/*      $NetBSD: subr_blist.c,v 1.16 2024/09/08 17:28:36 rillig Exp $   */

/*-
 * Copyright (c) 1998 Matthew Dillon.  All Rights Reserved.
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*
 * BLIST.C -    Bitmap allocator/deallocator, using a radix tree with hinting
 *
 *      This module implements a general bitmap allocator/deallocator.  The
 *      allocator eats around 2 bits per 'block'.  The module does not 
 *      try to interpret the meaning of a 'block' other than to return 
 *      BLIST_NONE on an allocation failure.
 *
 *      A radix tree is used to maintain the bitmap.  Two radix constants are
 *      involved:  One for the bitmaps contained in the leaf nodes (typically
 *      32), and one for the meta nodes (typically 16).  Both meta and leaf
 *      nodes have a hint field.  This field gives us a hint as to the largest
 *      free contiguous range of blocks under the node.  It may contain a
 *      value that is too high, but will never contain a value that is too 
 *      low.  When the radix tree is searched, allocation failures in subtrees
 *      update the hint. 
 *
 *      The radix tree also implements two collapsed states for meta nodes:
 *      the ALL-ALLOCATED state and the ALL-FREE state.  If a meta node is
 *      in either of these two states, all information contained underneath
 *      the node is considered stale.  These states are used to optimize
 *      allocation and freeing operations.
 *
 *      The hinting greatly increases code efficiency for allocations while
 *      the general radix structure optimizes both allocations and frees.  The
 *      radix tree should be able to operate well no matter how much 
 *      fragmentation there is and no matter how large a bitmap is used.
 *
 *      Unlike the rlist code, the blist code wires all necessary memory at
 *      creation time.  Neither allocations nor frees require interaction with
 *      the memory subsystem.  In contrast, the rlist code may allocate memory 
 *      on an rlist_free() call.  The non-blocking features of the blist code
 *      are used to great advantage in the swap code (vm/nswap_pager.c).  The
 *      rlist code uses a little less overall memory than the blist code (but
 *      due to swap interleaving not all that much less), but the blist code 
 *      scales much, much better.
 *
 *      LAYOUT: The radix tree is laid out recursively using a
 *      linear array.  Each meta node is immediately followed (laid out
 *      sequentially in memory) by BLIST_META_RADIX lower level nodes.  This
 *      is a recursive structure but one that can be easily scanned through
 *      a very simple 'skip' calculation.  In order to support large radixes, 
 *      portions of the tree may reside outside our memory allocation.  We 
 *      handle this with an early-termination optimization (when bighint is 
 *      set to -1) on the scan.  The memory allocation is only large enough 
 *      to cover the number of blocks requested at creation time even if it
 *      must be encompassed in larger root-node radix.
 *
 *      NOTE: the allocator cannot currently allocate more than 
 *      BLIST_BMAP_RADIX blocks per call.  It will panic with 'allocation too 
 *      large' if you try.  This is an area that could use improvement.  The 
 *      radix is large enough that this restriction does not affect the swap 
 *      system, though.  Currently only the allocation code is effected by
 *      this algorithmic unfeature.  The freeing code can handle arbitrary
 *      ranges.
 *
 *      This code can be compiled stand-alone for debugging.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_blist.c,v 1.16 2024/09/08 17:28:36 rillig Exp $");
#if 0
__FBSDID("$FreeBSD: src/sys/kern/subr_blist.c,v 1.17 2004/06/04 04:03:25 alc Exp $");
#endif

#ifdef _KERNEL

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/blist.h>
#include <sys/kmem.h>

#else

#ifndef BLIST_NO_DEBUG
#define BLIST_DEBUG
#endif

#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <inttypes.h>

#define KM_SLEEP 1
#define kmem_zalloc(a,b) calloc(1, (a))
#define kmem_alloc(a,b) malloc(a)
#define kmem_free(a,b) free(a)

#include "../sys/blist.h"

void panic(const char *ctl, ...) __printflike(1, 2);

