X-Git-Url: http://git.indexdata.com/?p=idzebra-moved-to-github.git;a=blobdiff_plain;f=isamc%2Fisamc.c;h=24beceba941a2d32fb243814b75602d0dacbc28c;hp=656cae0f46eb8214ae5ac900065959bcd007a1d3;hb=HEAD;hpb=16153aaaa1fcb0881ff7e3056bd9c991fcf57c29

diff --git a/isamc/isamc.c b/isamc/isamc.c
index 656cae0..24beceb 100644
--- a/isamc/isamc.c
+++ b/isamc/isamc.c
@@ -1,97 +1,104 @@
-/*
- * Copyright (c) 1995-1996, Index Data.
- * See the file LICENSE for details.
- * Sebastian Hammer, Adam Dickmeiss
- *
- * $Log: isamc.c,v $
- * Revision 1.5  1996-11-04 14:08:57  adam
- * Optimized free block usage.
- *
- * Revision 1.4  1996/11/01 13:36:46  adam
- * New element, max_blocks_mem, that control how many blocks of max size
- * to store in memory during isc_merge.
- * Function isc_merge now ignores delete/update of identical keys and
- * the proper blocks are then non-dirty and not written in flush_blocks.
- *
- * Revision 1.3  1996/11/01  08:59:14  adam
- * First version of isc_merge that supports update/delete.
- *
- * Revision 1.2  1996/10/29 16:44:56  adam
- * Work on isc_merge.
- *
- * Revision 1.1  1996/10/29  13:40:48  adam
- * First work.
- *
- */
+/* This file is part of the Zebra server.
+   Copyright (C) Index Data
+
+Zebra is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+Zebra is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
 
-/* 
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+*/
+
+/*
  * TODO:
- *   Reduction to lower categories in isc_merge
- *   Implementation of isc_numkeys
+ *   Reduction to lower categories in isamc_merge
  */
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif
 #include <stdlib.h>
 #include <assert.h>
 #include <string.h>
 #include <stdio.h>
 
-#include <log.h>
+#include <yaz/log.h>
+#include <yaz/xmalloc.h>
 #include "isamc-p.h"
 
+static void flush_block (ISAMC is, int cat);
 static void release_fc (ISAMC is, int cat);
 static void init_fc (ISAMC is, int cat);
 
-ISAMC_M isc_getmethod (void)
+#define ISAMC_FREELIST_CHUNK 0
+
+#define SMALL_TEST 0
+
+void isamc_getmethod (ISAMC_M *m)
 {
+
     static struct ISAMC_filecat_s def_cat[] = {
-        {   32,    28,     0,    20 },
-        {  512,   490,   100,    20 },
-        { 4096,  3950,  1000,    20 },
-        {32768, 32000, 10000,     0 },
-        {    0,     0,     0,     0 }
+#if SMALL_TEST
+        {    32,     28,      0,  3 },
+	{    64,     54,     30,  0 },
+#else
+        {    64,     56,     40,  5 },
+	{   128,    120,    100,  10 },
+        {   512,    490,    350,  10 },
+        {  2048,   1900,   1700,  10 },
+        {  8192,   8000,   7900,  10 },
+        { 32768,  32000,  31000,  0 },
+#endif
     };
-    ISAMC_M m = xmalloc (sizeof(*m));
     m->filecat = def_cat;
 
-    m->code_start = NULL;
-    m->code_item = NULL;
-    m->code_stop = NULL;
+    m->codec.start = NULL;
+    m->codec.decode  = NULL;
+    m->codec.encode = NULL;
+    m->codec.stop = NULL;
+    m->codec.reset = NULL;
 
     m->compare_item = NULL;
+    m->log_item = NULL;
 
-    m->debug = 0;
+    m->debug = 1;
 
     m->max_blocks_mem = 10;
-
-    return m;
 }
 
-
-ISAMC isc_open (const char *name, int writeflag, ISAMC_M method)
+ISAMC isamc_open (BFiles bfs, const char *name, int writeflag, ISAMC_M *method)
 {
     ISAMC is;
     ISAMC_filecat filecat;
-    int i, j;
+    int i = 0;
     int max_buf_size = 0;
 
