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GInputStream

GInputStream — Base class for implementing streaming input

Types and Values

Object Hierarchy

    GObject
    ╰── GInputStream
        ├── GFilterInputStream
        ├── GFileInputStream
        ├── GMemoryInputStream
        ╰── GUnixInputStream

Known Derived Interfaces

GInputStream is required by GPollableInputStream.

Includes

#include <gio/gio.h>

Description

GInputStream has functions to read from a stream (g_input_stream_read()), to close a stream (g_input_stream_close()) and to skip some content (g_input_stream_skip()).

To copy the content of an input stream to an output stream without manually handling the reads and writes, use g_output_stream_splice().

See the documentation for GIOStream for details of thread safety of streaming APIs.

All of these functions have async variants too.

Functions

g_input_stream_read ()

gssize
g_input_stream_read (GInputStream *stream,
                     void *buffer,
                     gsize count,
                     GCancellable *cancellable,
                     GError **error);

Tries to read count bytes from the stream into the buffer starting at buffer . Will block during this read.

If count is zero returns zero and does nothing. A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.

On success, the number of bytes read into the buffer is returned. It is not an error if this is not the same as the requested size, as it can happen e.g. near the end of a file. Zero is returned on end of file (or if count is zero), but never otherwise.

The returned buffer is not a nul-terminated string, it can contain nul bytes at any position, and this function doesn't nul-terminate the buffer .

If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.

On error -1 is returned and error is set accordingly.

Parameters

stream

a GInputStream.

 

buffer

a buffer to read data into (which should be at least count bytes long).

[array length=count][element-type guint8]

count

the number of bytes that will be read from the stream

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

Number of bytes read, or -1 on error, or 0 on end of file.


g_input_stream_read_all ()

gboolean
g_input_stream_read_all (GInputStream *stream,
                         void *buffer,
                         gsize count,
                         gsize *bytes_read,
                         GCancellable *cancellable,
                         GError **error);

Tries to read count bytes from the stream into the buffer starting at buffer . Will block during this read.

This function is similar to g_input_stream_read(), except it tries to read as many bytes as requested, only stopping on an error or end of stream.

On a successful read of count bytes, or if we reached the end of the stream, TRUE is returned, and bytes_read is set to the number of bytes read into buffer .

If there is an error during the operation FALSE is returned and error is set to indicate the error status.

As a special exception to the normal conventions for functions that use GError, if this function returns FALSE (and sets error ) then bytes_read will be set to the number of bytes that were successfully read before the error was encountered. This functionality is only available from C. If you need it from another language then you must write your own loop around g_input_stream_read().

Parameters

stream

a GInputStream.

 

buffer

a buffer to read data into (which should be at least count bytes long).

[array length=count][element-type guint8]

count

the number of bytes that will be read from the stream

 

bytes_read

location to store the number of bytes that was read from the stream.

[out]

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

TRUE on success, FALSE if there was an error


g_input_stream_read_all_async ()

void
g_input_stream_read_all_async (GInputStream *stream,
                               void *buffer,
                               gsize count,
                               int io_priority,
                               GCancellable *cancellable,
                               GAsyncReadyCallback callback,
                               gpointer user_data);

Request an asynchronous read of count bytes from the stream into the buffer starting at buffer .

This is the asynchronous equivalent of g_input_stream_read_all().

Call g_input_stream_read_all_finish() to collect the result.

Any outstanding I/O request with higher priority (lower numerical value) will be executed before an outstanding request with lower priority. Default priority is G_PRIORITY_DEFAULT.

Parameters

stream

A GInputStream

 

buffer

a buffer to read data into (which should be at least count bytes long).

[array length=count][element-type guint8]

count

the number of bytes that will be read from the stream

 

io_priority

the I/O priority of the request

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

Since: 2.44


g_input_stream_read_all_finish ()

gboolean
g_input_stream_read_all_finish (GInputStream *stream,
                                GAsyncResult *result,
                                gsize *bytes_read,
                                GError **error);

Finishes an asynchronous stream read operation started with g_input_stream_read_all_async().

As a special exception to the normal conventions for functions that use GError, if this function returns FALSE (and sets error ) then bytes_read will be set to the number of bytes that were successfully read before the error was encountered. This functionality is only available from C. If you need it from another language then you must write your own loop around g_input_stream_read_async().

Parameters

stream

a GInputStream

 

result

a GAsyncResult

 

bytes_read

location to store the number of bytes that was read from the stream.

