openjpeg/libopenjpeg/cio.c

/*
 * Copyright (c) 2002-2007, Communications and Remote Sensing Laboratory, Universite catholique de Louvain (UCL), Belgium
 * Copyright (c) 2002-2007, Professor Benoit Macq
 * Copyright (c) 2001-2003, David Janssens
 * Copyright (c) 2002-2003, Yannick Verschueren
 * Copyright (c) 2003-2007, Francois-Olivier Devaux and Antonin Descampe
 * Copyright (c) 2005, Herve Drolon, FreeImage Team
 * Copyright (c) 2008, Jerome Fimes, Communications & Systemes <jerome.fimes@c-s.fr>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS `AS IS'
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "cio.h"
#include "opj_includes.h"
#include "opj_malloc.h"
#include "event.h"

/* ----------------------------------------------------------------------- */


/**
 * Write some bytes to the given data buffer, this function is used in Big Endian cpus.
 * @param p_buffer		pointer the data buffer to write data to.
 * @param p_value		the value to write
 * @param p_nb_bytes	the number of bytes to write
*/
void opj_write_bytes_BE (OPJ_BYTE * p_buffer, OPJ_UINT32 p_value, OPJ_UINT32 p_nb_bytes)
{
	const OPJ_BYTE * l_data_ptr = ((const OPJ_BYTE *) &p_value) + p_nb_bytes;
	assert(p_nb_bytes > 0 && p_nb_bytes <=  sizeof(OPJ_UINT32));
	memcpy(p_buffer,l_data_ptr,p_nb_bytes);
}

/**
 * Write some bytes to the given data buffer, this function is used in Little Endian cpus.
 * @param p_buffer		pointer the data buffer to write data to.
 * @param p_value		the value to write
 * @param p_nb_bytes	the number of bytes to write
 * @return				the number of bytes written or -1 if an error occured
*/
void opj_write_bytes_LE (OPJ_BYTE * p_buffer, OPJ_UINT32 p_value, OPJ_UINT32 p_nb_bytes)
{
	const OPJ_BYTE * l_data_ptr = ((const OPJ_BYTE *) &p_value) + p_nb_bytes - 1;
	OPJ_UINT32 i;

	assert(p_nb_bytes > 0 && p_nb_bytes <= sizeof(OPJ_UINT32));
	for
		(i=0;i<p_nb_bytes;++i)
	{
		*(p_buffer++) = *(l_data_ptr--);
	}
}

/**
 * Reads some bytes from the given data buffer, this function is used in Big Endian cpus.
 * @param p_buffer		pointer the data buffer to read data from.
 * @param p_value		pointer to the value that will store the data.
 * @param p_nb_bytes	the nb bytes to read.
 * @return				the number of bytes read or -1 if an error occured.
 */
void opj_read_bytes_BE(const OPJ_BYTE * p_buffer, OPJ_UINT32 * p_value, OPJ_UINT32 p_nb_bytes)
{
	OPJ_BYTE * l_data_ptr = ((OPJ_BYTE *) p_value);
	assert(p_nb_bytes > 0 && p_nb_bytes <= sizeof(OPJ_UINT32));
	*p_value = 0;
	memcpy(l_data_ptr+4-p_nb_bytes,p_buffer,p_nb_bytes);
}

/**
 * Reads some bytes from the given data buffer, this function is used in Little Endian cpus.
 * @param p_buffer		pointer the data buffer to read data from.
 * @param p_value		pointer to the value that will store the data.
 * @param p_nb_bytes	the nb bytes to read.
 * @return				the number of bytes read or -1 if an error occured.
 */
void opj_read_bytes_LE(const OPJ_BYTE * p_buffer, OPJ_UINT32 * p_value, OPJ_UINT32 p_nb_bytes)
{
	OPJ_BYTE * l_data_ptr = ((OPJ_BYTE *) p_value) + p_nb_bytes-1;
	OPJ_UINT32 i;

	assert(p_nb_bytes > 0 && p_nb_bytes <= sizeof(OPJ_UINT32));
	*p_value = 0;
	for
		(i=0;i<p_nb_bytes;++i)
	{
		*(l_data_ptr--) = *(p_buffer++);
	}
}