-    is = xmalloc (sizeof(*is));
+    is = (ISAMC) xmalloc (sizeof(*is));
 
-    is->method = xmalloc (sizeof(*is->method));
+    is->method = (ISAMC_M *) xmalloc (sizeof(*is->method));
     memcpy (is->method, method, sizeof(*method));
     filecat = is->method->filecat;
     assert (filecat);
 
     /* determine number of block categories */
     if (is->method->debug)
-        logf (LOG_LOG, "isc: bsize  ifill  mfill mblocks");
-    for (i = 0; filecat[i].bsize; i++)
+        yaz_log (YLOG_LOG, "isc: bsize  ifill  mfill mblocks");
+    do
     {
         if (is->method->debug)
-            logf (LOG_LOG, "isc:%6d %6d %6d %6d",
-                  filecat[i].bsize, filecat[i].ifill, 
+            yaz_log (YLOG_LOG, "isc:%6d %6d %6d %6d",
+                  filecat[i].bsize, filecat[i].ifill,
                   filecat[i].mfill, filecat[i].mblocks);
         if (max_buf_size < filecat[i].mblocks * filecat[i].bsize)
             max_buf_size = filecat[i].mblocks * filecat[i].bsize;
-    }
+    } while (filecat[i++].mblocks);
     is->no_files = i;
     is->max_cat = --i;
     /* max_buf_size is the larget buffer to be used during merge */
@@ -99,157 +106,320 @@ ISAMC isc_open (const char *name, int writeflag, ISAMC_M method)
     if (max_buf_size < (1+is->method->max_blocks_mem) * filecat[i].bsize)
         max_buf_size = (1+is->method->max_blocks_mem) * filecat[i].bsize;
     if (is->method->debug)
-        logf (LOG_LOG, "isc: max_buf_size %d", max_buf_size);
-    
+        yaz_log (YLOG_LOG, "isc: max_buf_size %d", max_buf_size);
+
     assert (is->no_files > 0);
-    is->files = xmalloc (sizeof(*is->files)*is->no_files);
+    is->files = (ISAMC_file) xmalloc (sizeof(*is->files)*is->no_files);
     if (writeflag)
     {
-        is->merge_buf = xmalloc (max_buf_size+128);
-	memset (is->merge_buf, 0, max_buf_size+128);
+        is->merge_buf = (char *) xmalloc (max_buf_size+256);
+	memset (is->merge_buf, 0, max_buf_size+256);
     }
     else
         is->merge_buf = NULL;
     for (i = 0; i<is->no_files; i++)
     {
-        char fname[512];
-
-        sprintf (fname, "%s%c", name, i+'A');
-        is->files[i].bf = bf_open (fname, is->method->filecat[i].bsize,
-                                   writeflag);
+        is->files[i].bf = 0;
         is->files[i].head_is_dirty = 0;
-        if (!bf_read (is->files[i].bf, 0, 0, sizeof(ISAMC_head),
-                     &is->files[i].head))
-        {
-            is->files[i].head.lastblock = 1;
-            is->files[i].head.freelist = 0;
-        }
+        is->files[i].head.lastblock = 1;
+        is->files[i].head.freelist = 0;
+	is->files[i].alloc_entries_num = 0;
+	is->files[i].alloc_entries_max =
+	    is->method->filecat[i].bsize / sizeof(zint) - 1;
+	is->files[i].alloc_buf = (char *)
+	    xmalloc (is->method->filecat[i].bsize);
         is->files[i].no_writes = 0;
         is->files[i].no_reads = 0;
         is->files[i].no_skip_writes = 0;
         is->files[i].no_allocated = 0;
         is->files[i].no_released = 0;
         is->files[i].no_remap = 0;
+	is->files[i].no_forward = 0;
+	is->files[i].no_backward = 0;
+	is->files[i].sum_forward = 0;
+	is->files[i].sum_backward = 0;
+	is->files[i].no_next = 0;
+	is->files[i].no_prev = 0;
 
         init_fc (is, i);
     }
+
+    for (i = 0; i<is->no_files; i++)
+    {
+        char fname[FILENAME_MAX];
+        int r;
+
+        sprintf (fname, "%s%c", name, i+'A');
+        is->files[i].bf = bf_open (bfs, fname, is->method->filecat[i].bsize,
+                                   writeflag);
+        if (!is->files[i].bf)
+        {
+            isamc_close(is);
+            return 0;
+        }
+        r = bf_read(is->files[i].bf, 0, 0, sizeof(ISAMC_head),
+                     &is->files[i].head);
+        if (r == -1)
+        {
+            isamc_close(is);
+            return 0;
+        }
+    }
     return is;
 }
 
