bldc/include/lispbm_memory.h

/** \file lispbm_memory.h */
/*
    Copyright 2020, 2022 Joel Svensson        svenssonjoel@yahoo.se

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
   Motivation: Memory manager for allocation of strings and arrays
   that will not be be located on the lisp-heap. These kinds of values
   have thus far been allocated using the "malloc" function provided
   on the platform. Using malloc is something I want to move away from
   doing within the guts of lispBM as I want it to be possible on
   running on the bare metal.

   ** This is already done!
   Later perhaps things such as the symbol table with symbol mappings
   should also be located on this managed memory area.  Symbols,
   however, are never freed after being created in lispBM. Currently I
   dont know if that is a good idea? or if it is possible to free
   unused symbols at all. To become entirely free from malloc, the entire
   symbol table management must be rewritten.
*/

/*
  Notes:
  64Bytes = 16 * 4Byte words
  4Bytes = 32Bits = 16 * 2Bit of status

  Status Bitpatterns:
  00 - FREE or USED 4Byte word
  01 - END of a sequence of allocated words
  10 - START of a sequence of allocated words
  11 - START and END of a sequence of allocated words (a 1 word allocation)

    0  1  2  3  4  5  6  7  8  9
  [11 00 00 00 00 10 01 11 00 00]

  Favours allocation of small amounts of data.

  Requirements:
   - Memory space is a multiple of 64Bytes.
   - Memory status bitmap is the same multiple of 4Bytes.

  Number of bits in an offset from the base_address 
  MEMORY_SIZE_512  => 9
  MEMORY_SIZE_1K   => 10
  MEMORY_SIZE_2K   => 11 
  MEMORY_SIZE_1M   => 20
  MEMORY_SIZE_16M  => 24
  MEMORY_SIZE_32M  => 25
  MEMORY_SIZE_64M  => 26
  MEMORY_SIZE_128M => 27
  MEMORY_SIZE_256M => 28
  
  However, due to alignment on a address multiple of 4, the 2 least
  significant bits are zeroes. So an offset into memory of size up to
  1GB should be possible to represent within a lispBM VALUE. This that
  using the offset into memory could be used as the identity of a
  symbol when it comes to replacing the symbol table. 
   
*/
#ifndef _LISPBM_MEMORY_H_
#define _LISPBM_MEMORY_H_

#include <stdint.h>

//#define MEMORY_SIZE_64BYTES_TIMES_X(X) (64*(X))
//#define MEMORY_BITMAP_SIZE(X) (4*(X))
#define LBM_MEMORY_SIZE_64BYTES_TIMES_X(X) (16*(X))
#define LBM_MEMORY_BITMAP_SIZE(X) (X)


#define LBM_MEMORY_SIZE_512 LBM_MEMORY_SIZE_64BYTES_TIMES_X(8)
#define LBM_MEMORY_SIZE_1K LBM_MEMORY_SIZE_64BYTES_TIMES_X(16)
#define LBM_MEMORY_SIZE_2K LBM_MEMORY_SIZE_64BYTES_TIMES_X(32)
#define LBM_MEMORY_SIZE_4K LBM_MEMORY_SIZE_64BYTES_TIMES_X(64)
#define LBM_MEMORY_SIZE_8K LBM_MEMORY_SIZE_64BYTES_TIMES_X(128)
#define LBM_MEMORY_SIZE_16K LBM_MEMORY_SIZE_64BYTES_TIMES_X(256)
#define LBM_MEMORY_SIZE_32K LBM_MEMORY_SIZE_64BYTES_TIMES_X(512)
#define LBM_MEMORY_SIZE_1M LBM_MEMORY_SIZE_64BYTES_TIMES_X(16384)

#define LBM_MEMORY_BITMAP_SIZE_512 LBM_MEMORY_BITMAP_SIZE(8)
#define LBM_MEMORY_BITMAP_SIZE_1K  LBM_MEMORY_BITMAP_SIZE(16)
#define LBM_MEMORY_BITMAP_SIZE_2K  LBM_MEMORY_BITMAP_SIZE(32)
#define LBM_MEMORY_BITMAP_SIZE_4K  LBM_MEMORY_BITMAP_SIZE(64)
#define LBM_MEMORY_BITMAP_SIZE_8K  LBM_MEMORY_BITMAP_SIZE(128)
#define LBM_MEMORY_BITMAP_SIZE_16K LBM_MEMORY_BITMAP_SIZE(256)
#define LBM_MEMORY_BITMAP_SIZE_32K LBM_MEMORY_BITMAP_SIZE(512)
#define LBM_MEMORY_BITMAP_SIZE_1M  LBM_MEMORY_BITMAP_SIZE(16384)

/** Initialize the symbols and arrays memory
 *
 * \param data Pointer to an array of uint32_t for data storage.
 * \param data_size The size of the data storage array in number of uint32_t elements.
 * \param bitmap Pointer to an array of uint32_t for memory allocator meta-data.
 * \param bitmap_size The size of the meta-data in number of uint32_t elements.
 * \return
 */
extern int lbm_memory_init(uint32_t *data, uint32_t data_size,
                           uint32_t *bitmap, uint32_t bitmap_size);
/** Size of of the symbols and arrays memory in uint32_t chunks.
 *
 * \return Numberof uint32_t words.
 */
extern uint32_t lbm_memory_num_words(void);
/**
 *
 * \return The number of free words in the symbols and arrays memory.
 */
extern uint32_t lbm_memory_num_free(void);
/** Allocate a number of words from the symbols and arrays memory.
 *
 * \param num_words Number of words to allocate.
 * \return pointer to allocated array or NULL.
 */
extern uint32_t *lbm_memory_allocate(uint32_t num_words);
/** Free an allocated array int the symbols and arrays memory.
 *
 * \param ptr Pointer to array to free.
 * \return 1 on success and 0 on failure.
 */
extern int lbm_memory_free(uint32_t *ptr);

#endif