260 lines
9.2 KiB
Plaintext
260 lines
9.2 KiB
Plaintext
unit imjmemnobs;
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{ Delphi3 -- > jmemnobs from jmemwin }
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{ This file provides an Win32-compatible implementation of the system-
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dependent portion of the JPEG memory manager. }
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{ Check jmemnobs.c }
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{ Copyright (C) 1996, Jacques Nomssi Nzali }
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interface
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{$I imjconfig.inc}
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uses
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imjmorecfg,
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imjdeferr,
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imjerror,
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imjpeglib;
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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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const
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MAX_ALLOC_CHUNK = long(1000000000);
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{GLOBAL}
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procedure jpeg_open_backing_store (cinfo : j_common_ptr;
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info : backing_store_ptr;
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total_bytes_needed : long);
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{ These routines take care of any system-dependent initialization and
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cleanup required. }
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{GLOBAL}
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function jpeg_mem_init (cinfo : j_common_ptr) : long;
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{GLOBAL}
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procedure jpeg_mem_term (cinfo : j_common_ptr);
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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 NIL 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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{ Near-memory allocation and freeing are controlled by the regular library
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routines malloc() and free(). }
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{GLOBAL}
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function jpeg_get_small (cinfo : j_common_ptr;
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sizeofobject : size_t) : pointer;
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{GLOBAL}
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{object is a reserved word in Borland Pascal }
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procedure jpeg_free_small (cinfo : j_common_ptr;
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an_object : pointer;
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sizeofobject : size_t);
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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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{ "Large" objects are allocated in far memory, if possible }
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{GLOBAL}
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function jpeg_get_large (cinfo : j_common_ptr;
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sizeofobject : size_t) : voidp; {far}
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{GLOBAL}
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procedure jpeg_free_large (cinfo : j_common_ptr;
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{var?} an_object : voidp; {FAR}
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sizeofobject : size_t);
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{ This routine computes the total memory space available for allocation.
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It's impossible to do this in a portable way; our current solution is
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to make the user tell us (with a default value set at compile time).
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If you can actually get the available space, it's a good idea to subtract
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a slop factor of 5% or so. }
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{GLOBAL}
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function jpeg_mem_available (cinfo : j_common_ptr;
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min_bytes_needed : long;
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max_bytes_needed : long;
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already_allocated : long) : long;
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implementation
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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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{ 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 NIL 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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{ Near-memory allocation and freeing are controlled by the regular library
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routines malloc() and free(). }
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{GLOBAL}
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function jpeg_get_small (cinfo : j_common_ptr;
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sizeofobject : size_t) : pointer;
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var
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p : pointer;
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begin
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GetMem(p, sizeofobject);
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jpeg_get_small := p;
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end;
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{GLOBAL}
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{object is a reserved word in Object Pascal }
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procedure jpeg_free_small (cinfo : j_common_ptr;
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an_object : pointer;
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sizeofobject : size_t);
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begin
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FreeMem(an_object, sizeofobject);
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end;
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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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{GLOBAL}
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function jpeg_get_large (cinfo : j_common_ptr;
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sizeofobject : size_t) : voidp; {far}
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var
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p : pointer;
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begin
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GetMem(p, sizeofobject);
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jpeg_get_large := p;
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end;
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{GLOBAL}
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procedure jpeg_free_large (cinfo : j_common_ptr;
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{var?} an_object : voidp; {FAR}
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sizeofobject : size_t);
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begin
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Freemem(an_object, sizeofobject);
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end;
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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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{ This routine computes the total memory space available for allocation.
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It's impossible to do this in a portable way; our current solution is
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to make the user tell us (with a default value set at compile time).
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If you can actually get the available space, it's a good idea to subtract
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a slop factor of 5% or so. }
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const
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DEFAULT_MAX_MEM = long(300000); { for total usage about 450K }
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{GLOBAL}
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function jpeg_mem_available (cinfo : j_common_ptr;
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min_bytes_needed : long;
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max_bytes_needed : long;
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already_allocated : long) : long;
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begin
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{jpeg_mem_available := cinfo^.mem^.max_memory_to_use - already_allocated;}
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jpeg_mem_available := max_bytes_needed;
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end;
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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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{ Initial opening of a backing-store object. }
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{GLOBAL}
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procedure jpeg_open_backing_store (cinfo : j_common_ptr;
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info : backing_store_ptr;
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total_bytes_needed : long);
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begin
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ERREXIT(cinfo, JERR_NO_BACKING_STORE);
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end;
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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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{ These routines take care of any system-dependent initialization and
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cleanup required. }
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{GLOBAL}
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function jpeg_mem_init (cinfo : j_common_ptr) : long;
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begin
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jpeg_mem_init := DEFAULT_MAX_MEM; { default for max_memory_to_use }
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end;
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{GLOBAL}
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procedure jpeg_mem_term (cinfo : j_common_ptr);
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begin
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end;
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end.
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