#endif

/*
 * blmeta and bl_bitmap_t MUST be a power of 2 in size.
 */

typedef struct blmeta {
        union {
                blist_blkno_t   bmu_avail; /* space available under us  */
                blist_bitmap_t  bmu_bitmap; /* bitmap if we are a leaf  */
        } u;
        blist_blkno_t   bm_bighint;     /* biggest contiguous block hint*/
} blmeta_t;

struct blist {
        blist_blkno_t           bl_blocks;      /* area of coverage             */
        blist_blkno_t           bl_radix;       /* coverage radix               */
        blist_blkno_t           bl_skip;        /* starting skip                */
        blist_blkno_t           bl_free;        /* number of free blocks        */
        blmeta_t        *bl_root;       /* root of radix tree           */
        blist_blkno_t           bl_rootblks;    /* blks allocated for tree */
};

#define BLIST_META_RADIX        16

/*
 * static support functions
 */

static blist_blkno_t blst_leaf_alloc(blmeta_t *scan, blist_blkno_t blk,
    int count);
static blist_blkno_t blst_meta_alloc(blmeta_t *scan, blist_blkno_t blk, 
    blist_blkno_t count, blist_blkno_t radix, blist_blkno_t skip);
static void blst_leaf_free(blmeta_t *scan, blist_blkno_t relblk, int count);
static void blst_meta_free(blmeta_t *scan, blist_blkno_t freeBlk,
    blist_blkno_t count, blist_blkno_t radix, blist_blkno_t skip,
    blist_blkno_t blk);
static void blst_copy(blmeta_t *scan, blist_blkno_t blk, blist_blkno_t radix, 
    blist_blkno_t skip, blist_t dest, blist_blkno_t count);
static int blst_leaf_fill(blmeta_t *scan, blist_blkno_t blk, int count);
static blist_blkno_t blst_meta_fill(blmeta_t *scan, blist_blkno_t allocBlk,
    blist_blkno_t count, blist_blkno_t radix, blist_blkno_t skip,
    blist_blkno_t blk);
static blist_blkno_t blst_radix_init(blmeta_t *scan, blist_blkno_t radix, 
    blist_blkno_t skip, blist_blkno_t count);
#ifndef _KERNEL
static void blst_radix_print(blmeta_t *scan, blist_blkno_t blk,
    blist_blkno_t radix, blist_blkno_t skip, int tab);
#endif

/*
 * blist_create() - create a blist capable of handling up to the specified
 *                  number of blocks
 *
 *      blocks must be greater than 0
 *
 *      The smallest blist consists of a single leaf node capable of 
 *      managing BLIST_BMAP_RADIX blocks.
 */

blist_t 
blist_create(blist_blkno_t blocks)
{
        blist_t bl;
        blist_blkno_t radix;
        blist_blkno_t skip = 0;

        /*
         * Calculate radix and skip field used for scanning.
         *
         * XXX check overflow
         */
        radix = BLIST_BMAP_RADIX;

        while (radix < blocks) {
                radix *= BLIST_META_RADIX;
                skip = (skip + 1) * BLIST_META_RADIX;
        }

        bl = kmem_zalloc(sizeof(struct blist), KM_SLEEP);

        bl->bl_blocks = blocks;
        bl->bl_radix = radix;
        bl->bl_skip = skip;
        bl->bl_rootblks = 1 +
            blst_radix_init(NULL, bl->bl_radix, bl->bl_skip, blocks);
        bl->bl_root = kmem_alloc(sizeof(blmeta_t) * bl->bl_rootblks, KM_SLEEP);

#if defined(BLIST_DEBUG)
        printf(
                "BLIST representing %" PRIu64 " blocks (%" PRIu64 " MB of swap)"
                ", requiring %" PRIu64 "K of ram\n",
                (uint64_t)bl->bl_blocks,
                (uint64_t)bl->bl_blocks * 4 / 1024,
                ((uint64_t)bl->bl_rootblks * sizeof(blmeta_t) + 1023) / 1024
        );
        printf("BLIST raw radix tree contains %" PRIu64 " records\n",
            (uint64_t)bl->bl_rootblks);
#endif
        blst_radix_init(bl->bl_root, bl->bl_radix, bl->bl_skip, blocks);

        return(bl);
}

void 
blist_destroy(blist_t bl)
{

        kmem_free(bl->bl_root, sizeof(blmeta_t) * bl->bl_rootblks);
        kmem_free(bl, sizeof(struct blist));
}

