/*
 * CACHE.C
 *
 *      Block cache for dump
 */

#include <sys/param.h>
#include <sys/stat.h>
#include <sys/mman.h>

#ifdef sunos
#include <sys/vnode.h>

#include <ufs/fs.h>
#include <ufs/fsdir.h>
#include <ufs/inode.h>
#else
#include <ufs/ufs/dir.h>
#include <ufs/ufs/dinode.h>
#include <ufs/ffs/fs.h>
#endif

#include <protocols/dumprestore.h>

#include <ctype.h>
#include <stdio.h>
#ifdef __STDC__
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#endif
#include "dump.h"

typedef struct Block {
        struct Block    *b_HNext;       /* must be first field */
        off_t           b_Offset;
        char            *b_Data;
} Block;

#define HFACTOR         4
#define BLKFACTOR       4

static char  *DataBase;
static Block **BlockHash;
static int   BlockSize;
static int   HSize;
static int   NBlocks;

static void
cinit(void)
{
        int i;
        int hi;
        Block *base;

        if ((BlockSize = sblock->fs_bsize * BLKFACTOR) > MAXBSIZE)
                BlockSize = MAXBSIZE;
        NBlocks = cachesize / BlockSize;
        HSize = NBlocks / HFACTOR;

        msg("Cache %d MB, blocksize = %d\n", 
            NBlocks * BlockSize / (1024 * 1024), BlockSize);

        base = calloc(sizeof(Block), NBlocks);
        BlockHash = calloc(sizeof(Block *), HSize);
        DataBase = mmap(NULL, NBlocks * BlockSize, 
                        PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
        for (i = 0; i < NBlocks; ++i) {
                base[i].b_Data = DataBase + i * BlockSize;
                base[i].b_Offset = (off_t)-1;
                hi = i / HFACTOR;
                base[i].b_HNext = BlockHash[hi];
                BlockHash[hi] = &base[i];
        }
}

ssize_t
cread(int fd, void *buf, size_t nbytes, off_t offset)
{
        Block *blk;
        Block **pblk;
        Block **ppblk;
        int hi;
        int n;
        off_t mask;

        /*
         * If the cache is disabled, or we do not yet know the filesystem
         * block size, then revert to pread.  Otherwise initialize the
         * cache as necessary and continue.
         */
        if (cachesize <= 0 || sblock->fs_bsize == 0)
                return(pread(fd, buf, nbytes, offset));
        if (DataBase == NULL)
                cinit();

        /*
         * If the request crosses a cache block boundary, or the
         * request is larger or equal to the cache block size,
         * revert to pread().  Full-block-reads are typically
         * one-time calls and caching would be detrimental.
         */
        mask = ~(off_t)(BlockSize - 1);
        if (nbytes >= BlockSize ||
            ((offset ^ (offset + nbytes - 1)) & mask) != 0) {
                return(pread(fd, buf, nbytes, offset));
        }

        /*
         * Obtain and access the cache block.  Cache a successful
         * result.  If an error occurs, revert to pread() (this might
         * occur near the end of the media).
         */
        hi = (offset / BlockSize) % HSize;
        pblk = &BlockHash[hi];
        ppblk = NULL;
        while ((blk = *pblk) != NULL) {
                if (((blk->b_Offset ^ offset) & mask) == 0)
                        break;
                ppblk = pblk;
                pblk = &blk->b_HNext;
        }
        if (blk == NULL) {
                blk = *ppblk;
                pblk = ppblk;
                blk->b_Offset = offset & mask;
                n = pread(fd, blk->b_Data, BlockSize, blk->b_Offset);
                if (n != BlockSize) {
                        blk->b_Offset = (off_t)-1;
                        blk = NULL;
                }
        }
        if (blk) {
                bcopy(blk->b_Data + (offset - blk->b_Offset), buf, nbytes);
                *pblk = blk->b_HNext;
                blk->b_HNext = BlockHash[hi];
                BlockHash[hi] = blk;
                return(nbytes);
        } else {
                return(pread(fd, buf, nbytes, offset));
        }
}