compiler/libjpeg/main/jmemsys.h

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * jmemsys.h
   7  *
   8  * Copyright (C) 1992-1997, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This include file defines the interface between the system-independent
  13  * and system-dependent portions of the JPEG memory manager.  No other
  14  * modules need include it.  (The system-independent portion is jmemmgr.c;
  15  * there are several different versions of the system-dependent portion.)
  16  *
  17  * This file works as-is for the system-dependent memory managers supplied
  18  * in the IJG distribution.  You may need to modify it if you write a
  19  * custom memory manager.  If system-dependent changes are needed in
  20  * this file, the best method is to #ifdef them based on a configuration
  21  * symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR
  22  * and USE_MAC_MEMMGR.
  23  */
  24
  25
  26 /* Short forms of external names for systems with brain-damaged linkers. */
  27
  28 #ifdef NEED_SHORT_EXTERNAL_NAMES
  29 #define jpeg_get_small          jGetSmall
  30 #define jpeg_free_small         jFreeSmall
  31 #define jpeg_get_large          jGetLarge
  32 #define jpeg_free_large         jFreeLarge
  33 #define jpeg_mem_available      jMemAvail
  34 #define jpeg_open_backing_store jOpenBackStore
  35 #define jpeg_mem_init           jMemInit
  36 #define jpeg_mem_term           jMemTerm
  37 #endif /* NEED_SHORT_EXTERNAL_NAMES */
  38
  39
  40 /*
  41  * These two functions are used to allocate and release small chunks of
  42  * memory.  (Typically the total amount requested through jpeg_get_small is
  43  * no more than 20K or so; this will be requested in chunks of a few K each.)
  44  * Behavior should be the same as for the standard library functions malloc
  45  * and free; in particular, jpeg_get_small must return NULL on failure.
  46  * On most systems, these ARE malloc and free.  jpeg_free_small is passed the
  47  * size of the object being freed, just in case it's needed.
  48  * On an 80x86 machine using small-data memory model, these manage near heap.
  49  */
  50
  51 JEXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
  52 JEXTERN(void) jpeg_free_small JPP((j_common_ptr cinfo, void * object,
  53                                   size_t sizeofobject));
  54
  55 /*
  56  * These two functions are used to allocate and release large chunks of
  57  * memory (up to the total free space designated by jpeg_mem_available).
  58  * The interface is the same as above, except that on an 80x86 machine,
  59  * far pointers are used.  On most other machines these are identical to
  60  * the jpeg_get/free_small routines; but we keep them separate anyway,
  61  * in case a different allocation strategy is desirable for large chunks.
  62  */
  63
  64 JEXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo,
  65                                        size_t sizeofobject));
  66 JEXTERN(void) jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object,
  67                                   size_t sizeofobject));
  68
  69 /*
  70  * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
  71  * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
  72  * matter, but that case should never come into play).  This macro is needed
  73  * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
  74  * On those machines, we expect that jconfig.h will provide a proper value.
  75  * On machines with 32-bit flat address spaces, any large constant may be used.
  76  *
  77  * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
  78  * size_t and will be a multiple of sizeof(align_type).
  79  */
  80
  81 #ifndef MAX_ALLOC_CHUNK         /* may be overridden in jconfig.h */
  82 #define MAX_ALLOC_CHUNK  1000000000L
  83 #endif
  84
  85 /*
  86  * This routine computes the total space still available for allocation by
  87  * jpeg_get_large.  If more space than this is needed, backing store will be
  88  * used.  NOTE: any memory already allocated must not be counted.
  89  *
  90  * There is a minimum space requirement, corresponding to the minimum
  91  * feasible buffer sizes; jmemmgr.c will request that much space even if
  92  * jpeg_mem_available returns zero.  The maximum space needed, enough to hold
  93  * all working storage in memory, is also passed in case it is useful.
  94  * Finally, the total space already allocated is passed.  If no better
  95  * method is available, cinfo->mem->max_memory_to_use - already_allocated
  96  * is often a suitable calculation.
  97  *
  98  * It is OK for jpeg_mem_available to underestimate the space available
  99  * (that'll just lead to more backing-store access than is really necessary).
 100  * However, an overestimate will lead to failure.  Hence it's wise to subtract
 101  * a slop factor from the true available space.  5% should be enough.