/*
 * blist_alloc() - reserve space in the block bitmap.  Return the base
 *                   of a contiguous region or BLIST_NONE if space could
 *                   not be allocated.
 */

blist_blkno_t 
blist_alloc(blist_t bl, blist_blkno_t count)
{
        blist_blkno_t blk = BLIST_NONE;

        if (bl) {
                if (bl->bl_radix == BLIST_BMAP_RADIX)
                        blk = blst_leaf_alloc(bl->bl_root, 0, count);
                else
                        blk = blst_meta_alloc(bl->bl_root, 0, count, bl->bl_radix, bl->bl_skip);
                if (blk != BLIST_NONE)
                        bl->bl_free -= count;
        }
        return(blk);
}

/*
 * blist_free() -       free up space in the block bitmap.  Return the base
 *                      of a contiguous region.  Panic if an inconsistency is
 *                      found.
 */

void 
blist_free(blist_t bl, blist_blkno_t blkno, blist_blkno_t count)
{
        if (bl) {
                if (bl->bl_radix == BLIST_BMAP_RADIX)
                        blst_leaf_free(bl->bl_root, blkno, count);
                else
                        blst_meta_free(bl->bl_root, blkno, count, bl->bl_radix, bl->bl_skip, 0);
                bl->bl_free += count;
        }
}

/*
 * blist_fill() -       mark a region in the block bitmap as off-limits
 *                      to the allocator (i.e. allocate it), ignoring any
 *                      existing allocations.  Return the number of blocks
 *                      actually filled that were free before the call.
 */

blist_blkno_t
blist_fill(blist_t bl, blist_blkno_t blkno, blist_blkno_t count)
{
        blist_blkno_t filled;

        if (bl) {
                if (bl->bl_radix == BLIST_BMAP_RADIX)
                        filled = blst_leaf_fill(bl->bl_root, blkno, count);
                else
                        filled = blst_meta_fill(bl->bl_root, blkno, count,
                            bl->bl_radix, bl->bl_skip, 0);
                bl->bl_free -= filled;
                return filled;
        } else
                return 0;
}

/*
 * blist_resize() -     resize an existing radix tree to handle the
 *                      specified number of blocks.  This will reallocate
 *                      the tree and transfer the previous bitmap to the new
 *                      one.  When extending the tree you can specify whether
 *                      the new blocks are to left allocated or freed.
 */

void
blist_resize(blist_t *pbl, blist_blkno_t count, int freenew)
{
    blist_t newbl = blist_create(count);
    blist_t save = *pbl;

    *pbl = newbl;
    if (count > save->bl_blocks)
            count = save->bl_blocks;
    blst_copy(save->bl_root, 0, save->bl_radix, save->bl_skip, newbl, count);

    /*
     * If resizing upwards, should we free the new space or not?
     */
    if (freenew && count < newbl->bl_blocks) {
            blist_free(newbl, count, newbl->bl_blocks - count);
    }
    blist_destroy(save);
}

#ifdef BLIST_DEBUG

/*
 * blist_print()    - dump radix tree
 */

void
blist_print(blist_t bl)
{
        printf("BLIST {\n");
        blst_radix_print(bl->bl_root, 0, bl->bl_radix, bl->bl_skip, 4);
        printf("}\n");
}

#endif

/************************************************************************
 *                        ALLOCATION SUPPORT FUNCTIONS                  *
 ************************************************************************
 *
 *      These support functions do all the actual work.  They may seem 
 *      rather longish, but that's because I've commented them up.  The
 *      actual code is straight forward.
 *
 */

/*
 * blist_leaf_alloc() - allocate at a leaf in the radix tree (a bitmap).
 *
 *      This is the core of the allocator and is optimized for the 1 block
 *      and the BLIST_BMAP_RADIX block allocation cases.  Other cases are
 *      somewhat slower.  The 1 block allocation case is log2 and extremely
 *      quick.
 */

static blist_blkno_t
blst_leaf_alloc(
        blmeta_t *scan,
        blist_blkno_t blk,
        int count
) {
        blist_bitmap_t orig = scan->u.bmu_bitmap;

        if (orig == 0) {
                /*
                 * Optimize bitmap all-allocated case.  Also, count = 1
                 * case assumes at least 1 bit is free in the bitmap, so
                 * we have to take care of this case here.
                 */
                scan->bm_bighint = 0;
                return(BLIST_NONE);
        }
        if (count == 1) {
                /*
                 * Optimized code to allocate one bit out of the bitmap
                 */
                blist_bitmap_t mask;
                int j = BLIST_BMAP_RADIX/2;
                int r = 0;