/**
 * Write some bytes to the given data buffer, this function is used in Big Endian cpus.
 * @param p_buffer		pointer the data buffer to write data to.
 * @param p_value		the value to write
 * @return				the number of bytes written or -1 if an error occured
 */
void opj_write_double_BE(OPJ_BYTE * p_buffer, OPJ_FLOAT64 p_value)
{
	const OPJ_BYTE * l_data_ptr = ((const OPJ_BYTE *) &p_value);
	memcpy(p_buffer,l_data_ptr,sizeof(OPJ_FLOAT64));
}

/**
 * Write some bytes to the given data buffer, this function is used in Little Endian cpus.
 * @param p_buffer		pointer the data buffer to write data to.
 * @param p_value		the value to write
 */
void opj_write_double_LE(OPJ_BYTE * p_buffer, OPJ_FLOAT64 p_value)
{
	const OPJ_BYTE * l_data_ptr = ((const OPJ_BYTE *) &p_value) + sizeof(OPJ_FLOAT64) - 1;
	OPJ_UINT32 i;
	for
		(i=0;i<sizeof(OPJ_FLOAT64);++i)
	{
		*(p_buffer++) = *(l_data_ptr--);
	}
}

/**
 * Reads some bytes from the given data buffer, this function is used in Big Endian cpus.
 * @param p_buffer		pointer the data buffer to read data from.
 * @param p_value		pointer to the value that will store the data.
 */
void opj_read_double_BE(const OPJ_BYTE * p_buffer, OPJ_FLOAT64 * p_value)
{
	OPJ_BYTE * l_data_ptr = ((OPJ_BYTE *) p_value);
	memcpy(l_data_ptr,p_buffer,sizeof(OPJ_FLOAT64));
}


/**
 * Reads some bytes from the given data buffer, this function is used in Little Endian cpus.
 * @param p_buffer		pointer the data buffer to read data from.
 * @param p_value		pointer to the value that will store the data.
 */
void opj_read_double_LE(const OPJ_BYTE * p_buffer, OPJ_FLOAT64 * p_value)
{
	OPJ_BYTE * l_data_ptr = ((OPJ_BYTE *) p_value) + sizeof(OPJ_FLOAT64)-1;
	OPJ_UINT32 i;
	for
		(i=0;i<sizeof(OPJ_FLOAT64);++i)
	{
		*(l_data_ptr--) = *(p_buffer++);
	}
}

/**
 * Write some bytes to the given data buffer, this function is used in Big Endian cpus.
 * @param p_buffer		pointer the data buffer to write data to.
 * @param p_value		the value to write
 * @return				the number of bytes written or -1 if an error occured
 */
void opj_write_float_BE(OPJ_BYTE * p_buffer, OPJ_FLOAT32 p_value)
{
	const OPJ_BYTE * l_data_ptr = ((const OPJ_BYTE *) &p_value);
	memcpy(p_buffer,l_data_ptr,sizeof(OPJ_FLOAT32));
}

/**
 * Write some bytes to the given data buffer, this function is used in Little Endian cpus.
 * @param p_buffer		pointer the data buffer to write data to.
 * @param p_value		the value to write
 */
void opj_write_float_LE(OPJ_BYTE * p_buffer, OPJ_FLOAT32 p_value)
{
	const OPJ_BYTE * l_data_ptr = ((const OPJ_BYTE *) &p_value) + sizeof(OPJ_FLOAT32) - 1;
	OPJ_UINT32 i;
	for
		(i=0;i<sizeof(OPJ_FLOAT32);++i)
	{
		*(p_buffer++) = *(l_data_ptr--);
	}
}

/**
 * Reads some bytes from the given data buffer, this function is used in Big Endian cpus.
 * @param p_buffer		pointer the data buffer to read data from.
 * @param p_value		pointer to the value that will store the data.
 */
void opj_read_float_BE(const OPJ_BYTE * p_buffer, OPJ_FLOAT32 * p_value)
{
	OPJ_BYTE * l_data_ptr = ((OPJ_BYTE *) p_value);
	memcpy(l_data_ptr,p_buffer,sizeof(OPJ_FLOAT32));
}


/**
 * Reads some bytes from the given data buffer, this function is used in Little Endian cpus.
 * @param p_buffer		pointer the data buffer to read data from.
 * @param p_value		pointer to the value that will store the data.
 */
void opj_read_float_LE(const OPJ_BYTE * p_buffer, OPJ_FLOAT32 * p_value)
{
	OPJ_BYTE * l_data_ptr = ((OPJ_BYTE *) p_value) + sizeof(OPJ_FLOAT32)-1;
	OPJ_UINT32 i;
	for
		(i=0;i<sizeof(OPJ_FLOAT32);++i)
	{
		*(l_data_ptr--) = *(p_buffer++);
	}
}


