MCL/sf/mw/qt: comparison src/3rdparty/libjpeg/jmemmgr.c

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+:1918ee327afb
+/*
+* jmemmgr.c
+*
+* Copyright (C) 1991-1997, 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 file contains the JPEG system-independent memory management
+* routines.  This code is usable across a wide variety of machines; most
+* of the system dependencies have been isolated in a separate file.
+* The major functions provided here are:
+*   * pool-based allocation and freeing of memory;
+*   * policy decisions about how to divide available memory among the
+*     virtual arrays;
+*   * control logic for swapping virtual arrays between main memory and
+*     backing storage.
+* The separate system-dependent file provides the actual backing-storage
+* access code, and it contains the policy decision about how much total
+* main memory to use.
+* This file is system-dependent in the sense that some of its functions
+* are unnecessary in some systems.  For example, if there is enough virtual
+* memory so that backing storage will never be used, much of the virtual
+* array control logic could be removed.  (Of course, if you have that much
+* memory then you shouldn't care about a little bit of unused code...)
+*/
+#define JPEG_INTERNALS
+#define AM_MEMORY_MANAGER	/* we define jvirt_Xarray_control structs */
+#include "jinclude.h"
+#include "jpeglib.h"
+#include "jmemsys.h"		/* import the system-dependent declarations */
+#ifndef NO_GETENV
+#ifndef HAVE_STDLIB_H		/* <stdlib.h> should declare getenv() */
+extern char * getenv JPP((const char * name));
+#endif
+#endif
+/*
+* Some important notes:
+*   The allocation routines provided here must never return NULL.
+*   They should exit to error_exit if unsuccessful.
+*
+*   It's not a good idea to try to merge the sarray and barray routines,
+*   even though they are textually almost the same, because samples are
+*   usually stored as bytes while coefficients are shorts or ints.  Thus,
+*   in machines where byte pointers have a different representation from
+*   word pointers, the resulting machine code could not be the same.
+*/
+/*
+* Many machines require storage alignment: longs must start on 4-byte
+* boundaries, doubles on 8-byte boundaries, etc.  On such machines, malloc()
+* always returns pointers that are multiples of the worst-case alignment
+* requirement, and we had better do so too.
+* There isn't any really portable way to determine the worst-case alignment
+* requirement.  This module assumes that the alignment requirement is
+* multiples of sizeof(ALIGN_TYPE).
+* By default, we define ALIGN_TYPE as double.  This is necessary on some
+* workstations (where doubles really do need 8-byte alignment) and will work
+* fine on nearly everything.  If your machine has lesser alignment needs,
+* you can save a few bytes by making ALIGN_TYPE smaller.
+* The only place I know of where this will NOT work is certain Macintosh
+* 680x0 compilers that define double as a 10-byte IEEE extended float.
+* Doing 10-byte alignment is counterproductive because longwords won't be
+* aligned well.  Put "#define ALIGN_TYPE long" in jconfig.h if you have
+* such a compiler.
+*/
+#ifndef ALIGN_TYPE		/* so can override from jconfig.h */
+#define ALIGN_TYPE  double
+#endif
+/*
+* We allocate objects from "pools", where each pool is gotten with a single
+* request to jpeg_get_small() or jpeg_get_large().  There is no per-object
+* overhead within a pool, except for alignment padding.  Each pool has a
+* header with a link to the next pool of the same class.
+* Small and large pool headers are identical except that the latter's
+* link pointer must be FAR on 80x86 machines.
+* Notice that the "real" header fields are union'ed with a dummy ALIGN_TYPE
+* field.  This forces the compiler to make SIZEOF(small_pool_hdr) a multiple
+* of the alignment requirement of ALIGN_TYPE.
+*/
+typedef union small_pool_struct * small_pool_ptr;
+typedef union small_pool_struct {
+struct {
+small_pool_ptr next;	/* next in list of pools */
+size_t bytes_used;		/* how many bytes already used within pool */
+size_t bytes_left;		/* bytes still available in this pool */
+} hdr;
+ALIGN_TYPE dummy;		/* included in union to ensure alignment */
+} small_pool_hdr;
+typedef union large_pool_struct FAR * large_pool_ptr;
+typedef union large_pool_struct {
+struct {
+large_pool_ptr next;	/* next in list of pools */
+size_t bytes_used;		/* how many bytes already used within pool */
+size_t bytes_left;		/* bytes still available in this pool */
+} hdr;
+ALIGN_TYPE dummy;		/* included in union to ensure alignment */
+} large_pool_hdr;
+/*
+* Here is the full definition of a memory manager object.
+*/
+typedef struct {
+struct jpeg_memory_mgr pub;	/* public fields */
+/* Each pool identifier (lifetime class) names a linked list of pools. */
+small_pool_ptr small_list[JPOOL_NUMPOOLS];
+large_pool_ptr large_list[JPOOL_NUMPOOLS];
+/* Since we only have one lifetime class of virtual arrays, only one
+* linked list is necessary (for each datatype).  Note that the virtual
+* array control blocks being linked together are actually stored somewhere
+* in the small-pool list.
+*/
+jvirt_sarray_ptr virt_sarray_list;
+jvirt_barray_ptr virt_barray_list;
+/* This counts total space obtained from jpeg_get_small/large */
+long total_space_allocated;
+/* alloc_sarray and alloc_barray set this value for use by virtual
+* array routines.
+*/
+JDIMENSION last_rowsperchunk;	/* from most recent alloc_sarray/barray */
+} my_memory_mgr;
+typedef my_memory_mgr * my_mem_ptr;
+/*
+* The control blocks for virtual arrays.
+* Note that these blocks are allocated in the "small" pool area.
+* System-dependent info for the associated backing store (if any) is hidden
+* inside the backing_store_info struct.