                mask = (blist_bitmap_t)-1 >> (BLIST_BMAP_RADIX/2);

                while (j) {
                        if ((orig & mask) == 0) {
                            r += j;
                            orig >>= j;
                        }
                        j >>= 1;
                        mask >>= j;
                }
                scan->u.bmu_bitmap &= ~((blist_bitmap_t)1 << r);
                return(blk + r);
        }
        if (count <= BLIST_BMAP_RADIX) {
                /*
                 * non-optimized code to allocate N bits out of the bitmap.
                 * The more bits, the faster the code runs.  It will run
                 * the slowest allocating 2 bits, but since there aren't any
                 * memory ops in the core loop (or shouldn't be, anyway),
                 * you probably won't notice the difference.
                 */
                int j;
                int n = BLIST_BMAP_RADIX - count;
                blist_bitmap_t mask;

                mask = (blist_bitmap_t)-1 >> n;

                for (j = 0; j <= n; ++j) {
                        if ((orig & mask) == mask) {
                                scan->u.bmu_bitmap &= ~mask;
                                return(blk + j);
                        }
                        mask = (mask << 1);
                }
        }
        /*
         * We couldn't allocate count in this subtree, update bighint.
         */
        scan->bm_bighint = count - 1;
        return(BLIST_NONE);
}

/*
 * blist_meta_alloc() - allocate at a meta in the radix tree.
 *
 *      Attempt to allocate at a meta node.  If we can't, we update
 *      bighint and return a failure.  Updating bighint optimize future
 *      calls that hit this node.  We have to check for our collapse cases
 *      and we have a few optimizations strewn in as well.
 */

static blist_blkno_t
blst_meta_alloc(
        blmeta_t *scan, 
        blist_blkno_t blk,
        blist_blkno_t count,
        blist_blkno_t radix, 
        blist_blkno_t skip
) {
        blist_blkno_t i;
        blist_blkno_t next_skip = (skip / BLIST_META_RADIX);

        if (scan->u.bmu_avail == 0)  {
                /*
                 * ALL-ALLOCATED special case
                 */
                scan->bm_bighint = count;
                return(BLIST_NONE);
        }

        if (scan->u.bmu_avail == radix) {
                radix /= BLIST_META_RADIX;

                /*
                 * ALL-FREE special case, initialize uninitialize
                 * sublevel.
                 */
                for (i = 1; i <= skip; i += next_skip) {
                        if (scan[i].bm_bighint == (blist_blkno_t)-1)
                                break;
                        if (next_skip == 1) {
                                scan[i].u.bmu_bitmap = (blist_bitmap_t)-1;
                                scan[i].bm_bighint = BLIST_BMAP_RADIX;
                        } else {
                                scan[i].bm_bighint = radix;
                                scan[i].u.bmu_avail = radix;
                        }
                }
        } else {
                radix /= BLIST_META_RADIX;
        }

        for (i = 1; i <= skip; i += next_skip) {
                if (scan[i].bm_bighint == (blist_blkno_t)-1) {
                        /*
                         * Terminator
                         */
                        break;
                } else if (count <= scan[i].bm_bighint) {
                        /*
                         * count fits in object
                         */
                        blist_blkno_t r;
                        if (next_skip == 1) {
                                r = blst_leaf_alloc(&scan[i], blk, count);
                        } else {
                                r = blst_meta_alloc(&scan[i], blk, count, radix, next_skip - 1);
                        }
                        if (r != BLIST_NONE) {
                                scan->u.bmu_avail -= count;
                                if (scan->bm_bighint > scan->u.bmu_avail)
                                        scan->bm_bighint = scan->u.bmu_avail;
                                return(r);
                        }
                } else if (count > radix) {
                        /*
                         * count does not fit in object even if it were
                         * complete free.
                         */
                        panic("blist_meta_alloc: allocation too large");
                }
                blk += radix;
        }

        /*
         * We couldn't allocate count in this subtree, update bighint.
         */
        if (scan->bm_bighint >= count)
                scan->bm_bighint = count - 1;
        return(BLIST_NONE);
}