/**
 * Creates an abstract stream. This function does nothing except allocating memory and initializing the abstract stream.
 * @return a stream object.
*/
opj_stream_t* opj_stream_create(OPJ_UINT32 p_size,bool l_is_input)
{
	opj_stream_private_t * l_stream = 00;
	l_stream = (opj_stream_private_t*) opj_malloc(sizeof(opj_stream_private_t));
	if
		(! l_stream)
	{
		return 00;
	}
	memset(l_stream,0,sizeof(opj_stream_private_t));
	l_stream->m_buffer_size = p_size;
	l_stream->m_stored_data = (OPJ_BYTE *) opj_malloc(p_size);
	if
		(! l_stream->m_stored_data)
	{
		opj_free(l_stream);
		return 00;
	}
	l_stream->m_current_data = l_stream->m_stored_data;
	if
		(l_is_input)
	{
		l_stream->m_status |= opj_stream_e_input;
		l_stream->m_opj_skip = opj_stream_read_skip;
		l_stream->m_opj_seek = opj_stream_read_seek;
	}
	else
	{
		l_stream->m_status |= opj_stream_e_output;
		l_stream->m_opj_skip = opj_stream_write_skip;
		l_stream->m_opj_seek = opj_stream_write_seek;
	}
	l_stream->m_read_fn = opj_stream_default_read;
	l_stream->m_write_fn = opj_stream_default_write;
	l_stream->m_skip_fn = opj_stream_default_skip;
	l_stream->m_seek_fn = opj_stream_default_seek;

	return (opj_stream_t *) l_stream;
}

/**
 * Creates an abstract stream. This function does nothing except allocating memory and initializing the abstract stream.
 * @return a stream object.
*/
opj_stream_t* opj_stream_default_create(bool l_is_input)
{
	return opj_stream_create(J2K_STREAM_CHUNK_SIZE,l_is_input);
}

/**
 * Destroys a stream created by opj_create_stream. This function does NOT close the abstract stream. If needed the user must 
 * close its own implementation of the stream.
 */
OPJ_API void OPJ_CALLCONV opj_stream_destroy(opj_stream_t* p_stream)
{
	opj_stream_private_t* l_stream = (opj_stream_private_t*) p_stream;
	if
		(l_stream)
	{
		opj_free(l_stream->m_stored_data);
		l_stream->m_stored_data = 00;
		opj_free(l_stream);
	}

}

/**
 * Sets the given function to be used as a read function.
 * @param		p_stream	the stream to modify
 * @param		p_function	the function to use a read function.
*/
OPJ_API void OPJ_CALLCONV opj_stream_set_read_function(opj_stream_t* p_stream, opj_stream_read_fn p_function)
{
	opj_stream_private_t* l_stream = (opj_stream_private_t*) p_stream;
	if
		((!l_stream) || (! (l_stream->m_status & opj_stream_e_input)))
	{
		return;
	}
	l_stream->m_read_fn = p_function;
}

OPJ_API void OPJ_CALLCONV opj_stream_set_seek_function(opj_stream_t* p_stream, opj_stream_seek_fn p_function)
{
	opj_stream_private_t* l_stream = (opj_stream_private_t*) p_stream;
	if
		(!l_stream)
	{
		return;
	}
	l_stream->m_seek_fn = p_function;
}

/**
 * Sets the given function to be used as a write function.
 * @param		p_stream	the stream to modify
 * @param		p_function	the function to use a write function.
*/
OPJ_API void OPJ_CALLCONV opj_stream_set_write_function(opj_stream_t* p_stream, opj_stream_write_fn p_function)
{
	opj_stream_private_t* l_stream = (opj_stream_private_t*) p_stream;
	if
		((!l_stream )|| (! (l_stream->m_status & opj_stream_e_output)))
	{
		return;
	}
	l_stream->m_write_fn = p_function;
}

/**
 * Sets the given function to be used as a skip function.
 * @param		p_stream	the stream to modify
 * @param		p_function	the function to use a skip function.
*/
OPJ_API void OPJ_CALLCONV opj_stream_set_skip_function(opj_stream_t* p_stream, opj_stream_skip_fn p_function)
{
	opj_stream_private_t* l_stream = (opj_stream_private_t*) p_stream;
	if
		(! l_stream)
	{
		return;
	}
	l_stream->m_skip_fn = p_function;
}

