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/src/FreeImage/Source/LibJPEG/jmemsys.h

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C++ Header | 198 lines | 68 code | 31 blank | 99 comment | 0 complexity | 23e479350ba09f9be9c09d5812165194 MD5 | raw file
  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
 47EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
 48EXTERN(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
 60EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo,
 61				       size_t sizeofobject));
 62EXTERN(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
103EXTERN(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
121typedef unsigned short XMSH;	/* type of extended-memory handles */
122typedef unsigned short EMSH;	/* type of expanded-memory handles */
123
124typedef 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
137typedef struct backing_store_struct * backing_store_ptr;
138
139typedef 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
180EXTERN(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
197EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
198EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));