+*/
+struct jvirt_sarray_control {
+JSAMPARRAY mem_buffer;	/* => the in-memory buffer */
+JDIMENSION rows_in_array;	/* total virtual array height */
+JDIMENSION samplesperrow;	/* width of array (and of memory buffer) */
+JDIMENSION maxaccess;		/* max rows accessed by access_virt_sarray */
+JDIMENSION rows_in_mem;	/* height of memory buffer */
+JDIMENSION rowsperchunk;	/* allocation chunk size in mem_buffer */
+JDIMENSION cur_start_row;	/* first logical row # in the buffer */
+JDIMENSION first_undef_row;	/* row # of first uninitialized row */
+boolean pre_zero;		/* pre-zero mode requested? */
+boolean dirty;		/* do current buffer contents need written? */
+boolean b_s_open;		/* is backing-store data valid? */
+jvirt_sarray_ptr next;	/* link to next virtual sarray control block */
+backing_store_info b_s_info;	/* System-dependent control info */
+};
+struct jvirt_barray_control {
+JBLOCKARRAY mem_buffer;	/* => the in-memory buffer */
+JDIMENSION rows_in_array;	/* total virtual array height */
+JDIMENSION blocksperrow;	/* width of array (and of memory buffer) */
+JDIMENSION maxaccess;		/* max rows accessed by access_virt_barray */
+JDIMENSION rows_in_mem;	/* height of memory buffer */
+JDIMENSION rowsperchunk;	/* allocation chunk size in mem_buffer */
+JDIMENSION cur_start_row;	/* first logical row # in the buffer */
+JDIMENSION first_undef_row;	/* row # of first uninitialized row */
+boolean pre_zero;		/* pre-zero mode requested? */
+boolean dirty;		/* do current buffer contents need written? */
+boolean b_s_open;		/* is backing-store data valid? */
+jvirt_barray_ptr next;	/* link to next virtual barray control block */
+backing_store_info b_s_info;	/* System-dependent control info */
+};
+#ifdef MEM_STATS		/* optional extra stuff for statistics */
+LOCAL(void)
+print_mem_stats (j_common_ptr cinfo, int pool_id)
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+small_pool_ptr shdr_ptr;
+large_pool_ptr lhdr_ptr;
+/* Since this is only a debugging stub, we can cheat a little by using
+* fprintf directly rather than going through the trace message code.
+* This is helpful because message parm array can't handle longs.
+*/
+fprintf(stderr, "Freeing pool %d, total space = %ld\n",
+	  pool_id, mem->total_space_allocated);
+for (lhdr_ptr = mem->large_list[pool_id]; lhdr_ptr != NULL;
+lhdr_ptr = lhdr_ptr->hdr.next) {
+fprintf(stderr, "  Large chunk used %ld\n",
+	    (long) lhdr_ptr->hdr.bytes_used);
+}
+for (shdr_ptr = mem->small_list[pool_id]; shdr_ptr != NULL;
+shdr_ptr = shdr_ptr->hdr.next) {
+fprintf(stderr, "  Small chunk used %ld free %ld\n",
+	    (long) shdr_ptr->hdr.bytes_used,
+	    (long) shdr_ptr->hdr.bytes_left);
+}
+}
+#endif /* MEM_STATS */
+LOCAL(void)
+out_of_memory (j_common_ptr cinfo, int which)
+/* Report an out-of-memory error and stop execution */
+/* If we compiled MEM_STATS support, report alloc requests before dying */
+{
+#ifdef MEM_STATS
+cinfo->err->trace_level = 2;	/* force self_destruct to report stats */
+#endif
+ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, which);
+}
+/*
+* Allocation of "small" objects.
+*
+* For these, we use pooled storage.  When a new pool must be created,
+* we try to get enough space for the current request plus a "slop" factor,
+* where the slop will be the amount of leftover space in the new pool.
+* The speed vs. space tradeoff is largely determined by the slop values.
+* A different slop value is provided for each pool class (lifetime),
+* and we also distinguish the first pool of a class from later ones.
+* NOTE: the values given work fairly well on both 16- and 32-bit-int
+* machines, but may be too small if longs are 64 bits or more.
