy-function", destroy_function,
NULL);
return stream;
}
/**
* g_memory_output_stream_new_resizable:
*
* Creates a new #GMemoryOutputStream, using g_realloc() and g_free()
* for memory allocation.
*
* Since: 2.36
*/
GOutputStream *
g_memory_output_stream_new_resizable (void)
{
return g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
}
/**
* g_memory_output_stream_get_data:
* @ostream: a #GMemoryOutputStream
*
* Gets any loaded data from the @ostream.
*
* Note that the returned pointer may become invalid on the next
* write or truncate operation on the stream.
*
* Returns: (transfer none): pointer to the stream's data
**/
gpointer
g_memory_output_stream_get_data (GMemoryOutputStream *ostream)
{
g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
return ostream->priv->data;
}
/**
* g_memory_output_stream_get_size:
* @ostream: a #GMemoryOutputStream
*
* Gets the size of the currently allocated data area (available from
* g_memory_output_stream_get_data()). If the stream isn't
* growable (no realloc was passed to g_memory_output_stream_new()) then
* this is the maximum size of the stream and further writes
* will return %G_IO_ERROR_NO_SPACE.
*
* Note that for growable streams the returned size may become invalid on
* the next write or truncate operation on the stream.
*
* If you want the number of bytes currently written to the stream, use
* g_memory_output_stream_get_data_size().
*
* Returns: the number of bytes allocated for the data buffer
*/
gsize
g_memory_output_stream_get_size (GMemoryOutputStream *ostream)
{
g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
return ostream->priv->len;
}
/**
* g_memory_output_stream_get_data_size:
* @ostream: a #GMemoryOutputStream
*
* Returns the number of bytes from the start up
* to including the last byte written in the stream
* that has not been truncated away.
*
* Returns: the number of bytes written to the stream
*
* Since: 2.18
*/
gsize
g_memory_output_stream_get_data_size (GMemoryOutputStream *ostream)
{
g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
return ostream->priv->valid_len;
}
/**
* g_memory_output_stream_steal_data:
* @ostream: a #GMemoryOutputStream
*
* Gets any loaded data from the @ostream. Ownership of the data
* is transferred to the caller; when no longer needed it must be
* freed using the free function set in @ostream's
* #GMemoryOutputStream:destroy-function property.
*
* @ostream must be closed before calling this function.
*
* Returns: (transfer full): the stream's data
*
* Since: 2.26
**/
gpointer
g_memory_output_stream_steal_data (GMemoryOutputStream *ostream)
{
gpointer data;
g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
g_return_val_if_fail (g_output_stream_is_closed (G_OUTPUT_STREAM (ostream)), NULL);
data = ostream->priv->data;
ostream->priv->data = NULL;
return data;
}
/**
* g_memory_output_stream_steal_as_bytes:
* @ostream: a #GMemoryOutputStream
*
* Returns data from the @ostream as a #GBytes. @ostream must be
* closed before calling this function.
*
* Returns: (transfer full): the stream's data
*
* Since: 2.34
**/
GBytes *
g_memory_output_stream_steal_as_bytes (GMemoryOutputStream *ostream)
{
GBytes *result;
g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
g_return_val_if_fail (g_output_stream_is_closed (G_OUTPUT_STREAM (ostream)), NULL);
result = g_bytes_new_with_free_func (ostream->priv->data,
ostream->priv->valid_len,
ostream->priv->destroy,
ostream->priv->data);
ostream->priv->data = NULL;
return result;
}
static gboolean
array_resize (GMemoryOutputStream *ostream,
gsize size,
gboolean allow_partial,
GError **error)
{
GMemoryOutputStreamPrivate *priv;
gpointer data;
gsize len;
priv = ostream->priv;
if (priv->len == size)
return TRUE;
if (!priv->realloc_fn)
{
if (allow_partial &&
priv->pos < priv->len)
return TRUE; /* Short write */
g_set_error_literal (error,
G_IO_ERROR,
G_IO_ERROR_NO_SPACE,
_("Memory output stream not resizable"));
return FALSE;
}
len = priv->len;
data = priv->realloc_fn (priv->data, size);
if (size > 0 && !data)
{
if (allow_partial &&
priv->pos < priv->len)
return TRUE; /* Short write */
g_set_error_literal (error,
G_IO_ERROR,
G_IO_ERROR_NO_SPACE,
_("Failed to resize memory output stream"));
return FALSE;
}
if (size > len)
memset ((guint8 *)data + len, 0, size - len);
priv->data = data;
priv->len = size;
if (priv->len < priv->valid_len)
priv->valid_len = priv->len;
return TRUE;
}
static gint
g_nearest_pow (gint num)
{
gint n = 1;
while (n < num)
n <<= 1;
return n;
}
static gssize
g_memory_output_stream_write (GOutputStream *stream,
const void *buffer,
gsize count,
GCancellable *cancellable,
GError **error)
{
GMemoryOutputStream *ostream;
GMemoryOutputStreamPrivate *priv;
guint8 *dest;
gsize new_size;
ostream = G_MEMORY_OUTPUT_STREAM (stream);
priv = ostream->priv;
if (count == 0)
return 0;
/* Check for address space overflow, but only if the buffer is resizable.
Otherwise we just do a short write and don't worry. */
if (priv->realloc_fn && priv->pos + count < priv->pos)
goto overflow;
if (priv->pos + count > priv->len)
{
/* At least enought to fit the write, rounded up
for greater than linear growth.
