ot::Spinel::Buffer class

Clears the NCP frame buffer. All the frames are cleared/removed.

Sets the FrameAdded callback and its context. Subsequent calls to this method will overwrite the previous callback and its context.

Sets the FrameRemoved callback and its context. Subsequent calls to this method will overwrite the previous callback and its context.

Begins a new input frame (InFrame) to be added/written to the frame buffer. If there is a previous frame being written (for which `InFrameEnd()` has not yet been called), calling `InFrameBegin()` will discard and clear the previous unfinished frame.

Adds a single byte to current input frame. Before using this method `InFrameBegin()` must be called to start and prepare a new input frame. Otherwise, this method does nothing and returns error status `OT_ERROR_INVALID_STATE`. If no buffer space is available, this method will discard and clear the current input frame and return the error status `OT_ERROR_NO_BUFS`.

Adds data to the current input frame. Before using this method `InFrameBegin()` must be called to start and prepare a new input frame. Otherwise, this method does nothing and returns error status `OT_ERROR_INVALID_STATE`. If no buffer space is available, this method will discard and clear the current input frame and return the error status `OT_ERROR_NO_BUFS`.

Gets the current write position in the input frame. The write position is returned in @p aPosition. The saved position can later be used to overwrite the frame content (using `InFrameOverwrite()`) or discard a portion of written frame and move the write pointer back to the saved position (using `InFrameReset()`).

Overwrites the previously written content in the current input frame at a given write position. The write position @p aPostion must belong to the same input frame saved earlier with `InFrameGetPosition()`. Does not allow writing beyond the current end of the input frame (i.e., it can only write over previously added content). If writing @p aDataBufferLength bytes from write position @p aPosition goes beyond the end, this method does not change the input frame and returns error status `OT_ERROR_INVALID_ARGS`. Cannot be used if the input frame has an added `otMessage` (i.e., a previous call to `InFrameFeedMessage()`).

Resets the write position of input frame back to a previously saved position. Any previously added content after the write position is discarded. The write position @p aPosition must belong to the same input frame saved earlier with `InFrameGetPosition()`. Cannot be used if the input frame has an added `otMessage` (i.e., a previous call to `InFrameFeedMessage()`).

Gets the distance (number of bytes) from a given saved position to current end of frame. The write position @p aPosition must belong to the same input frame saved earlier with `InFrameGetPosition()`. Cannot be used if the input frame has an added `otMessage` (i.e., a previous call to `InFrameFeedMessage()`). In case of invalid argument, this method returns zero.

Finalizes/ends the current input frame being written to the buffer. Before using this method `InFrameBegin()` must be called to start and prepare a new input frame. Otherwise, this method does nothing and returns error status `OT_ERROR_INVALID_STATE`. If no buffer space is available, this method will discard and clear the frame and return error status `OT_ERROR_NO_BUFS`.

Returns the tag assigned to last successfully written/added frame to NcpBuffer (i.e., last input frame for which `InFrameEnd()` was called and returned success status). The tag is a unique value (within currently queued frames) associated with a frame in the `Buffer`. The tag can be used to identify the same frame when it is read and removed from the NcpBuffer. Tags can be compared using operator `==`.

Checks if the buffer is empty. A non-empty buffer contains at least one full frame for reading.

Begins/prepares an output frame to be read from the frame buffer if there is no current active output frame, or resets the read offset if there is a current active output frame. The NCP buffer maintains a read offset for the current frame being read. Before reading any bytes from the frame this method should be called to prepare the frame and set the read offset. If part or even all of current frame has been read, a sub-sequent call to this method will reset the read offset back to beginning of current output frame (note that the current output frame will remain unchanged even in case where a higher priority frame was written to buffer while reading current output frame). A prepared output frame will stay active as current output frame until it is explicitly removed using `OutFrameRemove()`.

Checks if the current output frame (being read) has ended. The NCP buffer maintains a read offset for the current output frame being read. This method returns `true` if the read offset has reached the end of the frame and there are no more bytes available to read, or if there is no currently active output frame.

Reads and returns the next byte from the current output frame. The NCP buffer maintains a read offset for the current output frame being read. This method reads and returns the next byte from the current frame and moves the read offset forward. If read offset is already at the end current output frame, this method returns zero.

Reads and copies bytes from the current output frame into a given buffer. The NCP buffer maintains a read offset for the current output frame being read. This method attempts to read the given number of bytes (@p aReadLength) from the current frame and copies the bytes into the given data buffer (@p aDataBuffer). It also moves the read offset forward accordingly. If there are fewer bytes remaining in current frame than the requested @p aReadLength, the available bytes are read/copied. This methods returns the number of bytes read from frame and copied into @p aDataBuffer.

Removes the current or front output frame from the buffer. If there is an active output from being read (an output frame was prepared earlier with a successful call to `OutFrameBegin()`), this method removes the current active output frame. If there is no current active frame, the front frame in the queue (the next frame which would have been read) will be removed. When a frame is removed all its associated messages will be freed. If the remove operation is successful, this method will invoke the `FrameRemovedCallback` (if not nullptr) before returning the success state.

Returns the number of bytes (length) of current or front frame in the NCP frame buffer. If there is an active output from being read (an output frame was prepared earlier with successful call to `OutFrameBegin()`), this method returns the length of the current output frame. If there is no current active frame, the length of the front frame in the queue (the next frame which would have been read) will be returned. If there is no frame in buffer, this method returns zero.

Returns the tag value associated to current or front frame in the NCP frame buffer. If there is an active output from being read (an output frame was prepared earlier with successful call to `OutFrameBegin()`), this method returns the tag associated with current output frame. If there is no current active frame, the tag associated with the front frame in the queue (the next frame which would have been read) will be returned. If there is no frame in buffer, this method returns `kInvalidTag`.