+*/
+static const size_t first_pool_slop[JPOOL_NUMPOOLS] =
+{
+	1600,			/* first PERMANENT pool */
+	16000			/* first IMAGE pool */
+};
+static const size_t extra_pool_slop[JPOOL_NUMPOOLS] =
+{
+	0,			/* additional PERMANENT pools */
+	5000			/* additional IMAGE pools */
+};
+#define MIN_SLOP  50		/* greater than 0 to avoid futile looping */
+METHODDEF(void *)
+alloc_small (j_common_ptr cinfo, int pool_id, size_t sizeofobject)
+/* Allocate a "small" object */
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+small_pool_ptr hdr_ptr, prev_hdr_ptr;
+char * data_ptr;
+size_t odd_bytes, min_request, slop;
+/* Check for unsatisfiable request (do now to ensure no overflow below) */
+if (sizeofobject > (size_t) (MAX_ALLOC_CHUNK-SIZEOF(small_pool_hdr)))
+out_of_memory(cinfo, 1);	/* request exceeds malloc's ability */
+/* Round up the requested size to a multiple of SIZEOF(ALIGN_TYPE) */
+odd_bytes = sizeofobject % SIZEOF(ALIGN_TYPE);
+if (odd_bytes > 0)
+sizeofobject += SIZEOF(ALIGN_TYPE) - odd_bytes;
+/* See if space is available in any existing pool */
+if (pool_id < 0 || pool_id >= JPOOL_NUMPOOLS)
+ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */
+prev_hdr_ptr = NULL;
+hdr_ptr = mem->small_list[pool_id];
+while (hdr_ptr != NULL) {
+if (hdr_ptr->hdr.bytes_left >= sizeofobject)
+break;			/* found pool with enough space */
+prev_hdr_ptr = hdr_ptr;
+hdr_ptr = hdr_ptr->hdr.next;
+}
+/* Time to make a new pool? */
+if (hdr_ptr == NULL) {
+/* min_request is what we need now, slop is what will be leftover */
+min_request = sizeofobject + SIZEOF(small_pool_hdr);
+if (prev_hdr_ptr == NULL)	/* first pool in class? */
+slop = first_pool_slop[pool_id];
+else
+slop = extra_pool_slop[pool_id];
+/* Don't ask for more than MAX_ALLOC_CHUNK */
+if (slop > (size_t) (MAX_ALLOC_CHUNK-min_request))
+slop = (size_t) (MAX_ALLOC_CHUNK-min_request);
+/* Try to get space, if fail reduce slop and try again */
+for (;;) {
+hdr_ptr = (small_pool_ptr) jpeg_get_small(cinfo, min_request + slop);
+if (hdr_ptr != NULL)
+	break;
+slop /= 2;
+if (slop < MIN_SLOP)	/* give up when it gets real small */
+	out_of_memory(cinfo, 2); /* jpeg_get_small failed */
+}
+mem->total_space_allocated += min_request + slop;
+/* Success, initialize the new pool header and add to end of list */
+hdr_ptr->hdr.next = NULL;
+hdr_ptr->hdr.bytes_used = 0;
+hdr_ptr->hdr.bytes_left = sizeofobject + slop;
+if (prev_hdr_ptr == NULL)	/* first pool in class? */
+mem->small_list[pool_id] = hdr_ptr;
+else
+prev_hdr_ptr->hdr.next = hdr_ptr;
+}
+/* OK, allocate the object from the current pool */
+data_ptr = (char *) (hdr_ptr + 1); /* point to first data byte in pool */
+data_ptr += hdr_ptr->hdr.bytes_used; /* point to place for object */
+hdr_ptr->hdr.bytes_used += sizeofobject;
+hdr_ptr->hdr.bytes_left -= sizeofobject;
+return (void *) data_ptr;
+}
+/*
+* Allocation of "large" objects.
+*
+* The external semantics of these are the same as "small" objects,
+* except that FAR pointers are used on 80x86.  However the pool
+* management heuristics are quite different.  We assume that each
+* request is large enough that it may as well be passed directly to
+* jpeg_get_large; the pool management just links everything together
+* so that we can free it all on demand.
+* Note: the major use of "large" objects is in JSAMPARRAY and JBLOCKARRAY
+* structures.  The routines that create these structures (see below)
+* deliberately bunch rows together to ensure a large request size.
+*/
+METHODDEF(void FAR *)
+alloc_large (j_common_ptr cinfo, int pool_id, size_t sizeofobject)
+/* Allocate a "large" object */
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+large_pool_ptr hdr_ptr;
+size_t odd_bytes;
+/* Check for unsatisfiable request (do now to ensure no overflow below) */
+if (sizeofobject > (size_t) (MAX_ALLOC_CHUNK-SIZEOF(large_pool_hdr)))
+out_of_memory(cinfo, 3);	/* request exceeds malloc's ability */
+/* Round up the requested size to a multiple of SIZEOF(ALIGN_TYPE) */
+odd_bytes = sizeofobject % SIZEOF(ALIGN_TYPE);
+if (odd_bytes > 0)
+sizeofobject += SIZEOF(ALIGN_TYPE) - odd_bytes;
+/* Always make a new pool */
+if (pool_id < 0 || pool_id >= JPOOL_NUMPOOLS)
+ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */
+hdr_ptr = (large_pool_ptr) jpeg_get_large(cinfo, sizeofobject +
+					    SIZEOF(large_pool_hdr));
+if (hdr_ptr == NULL)
+out_of_memory(cinfo, 4);	/* jpeg_get_large failed */
+mem->total_space_allocated += sizeofobject + SIZEOF(large_pool_hdr);
+/* Success, initialize the new pool header and add to list */
+hdr_ptr->hdr.next = mem->large_list[pool_id];
+/* We maintain space counts in each pool header for statistical purposes,
+* even though they are not needed for allocation.
+*/
+hdr_ptr->hdr.bytes_used = sizeofobject;
+hdr_ptr->hdr.bytes_left = 0;
+mem->large_list[pool_id] = hdr_ptr;
+return (void FAR *) (hdr_ptr + 1); /* point to first data byte in pool */
+}
+/*
+* Creation of 2-D sample arrays.
+* The pointers are in near heap, the samples themselves in FAR heap.
+*
+* To minimize allocation overhead and to allow I/O of large contiguous
+* blocks, we allocate the sample rows in groups of as many rows as possible
+* without exceeding MAX_ALLOC_CHUNK total bytes per allocation request.
+* NB: the virtual array control routines, later in this file, know about
+* this chunking of rows.  The rowsperchunk value is left in the mem manager
+* object so that it can be saved away if this sarray is the workspace for
+* a virtual array.