/**
 * Sets the given data to be used as a user data for the stream.
 * @param		p_stream	the stream to modify
 * @param		p_data		the data to set.
*/
OPJ_API void OPJ_CALLCONV opj_stream_set_user_data(opj_stream_t* p_stream, void * p_data)
{
	opj_stream_private_t* l_stream = (opj_stream_private_t*) p_stream;
	l_stream->m_user_data = p_data;
}

/**
 * Reads some bytes from the stream.
 * @param		p_stream	the stream to read data from.
 * @param		p_buffer	pointer to the data buffer that will receive the data.
 * @param		p_size		number of bytes to read.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes read, or -1 if an error occured or if the stream is at the end.
 */
OPJ_UINT32 opj_stream_read_data (opj_stream_private_t * p_stream,OPJ_BYTE * p_buffer, OPJ_UINT32 p_size, opj_event_mgr_t * p_event_mgr)
{
	OPJ_UINT32 l_read_nb_bytes = 0;
	if
		(p_stream->m_bytes_in_buffer >= p_size)
	{
		memcpy(p_buffer,p_stream->m_current_data,p_size);
		p_stream->m_current_data += p_size;
		p_stream->m_bytes_in_buffer -= p_size;
		l_read_nb_bytes += p_size;
		p_stream->m_byte_offset += p_size;
		return l_read_nb_bytes;
	}

	// we are now in the case when the remaining data if not sufficient
	if
		(p_stream->m_status & opj_stream_e_end)
	{
		l_read_nb_bytes += p_stream->m_bytes_in_buffer;
		memcpy(p_buffer,p_stream->m_current_data,p_stream->m_bytes_in_buffer);
		p_stream->m_current_data += p_stream->m_bytes_in_buffer;
		p_stream->m_byte_offset += p_stream->m_bytes_in_buffer;
		p_stream->m_bytes_in_buffer = 0;
		return l_read_nb_bytes ? l_read_nb_bytes : -1;
	}

	// the flag is not set, we copy data and then do an actual read on the stream
	if
		(p_stream->m_bytes_in_buffer)
	{
		l_read_nb_bytes += p_stream->m_bytes_in_buffer;
		memcpy(p_buffer,p_stream->m_current_data,p_stream->m_bytes_in_buffer);
		p_stream->m_current_data = p_stream->m_stored_data;
		p_buffer += p_stream->m_bytes_in_buffer;
		p_size -= p_stream->m_bytes_in_buffer;
		p_stream->m_byte_offset += p_stream->m_bytes_in_buffer;
		p_stream->m_bytes_in_buffer = 0;
	}

	while
		(true)
	{
		// we should read less than a chunk -> read a chunk
		if
			(p_size < p_stream->m_buffer_size)
		{
			// we should do an actual read on the media
			p_stream->m_bytes_in_buffer = p_stream->m_read_fn(p_stream->m_stored_data,p_stream->m_buffer_size,p_stream->m_user_data);
			if
				(p_stream->m_bytes_in_buffer == -1)
			{
				// end of stream
				opj_event_msg(p_event_mgr, EVT_INFO, "Stream reached its end !\n");
				p_stream->m_bytes_in_buffer = 0;
				p_stream->m_status |= opj_stream_e_end;
				// end of stream
				return l_read_nb_bytes ? l_read_nb_bytes : -1;
			}
			else if
				(p_stream->m_bytes_in_buffer < p_size)
			{
				// not enough data
				l_read_nb_bytes += p_stream->m_bytes_in_buffer;
				memcpy(p_buffer,p_stream->m_current_data,p_stream->m_bytes_in_buffer);
				p_stream->m_current_data = p_stream->m_stored_data;
				p_buffer += p_stream->m_bytes_in_buffer;
				p_size -= p_stream->m_bytes_in_buffer;
				p_stream->m_byte_offset += p_stream->m_bytes_in_buffer;
				p_stream->m_bytes_in_buffer = 0;
			}
			else
			{
				l_read_nb_bytes += p_size;
				memcpy(p_buffer,p_stream->m_current_data,p_size);
				p_stream->m_current_data += p_size;
				p_stream->m_bytes_in_buffer -= p_size;
				p_stream->m_byte_offset += p_size;
				return l_read_nb_bytes;
			}
		}
		else
		{
			// direct read on the dest buffer
			p_stream->m_bytes_in_buffer = p_stream->m_read_fn(p_buffer,p_size,p_stream->m_user_data);
			if
				(p_stream->m_bytes_in_buffer == -1)
			{
				// end of stream
				opj_event_msg(p_event_mgr, EVT_INFO, "Stream reached its end !\n");
				p_stream->m_bytes_in_buffer = 0;
				p_stream->m_status |= opj_stream_e_end;
				// end of stream
				return l_read_nb_bytes ? l_read_nb_bytes : -1;
			}
			else if
				(p_stream->m_bytes_in_buffer < p_size)
			{
				// not enough data
				l_read_nb_bytes += p_stream->m_bytes_in_buffer;
				p_stream->m_current_data = p_stream->m_stored_data;
				p_buffer += p_stream->m_bytes_in_buffer;
				p_size -= p_stream->m_bytes_in_buffer;
				p_stream->m_byte_offset += p_stream->m_bytes_in_buffer;
				p_stream->m_bytes_in_buffer = 0;
			}
			else
			{
				// we have read the exact size
				l_read_nb_bytes += p_stream->m_bytes_in_buffer;
				p_stream->m_byte_offset += p_stream->m_bytes_in_buffer;
				p_stream->m_current_data = p_stream->m_stored_data;
				p_stream->m_bytes_in_buffer = 0;
				return l_read_nb_bytes;
			}
		}
	}
}

