src/jpeg/jmemsys.h

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