+*/
+METHODDEF(JSAMPARRAY)
+alloc_sarray (j_common_ptr cinfo, int pool_id,
+	      JDIMENSION samplesperrow, JDIMENSION numrows)
+/* Allocate a 2-D sample array */
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+JSAMPARRAY result;
+JSAMPROW workspace;
+JDIMENSION rowsperchunk, currow, i;
+long ltemp;
+/* Calculate max # of rows allowed in one allocation chunk */
+ltemp = (MAX_ALLOC_CHUNK-SIZEOF(large_pool_hdr)) /
+	  ((long) samplesperrow * SIZEOF(JSAMPLE));
+if (ltemp <= 0)
+ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
+if (ltemp < (long) numrows)
+rowsperchunk = (JDIMENSION) ltemp;
+else
+rowsperchunk = numrows;
+mem->last_rowsperchunk = rowsperchunk;
+/* Get space for row pointers (small object) */
+result = (JSAMPARRAY) alloc_small(cinfo, pool_id,
+				    (size_t) (numrows * SIZEOF(JSAMPROW)));
+/* Get the rows themselves (large objects) */
+currow = 0;
+while (currow < numrows) {
+rowsperchunk = MIN(rowsperchunk, numrows - currow);
+workspace = (JSAMPROW) alloc_large(cinfo, pool_id,
+	(size_t) ((size_t) rowsperchunk * (size_t) samplesperrow
+		  * SIZEOF(JSAMPLE)));
+for (i = rowsperchunk; i > 0; i--) {
+result[currow++] = workspace;
+workspace += samplesperrow;
+}
+}
+return result;
+}
+/*
+* Creation of 2-D coefficient-block arrays.
+* This is essentially the same as the code for sample arrays, above.
+*/
+METHODDEF(JBLOCKARRAY)
+alloc_barray (j_common_ptr cinfo, int pool_id,
+	      JDIMENSION blocksperrow, JDIMENSION numrows)
+/* Allocate a 2-D coefficient-block array */
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+JBLOCKARRAY result;
+JBLOCKROW workspace;
+JDIMENSION rowsperchunk, currow, i;
+long ltemp;
+/* Calculate max # of rows allowed in one allocation chunk */
+ltemp = (MAX_ALLOC_CHUNK-SIZEOF(large_pool_hdr)) /
+	  ((long) blocksperrow * SIZEOF(JBLOCK));
+if (ltemp <= 0)
+ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
+if (ltemp < (long) numrows)
+rowsperchunk = (JDIMENSION) ltemp;
+else
+rowsperchunk = numrows;
+mem->last_rowsperchunk = rowsperchunk;
+/* Get space for row pointers (small object) */
+result = (JBLOCKARRAY) alloc_small(cinfo, pool_id,
+				     (size_t) (numrows * SIZEOF(JBLOCKROW)));
+/* Get the rows themselves (large objects) */
+currow = 0;
+while (currow < numrows) {
+rowsperchunk = MIN(rowsperchunk, numrows - currow);
+workspace = (JBLOCKROW) alloc_large(cinfo, pool_id,
+	(size_t) ((size_t) rowsperchunk * (size_t) blocksperrow
+		  * SIZEOF(JBLOCK)));
+for (i = rowsperchunk; i > 0; i--) {
+result[currow++] = workspace;
+workspace += blocksperrow;
+}
+}
+return result;
+}
+/*
+* About virtual array management:
+*
+* The above "normal" array routines are only used to allocate strip buffers
+* (as wide as the image, but just a few rows high).  Full-image-sized buffers
+* are handled as "virtual" arrays.  The array is still accessed a strip at a
+* time, but the memory manager must save the whole array for repeated
+* accesses.  The intended implementation is that there is a strip buffer in
+* memory (as high as is possible given the desired memory limit), plus a
+* backing file that holds the rest of the array.
+*
+* The request_virt_array routines are told the total size of the image and
+* the maximum number of rows that will be accessed at once.  The in-memory
+* buffer must be at least as large as the maxaccess value.
+*
+* The request routines create control blocks but not the in-memory buffers.
+* That is postponed until realize_virt_arrays is called.  At that time the
+* total amount of space needed is known (approximately, anyway), so free
+* memory can be divided up fairly.
+*
+* The access_virt_array routines are responsible for making a specific strip
+* area accessible (after reading or writing the backing file, if necessary).
+* Note that the access routines are told whether the caller intends to modify
+* the accessed strip; during a read-only pass this saves having to rewrite
+* data to disk.  The access routines are also responsible for pre-zeroing
+* any newly accessed rows, if pre-zeroing was requested.
+*
+* In current usage, the access requests are usually for nonoverlapping
+* strips; that is, successive access start_row numbers differ by exactly
+* num_rows = maxaccess.  This means we can get good performance with simple
+* buffer dump/reload logic, by making the in-memory buffer be a multiple
+* of the access height; then there will never be accesses across bufferload
+* boundaries.  The code will still work with overlapping access requests,
+* but it doesn't handle bufferload overlaps very efficiently.
+*/
+METHODDEF(jvirt_sarray_ptr)
+request_virt_sarray (j_common_ptr cinfo, int pool_id, boolean pre_zero,
+		     JDIMENSION samplesperrow, JDIMENSION numrows,
+		     JDIMENSION maxaccess)
+/* Request a virtual 2-D sample array */
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+jvirt_sarray_ptr result;
+/* Only IMAGE-lifetime virtual arrays are currently supported */
+if (pool_id != JPOOL_IMAGE)
+ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */
+/* get control block */
+result = (jvirt_sarray_ptr) alloc_small(cinfo, pool_id,
+					  SIZEOF(struct jvirt_sarray_control));
+result->mem_buffer = NULL;	/* marks array not yet realized */
+result->rows_in_array = numrows;
+result->samplesperrow = samplesperrow;
+result->maxaccess = maxaccess;
+result->pre_zero = pre_zero;
+result->b_s_open = FALSE;	/* no associated backing-store object */
+result->next = mem->virt_sarray_list; /* add to list of virtual arrays */
+mem->virt_sarray_list = result;
+return result;
+}
+METHODDEF(jvirt_barray_ptr)
+request_virt_barray (j_common_ptr cinfo, int pool_id, boolean pre_zero,
+		     JDIMENSION blocksperrow, JDIMENSION numrows,
+		     JDIMENSION maxaccess)
+/* Request a virtual 2-D coefficient-block array */
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+jvirt_barray_ptr result;
+/* Only IMAGE-lifetime virtual arrays are currently supported */
+if (pool_id != JPOOL_IMAGE)
+ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */
+/* get control block */
+result = (jvirt_barray_ptr) alloc_small(cinfo, pool_id,
+					  SIZEOF(struct jvirt_barray_control));
+result->mem_buffer = NULL;	/* marks array not yet realized */
+result->rows_in_array = numrows;
+result->blocksperrow = blocksperrow;
+result->maxaccess = maxaccess;
+result->pre_zero = pre_zero;
+result->b_s_open = FALSE;	/* no associated backing-store object */
+result->next = mem->virt_barray_list; /* add to list of virtual arrays */
+mem->virt_barray_list = result;
+return result;
+}
+METHODDEF(void)
+realize_virt_arrays (j_common_ptr cinfo)
+/* Allocate the in-memory buffers for any unrealized virtual arrays */
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+long space_per_minheight, maximum_space, avail_mem;
+long minheights, max_minheights;
+jvirt_sarray_ptr sptr;
+jvirt_barray_ptr bptr;
+/* Compute the minimum space needed (maxaccess rows in each buffer)
+* and the maximum space needed (full image height in each buffer).