/**
 * Writes some bytes from the stream.
 * @param		p_stream	the stream to write data to.
 * @param		p_buffer	pointer to the data buffer holds the data to be writtent.
 * @param		p_size		number of bytes to write.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes writtent, or -1 if an error occured.
 */
OPJ_UINT32 opj_stream_write_data (opj_stream_private_t * p_stream,const OPJ_BYTE * p_buffer,OPJ_UINT32 p_size, opj_event_mgr_t * p_event_mgr)
{
	OPJ_UINT32 l_remaining_bytes = 0;
	OPJ_UINT32 l_write_nb_bytes = 0;

	if
		(p_stream->m_status & opj_stream_e_error)
	{
		return -1;
	}

	while
		(true)
	{
		l_remaining_bytes = p_stream->m_buffer_size - p_stream->m_bytes_in_buffer;
		// we have more memory than required
		if
			(l_remaining_bytes >= p_size)
		{
			memcpy(p_stream->m_current_data,p_buffer,p_size);
			p_stream->m_current_data += p_size;
			p_stream->m_bytes_in_buffer += p_size;
			l_write_nb_bytes += p_size;
			p_stream->m_byte_offset += p_size;
			return l_write_nb_bytes;
		}

		// we copy data and then do an actual read on the stream
		if
			(l_remaining_bytes)
		{
			l_write_nb_bytes += l_remaining_bytes;
			memcpy(p_stream->m_current_data,p_buffer,l_remaining_bytes);
			p_stream->m_current_data = p_stream->m_stored_data;
			p_buffer += l_remaining_bytes;
			p_size -= l_remaining_bytes;
			p_stream->m_bytes_in_buffer += l_remaining_bytes;
			p_stream->m_byte_offset += l_remaining_bytes;
		}
		if
			(! opj_stream_flush(p_stream, p_event_mgr))
		{
			return -1;
		}
	}

}

/**
 * Writes the content of the stream buffer to the stream.
 * @param		p_stream	the stream to write data to.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes written, or -1 if an error occured.
 */
bool opj_stream_flush (opj_stream_private_t * p_stream, opj_event_mgr_t * p_event_mgr)
{
	// the number of bytes written on the media.
	OPJ_UINT32 l_current_write_nb_bytes = 0;
	p_stream->m_current_data = p_stream->m_stored_data;

	while
		(p_stream->m_bytes_in_buffer)
	{
		// we should do an actual write on the media
		l_current_write_nb_bytes = p_stream->m_write_fn(p_stream->m_current_data,p_stream->m_bytes_in_buffer,p_stream->m_user_data);
		if
			(l_current_write_nb_bytes == -1)
		{
			p_stream->m_status |= opj_stream_e_error;
			opj_event_msg(p_event_mgr, EVT_INFO, "Error on writting stream!\n");
			return false;
		}
		p_stream->m_current_data += l_current_write_nb_bytes;
		p_stream->m_bytes_in_buffer -= l_current_write_nb_bytes;
	}
	p_stream->m_current_data = p_stream->m_stored_data;
	return true;
}