/*
 * BLST_LEAF_FREE() -   free allocated block from leaf bitmap
 *
 */

static void
blst_leaf_free(
        blmeta_t *scan,
        blist_blkno_t blk,
        int count
) {
        /*
         * free some data in this bitmap
         *
         * e.g.
         *      0000111111111110000
         *          \_________/\__/
         *              v        n
         */
        int n = blk & (BLIST_BMAP_RADIX - 1);
        blist_bitmap_t mask;

        mask = ((blist_bitmap_t)-1 << n) &
            ((blist_bitmap_t)-1 >> (BLIST_BMAP_RADIX - count - n));

        if (scan->u.bmu_bitmap & mask)
                panic("blst_radix_free: freeing free block");
        scan->u.bmu_bitmap |= mask;

        /*
         * We could probably do a better job here.  We are required to make
         * bighint at least as large as the biggest contiguous block of 
         * data.  If we just shoehorn it, a little extra overhead will
         * be incured on the next allocation (but only that one typically).
         */
        scan->bm_bighint = BLIST_BMAP_RADIX;
}

/*
 * BLST_META_FREE() - free allocated blocks from radix tree meta info
 *
 *      This support routine frees a range of blocks from the bitmap.
 *      The range must be entirely enclosed by this radix node.  If a
 *      meta node, we break the range down recursively to free blocks
 *      in subnodes (which means that this code can free an arbitrary
 *      range whereas the allocation code cannot allocate an arbitrary
 *      range).
 */

static void 
blst_meta_free(
        blmeta_t *scan, 
        blist_blkno_t freeBlk,
        blist_blkno_t count,
        blist_blkno_t radix, 
        blist_blkno_t skip,
        blist_blkno_t blk
) {
        blist_blkno_t i;
        blist_blkno_t next_skip = (skip / BLIST_META_RADIX);

#if 0
        printf("FREE (%" PRIx64 ",%" PRIu64
            ") FROM (%" PRIx64 ",%" PRIu64 ")\n",
            (uint64_t)freeBlk, (uint64_t)count,
            (uint64_t)blk, (uint64_t)radix
        );
#endif

        if (scan->u.bmu_avail == 0) {
                /*
                 * ALL-ALLOCATED special case, with possible
                 * shortcut to ALL-FREE special case.
                 */
                scan->u.bmu_avail = count;
                scan->bm_bighint = count;

                if (count != radix)  {
                        for (i = 1; i <= skip; i += next_skip) {
                                if (scan[i].bm_bighint == (blist_blkno_t)-1)
                                        break;
                                scan[i].bm_bighint = 0;
                                if (next_skip == 1) {
                                        scan[i].u.bmu_bitmap = 0;
                                } else {
                                        scan[i].u.bmu_avail = 0;
                                }
                        }
                        /* fall through */
                }
        } else {
                scan->u.bmu_avail += count;
                /* scan->bm_bighint = radix; */
        }

        /*
         * ALL-FREE special case.
         */

        if (scan->u.bmu_avail == radix)
                return;
        if (scan->u.bmu_avail > radix)
                panic("blst_meta_free: freeing already free blocks (%"
                    PRIu64 ") %" PRIu64 "/%" PRIu64,
                    (uint64_t)count,
                    (uint64_t)scan->u.bmu_avail,
                    (uint64_t)radix);

        /*
         * Break the free down into its components
         */

        radix /= BLIST_META_RADIX;

        i = (freeBlk - blk) / radix;
        blk += i * radix;
        i = i * next_skip + 1;

        while (i <= skip && blk < freeBlk + count) {
                blist_blkno_t v;

                v = blk + radix - freeBlk;
                if (v > count)
                        v = count;

                if (scan->bm_bighint == (blist_blkno_t)-1)
                        panic("blst_meta_free: freeing unexpected range");

                if (next_skip == 1) {
                        blst_leaf_free(&scan[i], freeBlk, v);
                } else {
                        blst_meta_free(&scan[i], freeBlk, v, radix, next_skip - 1, blk);
                }
                if (scan->bm_bighint < scan[i].bm_bighint)
                    scan->bm_bighint = scan[i].bm_bighint;
                count -= v;
                freeBlk += v;
                blk += radix;
                i += next_skip;
        }
}