+* These may be of use to the system-dependent jpeg_mem_available routine.
+*/
+space_per_minheight = 0;
+maximum_space = 0;
+for (sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next) {
+if (sptr->mem_buffer == NULL) { /* if not realized yet */
+space_per_minheight += (long) sptr->maxaccess *
+			     (long) sptr->samplesperrow * SIZEOF(JSAMPLE);
+maximum_space += (long) sptr->rows_in_array *
+		       (long) sptr->samplesperrow * SIZEOF(JSAMPLE);
+}
+}
+for (bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next) {
+if (bptr->mem_buffer == NULL) { /* if not realized yet */
+space_per_minheight += (long) bptr->maxaccess *
+			     (long) bptr->blocksperrow * SIZEOF(JBLOCK);
+maximum_space += (long) bptr->rows_in_array *
+		       (long) bptr->blocksperrow * SIZEOF(JBLOCK);
+}
+}
+if (space_per_minheight <= 0)
+return;			/* no unrealized arrays, no work */
+/* Determine amount of memory to actually use; this is system-dependent. */
+avail_mem = jpeg_mem_available(cinfo, space_per_minheight, maximum_space,
+				 mem->total_space_allocated);
+/* If the maximum space needed is available, make all the buffers full
+* height; otherwise parcel it out with the same number of minheights
+* in each buffer.
+*/
+if (avail_mem >= maximum_space)
+max_minheights = 1000000000L;
+else {
+max_minheights = avail_mem / space_per_minheight;
+/* If there doesn't seem to be enough space, try to get the minimum
+* anyway.  This allows a "stub" implementation of jpeg_mem_available().
+*/
+if (max_minheights <= 0)
+max_minheights = 1;
+}
+/* Allocate the in-memory buffers and initialize backing store as needed. */
+for (sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next) {
+if (sptr->mem_buffer == NULL) { /* if not realized yet */
+minheights = ((long) sptr->rows_in_array - 1L) / sptr->maxaccess + 1L;
+if (minheights <= max_minheights) {
+	/* This buffer fits in memory */
+	sptr->rows_in_mem = sptr->rows_in_array;
+} else {
+	/* It doesn't fit in memory, create backing store. */
+	sptr->rows_in_mem = (JDIMENSION) (max_minheights * sptr->maxaccess);
+	jpeg_open_backing_store(cinfo, & sptr->b_s_info,
+				(long) sptr->rows_in_array *
+				(long) sptr->samplesperrow *
+				(long) SIZEOF(JSAMPLE));
+	sptr->b_s_open = TRUE;
+}
+sptr->mem_buffer = alloc_sarray(cinfo, JPOOL_IMAGE,
+				      sptr->samplesperrow, sptr->rows_in_mem);
+sptr->rowsperchunk = mem->last_rowsperchunk;
+sptr->cur_start_row = 0;
+sptr->first_undef_row = 0;
+sptr->dirty = FALSE;
+}
+}
+for (bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next) {
+if (bptr->mem_buffer == NULL) { /* if not realized yet */
+minheights = ((long) bptr->rows_in_array - 1L) / bptr->maxaccess + 1L;
+if (minheights <= max_minheights) {
+	/* This buffer fits in memory */
+	bptr->rows_in_mem = bptr->rows_in_array;
+} else {
+	/* It doesn't fit in memory, create backing store. */
+	bptr->rows_in_mem = (JDIMENSION) (max_minheights * bptr->maxaccess);
+	jpeg_open_backing_store(cinfo, & bptr->b_s_info,
+				(long) bptr->rows_in_array *
+				(long) bptr->blocksperrow *
+				(long) SIZEOF(JBLOCK));
+	bptr->b_s_open = TRUE;
+}
+bptr->mem_buffer = alloc_barray(cinfo, JPOOL_IMAGE,
+				      bptr->blocksperrow, bptr->rows_in_mem);
+bptr->rowsperchunk = mem->last_rowsperchunk;
+bptr->cur_start_row = 0;
+bptr->first_undef_row = 0;
+bptr->dirty = FALSE;
+}
+}
+}
+LOCAL(void)
+do_sarray_io (j_common_ptr cinfo, jvirt_sarray_ptr ptr, boolean writing)
+/* Do backing store read or write of a virtual sample array */
+{
+long bytesperrow, file_offset, byte_count, rows, thisrow, i;
+bytesperrow = (long) ptr->samplesperrow * SIZEOF(JSAMPLE);
+file_offset = ptr->cur_start_row * bytesperrow;
+/* Loop to read or write each allocation chunk in mem_buffer */
+for (i = 0; i < (long) ptr->rows_in_mem; i += ptr->rowsperchunk) {
+/* One chunk, but check for short chunk at end of buffer */
+rows = MIN((long) ptr->rowsperchunk, (long) ptr->rows_in_mem - i);
+/* Transfer no more than is currently defined */