 102  *
 103  * On machines with lots of virtual memory, any large constant may be returned.
 104  * Conversely, zero may be returned to always use the minimum amount of memory.
 105  */
 106
 107 JEXTERN(long) jpeg_mem_available JPP((j_common_ptr cinfo,
 108                                      long min_bytes_needed,
 109                                      long max_bytes_needed,
 110                                      long already_allocated));
 111
 112
 113 /*
 114  * This structure holds whatever state is needed to access a single
 115  * backing-store object.  The read/write/close method pointers are called
 116  * by jmemmgr.c to manipulate the backing-store object; all other fields
 117  * are private to the system-dependent backing store routines.
 118  */
 119
 120 #define TEMP_NAME_LENGTH   64   /* max length of a temporary file's name */
 121
 122
 123 #ifdef USE_MSDOS_MEMMGR         /* DOS-specific junk */
 124
 125 typedef unsigned short XMSH;    /* type of extended-memory handles */
 126 typedef unsigned short EMSH;    /* type of expanded-memory handles */
 127
 128 typedef union {
 129   short file_handle;            /* DOS file handle if it's a temp file */
 130   XMSH xms_handle;              /* handle if it's a chunk of XMS */
 131   EMSH ems_handle;              /* handle if it's a chunk of EMS */
 132 } handle_union;
 133
 134 #endif /* USE_MSDOS_MEMMGR */
 135
 136 #ifdef USE_MAC_MEMMGR           /* Mac-specific junk */
 137 #include <Files.h>
 138 #endif /* USE_MAC_MEMMGR */
 139
 140
 141 typedef struct backing_store_struct * backing_store_ptr;
 142
 143 typedef struct backing_store_struct {
 144   /* Methods for reading/writing/closing this backing-store object */
 145   JMETHOD(void, read_backing_store, (j_common_ptr cinfo,
 146                                      backing_store_ptr info,
 147                                      void FAR * buffer_address,
 148                                      long file_offset, long byte_count));
 149   JMETHOD(void, write_backing_store, (j_common_ptr cinfo,
 150                                       backing_store_ptr info,
 151                                       void FAR * buffer_address,
 152                                       long file_offset, long byte_count));
 153   JMETHOD(void, close_backing_store, (j_common_ptr cinfo,
 154                                       backing_store_ptr info));
 155
 156   /* Private fields for system-dependent backing-store management */
 157 #ifdef USE_MSDOS_MEMMGR
 158   /* For the MS-DOS manager (jmemdos.c), we need: */
 159   handle_union handle;          /* reference to backing-store storage object */
 160   char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
 161 #else
 162 #ifdef USE_MAC_MEMMGR
 163   /* For the Mac manager (jmemmac.c), we need: */
 164   short temp_file;              /* file reference number to temp file */
 165   FSSpec tempSpec;              /* the FSSpec for the temp file */
 166   char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
 167 #else
 168   /* For a typical implementation with temp files, we need: */
 169   FILE * temp_file;             /* stdio reference to temp file */
 170   char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
 171 #endif
 172 #endif
 173 } backing_store_info;
 174
 175
 176 /*
 177  * Initial opening of a backing-store object.  This must fill in the
 178  * read/write/close pointers in the object.  The read/write routines
 179  * may take an error exit if the specified maximum file size is exceeded.
 180  * (If jpeg_mem_available always returns a large value, this routine can
 181  * just take an error exit.)
 182  */
 183
 184 JEXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo,
 185                                           backing_store_ptr info,
 186                                           long total_bytes_needed));
 187
 188
 189 /*
 190  * These routines take care of any system-dependent initialization and
 191  * cleanup required.  jpeg_mem_init will be called before anything is
 192  * allocated (and, therefore, nothing in cinfo is of use except the error
 193  * manager pointer).  It should return a suitable default value for
 194  * max_memory_to_use; this may subsequently be overridden by the surrounding
 195  * application.  (Note that max_memory_to_use is only important if
 196  * jpeg_mem_available chooses to consult it ... no one else will.)
 197  * jpeg_mem_term may assume that all requested memory has been freed and that
 198  * all opened backing-store objects have been closed.
 199  */
 200
 201 JEXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
 202 JEXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));