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 /*

  * jmemsys.h

  *

  * Copyright (C) 1992-1997, Thomas G. Lane.

  * This file is part of the Independent JPEG Group's software.

  * For conditions of distribution and use, see the accompanying README file.

  *

  * This include file defines the interface between the system-independent

  * and system-dependent portions of the JPEG memory manager.  No other

  * modules need include it.  (The system-independent portion is jmemmgr.c;

  * there are several different versions of the system-dependent portion.)

  *

  * This file works as-is for the system-dependent memory managers supplied

  * in the IJG distribution.  You may need to modify it if you write a

  * custom memory manager.  If system-dependent changes are needed in

  * this file, the best method is to #ifdef them based on a configuration

  * symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR

  * and USE_MAC_MEMMGR.

  */

 /* 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 NULL 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 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 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(size_t) jpeg_mem_available JPP((j_common_ptr cinfo,

 				     size_t min_bytes_needed,

 				     size_t max_bytes_needed,

 				     size_t 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));