-int isc_close (ISAMC is)
+zint isamc_block_used (ISAMC is, int type)
+{
+    if (type < 0 || type >= is->no_files)
+	return -1;
+    return is->files[type].head.lastblock-1;
+}
+
+int isamc_block_size (ISAMC is, int type)
+{
+    ISAMC_filecat filecat = is->method->filecat;
+    if (type < 0 || type >= is->no_files)
+	return -1;
+    return filecat[type].bsize;
+}
+
+int isamc_close (ISAMC is)
 {
     int i;
 
     if (is->method->debug)
-        logf (LOG_LOG, "isc:  writes   reads skipped   alloc released  remap");
+    {
+	yaz_log (YLOG_LOG, "isc:    next    forw   mid-f    prev   backw   mid-b");
+	for (i = 0; i<is->no_files; i++)
+	    yaz_log (YLOG_LOG, "isc:%8d%8d%8.1f%8d%8d%8.1f",
+		  is->files[i].no_next,
+		  is->files[i].no_forward,
+		  is->files[i].no_forward ?
+		  (double) is->files[i].sum_forward/is->files[i].no_forward
+		  : 0.0,
+		  is->files[i].no_prev,
+		  is->files[i].no_backward,
+		  is->files[i].no_backward ?
+		  (double) is->files[i].sum_backward/is->files[i].no_backward
+		  : 0.0);
+    }
+    if (is->method->debug)
+        yaz_log (YLOG_LOG, "isc:  writes   reads skipped   alloc released  remap");
     for (i = 0; i<is->no_files; i++)
     {
         release_fc (is, i);
-        assert (is->files[i].bf);
-        if (is->files[i].head_is_dirty)
-            bf_write (is->files[i].bf, 0, 0, sizeof(ISAMC_head),
-                 &is->files[i].head);
         if (is->method->debug)
-            logf (LOG_LOG, "isc:%8d%8d%8d%8d%8d%8d",
-                  is->files[i].no_writes,
-                  is->files[i].no_reads,
-                  is->files[i].no_skip_writes,
-                  is->files[i].no_allocated,
-                  is->files[i].no_released,
-                  is->files[i].no_remap);
-        xfree (is->files[i].fc_list);
-        bf_close (is->files[i].bf);
+            yaz_log (YLOG_LOG, "isc:%8d%8d%8d%8d%8d%8d",
+                     is->files[i].no_writes,
+                     is->files[i].no_reads,
+                     is->files[i].no_skip_writes,
+                     is->files[i].no_allocated,
+                     is->files[i].no_released,
+                     is->files[i].no_remap);
+        if (is->files[i].bf)
+        {
+            if (is->files[i].head_is_dirty)
+                bf_write (is->files[i].bf, 0, 0, sizeof(ISAMC_head),
+                          &is->files[i].head);
+            flush_block (is, i);
+            bf_close (is->files[i].bf);
+        }
+        xfree(is->files[i].fc_list);
+        xfree(is->files[i].alloc_buf);
     }
     xfree (is->files);
     xfree (is->merge_buf);
+    xfree (is->method);
     xfree (is);
     return 0;
 }
 
-int isc_read_block (ISAMC is, int cat, int pos, char *dst)
+int isamc_read_block (ISAMC is, int cat, zint pos, char *dst)
 {
     ++(is->files[cat].no_reads);
-    if (is->method->debug > 2)
-        logf (LOG_LOG, "isc: read_block %d %d", cat, pos);
     return bf_read (is->files[cat].bf, pos, 0, 0, dst);
 }
 