+thisrow = (long) ptr->cur_start_row + i;
+rows = MIN(rows, (long) ptr->first_undef_row - thisrow);
+/* Transfer no more than fits in file */
+rows = MIN(rows, (long) ptr->rows_in_array - thisrow);
+if (rows <= 0)		/* this chunk might be past end of file! */
+break;
+byte_count = rows * bytesperrow;
+if (writing)
+(*ptr->b_s_info.write_backing_store) (cinfo, & ptr->b_s_info,
+					    (void FAR *) ptr->mem_buffer[i],
+					    file_offset, byte_count);
+else
+(*ptr->b_s_info.read_backing_store) (cinfo, & ptr->b_s_info,
+					   (void FAR *) ptr->mem_buffer[i],
+					   file_offset, byte_count);
+file_offset += byte_count;
+}
+}
+LOCAL(void)
+do_barray_io (j_common_ptr cinfo, jvirt_barray_ptr ptr, boolean writing)
+/* Do backing store read or write of a virtual coefficient-block array */
+{
+long bytesperrow, file_offset, byte_count, rows, thisrow, i;
+bytesperrow = (long) ptr->blocksperrow * SIZEOF(JBLOCK);
+file_offset = ptr->cur_start_row * bytesperrow;
+/* Loop to read or write each allocation chunk in mem_buffer */
+for (i = 0; i < (long) ptr->rows_in_mem; i += ptr->rowsperchunk) {
+/* One chunk, but check for short chunk at end of buffer */
+rows = MIN((long) ptr->rowsperchunk, (long) ptr->rows_in_mem - i);
+/* Transfer no more than is currently defined */
+thisrow = (long) ptr->cur_start_row + i;
+rows = MIN(rows, (long) ptr->first_undef_row - thisrow);
+/* Transfer no more than fits in file */
+rows = MIN(rows, (long) ptr->rows_in_array - thisrow);
+if (rows <= 0)		/* this chunk might be past end of file! */
+break;
+byte_count = rows * bytesperrow;
+if (writing)
+(*ptr->b_s_info.write_backing_store) (cinfo, & ptr->b_s_info,
+					    (void FAR *) ptr->mem_buffer[i],
+					    file_offset, byte_count);
+else
+(*ptr->b_s_info.read_backing_store) (cinfo, & ptr->b_s_info,
+					   (void FAR *) ptr->mem_buffer[i],
+					   file_offset, byte_count);
+file_offset += byte_count;
+}
+}
+METHODDEF(JSAMPARRAY)
+access_virt_sarray (j_common_ptr cinfo, jvirt_sarray_ptr ptr,
+		    JDIMENSION start_row, JDIMENSION num_rows,
+		    boolean writable)
+/* Access the part of a virtual sample array starting at start_row */
+/* and extending for num_rows rows.  writable is true if  */
+/* caller intends to modify the accessed area. */
+{
+JDIMENSION end_row = start_row + num_rows;
+JDIMENSION undef_row;
+/* debugging check */
+if (end_row > ptr->rows_in_array || num_rows > ptr->maxaccess ||
+ptr->mem_buffer == NULL)
+ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
+/* Make the desired part of the virtual array accessible */
+if (start_row < ptr->cur_start_row ||
+end_row > ptr->cur_start_row+ptr->rows_in_mem) {
+if (! ptr->b_s_open)
+ERREXIT(cinfo, JERR_VIRTUAL_BUG);
+/* Flush old buffer contents if necessary */
+if (ptr->dirty) {
+do_sarray_io(cinfo, ptr, TRUE);
+ptr->dirty = FALSE;
+}
+/* Decide what part of virtual array to access.
+* Algorithm: if target address > current window, assume forward scan,
+* load starting at target address.  If target address < current window,
+* assume backward scan, load so that target area is top of window.
+* Note that when switching from forward write to forward read, will have
+* start_row = 0, so the limiting case applies and we load from 0 anyway.
+*/
+if (start_row > ptr->cur_start_row) {
+ptr->cur_start_row = start_row;
+} else {
+/* use long arithmetic here to avoid overflow & unsigned problems */
+long ltemp;
+ltemp = (long) end_row - (long) ptr->rows_in_mem;
+if (ltemp < 0)
+	ltemp = 0;		/* don't fall off front end of file */
+ptr->cur_start_row = (JDIMENSION) ltemp;
+}
+/* Read in the selected part of the array.
+* During the initial write pass, we will do no actual read
+* because the selected part is all undefined.
+*/
+do_sarray_io(cinfo, ptr, FALSE);
+}
+/* Ensure the accessed part of the array is defined; prezero if needed.
+* To improve locality of access, we only prezero the part of the array
+* that the caller is about to access, not the entire in-memory array.
