tor-browser

jmemmgr.c (50008B)

---

/*
* jmemmgr.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1997, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2016, 2021-2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* 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 */
#if !defined(_MSC_VER) || _MSC_VER > 1600
#include <stdint.h>
#endif
#include <limits.h>


LOCAL(size_t)
round_up_pow2(size_t a, size_t b)
/* a rounded up to the next multiple of b, i.e. ceil(a/b)*b */
/* Assumes a >= 0, b > 0, and b is a power of 2 */
{
 return ((a + b - 1) & (~(b - 1)));
}


/*
* 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 ALIGN_SIZE.
* By default, we define ALIGN_SIZE as the maximum of sizeof(double) and
* sizeof(void *).  This is necessary on some workstations (where doubles
* really do need 8-byte alignment) and will work fine on nearly everything.
* We use the maximum of sizeof(double) and sizeof(void *) since sizeof(double)
* may be insufficient, for example, on CHERI-enabled platforms with 16-byte
* pointers and a 16-byte alignment requirement.  If your machine has lesser
* alignment needs, you can save a few bytes by making ALIGN_SIZE 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_SIZE 4" in jconfig.h if you have
* such a compiler.
*/

#ifndef ALIGN_SIZE              /* so can override from jconfig.h */
#ifndef WITH_SIMD
#define ALIGN_SIZE  MAX(sizeof(void *), sizeof(double))
#else
#define ALIGN_SIZE  32 /* Most of the SIMD instructions we support require
                         16-byte (128-bit) alignment, but AVX2 requires
                         32-byte alignment. */
#endif
#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.
*/

typedef struct small_pool_struct *small_pool_ptr;

typedef struct small_pool_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 */
} small_pool_hdr;

typedef struct large_pool_struct *large_pool_ptr;

typedef struct large_pool_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 */
} 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 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 (if
                                  cinfo->data_precision is 12, then this is
                                  actually a J12SAMPARRAY) */
 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->next) {
   fprintf(stderr, "  Large chunk used %ld\n", (long)lhdr_ptr->bytes_used);
 }

 for (shdr_ptr = mem->small_list[pool_id]; shdr_ptr != NULL;
      shdr_ptr = shdr_ptr->next) {
   fprintf(stderr, "  Small chunk used %ld free %ld\n",
           (long)shdr_ptr->bytes_used, (long)shdr_ptr->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.
*
* Since we do not know what alignment malloc() gives us, we have to
* allocate ALIGN_SIZE-1 extra space per pool to have room for alignment
* adjustment.
*/

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 min_request, slop;

 /*
  * Round up the requested size to a multiple of ALIGN_SIZE in order
  * to assure alignment for the next object allocated in the same pool
  * and so that algorithms can straddle outside the proper area up
  * to the next alignment.
  */
 if (sizeofobject > MAX_ALLOC_CHUNK) {
   /* This prevents overflow/wrap-around in round_up_pow2() if sizeofobject
      is close to SIZE_MAX. */
   out_of_memory(cinfo, 7);
 }
 sizeofobject = round_up_pow2(sizeofobject, ALIGN_SIZE);

 /* Check for unsatisfiable request (do now to ensure no overflow below) */
 if ((sizeof(small_pool_hdr) + sizeofobject + ALIGN_SIZE - 1) >
     MAX_ALLOC_CHUNK)
   out_of_memory(cinfo, 1);    /* request exceeds malloc's ability */

 /* 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->bytes_left >= sizeofobject)
     break;                    /* found pool with enough space */
   prev_hdr_ptr = hdr_ptr;
   hdr_ptr = hdr_ptr->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 = sizeof(small_pool_hdr) + sizeofobject + ALIGN_SIZE - 1;
   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->next = NULL;
   hdr_ptr->bytes_used = 0;
   hdr_ptr->bytes_left = sizeofobject + slop;
   if (prev_hdr_ptr == NULL)   /* first pool in class? */
     mem->small_list[pool_id] = hdr_ptr;
   else
     prev_hdr_ptr->next = hdr_ptr;
 }

