The Independent JPEG Group's JPEG software v5

1 files changed, 113 insertions, 58 deletions

diff --git a/jmemsys.h b/jmemsys.h
index 1766a95..033d29a 100644
--- a/jmemsys.h
+++ b/jmemsys.h
@@ -1,78 +1,107 @@
 /*
  * jmemsys.h
  *
- * Copyright (C) 1992, Thomas G. Lane.
+ * Copyright (C) 1992-1994, 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.)
+ * and system-dependent portions of the JPEG memory manager.  No other
+ * modules need include it.  (The system-independent portion is jmemmgr.c;
+ * there are several different versions of the system-dependent portion.)
  *
- * 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.
+ * This file works as-is for the system-dependent memory managers supplied
+ * in the IJG distribution.  You may need to modify it if you write a
+ * custom memory manager.  If system-dependent changes are needed in
+ * this file, the best method is to #ifdef them based on a configuration
+ * symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR.
  */
 
 
+/* Short forms of external names for systems with brain-damaged linkers. */
+
+#ifdef NEED_SHORT_EXTERNAL_NAMES
+#define jpeg_get_small		jGetSmall
+#define jpeg_free_small		jFreeSmall
+#define jpeg_get_large		jGetLarge
+#define jpeg_free_large		jFreeLarge
+#define jpeg_mem_available	jMemAvail
+#define jpeg_open_backing_store	jOpenBackStore
+#define jpeg_mem_init		jMemInit
+#define jpeg_mem_term		jMemTerm
+#endif /* NEED_SHORT_EXTERNAL_NAMES */
+
+
 /*
  * 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.
+ * memory.  (Typically the total amount requested through jpeg_get_small is
+ * no more than 20K or so; this will be requested in chunks of a few K each.)
+ * Behavior should be the same as for the standard library functions malloc
+ * and free; in particular, jpeg_get_small must return NULL on failure.
+ * On most systems, these ARE malloc and free.  jpeg_free_small is passed the
+ * size of the object being freed, just in case it's needed.
  * 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 * jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
+EXTERN void jpeg_free_small JPP((j_common_ptr cinfo, void * object,
+				 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).
+ * memory (up to the total free space designated by jpeg_mem_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.
+ * far pointers are used.  On most other machines these are identical to
+ * the jpeg_get/free_small routines; but we keep them separate anyway,
+ * in case a different allocation strategy is desirable for large chunks.
  */
 
-#ifdef NEED_FAR_POINTERS	/* typically not needed except on 80x86 */
-EXTERN void FAR * jget_large PP((size_t sizeofobject));
-EXTERN void jfree_large PP((void FAR * object));
-#else
-#define jget_large(sizeofobject)	jget_small(sizeofobject)
-#define jfree_large(object)		jfree_small(object)
-#endif
+EXTERN void FAR * jpeg_get_large JPP((j_common_ptr cinfo,size_t sizeofobject));
+EXTERN void jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object,
+				 size_t sizeofobject));
 
 /*
  * 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
+ * be requested in a single call to jpeg_get_large (and jpeg_get_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.
+ * On those machines, we expect that jconfig.h will provide a proper value.
+ * On machines with 32-bit flat address spaces, any large constant may be used.
+ *
+ * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
+ * size_t and will be a multiple of sizeof(align_type).
  */
 
-#define MAX_ALLOC_CHUNK		1000000000L
+#ifndef MAX_ALLOC_CHUNK		/* may be overridden in jconfig.h */
+#define MAX_ALLOC_CHUNK  1000000000L
+#endif
 
 /*
- * 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.
+ * This routine computes the total space still available for allocation by
+ * jpeg_get_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
+ * jpeg_mem_available returns zero.  The maximum space needed, enough to hold
  * all working storage in memory, is also passed in case it is useful.
+ * Finally, the total space already allocated is passed.  If no better
+ * method is available, cinfo->mem->max_memory_to_use - already_allocated
+ * is often a suitable calculation.
  *
- * It is OK for jmem_available to underestimate the space available (that'll
- * just lead to more backing-store access than is really necessary).
+ * It is OK for jpeg_mem_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.
+ * a slop factor from the true available space.  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 jpeg_mem_available JPP((j_common_ptr cinfo,
+				    long min_bytes_needed,
+				    long max_bytes_needed,
+				    long already_allocated));
 
 
 /*
@@ -84,44 +113,70 @@ EXTERN long jmem_available PP((long min_bytes_needed, long max_bytes_needed));
 
 #define TEMP_NAME_LENGTH   64	/* max length of a temporary file's name */
 
+#ifdef USE_MSDOS_MEMMGR		/* DOS-specific junk */
+
+typedef unsigned short XMSH;	/* type of extended-memory handles */
+typedef unsigned short EMSH;	/* type of expanded-memory handles */
+
+typedef union {
+  short file_handle;		/* DOS file handle if it's a temp file */
+  XMSH xms_handle;		/* handle if it's a chunk of XMS */
+  EMSH ems_handle;		/* handle if it's a chunk of EMS */
+} handle_union;
+
+#endif /* USE_MSDOS_MEMMGR */
+
 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;
+  /* Methods for reading/writing/closing this backing-store object */
+  JMETHOD(void, read_backing_store, (j_common_ptr cinfo,
+				     backing_store_ptr info,
+				     void FAR * buffer_address,
+				     long file_offset, long byte_count));
+  JMETHOD(void, write_backing_store, (j_common_ptr cinfo,
+				      backing_store_ptr info,
+				      void FAR * buffer_address,
+				      long file_offset, long byte_count));
+  JMETHOD(void, close_backing_store, (j_common_ptr cinfo,
+				      backing_store_ptr info));
+
+  /* Private fields for system-dependent backing-store management */
+#ifdef USE_MSDOS_MEMMGR
+  /* For the MS-DOS manager (jmemdos.c), we need: */
+  handle_union handle;		/* reference to backing-store storage object */
+  char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
+#else
+  /* For a typical implementation with temp files, we need: */
+  FILE * temp_file;		/* stdio reference to temp file */
+  char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
+#endif
+} 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.)
+ * (If jpeg_mem_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));
+EXTERN void jpeg_open_backing_store JPP((j_common_ptr cinfo,
+					 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.
+ * cleanup required.  jpeg_mem_init will be called before anything is
+ * allocated (and, therefore, nothing in cinfo is of use except the error
+ * manager pointer).  It should return a suitable default value for
+ * max_memory_to_use; this may subsequently be overridden by the surrounding
+ * application.  (Note that max_memory_to_use is only important if
+ * jpeg_mem_available chooses to consult it ... no one else will.)
+ * jpeg_mem_term may assume that all requested memory has been freed and that
+ * all opened backing-store objects have been closed.
  */
 
-EXTERN void jmem_init PP((external_methods_ptr emethods));
-EXTERN void jmem_term PP((void));
+EXTERN long jpeg_mem_init JPP((j_common_ptr cinfo));
+EXTERN void jpeg_mem_term JPP((j_common_ptr cinfo));