/**
 * Skips a number of bytes from the stream.
 * @param		p_stream	the stream to skip data from.
 * @param		p_size		the number of bytes to skip.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes skipped, or -1 if an error occured.
 */
OPJ_SIZE_T opj_stream_read_skip (opj_stream_private_t * p_stream, OPJ_SIZE_T p_size, opj_event_mgr_t * p_event_mgr)
{
	OPJ_SIZE_T l_skip_nb_bytes = 0;
	OPJ_SIZE_T l_current_skip_nb_bytes = 0;
	
	if
		(p_stream->m_bytes_in_buffer >= p_size)
	{
		p_stream->m_current_data += p_size;
		p_stream->m_bytes_in_buffer -= p_size;
		l_skip_nb_bytes += p_size;
		p_stream->m_byte_offset += l_skip_nb_bytes;
		return l_skip_nb_bytes;
	}

	// we are now in the case when the remaining data if not sufficient
	if
		(p_stream->m_status & opj_stream_e_end)
	{
		l_skip_nb_bytes += p_stream->m_bytes_in_buffer;
		p_stream->m_current_data += p_stream->m_bytes_in_buffer;
		p_stream->m_bytes_in_buffer = 0;
		p_stream->m_byte_offset += l_skip_nb_bytes;
		return l_skip_nb_bytes ? l_skip_nb_bytes : (OPJ_SIZE_T) -1;
	}
	
	// the flag is not set, we copy data and then do an actual skip on the stream
	if
		(p_stream->m_bytes_in_buffer)
	{
		l_skip_nb_bytes += p_stream->m_bytes_in_buffer;
		p_stream->m_current_data = p_stream->m_stored_data;
		p_size -= p_stream->m_bytes_in_buffer;
		p_stream->m_bytes_in_buffer = 0;
	}
	
	while
		(p_size > 0)
	{
		// we should do an actual skip on the media
		l_current_skip_nb_bytes = p_stream->m_skip_fn(p_size, p_stream->m_user_data);
		if
			(l_current_skip_nb_bytes == (OPJ_SIZE_T) -1)
		{
			opj_event_msg(p_event_mgr, EVT_INFO, "Stream reached its end !\n");
			p_stream->m_status |= opj_stream_e_end;
			p_stream->m_byte_offset += l_skip_nb_bytes;
			// end if stream
			return l_skip_nb_bytes ? l_skip_nb_bytes : (OPJ_SIZE_T) -1;
		}
		p_size -= l_current_skip_nb_bytes;
		l_skip_nb_bytes += l_current_skip_nb_bytes;
	}
	p_stream->m_byte_offset += l_skip_nb_bytes;
	return l_skip_nb_bytes;
}

/**
 * Skips a number of bytes from the stream.
 * @param		p_stream	the stream to skip data from.
 * @param		p_size		the number of bytes to skip.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes skipped, or -1 if an error occured.
 */
OPJ_SIZE_T opj_stream_write_skip (opj_stream_private_t * p_stream, OPJ_SIZE_T p_size, opj_event_mgr_t * p_event_mgr)
{
	bool l_is_written = 0;
	OPJ_SIZE_T l_current_skip_nb_bytes = 0;
	OPJ_SIZE_T l_skip_nb_bytes = 0;

	if
		(p_stream->m_status & opj_stream_e_error)
	{
		return (OPJ_SIZE_T) -1;
	}
	
	// we should flush data
	l_is_written = opj_stream_flush (p_stream, p_event_mgr);
	if
		(! l_is_written)
	{
		p_stream->m_status |= opj_stream_e_error;
		p_stream->m_bytes_in_buffer = 0;
		p_stream->m_current_data = p_stream->m_current_data;
		return (OPJ_SIZE_T) -1;
	}
	// then skip

	while
		(p_size > 0)
	{
		// we should do an actual skip on the media
		l_current_skip_nb_bytes = p_stream->m_skip_fn(p_size, p_stream->m_user_data);
		if
			(l_current_skip_nb_bytes == (OPJ_SIZE_T)-1)
		{
			opj_event_msg(p_event_mgr, EVT_INFO, "Stream error!\n");
			p_stream->m_status |= opj_stream_e_error;
			p_stream->m_byte_offset += l_skip_nb_bytes;
			// end if stream
			return l_skip_nb_bytes ? l_skip_nb_bytes : (OPJ_SIZE_T)-1;
		}
		p_size -= l_current_skip_nb_bytes;
		l_skip_nb_bytes += l_current_skip_nb_bytes;
	}
	p_stream->m_byte_offset += l_skip_nb_bytes;
	return l_skip_nb_bytes;
}