+*/
+if (ptr->first_undef_row < end_row) {
+if (ptr->first_undef_row < start_row) {
+if (writable)		/* writer skipped over a section of array */
+	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
+undef_row = start_row;	/* but reader is allowed to read ahead */
+} else {
+undef_row = ptr->first_undef_row;
+}
+if (writable)
+ptr->first_undef_row = end_row;
+if (ptr->pre_zero) {
+size_t bytesperrow = (size_t) ptr->samplesperrow * SIZEOF(JSAMPLE);
+undef_row -= ptr->cur_start_row; /* make indexes relative to buffer */
+end_row -= ptr->cur_start_row;
+while (undef_row < end_row) {
+	jzero_far((void FAR *) ptr->mem_buffer[undef_row], bytesperrow);
+	undef_row++;
+}
+} else {
+if (! writable)		/* reader looking at undefined data */
+	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
+}
+}
+/* Flag the buffer dirty if caller will write in it */
+if (writable)
+ptr->dirty = TRUE;
+/* Return address of proper part of the buffer */
+return ptr->mem_buffer + (start_row - ptr->cur_start_row);
+}
+METHODDEF(JBLOCKARRAY)
+access_virt_barray (j_common_ptr cinfo, jvirt_barray_ptr ptr,
+		    JDIMENSION start_row, JDIMENSION num_rows,
+		    boolean writable)
+/* Access the part of a virtual block array starting at start_row */
+/* and extending for num_rows rows.  writable is true if  */
+/* caller intends to modify the accessed area. */
+{
+JDIMENSION end_row = start_row + num_rows;
+JDIMENSION undef_row;
+/* debugging check */
+if (end_row > ptr->rows_in_array || num_rows > ptr->maxaccess ||
+ptr->mem_buffer == NULL)
+ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
+/* Make the desired part of the virtual array accessible */
+if (start_row < ptr->cur_start_row ||
+end_row > ptr->cur_start_row+ptr->rows_in_mem) {
+if (! ptr->b_s_open)
+ERREXIT(cinfo, JERR_VIRTUAL_BUG);
+/* Flush old buffer contents if necessary */
+if (ptr->dirty) {
+do_barray_io(cinfo, ptr, TRUE);
+ptr->dirty = FALSE;
+}
+/* Decide what part of virtual array to access.
+* Algorithm: if target address > current window, assume forward scan,
+* load starting at target address.  If target address < current window,
+* assume backward scan, load so that target area is top of window.
+* Note that when switching from forward write to forward read, will have
+* start_row = 0, so the limiting case applies and we load from 0 anyway.
+*/
+if (start_row > ptr->cur_start_row) {
+ptr->cur_start_row = start_row;
+} else {
+/* use long arithmetic here to avoid overflow & unsigned problems */
+long ltemp;
+ltemp = (long) end_row - (long) ptr->rows_in_mem;
+if (ltemp < 0)
+	ltemp = 0;		/* don't fall off front end of file */
+ptr->cur_start_row = (JDIMENSION) ltemp;
+}
+/* Read in the selected part of the array.
+* During the initial write pass, we will do no actual read
+* because the selected part is all undefined.
+*/
+do_barray_io(cinfo, ptr, FALSE);
+}
+/* Ensure the accessed part of the array is defined; prezero if needed.
+* To improve locality of access, we only prezero the part of the array
+* that the caller is about to access, not the entire in-memory array.
+*/
+if (ptr->first_undef_row < end_row) {
+if (ptr->first_undef_row < start_row) {
+if (writable)		/* writer skipped over a section of array */
+	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
+undef_row = start_row;	/* but reader is allowed to read ahead */
+} else {
+undef_row = ptr->first_undef_row;
+}
+if (writable)
+ptr->first_undef_row = end_row;
+if (ptr->pre_zero) {
+size_t bytesperrow = (size_t) ptr->blocksperrow * SIZEOF(JBLOCK);
+undef_row -= ptr->cur_start_row; /* make indexes relative to buffer */
+end_row -= ptr->cur_start_row;
+while (undef_row < end_row) {
+	jzero_far((void FAR *) ptr->mem_buffer[undef_row], bytesperrow);
+	undef_row++;
+}
+} else {
+if (! writable)		/* reader looking at undefined data */
+	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
+}
+}
+/* Flag the buffer dirty if caller will write in it */
+if (writable)
+ptr->dirty = TRUE;
+/* Return address of proper part of the buffer */
+return ptr->mem_buffer + (start_row - ptr->cur_start_row);
+}
+/*
+* Release all objects belonging to a specified pool.
+*/
+METHODDEF(void)
+free_pool (j_common_ptr cinfo, int pool_id)
+{
+my_mem_ptr mem = (my_mem_ptr) cinfo->mem;
+small_pool_ptr shdr_ptr;
+large_pool_ptr lhdr_ptr;
+size_t space_freed;
+if (pool_id < 0 || pool_id >= JPOOL_NUMPOOLS)
+ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */
+#ifdef MEM_STATS
+if (cinfo->err->trace_level > 1)
+print_mem_stats(cinfo, pool_id); /* print pool's memory usage statistics */
+#endif
+/* If freeing IMAGE pool, close any virtual arrays first */
+if (pool_id == JPOOL_IMAGE) {
+jvirt_sarray_ptr sptr;
+jvirt_barray_ptr bptr;
+for (sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next) {
+if (sptr->b_s_open) {	/* there may be no backing store */
+	sptr->b_s_open = FALSE;	/* prevent recursive close if error */
+	(*sptr->b_s_info.close_backing_store) (cinfo, & sptr->b_s_info);
+}
+}
+mem->virt_sarray_list = NULL;
+for (bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next) {
+if (bptr->b_s_open) {	/* there may be no backing store */
+	bptr->b_s_open = FALSE;	/* prevent recursive close if error */
+	(*bptr->b_s_info.close_backing_store) (cinfo, & bptr->b_s_info);
+}
+}
+mem->virt_barray_list = NULL;
+}
+/* Release large objects */
+lhdr_ptr = mem->large_list[pool_id];
+mem->large_list[pool_id] = NULL;
+while (lhdr_ptr != NULL) {
+large_pool_ptr next_lhdr_ptr = lhdr_ptr->hdr.next;
+space_freed = lhdr_ptr->hdr.bytes_used +
+		  lhdr_ptr->hdr.bytes_left +
+		  SIZEOF(large_pool_hdr);
+jpeg_free_large(cinfo, (void FAR *) lhdr_ptr, space_freed);
+mem->total_space_allocated -= space_freed;
+lhdr_ptr = next_lhdr_ptr;
+}
+/* Release small objects */
+shdr_ptr = mem->small_list[pool_id];
+mem->small_list[pool_id] = NULL;
+while (shdr_ptr != NULL) {
+small_pool_ptr next_shdr_ptr = shdr_ptr->hdr.next;
+space_freed = shdr_ptr->hdr.bytes_used +
+		  shdr_ptr->hdr.bytes_left +
+		  SIZEOF(small_pool_hdr);
+jpeg_free_small(cinfo, (void *) shdr_ptr, space_freed);
+mem->total_space_allocated -= space_freed;
+shdr_ptr = next_shdr_ptr;
+}
+}
+/*
+* Close up shop entirely.
