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