 /* OK, allocate the object from the current pool */
 data_ptr = (char *)hdr_ptr; /* point to first data byte in pool... */
 data_ptr += sizeof(small_pool_hdr); /* ...by skipping the header... */
 if ((size_t)data_ptr % ALIGN_SIZE) /* ...and adjust for alignment */
   data_ptr += ALIGN_SIZE - (size_t)data_ptr % ALIGN_SIZE;
 data_ptr += hdr_ptr->bytes_used; /* point to place for object */
 hdr_ptr->bytes_used += sizeofobject;
 hdr_ptr->bytes_left -= sizeofobject;

 return (void *)data_ptr;
}


/*
* Allocation of "large" objects.
*
* The external semantics of these are the same as "small" objects.  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/J12SAMPARRAY/J16SAMPARRAY and JBLOCKARRAY structures.  The
* routines that create these structures (see below) deliberately bunch rows
* together to ensure a large request size.
*/

METHODDEF(void *)
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;
 char *data_ptr;

 /*
  * Round up the requested size to a multiple of ALIGN_SIZE so that
  * algorithms can straddle outside the proper area up to the next
  * alignment.
  */
 if (sizeofobject > MAX_ALLOC_CHUNK) {
   /* This prevents overflow/wrap-around in round_up_pow2() if sizeofobject
      is close to SIZE_MAX. */
   out_of_memory(cinfo, 8);
 }
 sizeofobject = round_up_pow2(sizeofobject, ALIGN_SIZE);

 /* Check for unsatisfiable request (do now to ensure no overflow below) */
 if ((sizeof(large_pool_hdr) + sizeofobject + ALIGN_SIZE - 1) >
     MAX_ALLOC_CHUNK)
   out_of_memory(cinfo, 3);    /* request exceeds malloc's ability */

 /* 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) +
                                          ALIGN_SIZE - 1);
 if (hdr_ptr == NULL)
   out_of_memory(cinfo, 4);    /* jpeg_get_large failed */
 mem->total_space_allocated += sizeofobject + sizeof(large_pool_hdr) +
                               ALIGN_SIZE - 1;

 /* Success, initialize the new pool header and add to list */
 hdr_ptr->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->bytes_used = sizeofobject;
 hdr_ptr->bytes_left = 0;
 mem->large_list[pool_id] = hdr_ptr;

 data_ptr = (char *)hdr_ptr; /* point to first data byte in pool... */
 data_ptr += sizeof(small_pool_hdr); /* ...by skipping the header... */
 if ((size_t)data_ptr % ALIGN_SIZE) /* ...and adjust for alignment */
   data_ptr += ALIGN_SIZE - (size_t)data_ptr % ALIGN_SIZE;

 return (void *)data_ptr;
}


/*
* Creation of 2-D sample arrays.
*
* 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.
*
* Since we are often upsampling with a factor 2, we align the size (not
* the start) to 2 * ALIGN_SIZE so that the upsampling routines don't have
* to be as careful about size.
*/

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;
 J12SAMPARRAY result12;
 J12SAMPROW workspace12;
#if defined(C_LOSSLESS_SUPPORTED) || defined(D_LOSSLESS_SUPPORTED)
 J16SAMPARRAY result16;
 J16SAMPROW workspace16;
#endif
 int data_precision = cinfo->is_decompressor ?
                       ((j_decompress_ptr)cinfo)->data_precision :
                       ((j_compress_ptr)cinfo)->data_precision;
 size_t sample_size = data_precision == 16 ?
                      sizeof(J16SAMPLE) : (data_precision == 12 ?
                                           sizeof(J12SAMPLE) :
                                           sizeof(JSAMPLE));

 /* Make sure each row is properly aligned */
 if ((ALIGN_SIZE % sample_size) != 0)
   out_of_memory(cinfo, 5);    /* safety check */

 if (samplesperrow > MAX_ALLOC_CHUNK) {
   /* This prevents overflow/wrap-around in round_up_pow2() if sizeofobject
      is close to SIZE_MAX. */
   out_of_memory(cinfo, 9);
 }
 samplesperrow = (JDIMENSION)round_up_pow2(samplesperrow, (2 * ALIGN_SIZE) /
                                                          sample_size);

