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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 #ifdef USE_ANDROID_ASHMEM
165   short temp_file;		/* file reference number to temp file */
166   unsigned char* addr;  /* the memory address mapped to ashmem */
167   long size;            /* the requested ashmem size */
168 #else
169   /* For a typical implementation with temp files, we need: */
170   FILE * temp_file;		/* stdio reference to temp file */
171   char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
172 #endif
173 #endif
174 #endif
175 } backing_store_info;
176 
177 
178 /*
179  * Initial opening of a backing-store object.  This must fill in the
180  * read/write/close pointers in the object.  The read/write routines
181  * may take an error exit if the specified maximum file size is exceeded.
182  * (If jpeg_mem_available always returns a large value, this routine can
183  * just take an error exit.)
184  */
185 
186 EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo,
187 					  backing_store_ptr info,
188 					  long total_bytes_needed));
189 
190 
191 /*
192  * These routines take care of any system-dependent initialization and
193  * cleanup required.  jpeg_mem_init will be called before anything is
194  * allocated (and, therefore, nothing in cinfo is of use except the error
195  * manager pointer).  It should return a suitable default value for
196  * max_memory_to_use; this may subsequently be overridden by the surrounding
197  * application.  (Note that max_memory_to_use is only important if
198  * jpeg_mem_available chooses to consult it ... no one else will.)
199  * jpeg_mem_term may assume that all requested memory has been freed and that
200  * all opened backing-store objects have been closed.
201  */
202 
203 EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
204 EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));
205