/**
 * Tells the byte offset on the stream (similar to ftell).
 * 
 * @param		p_stream	the stream to get the information from.
 * 
 * @return		the current position o fthe stream.
 */
OPJ_SIZE_T opj_stream_tell (const opj_stream_private_t * p_stream)
{
	return p_stream->m_byte_offset;
}

/**
 * Skips a number of bytes from the stream.
 * @param		p_stream	the stream to skip data from.
 * @param		p_size		the number of bytes to skip.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes skipped, or -1 if an error occured.
 */
OPJ_SIZE_T opj_stream_skip (opj_stream_private_t * p_stream, OPJ_SIZE_T p_size, opj_event_mgr_t * p_event_mgr)
{
	return p_stream->m_opj_skip(p_stream,p_size,p_event_mgr);
}


/**
 * Skips a number of bytes from the stream.
 * @param		p_stream	the stream to skip data from.
 * @param		p_size		the number of bytes to skip.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes skipped, or -1 if an error occured.
 */
bool opj_stream_read_seek (opj_stream_private_t * p_stream, OPJ_SIZE_T p_size, opj_event_mgr_t * p_event_mgr)
{
	p_stream->m_current_data = p_stream->m_stored_data;
	p_stream->m_bytes_in_buffer = 0;
	if
		(! p_stream->m_seek_fn(p_size,p_stream->m_user_data))
	{
		p_stream->m_status |= opj_stream_e_end;
		return false;
	}
	else
	{
		// reset stream status
		p_stream->m_status &= (~opj_stream_e_end);
		p_stream->m_byte_offset = p_size;

	}
	return true;
}

/**
 * Skips a number of bytes from the stream.
 * @param		p_stream	the stream to skip data from.
 * @param		p_size		the number of bytes to skip.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		the number of bytes skipped, or -1 if an error occured.
 */
bool opj_stream_write_seek (opj_stream_private_t * p_stream, OPJ_SIZE_T p_size, opj_event_mgr_t * p_event_mgr)
{
	if
		(! opj_stream_flush(p_stream,p_event_mgr))
	{
		p_stream->m_status |= opj_stream_e_error;
		return false;
	}

	p_stream->m_current_data = p_stream->m_stored_data;
	p_stream->m_bytes_in_buffer = 0;
	
	if
		(! p_stream->m_seek_fn(p_size,p_stream->m_user_data))
	{
		p_stream->m_status |= opj_stream_e_error;
		return false;
	}
	else
	{
		p_stream->m_byte_offset = p_size;
	}
	return true;
}


/**
 * Seeks a number of bytes from the stream.
 * @param		p_stream	the stream to skip data from.
 * @param		p_size		the number of bytes to skip.
 * @param		p_event_mgr	the user event manager to be notified of special events.
 * @return		true if the stream is seekable.
 */
bool opj_stream_seek (opj_stream_private_t * p_stream, OPJ_SIZE_T p_size, struct opj_event_mgr * p_event_mgr)
{
	return p_stream->m_opj_seek(p_stream,p_size,p_event_mgr);
}

/**
 * Tells if the given stream is seekable.
 */
bool opj_stream_has_seek (const opj_stream_private_t * p_stream)
{
	return p_stream->m_seek_fn != opj_stream_default_seek;
}





OPJ_UINT32 opj_stream_default_read (void * p_buffer, OPJ_UINT32 p_nb_bytes, void * p_user_data)
{
	return (OPJ_UINT32) -1;
}
OPJ_UINT32 opj_stream_default_write (void * p_buffer, OPJ_UINT32 p_nb_bytes, void * p_user_data)
{
	return (OPJ_UINT32) -1;
}
OPJ_SIZE_T opj_stream_default_skip (OPJ_SIZE_T p_nb_bytes, void * p_user_data)
{
	return (OPJ_SIZE_T) -1;
}

bool opj_stream_default_seek (OPJ_SIZE_T p_nb_bytes, void * p_user_data)
{
	return false;
}