 /* Calculate max # of rows allowed in one allocation chunk */
 ltemp = (MAX_ALLOC_CHUNK - sizeof(large_pool_hdr)) /
         ((long)samplesperrow * (long)sample_size);
 if (ltemp <= 0)
   ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
 if (ltemp < (long)numrows)
   rowsperchunk = (JDIMENSION)ltemp;
 else
   rowsperchunk = numrows;
 mem->last_rowsperchunk = rowsperchunk;

 if (data_precision == 16) {
#if defined(C_LOSSLESS_SUPPORTED) || defined(D_LOSSLESS_SUPPORTED)
   /* Get space for row pointers (small object) */
   result16 = (J16SAMPARRAY)alloc_small(cinfo, pool_id,
                                        (size_t)(numrows *
                                                 sizeof(J16SAMPROW)));

   /* Get the rows themselves (large objects) */
   currow = 0;
   while (currow < numrows) {
     rowsperchunk = MIN(rowsperchunk, numrows - currow);
     workspace16 = (J16SAMPROW)alloc_large(cinfo, pool_id,
       (size_t)((size_t)rowsperchunk * (size_t)samplesperrow * sample_size));
     for (i = rowsperchunk; i > 0; i--) {
       result16[currow++] = workspace16;
       workspace16 += samplesperrow;
     }
   }

   return (JSAMPARRAY)result16;
#else
   ERREXIT1(cinfo, JERR_BAD_PRECISION, data_precision);
   return NULL;
#endif
 } else if (data_precision == 12) {
   /* Get space for row pointers (small object) */
   result12 = (J12SAMPARRAY)alloc_small(cinfo, pool_id,
                                        (size_t)(numrows *
                                                 sizeof(J12SAMPROW)));

   /* Get the rows themselves (large objects) */
   currow = 0;
   while (currow < numrows) {
     rowsperchunk = MIN(rowsperchunk, numrows - currow);
     workspace12 = (J12SAMPROW)alloc_large(cinfo, pool_id,
       (size_t)((size_t)rowsperchunk * (size_t)samplesperrow * sample_size));
     for (i = rowsperchunk; i > 0; i--) {
       result12[currow++] = workspace12;
       workspace12 += samplesperrow;
     }
   }

   return (JSAMPARRAY)result12;
 } else {
   /* 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 * sample_size));
     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;

 /* Make sure each row is properly aligned */
 if ((sizeof(JBLOCK) % ALIGN_SIZE) != 0)
   out_of_memory(cinfo, 6);    /* safety check */

 /* 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;
 size_t space_per_minheight, maximum_space, avail_mem;
 size_t minheights, max_minheights;
 jvirt_sarray_ptr sptr;
 jvirt_barray_ptr bptr;
 int data_precision = cinfo->is_decompressor ?
                       ((j_decompress_ptr)cinfo)->data_precision :
                       ((j_compress_ptr)cinfo)->data_precision;
 size_t sample_size = data_precision == 16 ?
                      sizeof(J16SAMPLE) : (data_precision == 12 ?
                                           sizeof(J12SAMPLE) :
                                           sizeof(JSAMPLE));

 /* 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 */
     size_t new_space = (long)sptr->rows_in_array *
                        (long)sptr->samplesperrow * sample_size;

     space_per_minheight += (long)sptr->maxaccess *
                            (long)sptr->samplesperrow * sample_size;
     if (SIZE_MAX - maximum_space < new_space)
       out_of_memory(cinfo, 10);
     maximum_space += new_space;
   }
 }
 for (bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next) {
   if (bptr->mem_buffer == NULL) { /* if not realized yet */
     size_t new_space = (long)bptr->rows_in_array *
                        (long)bptr->blocksperrow * sizeof(JBLOCK);

     space_per_minheight += (long)bptr->maxaccess *
                            (long)bptr->blocksperrow * sizeof(JBLOCK);
     if (SIZE_MAX - maximum_space < new_space)
       out_of_memory(cinfo, 11);
     maximum_space += new_space;
   }
 }

