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* Copyright (C) 1992-1997, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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* This include file defines the interface between the system-independent
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* and system-dependent portions of the JPEG memory manager. No other
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* modules need include it. (The system-independent portion is jmemmgr.c;
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* there are several different versions of the system-dependent portion.)
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* This file works as-is for the system-dependent memory managers supplied
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* in the IJG distribution. You may need to modify it if you write a
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* custom memory manager. If system-dependent changes are needed in
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* this file, the best method is to #ifdef them based on a configuration
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* symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR
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/* Short forms of external names for systems with brain-damaged linkers. */
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#ifdef NEED_SHORT_EXTERNAL_NAMES
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#define jpeg_get_small jGetSmall
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#define jpeg_free_small jFreeSmall
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#define jpeg_get_large jGetLarge
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#define jpeg_free_large jFreeLarge
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#define jpeg_mem_available jMemAvail
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#define jpeg_open_backing_store jOpenBackStore
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#define jpeg_mem_init jMemInit
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#define jpeg_mem_term jMemTerm
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#endif /* NEED_SHORT_EXTERNAL_NAMES */
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* These two functions are used to allocate and release small chunks of
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* memory. (Typically the total amount requested through jpeg_get_small is
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* no more than 20K or so; this will be requested in chunks of a few K each.)
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* Behavior should be the same as for the standard library functions malloc
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* and free; in particular, jpeg_get_small must return NULL on failure.
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* On most systems, these ARE malloc and free. jpeg_free_small is passed the
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* size of the object being freed, just in case it's needed.
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* On an 80x86 machine using small-data memory model, these manage near heap.
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EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
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EXTERN(void) jpeg_free_small JPP((j_common_ptr cinfo, void * object,
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size_t sizeofobject));
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* These two functions are used to allocate and release large chunks of
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* memory (up to the total free space designated by jpeg_mem_available).
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* The interface is the same as above, except that on an 80x86 machine,
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* far pointers are used. On most other machines these are identical to
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* the jpeg_get/free_small routines; but we keep them separate anyway,
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* in case a different allocation strategy is desirable for large chunks.
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EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo,
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size_t sizeofobject));
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EXTERN(void) jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object,
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size_t sizeofobject));
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* The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
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* be requested in a single call to jpeg_get_large (and jpeg_get_small for that
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* matter, but that case should never come into play). This macro is needed
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* to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
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* On those machines, we expect that jconfig.h will provide a proper value.
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* On machines with 32-bit flat address spaces, any large constant may be used.
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* NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
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* size_t and will be a multiple of sizeof(align_type).
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#ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */
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#define MAX_ALLOC_CHUNK 1000000000L
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* This routine computes the total space still available for allocation by
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* jpeg_get_large. If more space than this is needed, backing store will be
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* used. NOTE: any memory already allocated must not be counted.
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* There is a minimum space requirement, corresponding to the minimum
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* feasible buffer sizes; jmemmgr.c will request that much space even if
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* jpeg_mem_available returns zero. The maximum space needed, enough to hold
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* all working storage in memory, is also passed in case it is useful.
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* Finally, the total space already allocated is passed. If no better
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* method is available, cinfo->mem->max_memory_to_use - already_allocated
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* is often a suitable calculation.
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* It is OK for jpeg_mem_available to underestimate the space available
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* (that'll just lead to more backing-store access than is really necessary).
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* However, an overestimate will lead to failure. Hence it's wise to subtract
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* a slop factor from the true available space. 5% should be enough.
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* On machines with lots of virtual memory, any large constant may be returned.
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* Conversely, zero may be returned to always use the minimum amount of memory.
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EXTERN(long) jpeg_mem_available JPP((j_common_ptr cinfo,
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long min_bytes_needed,
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long max_bytes_needed,
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long already_allocated));
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* This structure holds whatever state is needed to access a single
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* backing-store object. The read/write/close method pointers are called
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* by jmemmgr.c to manipulate the backing-store object; all other fields
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* are private to the system-dependent backing store routines.
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#define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */
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#ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */
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typedef unsigned short XMSH; /* type of extended-memory handles */
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typedef unsigned short EMSH; /* type of expanded-memory handles */
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short file_handle; /* DOS file handle if it's a temp file */
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XMSH xms_handle; /* handle if it's a chunk of XMS */
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EMSH ems_handle; /* handle if it's a chunk of EMS */
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#endif /* USE_MSDOS_MEMMGR */
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#ifdef USE_MAC_MEMMGR /* Mac-specific junk */
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#endif /* USE_MAC_MEMMGR */
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typedef struct backing_store_struct * backing_store_ptr;
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typedef struct backing_store_struct {
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/* Methods for reading/writing/closing this backing-store object */
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JMETHOD(void, read_backing_store, (j_common_ptr cinfo,
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backing_store_ptr info,
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void FAR * buffer_address,
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long file_offset, long byte_count));
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JMETHOD(void, write_backing_store, (j_common_ptr cinfo,
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backing_store_ptr info,
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void FAR * buffer_address,
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long file_offset, long byte_count));
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JMETHOD(void, close_backing_store, (j_common_ptr cinfo,
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backing_store_ptr info));
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/* Private fields for system-dependent backing-store management */
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#ifdef USE_MSDOS_MEMMGR
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/* For the MS-DOS manager (jmemdos.c), we need: */
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handle_union handle; /* reference to backing-store storage object */
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char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
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#ifdef USE_MAC_MEMMGR
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/* For the Mac manager (jmemmac.c), we need: */
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short temp_file; /* file reference number to temp file */
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FSSpec tempSpec; /* the FSSpec for the temp file */
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char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
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/* For a typical implementation with temp files, we need: */
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FILE * temp_file; /* stdio reference to temp file */
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char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
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} backing_store_info;
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* Initial opening of a backing-store object. This must fill in the
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* read/write/close pointers in the object. The read/write routines
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* may take an error exit if the specified maximum file size is exceeded.
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* (If jpeg_mem_available always returns a large value, this routine can
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* just take an error exit.)
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EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo,
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backing_store_ptr info,
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long total_bytes_needed));
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* These routines take care of any system-dependent initialization and
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* cleanup required. jpeg_mem_init will be called before anything is
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* allocated (and, therefore, nothing in cinfo is of use except the error
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* manager pointer). It should return a suitable default value for
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* max_memory_to_use; this may subsequently be overridden by the surrounding
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* application. (Note that max_memory_to_use is only important if
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* jpeg_mem_available chooses to consult it ... no one else will.)
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* jpeg_mem_term may assume that all requested memory has been freed and that
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* all opened backing-store objects have been closed.
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EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
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EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));
added
removed
jpeg/jmemsys.h
