/* * 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(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 *///#if 0typedef 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;//#endif/* * 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.) *///#if 0EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo,					  backing_store_ptr info,					  long total_bytes_needed));//#endif/* * 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));