 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)sample_size);
       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;
 int data_precision = cinfo->is_decompressor ?
                       ((j_decompress_ptr)cinfo)->data_precision :
                       ((j_compress_ptr)cinfo)->data_precision;
 size_t sample_size = data_precision == 16 ?
                      sizeof(J16SAMPLE) : (data_precision == 12 ?
                                           sizeof(J12SAMPLE) :
                                           sizeof(JSAMPLE));

 bytesperrow = (long)ptr->samplesperrow * (long)sample_size;
 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 (data_precision == 16) {
#if defined(C_LOSSLESS_SUPPORTED) || defined(D_LOSSLESS_SUPPORTED)
     J16SAMPARRAY mem_buffer16 = (J16SAMPARRAY)ptr->mem_buffer;

     if (writing)
       (*ptr->b_s_info.write_backing_store) (cinfo, &ptr->b_s_info,
                                             (void *)mem_buffer16[i],
                                             file_offset, byte_count);
     else
       (*ptr->b_s_info.read_backing_store) (cinfo, &ptr->b_s_info,
                                            (void *)mem_buffer16[i],
                                            file_offset, byte_count);
#else
     ERREXIT1(cinfo, JERR_BAD_PRECISION, data_precision);
#endif
   } else if (data_precision == 12) {
     J12SAMPARRAY mem_buffer12 = (J12SAMPARRAY)ptr->mem_buffer;

     if (writing)
       (*ptr->b_s_info.write_backing_store) (cinfo, &ptr->b_s_info,
                                             (void *)mem_buffer12[i],
                                             file_offset, byte_count);
     else
       (*ptr->b_s_info.read_backing_store) (cinfo, &ptr->b_s_info,
                                            (void *)mem_buffer12[i],
                                            file_offset, byte_count);
   } else {
     if (writing)
       (*ptr->b_s_info.write_backing_store) (cinfo, &ptr->b_s_info,
                                             (void *)ptr->mem_buffer[i],
                                             file_offset, byte_count);
     else
       (*ptr->b_s_info.read_backing_store) (cinfo, &ptr->b_s_info,
                                            (void *)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 *)ptr->mem_buffer[i],
                                           file_offset, byte_count);
   else
     (*ptr->b_s_info.read_backing_store) (cinfo, &ptr->b_s_info,
                                          (void *)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;
 int data_precision = cinfo->is_decompressor ?
                       ((j_decompress_ptr)cinfo)->data_precision :
                       ((j_compress_ptr)cinfo)->data_precision;
 size_t sample_size = data_precision == 16 ?
                      sizeof(J16SAMPLE) : (data_precision == 12 ?
                                           sizeof(J12SAMPLE) :
                                           sizeof(JSAMPLE));

 /* 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 * sample_size;
     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 *)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 *)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->next;
   space_freed = lhdr_ptr->bytes_used +
                 lhdr_ptr->bytes_left +
                 sizeof(large_pool_hdr) + ALIGN_SIZE - 1;
   jpeg_free_large(cinfo, (void *)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->next;
   space_freed = shdr_ptr->bytes_used + shdr_ptr->bytes_left +
                 sizeof(small_pool_hdr) + ALIGN_SIZE - 1;
   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 ((ALIGN_SIZE & (ALIGN_SIZE - 1)) != 0)
   ERREXIT(cinfo, JERR_BAD_ALIGN_TYPE);
 /* MAX_ALLOC_CHUNK must be representable as type size_t, and must be
  * a multiple of ALIGN_SIZE.
  * 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 % ALIGN_SIZE) != 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[30] = { 0 };

   if (!GETENV_S(memenv, 30, "JPEGMEM") && strlen(memenv) > 0) {
     char ch = 'x';

#ifdef _MSC_VER
     if (sscanf_s(memenv, "%ld%c", &max_to_use, &ch, 1) > 0) {
#else
     if (sscanf(memenv, "%ld%c", &max_to_use, &ch) > 0) {
#endif
       if (ch == 'm' || ch == 'M')
         max_to_use *= 1000L;
       mem->pub.max_memory_to_use = max_to_use * 1000L;
     }
   }
 }
#endif

}