[out]

error

a GError location to store the error occurring, or NULL to ignore

 

Returns

TRUE on success, FALSE if there was an error

Since: 2.44


g_input_stream_skip ()

gssize
g_input_stream_skip (GInputStream *stream,
                     gsize count,
                     GCancellable *cancellable,
                     GError **error);

Tries to skip count bytes from the stream. Will block during the operation.

This is identical to g_input_stream_read(), from a behaviour standpoint, but the bytes that are skipped are not returned to the user. Some streams have an implementation that is more efficient than reading the data.

This function is optional for inherited classes, as the default implementation emulates it using read.

If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.

Parameters

stream

a GInputStream.

 

count

the number of bytes that will be skipped from the stream

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

Number of bytes skipped, or -1 on error


g_input_stream_close ()

gboolean
g_input_stream_close (GInputStream *stream,
                      GCancellable *cancellable,
                      GError **error);

Closes the stream, releasing resources related to it.

Once the stream is closed, all other operations will return G_IO_ERROR_CLOSED. Closing a stream multiple times will not return an error.

Streams will be automatically closed when the last reference is dropped, but you might want to call this function to make sure resources are released as early as possible.

Some streams might keep the backing store of the stream (e.g. a file descriptor) open after the stream is closed. See the documentation for the individual stream for details.

On failure the first error that happened will be reported, but the close operation will finish as much as possible. A stream that failed to close will still return G_IO_ERROR_CLOSED for all operations. Still, it is important to check and report the error to the user.

If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. Cancelling a close will still leave the stream closed, but some streams can use a faster close that doesn't block to e.g. check errors.

Parameters

stream

A GInputStream.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

TRUE on success, FALSE on failure


g_input_stream_read_async ()

void
g_input_stream_read_async (GInputStream *stream,
                           void *buffer,
                           gsize count,
                           int io_priority,
                           GCancellable *cancellable,
                           GAsyncReadyCallback callback,
                           gpointer user_data);

Request an asynchronous read of count bytes from the stream into the buffer starting at buffer . When the operation is finished callback will be called. You can then call g_input_stream_read_finish() to get the result of the operation.

During an async request no other sync and async calls are allowed on stream , and will result in G_IO_ERROR_PENDING errors.

A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.

On success, the number of bytes read into the buffer will be passed to the callback. It is not an error if this is not the same as the requested size, as it can happen e.g. near the end of a file, but generally we try to read as many bytes as requested. Zero is returned on end of file (or if count is zero), but never otherwise.

Any outstanding i/o request with higher priority (lower numerical value) will be executed before an outstanding request with lower priority. Default priority is G_PRIORITY_DEFAULT.

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one you must override all.

Parameters

stream

A GInputStream.

 

buffer

a buffer to read data into (which should be at least count bytes long).

[array length=count][element-type guint8]

count

the number of bytes that will be read from the stream

 

io_priority

the I/O priority of the request.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

g_input_stream_read_finish ()

gssize
g_input_stream_read_finish (GInputStream *stream,
                            GAsyncResult *result,
                            GError **error);

Finishes an asynchronous stream read operation.

Parameters

stream

a GInputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

number of bytes read in, or -1 on error, or 0 on end of file.


g_input_stream_skip_async ()

void
g_input_stream_skip_async (GInputStream *stream,
                           gsize count,
                           int io_priority,
                           GCancellable *cancellable,
                           GAsyncReadyCallback callback,
                           gpointer user_data);

Request an asynchronous skip of count bytes from the stream. When the operation is finished callback will be called. You can then call g_input_stream_skip_finish() to get the result of the operation.

During an async request no other sync and async calls are allowed, and will result in G_IO_ERROR_PENDING errors.

A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.

On success, the number of bytes skipped will be passed to the callback. It is not an error if this is not the same as the requested size, as it can happen e.g. near the end of a file, but generally we try to skip as many bytes as requested. Zero is returned on end of file (or if count is zero), but never otherwise.

Any outstanding i/o request with higher priority (lower numerical value) will be executed before an outstanding request with lower priority. Default priority is G_PRIORITY_DEFAULT.

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one, you must override all.

Parameters

stream

A GInputStream.

 

count

the number of bytes that will be skipped from the stream

 

io_priority

the I/O priority of the request

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

g_input_stream_skip_finish ()

gssize
g_input_stream_skip_finish (GInputStream *stream,
                            GAsyncResult *result,
                            GError **error);

Finishes a stream skip operation.

