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GIO Reference Manual | ![]() |
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Top | Description | Object Hierarchy | Implemented Interfaces | Properties |
#include <gio/gio.h> gpointer (*GReallocFunc) (gpointer data
,gsize size
); GMemoryOutputStream; GOutputStream * g_memory_output_stream_new (gpointer data
,gsize size
,GReallocFunc realloc_function
,GDestroyNotify destroy_function
); GOutputStream * g_memory_output_stream_new_resizable (void
); gpointer g_memory_output_stream_get_data (GMemoryOutputStream *ostream
); gsize g_memory_output_stream_get_size (GMemoryOutputStream *ostream
); gsize g_memory_output_stream_get_data_size (GMemoryOutputStream *ostream
); gpointer g_memory_output_stream_steal_data (GMemoryOutputStream *ostream
); GBytes * g_memory_output_stream_steal_as_bytes (GMemoryOutputStream *ostream
);
"data" gpointer : Read / Write / Construct Only "data-size" gulong : Read "destroy-function" gpointer : Read / Write / Construct Only "realloc-function" gpointer : Read / Write / Construct Only "size" gulong : Read / Write / Construct Only
GMemoryOutputStream is a class for using arbitrary memory chunks as output for GIO streaming output operations.
As of GLib 2.34, GMemoryOutputStream trivially implements GPollableOutputStream: it always polls as ready.
gpointer (*GReallocFunc) (gpointer data
,gsize size
);
Changes the size of the memory block pointed to by data
to
size
bytes.
The function should have the same semantics as realloc()
.
|
memory block to reallocate |
|
size to reallocate data to |
Returns : |
a pointer to the reallocated memory |
typedef struct _GMemoryOutputStream GMemoryOutputStream;
Implements GOutputStream for arbitrary memory chunks.
GOutputStream * g_memory_output_stream_new (gpointer data
,gsize size
,GReallocFunc realloc_function
,GDestroyNotify destroy_function
);
Creates a new GMemoryOutputStream.
In most cases this is not the function you want. See
g_memory_output_stream_new_resizable()
instead.
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 and the stream will be considered resizable.
In that case, the stream will start out being (conceptually) empty.
size
is used only as a hint for how big data
is. Specifically,
seeking to the end of a newly-created stream will seek to zero, not
size
. Seeking past the end of the stream and then writing will
introduce a zero-filled gap.
If realloc_fn
is NULL
then the stream is fixed-sized. Seeking to
the end will seek to size
exactly. Writing past the end will give
an 'out of space' error. Attempting to seek past the end will fail.
Unlike the resizable case, seeking to an offset within the stream and
writing will preserve the bytes passed in as data
before that point
and will return them as part of g_memory_output_stream_steal_data()
.
If you intend to seek you should probably therefore ensure that data
is properly initialised.
It is probably only meaningful to provide data
and size
in the case
that you want a fixed-sized stream. Put another way: if realloc_fn
is non-NULL
then it makes most sense to give data
as NULL
and
size
as 0 (allowing GMemoryOutputStream to do the initial
allocation for itself).
1 2 3 4 5 6 7 8 9 |
/* a stream that can grow */ stream = g_memory_output_stream_new (NULL, 0, realloc, free); /* another stream that can grow */ stream2 = g_memory_output_stream_new (NULL, 0, g_realloc, g_free); /* a fixed-size stream */ data = malloc (200); stream3 = g_memory_output_stream_new (data, 200, NULL, free); |
|
pointer to a chunk of memory to use, or NULL . [allow-none]
|
|
the size of data
|
|
a function with realloc() semantics (like g_realloc() )
to be called when data needs to be grown, or NULL . [allow-none]
|
|
a function to be called on data when the stream is
finalized, or NULL . [allow-none]
|
Returns : |
A newly created GMemoryOutputStream object. |
GOutputStream * g_memory_output_stream_new_resizable
(void
);
Creates a new GMemoryOutputStream, using g_realloc()
and g_free()
for memory allocation.
Since 2.36
gpointer g_memory_output_stream_get_data (GMemoryOutputStream *ostream
);
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.
|
a GMemoryOutputStream |
Returns : |
pointer to the stream's data. [transfer none] |
gsize g_memory_output_stream_get_size (GMemoryOutputStream *ostream
);
Gets the size of the currently allocated data area (available from
g_memory_output_stream_get_data()
).
You probably don't want to use this function on resizable streams.
See g_memory_output_stream_get_data_size()
instead. For resizable
streams the size returned by this function is an implementation
detail and may be change at any time in response to operations on the
stream.
If the stream is fixed-sized (ie: 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
.
In any case, if you want the number of bytes currently written to the
stream, use g_memory_output_stream_get_data_size()
.
|
a GMemoryOutputStream |
Returns : |
the number of bytes allocated for the data buffer |
gsize g_memory_output_stream_get_data_size
(GMemoryOutputStream *ostream
);
Returns the number of bytes from the start up to including the last byte written in the stream that has not been truncated away.
|
a GMemoryOutputStream |
Returns : |
the number of bytes written to the stream |
Since 2.18
gpointer g_memory_output_stream_steal_data (GMemoryOutputStream *ostream
);
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
"destroy-function" property.
ostream
must be closed before calling this function.
|
a GMemoryOutputStream |
Returns : |
the stream's data. [transfer full] |
Since 2.26
GBytes * g_memory_output_stream_steal_as_bytes
(GMemoryOutputStream *ostream
);
Returns data from the ostream
as a GBytes. ostream
must be
closed before calling this function.
|
a GMemoryOutputStream |
Returns : |
the stream's data. [transfer full] |
Since 2.34
"data"
property"data" gpointer : Read / Write / Construct Only
Pointer to buffer where data will be written.
Since 2.24
"destroy-function"
property"destroy-function" gpointer : Read / Write / Construct Only
Function called with the buffer as argument when the stream is destroyed.
Since 2.24
"realloc-function"
property"realloc-function" gpointer : Read / Write / Construct Only
Function with realloc semantics called to enlarge the buffer.
Since 2.24
"size"
property"size" gulong : Read / Write / Construct Only
Current size of the data buffer.
Since 2.24