/*
 * BLIST_RADIX_COPY() - copy one radix tree to another
 *
 *      Locates free space in the source tree and frees it in the destination
 *      tree.  The space may not already be free in the destination.
 */

static void blst_copy(
        blmeta_t *scan, 
        blist_blkno_t blk,
        blist_blkno_t radix, 
        blist_blkno_t skip, 
        blist_t dest,
        blist_blkno_t count
) {
        blist_blkno_t next_skip;
        blist_blkno_t i;

        /*
         * Leaf node
         */

        if (radix == BLIST_BMAP_RADIX) {
                blist_bitmap_t v = scan->u.bmu_bitmap;

                if (v == (blist_bitmap_t)-1) {
                        blist_free(dest, blk, count);
                } else if (v != 0) {
                        int j;

                        for (j = 0; j < BLIST_BMAP_RADIX && j < count; ++j) {
                                if (v & (1 << j))
                                        blist_free(dest, blk + j, 1);
                        }
                }
                return;
        }

        /*
         * Meta node
         */

        if (scan->u.bmu_avail == 0) {
                /*
                 * Source all allocated, leave dest allocated
                 */
                return;
        } 
        if (scan->u.bmu_avail == radix) {
                /*
                 * Source all free, free entire dest
                 */
                if (count < radix)
                        blist_free(dest, blk, count);
                else
                        blist_free(dest, blk, radix);
                return;
        }


        radix /= BLIST_META_RADIX;
        next_skip = (skip / BLIST_META_RADIX);

        for (i = 1; count && i <= skip; i += next_skip) {
                if (scan[i].bm_bighint == (blist_blkno_t)-1)
                        break;

                if (count >= radix) {
                        blst_copy(
                            &scan[i],
                            blk,
                            radix,
                            next_skip - 1,
                            dest,
                            radix
                        );
                        count -= radix;
                } else {
                        if (count) {
                                blst_copy(
                                    &scan[i],
                                    blk,
                                    radix,
                                    next_skip - 1,
                                    dest,
                                    count
                                );
                        }
                        count = 0;
                }
                blk += radix;
        }
}

/*
 * BLST_LEAF_FILL() -   allocate specific blocks in leaf bitmap
 *
 *      This routine allocates all blocks in the specified range
 *      regardless of any existing allocations in that range.  Returns
 *      the number of blocks allocated by the call.
 */

static int
blst_leaf_fill(blmeta_t *scan, blist_blkno_t blk, int count)
{
        int n = blk & (BLIST_BMAP_RADIX - 1);
        int nblks;
        blist_bitmap_t mask, bitmap;

        mask = ((blist_bitmap_t)-1 << n) &
            ((blist_bitmap_t)-1 >> (BLIST_BMAP_RADIX - count - n));

        /* Count the number of blocks we're about to allocate */
        bitmap = scan->u.bmu_bitmap & mask;
        for (nblks = 0; bitmap != 0; nblks++)
                bitmap &= bitmap - 1;

        scan->u.bmu_bitmap &= ~mask;
        return nblks;
}

/*
 * BLIST_META_FILL() -  allocate specific blocks at a meta node
 *
 *      This routine allocates the specified range of blocks,
 *      regardless of any existing allocations in the range.  The
 *      range must be within the extent of this node.  Returns the
 *      number of blocks allocated by the call.
 */
static blist_blkno_t
blst_meta_fill(
        blmeta_t *scan,
        blist_blkno_t allocBlk,
        blist_blkno_t count,
        blist_blkno_t radix, 
        blist_blkno_t skip,
        blist_blkno_t blk
) {
        blist_blkno_t i;
        blist_blkno_t next_skip = (skip / BLIST_META_RADIX);
        blist_blkno_t nblks = 0;

        if (count == radix || scan->u.bmu_avail == 0)  {
                /*
                 * ALL-ALLOCATED special case
                 */
                nblks = scan->u.bmu_avail;
                scan->u.bmu_avail = 0;
                scan->bm_bighint = count;
                return nblks;
        }

        if (count > radix)
                panic("blist_meta_fill: allocation too large");

        if (scan->u.bmu_avail == radix) {
                radix /= BLIST_META_RADIX;

