jmemmgr.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#define JPEG_INTERNALS
#define AM_MEMORY_MANAGER /* we define jvirt_Xarray_control structs */
#include "jinclude.h"
#include "mrpt_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 mrpt_jconfig.h if you have
 * such a compiler.
 */

#ifndef ALIGN_TYPE /* so can override from mrpt_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 */
        size_t /*JLBC for MRPT, was: 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 != nullptr;
                 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 != nullptr;
                 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 = nullptr;
        hdr_ptr = mem->small_list[pool_id];
        while (hdr_ptr != nullptr)
        {
                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 == nullptr)
        {
                /* min_request is what we need now, slop is what will be leftover */
                min_request = sizeofobject + SIZEOF(small_pool_hdr);
                if (prev_hdr_ptr == nullptr) /* 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 != nullptr) 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 = nullptr;
                hdr_ptr->hdr.bytes_used = 0;
                hdr_ptr->hdr.bytes_left = sizeofobject + slop;
                if (prev_hdr_ptr == nullptr) /* 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 == nullptr) 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 = nullptr; /* 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 = nullptr; /* 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 != nullptr; sptr = sptr->next)
        {
                if (sptr->mem_buffer == nullptr)
                { /* 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 != nullptr; bptr = bptr->next)
        {
                if (bptr->mem_buffer == nullptr)
                { /* 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,
                (long)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 != nullptr; sptr = sptr->next)
        {
                if (sptr->mem_buffer == nullptr)
                { /* 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 != nullptr; bptr = bptr->next)
        {
                if (bptr->mem_buffer == nullptr)
                { /* 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 == nullptr)
                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 == nullptr)
                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 != nullptr; 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 = nullptr;
                for (bptr = mem->virt_barray_list; bptr != nullptr; 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 = nullptr;
        }

        /* Release large objects */
        lhdr_ptr = mem->large_list[pool_id];
        mem->large_list[pool_id] = nullptr;

        while (lhdr_ptr != nullptr)
        {
                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] = nullptr;

        while (shdr_ptr != nullptr)
        {
                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 = nullptr; /* 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 = nullptr; /* 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 == nullptr)
        {
                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] = nullptr;
                mem->large_list[pool] = nullptr;
        }
        mem->virt_sarray_list = nullptr;
        mem->virt_barray_list = nullptr;

        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")) != nullptr)
                {
                        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
}