Parameters

stream

a GInputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

the size of the bytes skipped, or -1 on error.


g_input_stream_close_async ()

void
g_input_stream_close_async (GInputStream *stream,
                            int io_priority,
                            GCancellable *cancellable,
                            GAsyncReadyCallback callback,
                            gpointer user_data);

Requests an asynchronous closes of the stream, releasing resources related to it. When the operation is finished callback will be called. You can then call g_input_stream_close_finish() to get the result of the operation.

For behaviour details see g_input_stream_close().

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one you must override all.

Parameters

stream

A GInputStream.

 

io_priority

the I/O priority of the request

 

cancellable

optional cancellable object.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

g_input_stream_close_finish ()

gboolean
g_input_stream_close_finish (GInputStream *stream,
                             GAsyncResult *result,
                             GError **error);

Finishes closing a stream asynchronously, started from g_input_stream_close_async().

Parameters

stream

a GInputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

TRUE if the stream was closed successfully.


g_input_stream_is_closed ()

gboolean
g_input_stream_is_closed (GInputStream *stream);

Checks if an input stream is closed.

Parameters

stream

input stream.

 

Returns

TRUE if the stream is closed.


g_input_stream_has_pending ()

gboolean
g_input_stream_has_pending (GInputStream *stream);

Checks if an input stream has pending actions.

Parameters

stream

input stream.

 

Returns

TRUE if stream has pending actions.


g_input_stream_set_pending ()

gboolean
g_input_stream_set_pending (GInputStream *stream,
                            GError **error);

Sets stream to have actions pending. If the pending flag is already set or stream is closed, it will return FALSE and set error .

Parameters

stream

input stream

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

TRUE if pending was previously unset and is now set.


g_input_stream_clear_pending ()

void
g_input_stream_clear_pending (GInputStream *stream);

Clears the pending flag on stream .

Parameters

stream

input stream

 

g_input_stream_read_bytes ()

GBytes *
g_input_stream_read_bytes (GInputStream *stream,
                           gsize count,
                           GCancellable *cancellable,
                           GError **error);

Like g_input_stream_read(), this tries to read count bytes from the stream in a blocking fashion. However, rather than reading into a user-supplied buffer, this will create a new GBytes containing the data that was read. This may be easier to use from language bindings.

If count is zero, returns a zero-length GBytes and does nothing. A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.

On success, a new GBytes is returned. It is not an error if the size of this object is not the same as the requested size, as it can happen e.g. near the end of a file. A zero-length GBytes is returned on end of file (or if count is zero), but never otherwise.

If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.

On error NULL is returned and error is set accordingly.

Parameters

stream

a GInputStream.

 

count

maximum number of bytes that will be read from the stream. Common values include 4096 and 8192.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

a new GBytes, or NULL on error.

[transfer full]

Since: 2.34


g_input_stream_read_bytes_async ()

void
g_input_stream_read_bytes_async (GInputStream *stream,
                                 gsize count,
                                 int io_priority,
                                 GCancellable *cancellable,
                                 GAsyncReadyCallback callback,
                                 gpointer user_data);

Request an asynchronous read of count bytes from the stream into a new GBytes. When the operation is finished callback will be called. You can then call g_input_stream_read_bytes_finish() to get the result of the operation.

During an async request no other sync and async calls are allowed on stream , and will result in G_IO_ERROR_PENDING errors.

A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.

On success, the new GBytes will be passed to the callback. It is not an error if this is smaller than the requested size, as it can happen e.g. near the end of a file, but generally we try to read as many bytes as requested. Zero is returned on end of file (or if count is zero), but never otherwise.

Any outstanding I/O request with higher priority (lower numerical value) will be executed before an outstanding request with lower priority. Default priority is G_PRIORITY_DEFAULT.

Parameters

stream

A GInputStream.

 

count

the number of bytes that will be read from the stream

 

io_priority

the I/O priority of the request

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

Since: 2.34


g_input_stream_read_bytes_finish ()

GBytes *
g_input_stream_read_bytes_finish (GInputStream *stream,
                                  GAsyncResult *result,
                                  GError **error);

Finishes an asynchronous stream read-into-GBytes operation.

Parameters

stream

a GInputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

the newly-allocated GBytes, or NULL on error.

[transfer full]

Since: 2.34

Types and Values

GInputStream

typedef struct _GInputStream GInputStream;

Base class for streaming input operations.

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