                /*
                 * ALL-FREE special case, initialize sublevel
                 */
                for (i = 1; i <= skip; i += next_skip) {
                        if (scan[i].bm_bighint == (blist_blkno_t)-1)
                                break;
                        if (next_skip == 1) {
                                scan[i].u.bmu_bitmap = (blist_bitmap_t)-1;
                                scan[i].bm_bighint = BLIST_BMAP_RADIX;
                        } else {
                                scan[i].bm_bighint = radix;
                                scan[i].u.bmu_avail = radix;
                        }
                }
        } else {
                radix /= BLIST_META_RADIX;
        }

        i = (allocBlk - blk) / radix;
        blk += i * radix;
        i = i * next_skip + 1;

        while (i <= skip && blk < allocBlk + count) {
                blist_blkno_t v;

                v = blk + radix - allocBlk;
                if (v > count)
                        v = count;

                if (scan->bm_bighint == (blist_blkno_t)-1)
                        panic("blst_meta_fill: filling unexpected range");

                if (next_skip == 1) {
                        nblks += blst_leaf_fill(&scan[i], allocBlk, v);
                } else {
                        nblks += blst_meta_fill(&scan[i], allocBlk, v,
                            radix, next_skip - 1, blk);
                }
                count -= v;
                allocBlk += v;
                blk += radix;
                i += next_skip;
        }
        scan->u.bmu_avail -= nblks;
        return nblks;
}

/*
 * BLST_RADIX_INIT() - initialize radix tree
 *
 *      Initialize our meta structures and bitmaps and calculate the exact
 *      amount of space required to manage 'count' blocks - this space may
 *      be considerably less than the calculated radix due to the large
 *      RADIX values we use.
 */

static blist_blkno_t    
blst_radix_init(blmeta_t *scan, blist_blkno_t radix, blist_blkno_t skip,
    blist_blkno_t count)
{
        blist_blkno_t i;
        blist_blkno_t next_skip;
        blist_blkno_t memindex = 0;

        /*
         * Leaf node
         */

        if (radix == BLIST_BMAP_RADIX) {
                if (scan) {
                        scan->bm_bighint = 0;
                        scan->u.bmu_bitmap = 0;
                }
                return(memindex);
        }

        /*
         * Meta node.  If allocating the entire object we can special
         * case it.  However, we need to figure out how much memory
         * is required to manage 'count' blocks, so we continue on anyway.
         */

        if (scan) {
                scan->bm_bighint = 0;
                scan->u.bmu_avail = 0;
        }

        radix /= BLIST_META_RADIX;
        next_skip = (skip / BLIST_META_RADIX);

        for (i = 1; i <= skip; i += next_skip) {
                if (count >= radix) {
                        /*
                         * Allocate the entire object
                         */
                        memindex = i + blst_radix_init(
                            ((scan) ? &scan[i] : NULL),
                            radix,
                            next_skip - 1,
                            radix
                        );
                        count -= radix;
                } else if (count > 0) {
                        /*
                         * Allocate a partial object
                         */
                        memindex = i + blst_radix_init(
                            ((scan) ? &scan[i] : NULL),
                            radix,
                            next_skip - 1,
                            count
                        );
                        count = 0;
                } else {
                        /*
                         * Add terminator and break out
                         */
                        if (scan)
                                scan[i].bm_bighint = (blist_blkno_t)-1;
                        break;
                }
        }
        if (memindex < i)
                memindex = i;
        return(memindex);
}

#ifdef BLIST_DEBUG

static void     
blst_radix_print(blmeta_t *scan, blist_blkno_t blk, blist_blkno_t radix,
    blist_blkno_t skip, int tab)
{
        blist_blkno_t i;
        blist_blkno_t next_skip;
        int lastState = 0;

        if (radix == BLIST_BMAP_RADIX) {
                printf(
                    "%*.*s(%0*" PRIx64 ",%" PRIu64
                    "): bitmap %0*" PRIx64 " big=%" PRIu64 "\n", 
                    tab, tab, "",
                    sizeof(blk) * 2,
                    (uint64_t)blk,
                    (uint64_t)radix,
                    sizeof(scan->u.bmu_bitmap) * 2,
                    (uint64_t)scan->u.bmu_bitmap,
                    (uint64_t)scan->bm_bighint
                );
                return;
        }

        if (scan->u.bmu_avail == 0) {
                printf(
                    "%*.*s(%0*" PRIx64 ",%" PRIu64") ALL ALLOCATED\n",
                    tab, tab, "",
                    sizeof(blk) * 2,
                    (uint64_t)blk,
                    (uint64_t)radix
                );
                return;
        }
        if (scan->u.bmu_avail == radix) {
                printf(
                    "%*.*s(%0*" PRIx64 ",%" PRIu64 ") ALL FREE\n",
                    tab, tab, "",
                    sizeof(blk) * 2,
                    (uint64_t)blk,
                    (uint64_t)radix
                );
                return;
        }