TODO: This wastes a lot of memory at large stream sizes.
Figure out a more rational allocation strategy. */
new_size = g_nearest_pow (priv->pos + count);
/* Check for overflow again. We have only checked if
pos + count > G_MAXSIZE, but it only catches the case of writing
more than 4GiB total on a 32-bit system. There's still the problem
of g_nearest_pow overflowing above 0x7fffffff, so we're
effectively limited to 2GiB. */
if (new_size < priv->len)
goto overflow;
new_size = MAX (new_size, MIN_ARRAY_SIZE);
if (!array_resize (ostream, new_size, TRUE, error))
return -1;
}
/* Make sure we handle short writes if the array_resize
only added part of the required memory */
count = MIN (count, priv->len - priv->pos);
dest = (guint8 *)priv->data + priv->pos;
memcpy (dest, buffer, count);
priv->pos += count;
if (priv->pos > priv->valid_len)
priv->valid_len = priv->pos;
return count;
overflow:
/* Overflow: buffer size would need to be bigger than G_MAXSIZE. */
g_set_error_literal (error,
G_IO_ERROR,
G_IO_ERROR_NO_SPACE,
_("Amount of memory required to process the write is "
"larger than available address space"));
return -1;
}
static gboolean
g_memory_output_stream_close (GOutputStream *stream,
GCancellable *cancellable,
GError **error)
{
return TRUE;
}
static void
g_memory_output_stream_close_async (GOutputStream *stream,
int io_priority,
GCancellable *cancellable,
GAsyncReadyCallback callback,
gpointer data)
{
GTask *task;
task = g_task_new (stream, cancellable, callback, data);
/* will always return TRUE */
g_memory_output_stream_close (stream, cancellable, NULL);
g_task_return_boolean (task, TRUE);
g_object_unref (task);
}
static gboolean
g_memory_output_stream_close_finish (GOutputStream *stream,
GAsyncResult *result,
GError **error)
{
g_return_val_if_fail (g_task_is_valid (result, stream), FALSE);
return g_task_propagate_boolean (G_TASK (result), error);
}
static goffset
g_memory_output_stream_tell (GSeekable *seekable)
{
GMemoryOutputStream *stream;
GMemoryOutputStreamPrivate *priv;
stream = G_MEMORY_OUTPUT_STREAM (seekable);
priv = stream->priv;
return priv->pos;
}
static gboolean
g_memory_output_stream_can_seek (GSeekable *seekable)
{
return TRUE;
}
static gboolean
g_memory_output_stream_seek (GSeekable *seekable,
goffset offset,
GSeekType type,
GCancellable *cancellable,
GError **error)
{
GMemoryOutputStream *stream;
GMemoryOutputStreamPrivate *priv;
goffset absolute;
stream = G_MEMORY_OUTPUT_STREAM (seekable);
priv = stream->priv;
switch (type)
{
case G_SEEK_CUR:
absolute = priv->pos + offset;
break;
case G_SEEK_SET:
absolute = offset;
break;
case G_SEEK_END:
/* For resizable streams, we consider the end to be the data
* length. For fixed-sized streams, we consider the end to be the
* size of the buffer.
*/
if (priv->realloc_fn)
absolute = priv->valid_len + offset;
else
absolute = priv->len + offset;
break;
default:
g_set_error_literal (error,
G_IO_ERROR,
G_IO_ERROR_INVALID_ARGUMENT,
_("Invalid GSeekType supplied"));
return FALSE;
}
if (absolute < 0)
{
g_set_error_literal (error,
G_IO_ERROR,
G_IO_ERROR_INVALID_ARGUMENT,
_("Requested seek before the beginning of the stream"));
return FALSE;
}
/* Can't seek past the end of a fixed-size stream.
*
* Note: seeking to the non-existent byte at the end of a fixed-sized
* stream is valid (eg: a 1-byte fixed sized stream can have position
* 0 or 1). Therefore '>' is what we want.
* */
if (priv->realloc_fn == NULL && absolute > priv->len)
{
g_set_error_literal (error,
G_IO_ERROR,
G_IO_ERROR_INVALID_ARGUMENT,
_("Requested seek beyond the end of the stream"));
return FALSE;
}
priv->pos = absolute;
return TRUE;
}
static gboolean
g_memory_output_stream_can_truncate (GSeekable *seekable)
{
GMemoryOutputStream *ostream;
GMemoryOutputStreamPrivate *priv;
ostream = G_MEMORY_OUTPUT_STREAM (seekable);
priv = ostream->priv;
return priv->realloc_fn != NULL;
}
static gboolean
g_memory_output_stream_truncate (GSeekable *seekable,
goffset offset,
GCancellable *cancellable,
GError **error)
{
GMemoryOutputStream *ostream = G_MEMORY_OUTPUT_STREAM (seekable);
if (!array_resize (ostream, offset, FALSE, error))
return FALSE;
return TRUE;
}
static gboolean
g_memory_output_stream_is_writable (GPollableOutputStream *stream)
{
return TRUE;
}
static GSource *
g_memory_output_stream_create_source (GPollableOutputStream *stream,
GCancellable *cancellable)
{
GSource *base_source, *pollable_source;
base_source = g_timeout_source_new (0);
pollable_source = g_pollable_source_new_full (stream, base_source,
cancellable);
g_source_unref (base_source);
return pollable_source;
}
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