+* Note that this cannot be called unless cinfo->mem is non-NULL.
+*/
+METHODDEF(void)
+self_destruct (j_common_ptr cinfo)
+{
+int pool;
+/* Close all backing store, release all memory.
+* Releasing pools in reverse order might help avoid fragmentation
+* with some (brain-damaged) malloc libraries.
+*/
+for (pool = JPOOL_NUMPOOLS-1; pool >= JPOOL_PERMANENT; pool--) {
+free_pool(cinfo, pool);
+}
+/* Release the memory manager control block too. */
+jpeg_free_small(cinfo, (void *) cinfo->mem, SIZEOF(my_memory_mgr));
+cinfo->mem = NULL;		/* ensures I will be called only once */
+jpeg_mem_term(cinfo);		/* system-dependent cleanup */
+}
+/*
+* Memory manager initialization.
+* When this is called, only the error manager pointer is valid in cinfo!
+*/
+GLOBAL(void)
+jinit_memory_mgr (j_common_ptr cinfo)
+{
+my_mem_ptr mem;
+long max_to_use;
+int pool;
+size_t test_mac;
+cinfo->mem = NULL;		/* for safety if init fails */
+/* Check for configuration errors.
+* SIZEOF(ALIGN_TYPE) should be a power of 2; otherwise, it probably
+* doesn't reflect any real hardware alignment requirement.
+* The test is a little tricky: for X>0, X and X-1 have no one-bits
+* in common if and only if X is a power of 2, ie has only one one-bit.
+* Some compilers may give an "unreachable code" warning here; ignore it.
+*/
+if ((SIZEOF(ALIGN_TYPE) & (SIZEOF(ALIGN_TYPE)-1)) != 0)
+ERREXIT(cinfo, JERR_BAD_ALIGN_TYPE);
+/* MAX_ALLOC_CHUNK must be representable as type size_t, and must be
+* a multiple of SIZEOF(ALIGN_TYPE).
+* Again, an "unreachable code" warning may be ignored here.
+* But a "constant too large" warning means you need to fix MAX_ALLOC_CHUNK.
+*/
+test_mac = (size_t) MAX_ALLOC_CHUNK;
+if ((long) test_mac != MAX_ALLOC_CHUNK ||
+(MAX_ALLOC_CHUNK % SIZEOF(ALIGN_TYPE)) != 0)
+ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);
+max_to_use = jpeg_mem_init(cinfo); /* system-dependent initialization */
+/* Attempt to allocate memory manager's control block */
+mem = (my_mem_ptr) jpeg_get_small(cinfo, SIZEOF(my_memory_mgr));
+if (mem == NULL) {
+jpeg_mem_term(cinfo);	/* system-dependent cleanup */
+ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 0);
+}
+/* OK, fill in the method pointers */
+mem->pub.alloc_small = alloc_small;
+mem->pub.alloc_large = alloc_large;
+mem->pub.alloc_sarray = alloc_sarray;
+mem->pub.alloc_barray = alloc_barray;
+mem->pub.request_virt_sarray = request_virt_sarray;
+mem->pub.request_virt_barray = request_virt_barray;
+mem->pub.realize_virt_arrays = realize_virt_arrays;
+mem->pub.access_virt_sarray = access_virt_sarray;
+mem->pub.access_virt_barray = access_virt_barray;
+mem->pub.free_pool = free_pool;
+mem->pub.self_destruct = self_destruct;
+/* Make MAX_ALLOC_CHUNK accessible to other modules */
+mem->pub.max_alloc_chunk = MAX_ALLOC_CHUNK;
+/* Initialize working state */
+mem->pub.max_memory_to_use = max_to_use;
+for (pool = JPOOL_NUMPOOLS-1; pool >= JPOOL_PERMANENT; pool--) {
+mem->small_list[pool] = NULL;
+mem->large_list[pool] = NULL;
+}
+mem->virt_sarray_list = NULL;
+mem->virt_barray_list = NULL;
+mem->total_space_allocated = SIZEOF(my_memory_mgr);
+/* Declare ourselves open for business */
+cinfo->mem = & mem->pub;
+/* Check for an environment variable JPEGMEM; if found, override the
+* default max_memory setting from jpeg_mem_init.  Note that the
+* surrounding application may again override this value.
+* If your system doesn't support getenv(), define NO_GETENV to disable
+* this feature.
+*/
+#ifndef NO_GETENV
+{ char * memenv;
+if ((memenv = getenv("JPEGMEM")) != NULL) {
+char ch = 'x';
+if (sscanf(memenv, "%ld%c", &max_to_use, &ch) > 0) {
+	if (ch == 'm' || ch == 'M')
+	  max_to_use *= 1000L;
+	mem->pub.max_memory_to_use = max_to_use * 1000L;
+}
+}
+}
+#endif
+}