        printf(
            "%*.*s(%0*" PRIx64 ",%" PRIu64 "): subtree (%" PRIu64 "/%"
            PRIu64 ") big=%" PRIu64 " {\n",
            tab, tab, "",
            sizeof(blk) * 2,
            (uint64_t)blk,
            (uint64_t)radix,
            (uint64_t)scan->u.bmu_avail,
            (uint64_t)radix,
            (uint64_t)scan->bm_bighint
        );

        radix /= BLIST_META_RADIX;
        next_skip = (skip / BLIST_META_RADIX);
        tab += 4;

        for (i = 1; i <= skip; i += next_skip) {
                if (scan[i].bm_bighint == (blist_blkno_t)-1) {
                        printf(
                            "%*.*s(%0*" PRIx64 ",%" PRIu64 "): Terminator\n",
                            tab, tab, "",
                            sizeof(blk) * 2,
                            (uint64_t)blk,
                            (uint64_t)radix
                        );
                        lastState = 0;
                        break;
                }
                blst_radix_print(
                    &scan[i],
                    blk,
                    radix,
                    next_skip - 1,
                    tab
                );
                blk += radix;
        }
        tab -= 4;

        printf(
            "%*.*s}\n",
            tab, tab, ""
        );
}

#endif

#ifdef BLIST_DEBUG

int
main(int ac, char **av)
{
        blist_blkno_t size = 1024;
        int i;
        blist_t bl;

        for (i = 1; i < ac; ++i) {
                const char *ptr = av[i];
                if (*ptr != '-') {
                        size = strtol(ptr, NULL, 0);
                        continue;
                }
                ptr += 2;
                fprintf(stderr, "Bad option: %s\n", ptr - 2);
                exit(1);
        }
        bl = blist_create(size);
        blist_free(bl, 0, size);

        for (;;) {
                char buf[1024];
                uint64_t da = 0;
                uint64_t count = 0;

                printf("%" PRIu64 "/%" PRIu64 "/%" PRIu64 "> ",
                    (uint64_t)bl->bl_free,
                    (uint64_t)size,
                    (uint64_t)bl->bl_radix);
                fflush(stdout);
                if (fgets(buf, sizeof(buf), stdin) == NULL)
                        break;
                switch(buf[0]) {
                case 'r':
                        if (sscanf(buf + 1, "%" SCNu64, &count) == 1) {
                                blist_resize(&bl, count, 1);
                        } else {
                                printf("?\n");
                        }
                case 'p':
                        blist_print(bl);
                        break;
                case 'a':
                        if (sscanf(buf + 1, "%" SCNu64, &count) == 1) {
                                blist_blkno_t blk = blist_alloc(bl, count);
                                printf("    R=%0*" PRIx64 "\n",
                                    sizeof(blk) * 2,
                                    (uint64_t)blk);
                        } else {
                                printf("?\n");
                        }
                        break;
                case 'f':
                        if (sscanf(buf + 1, "%" SCNx64 " %" SCNu64,
                            &da, &count) == 2) {
                                blist_free(bl, da, count);
                        } else {
                                printf("?\n");
                        }
                        break;
                case 'l':
                        if (sscanf(buf + 1, "%" SCNx64 " %" SCNu64,
                            &da, &count) == 2) {
                                printf("    n=%" PRIu64 "\n",
                                    (uint64_t)blist_fill(bl, da, count));
                        } else {
                                printf("?\n");
                        }
                        break;
                case '?':
                case 'h':
                        puts(
                            "p          -print\n"
                            "a %d       -allocate\n"
                            "f %x %d    -free\n"
                            "l %x %d    -fill\n"
                            "r %d       -resize\n"
                            "h/?        -help"
                        );
                        break;
                default:
                        printf("?\n");
                        break;
                }
        }
        return(0);
}

void
panic(const char *ctl, ...)
{
        va_list va;

        va_start(va, ctl);
        vfprintf(stderr, ctl, va);
        fprintf(stderr, "\n");
        va_end(va);
        exit(1);
}

#endif