jmemsys.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

/* Short forms of external names for systems with brain-damaged linkers. */

#ifdef NEED_SHORT_EXTERNAL_NAMES
#define jpeg_get_small jGetSmall
#define jpeg_free_small jFreeSmall
#define jpeg_get_large jGetLarge
#define jpeg_free_large jFreeLarge
#define jpeg_mem_available jMemAvail
#define jpeg_open_backing_store jOpenBackStore
#define jpeg_mem_init jMemInit
#define jpeg_mem_term jMemTerm
#endif /* NEED_SHORT_EXTERNAL_NAMES */

/*
 * These two functions are used to allocate and release small chunks of
 * memory.  (Typically the total amount requested through jpeg_get_small is
 * no more than 20K or so; this will be requested in chunks of a few K each.)
 * Behavior should be the same as for the standard library functions malloc
 * and free; in particular, jpeg_get_small must return nullptr on failure.
 * On most systems, these ARE malloc and free.  jpeg_free_small is passed the
 * size of the object being freed, just in case it's needed.
 * On an 80x86 machine using small-data memory model, these manage near heap.
 */

EXTERN(void*) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
EXTERN(void)
jpeg_free_small JPP((j_common_ptr cinfo, void* object, size_t sizeofobject));

/*
 * These two functions are used to allocate and release large chunks of
 * memory (up to the total free space designated by jpeg_mem_available).
 * The interface is the same as above, except that on an 80x86 machine,
 * far pointers are used.  On most other machines these are identical to
 * the jpeg_get/free_small routines; but we keep them separate anyway,
 * in case a different allocation strategy is desirable for large chunks.
 */

EXTERN(void FAR*) jpeg_get_large JPP((j_common_ptr cinfo, size_t sizeofobject));
EXTERN(void)
jpeg_free_large JPP(
        (j_common_ptr cinfo, void FAR* object, size_t sizeofobject));

/*
 * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
 * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
 * matter, but that case should never come into play).  This macro is needed
 * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
 * On those machines, we expect that mrpt_jconfig.h will provide a proper value.
 * On machines with 32-bit flat address spaces, any large constant may be used.
 *
 * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
 * size_t and will be a multiple of sizeof(align_type).
 */

#ifndef MAX_ALLOC_CHUNK /* may be overridden in mrpt_jconfig.h */
#define MAX_ALLOC_CHUNK 1000000000L
#endif

/*
 * This routine computes the total space still available for allocation by
 * jpeg_get_large.  If more space than this is needed, backing store will be
 * used.  NOTE: any memory already allocated must not be counted.
 *
 * There is a minimum space requirement, corresponding to the minimum
 * feasible buffer sizes; jmemmgr.c will request that much space even if
 * jpeg_mem_available returns zero.  The maximum space needed, enough to hold
 * all working storage in memory, is also passed in case it is useful.
 * Finally, the total space already allocated is passed.  If no better
 * method is available, cinfo->mem->max_memory_to_use - already_allocated
 * is often a suitable calculation.
 *
 * It is OK for jpeg_mem_available to underestimate the space available
 * (that'll just lead to more backing-store access than is really necessary).
 * However, an overestimate will lead to failure.  Hence it's wise to subtract
 * a slop factor from the true available space.  5% should be enough.
 *
 * On machines with lots of virtual memory, any large constant may be returned.
 * Conversely, zero may be returned to always use the minimum amount of memory.
 */

EXTERN(long)
jpeg_mem_available JPP(
        (j_common_ptr cinfo, long min_bytes_needed, long max_bytes_needed,
         long already_allocated));

/*
 * This structure holds whatever state is needed to access a single
 * backing-store object.  The read/write/close method pointers are called
 * by jmemmgr.c to manipulate the backing-store object; all other fields
 * are private to the system-dependent backing store routines.
 */

#define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */

#ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */

typedef unsigned short XMSH; /* type of extended-memory handles */
typedef unsigned short EMSH; /* type of expanded-memory handles */

typedef union {
        short file_handle; /* DOS file handle if it's a temp file */
        XMSH xms_handle; /* handle if it's a chunk of XMS */
        EMSH ems_handle; /* handle if it's a chunk of EMS */
} handle_union;

#endif /* USE_MSDOS_MEMMGR */

#ifdef USE_MAC_MEMMGR /* Mac-specific junk */
#include <Files.h>
#endif /* USE_MAC_MEMMGR */

typedef struct backing_store_struct* backing_store_ptr;

typedef struct backing_store_struct
{
        /* Methods for reading/writing/closing this backing-store object */
        JMETHOD(
                void, read_backing_store,
                (j_common_ptr cinfo, backing_store_ptr info, void FAR* buffer_address,
                 long file_offset, long byte_count));
        JMETHOD(
                void, write_backing_store,
                (j_common_ptr cinfo, backing_store_ptr info, void FAR* buffer_address,
                 long file_offset, long byte_count));
        JMETHOD(
                void, close_backing_store,
                (j_common_ptr cinfo, backing_store_ptr info));

/* Private fields for system-dependent backing-store management */
#ifdef USE_MSDOS_MEMMGR
        /* For the MS-DOS manager (jmemdos.c), we need: */
        handle_union handle; /* reference to backing-store storage object */
        char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
#else
#ifdef USE_MAC_MEMMGR
        /* For the Mac manager (jmemmac.c), we need: */
        short temp_file; /* file reference number to temp file */
        FSSpec tempSpec; /* the FSSpec for the temp file */
        char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
#else
        /* For a typical implementation with temp files, we need: */
        FILE* temp_file; /* stdio reference to temp file */
        char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
#endif
#endif
} backing_store_info;

/*
 * Initial opening of a backing-store object.  This must fill in the
 * read/write/close pointers in the object.  The read/write routines
 * may take an error exit if the specified maximum file size is exceeded.
 * (If jpeg_mem_available always returns a large value, this routine can
 * just take an error exit.)
 */

EXTERN(void)
jpeg_open_backing_store JPP(
        (j_common_ptr cinfo, backing_store_ptr info, long total_bytes_needed));

/*
 * These routines take care of any system-dependent initialization and
 * cleanup required.  jpeg_mem_init will be called before anything is
 * allocated (and, therefore, nothing in cinfo is of use except the error
 * manager pointer).  It should return a suitable default value for
 * max_memory_to_use; this may subsequently be overridden by the surrounding
 * application.  (Note that max_memory_to_use is only important if
 * jpeg_mem_available chooses to consult it ... no one else will.)
 * jpeg_mem_term may assume that all requested memory has been freed and that
 * all opened backing-store objects have been closed.
 */

EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));