/* $Log: S:\jpeg32\inc\jmemsys.h_v $ * * Rev 1.0 02 May 1995 16:16:08 JAR * Initial entry * * Rev 1.0 02 May 1995 15:57:46 JAR * Initial entry */ /* * jmemsys.h * * Copyright (C) 1992, Thomas G. Lane. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README file. * * This include file defines the interface between the system-independent * and system-dependent portions of the JPEG memory manager. (The system- * independent portion is jmemmgr.c; there are several different versions * of the system-dependent portion, and of this file for that matter.) * * This is a "generic" skeleton that may need to be modified for particular * systems. It should be usable as-is on the majority of non-MSDOS machines. */ /* * These two functions are used to allocate and release small chunks of * memory (typically the total amount requested through jget_small is * no more than 20Kb or so). Behavior should be the same as for the * standard library functions malloc and free; in particular, jget_small * returns NULL on failure. On most systems, these ARE malloc and free. * On an 80x86 machine using small-data memory model, these manage near heap. */ EXTERN void * jget_small PP((size_t sizeofobject)); EXTERN void jfree_small PP((void * object)); EXTERN void * jget_small_c PP((size_t sizeofobject)); /* * These two functions are used to allocate and release large chunks of * memory (up to the total free space designated by jmem_available). * The interface is the same as above, except that on an 80x86 machine, * far pointers are used. On other systems these ARE the same as above. */ /*#ifdef NEED_FAR_POINTERS typically not needed except on 80x86 */ /* EXTERN void FAR * jget_large PP((size_t sizeofobject)); EXTERN void FAR * jget_large_c PP((size_t sizeofobject)); EXTERN void jfree_large PP((void FAR * object)); #else */ /*#define jget_large(sizeofobject) jget_small(sizeofobject) #define jget_large_c(sizeofobject) jget_small_c(sizeofobject) #define jfree_large(object) jfree_small(object) */ EXTERN void FAR * jget_large PP((size_t sizeofobject)); EXTERN void FAR * jget_large_c PP((size_t sizeofobject)); EXTERN void jfree_large PP((void FAR * object)); /* #endif */ /* * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may * be requested in a single call on jget_large (and jget_small for that * matter, but that case should never come into play). This macro is needed * to model the 64Kb-segment-size limit of far addressing on 80x86 machines. * On machines with flat address spaces, any large constant may be used here. */ #define MAX_ALLOC_CHUNK 1000000000L /* * This routine computes the total space available for allocation by * jget_large. If more space than this is needed, backing store will be used. * NOTE: any memory already allocated must not be counted. * * There is a minimum space requirement, corresponding to the minimum * feasible buffer sizes; jmemmgr.c will request that much space even if * jmem_available returns zero. The maximum space needed, enough to hold * all working storage in memory, is also passed in case it is useful. * * It is OK for jmem_available to underestimate the space available (that'll * just lead to more backing-store access than is really necessary). * However, an overestimate will lead to failure. Hence it's wise to subtract * a slop factor from the true available space, especially if jget_small space * comes from the same pool. 5% should be enough. * * On machines with lots of virtual memory, any large constant may be returned. * Conversely, zero may be returned to always use the minimum amount of memory. */ EXTERN long jmem_available PP((long min_bytes_needed, long max_bytes_needed)); EXTERN long jmem_available_c PP((long min_bytes_needed, long max_bytes_needed)); /* * This structure holds whatever state is needed to access a single * backing-store object. The read/write/close method pointers are called * by jmemmgr.c to manipulate the backing-store object; all other fields * are private to the system-dependent backing store routines. */ #define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */ typedef struct backing_store_struct * backing_store_ptr; typedef struct backing_store_struct { /* Methods for reading/writing/closing this backing-store object */ METHOD(void, read_backing_store, (backing_store_ptr info, void FAR * buffer_address, long file_offset, long byte_count)); METHOD(void, write_backing_store, (backing_store_ptr info, void FAR * buffer_address, long file_offset, long byte_count)); METHOD(void, close_backing_store, (backing_store_ptr info)); /* Private fields for system-dependent backing-store management */ /* For a typical implementation with temp files, we might need: */ FILE * temp_file; /* stdio reference to temp file */ char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */ } backing_store_info; /* * Initial opening of a backing-store object. This must fill in the * read/write/close pointers in the object. The read/write routines * may take an error exit if the specified maximum file size is exceeded. * (If jmem_available always returns a large value, this routine can just * take an error exit.) */ EXTERN void jopen_backing_store PP((backing_store_ptr info, long total_bytes_needed)); /* * These routines take care of any system-dependent initialization and * cleanup required. The system methods struct address should be saved * by jmem_init in case an error exit must be taken. jmem_term may assume * that all requested memory has been freed and that all opened backing- * store objects have been closed. * NB: jmem_term may be called more than once, and must behave reasonably * if that happens. */ EXTERN void jmem_init PP((external_methods_ptr emethods)); EXTERN void jmem_term PP((void)); EXTERN void jmem_init_c PP((external_methods_ptr emethods));