/**************************************************************************
   *
   * Copyright 2010 Pauli Nieminen.
   * All Rights Reserved.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a
   * copy of this software and associated documentation files (the
   * "Software"), to deal in the Software without restriction, including
   * without limitation the rights to use, copy, modify, merge, publish,
   * distribute, sub license, and/or sell copies of the Software, and to
   * permit persons to whom the Software is furnished to do so, subject to
   * the following conditions:
   *
   * The above copyright notice and this permission notice (including the
   * next paragraph) shall be included in all copies or substantial portions
   * of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
   * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
   * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
   * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
   * USE OR OTHER DEALINGS IN THE SOFTWARE.
   *
   *
   **************************************************************************/
  /*
   * Multipart buffer for coping data which is larger than the page size.
   *
   * Authors:
   * Pauli Nieminen <suokkos-at-gmail-dot-com>
   */
  
  #ifndef _DRM_BUFFER_H_
  #define _DRM_BUFFER_H_
  
  #include <drm/drmP.h>
  
  struct drm_buffer {
  	int iterator;
  	int size;
  	char *data[];
  };
  
  
  /**
   * Return the index of page that buffer is currently pointing at.
   */
  static inline int drm_buffer_page(struct drm_buffer *buf)
  {
  	return buf->iterator / PAGE_SIZE;
  }
  /**
   * Return the index of the current byte in the page
   */
  static inline int drm_buffer_index(struct drm_buffer *buf)
  {
  	return buf->iterator & (PAGE_SIZE - 1);
  }
  /**
   * Return number of bytes that is left to process
   */
  static inline int drm_buffer_unprocessed(struct drm_buffer *buf)
  {
  	return buf->size - buf->iterator;
  }
  
  /**
   * Advance the buffer iterator number of bytes that is given.
   */
  static inline void drm_buffer_advance(struct drm_buffer *buf, int bytes)
  {
  	buf->iterator += bytes;
  }
  
  /**
   * Allocate the drm buffer object.
   *
   *   buf: A pointer to a pointer where the object is stored.
   *   size: The number of bytes to allocate.
   */
  extern int drm_buffer_alloc(struct drm_buffer **buf, int size);
  
  /**
   * Copy the user data to the begin of the buffer and reset the processing
   * iterator.
   *
   *   user_data: A pointer the data that is copied to the buffer.
   *   size: The Number of bytes to copy.
   */
  extern int drm_buffer_copy_from_user(struct drm_buffer *buf,
  		void __user *user_data, int size);
  
  /**
   * Free the drm buffer object
   */
  extern void drm_buffer_free(struct drm_buffer *buf);
  
  /**
   * Read an object from buffer that may be split to multiple parts. If object
   * is not split function just returns the pointer to object in buffer. But in
   * case of split object data is copied to given stack object that is suplied
   * by caller.
   *
   * The processing location of the buffer is also advanced to the next byte
   * after the object.
   *
   *   objsize: The size of the objet in bytes.
   *   stack_obj: A pointer to a memory location where object can be copied.
   */
  extern void *drm_buffer_read_object(struct drm_buffer *buf,
  		int objsize, void *stack_obj);
  
  /**
   * Returns the pointer to the dword which is offset number of elements from the
   * current processing location.
   *
   * Caller must make sure that dword is not split in the buffer. This
   * requirement is easily met if all the sizes of objects in buffer are
   * multiples of dword and PAGE_SIZE is multiple dword.
   *
   * Call to this function doesn't change the processing location.
   *
   *   offset: The index of the dword relative to the internat iterator.
   */
  static inline void *drm_buffer_pointer_to_dword(struct drm_buffer *buffer,
  		int offset)
  {
  	int iter = buffer->iterator + offset * 4;
  	return &buffer->data[iter / PAGE_SIZE][iter & (PAGE_SIZE - 1)];
  }
  /**
   * Returns the pointer to the dword which is offset number of elements from
   * the current processing location.
   *
   * Call to this function doesn't change the processing location.
   *
   *   offset: The index of the byte relative to the internat iterator.
   */
  static inline void *drm_buffer_pointer_to_byte(struct drm_buffer *buffer,
  		int offset)
  {
  	int iter = buffer->iterator + offset;
  	return &buffer->data[iter / PAGE_SIZE][iter & (PAGE_SIZE - 1)];
  }
  
  #endif