-int isc_write_block (ISAMC is, int cat, int pos, char *src)
+int isamc_write_block (ISAMC is, int cat, zint pos, char *src)
 {
     ++(is->files[cat].no_writes);
     if (is->method->debug > 2)
-        logf (LOG_LOG, "isc: write_block %d %d", cat, pos);
+        yaz_log (YLOG_LOG, "isc: write_block %d " ZINT_FORMAT, cat, pos);
     return bf_write (is->files[cat].bf, pos, 0, 0, src);
 }
 
-int isc_write_dblock (ISAMC is, int cat, int pos, char *src,
-                      int nextpos, int offset)
+int isamc_write_dblock (ISAMC is, int cat, zint pos, char *src,
+                      zint nextpos, int offset)
 {
-    int xoffset = offset + 2*sizeof(int);
+    ISAMC_BLOCK_SIZE size = offset + ISAMC_BLOCK_OFFSET_N;
     if (is->method->debug > 2)
-        logf (LOG_LOG, "isc: write_dblock. size=%d nextpos=%d",
-              offset, nextpos);
-    memcpy (src - sizeof(int)*2, &nextpos, sizeof(int));
-    memcpy (src - sizeof(int), &xoffset, sizeof(int));
-    return isc_write_block (is, cat, pos, src - sizeof(int)*2);
+        yaz_log (YLOG_LOG, "isc: write_dblock. size=%d nextpos=" ZINT_FORMAT,
+              (int) size, nextpos);
+    src -= ISAMC_BLOCK_OFFSET_N;
+    memcpy (src, &nextpos, sizeof(nextpos));
+    memcpy (src + sizeof(nextpos), &size, sizeof(size));
+    return isamc_write_block (is, cat, pos, src);
+}
+
+#if ISAMC_FREELIST_CHUNK
+static void flush_block (ISAMC is, int cat)
+{
+    char *abuf = is->files[cat].alloc_buf;
+    zint block = is->files[cat].head.freelist;
+    if (block && is->files[cat].alloc_entries_num)
+    {
+	memcpy (abuf, &is->files[cat].alloc_entries_num, sizeof(block));
+	bf_write (is->files[cat].bf, block, 0, 0, abuf);
+	is->files[cat].alloc_entries_num = 0;
+    }
 }
 
-static int alloc_block (ISAMC is, int cat)
+static zint alloc_block (ISAMC is, int cat)
 {
-    int block;
-    char buf[sizeof(int)];
+    zint block = is->files[cat].head.freelist;
+    char *abuf = is->files[cat].alloc_buf;
+
+    (is->files[cat].no_allocated)++;
+
+    if (!block)
+    {
+        block = (is->files[cat].head.lastblock)++;   /* no free list */
+	is->files[cat].head_is_dirty = 1;
+    }
+    else
+    {
+	if (!is->files[cat].alloc_entries_num) /* read first time */
+	{
+	    bf_read (is->files[cat].bf, block, 0, 0, abuf);
+	    memcpy (&is->files[cat].alloc_entries_num, abuf,
+		    sizeof(is->files[cat].alloc_entries_num));
+	    assert (is->files[cat].alloc_entries_num > 0);
+	}
+	/* have some free blocks now */
+	assert (is->files[cat].alloc_entries_num > 0);
+	is->files[cat].alloc_entries_num--;
+	if (!is->files[cat].alloc_entries_num)  /* last one in block? */
+	{
+	    memcpy (&is->files[cat].head.freelist, abuf + sizeof(int),
+		    sizeof(zint));
+	    is->files[cat].head_is_dirty = 1;
+
+	    if (is->files[cat].head.freelist)
+	    {
+		bf_read (is->files[cat].bf, is->files[cat].head.freelist,
+			 0, 0, abuf);
+		memcpy (&is->files[cat].alloc_entries_num, abuf,
+			sizeof(is->files[cat].alloc_entries_num));
+		assert (is->files[cat].alloc_entries_num);
+	    }
+	}
+	else
+	    memcpy (&block, abuf + sizeof(zint) + sizeof(int) *
+		    is->files[cat].alloc_entries_num, sizeof(zint));
+    }
+    return block;
+}
+
+static void release_block (ISAMC is, int cat, zint pos)
+{
+    char *abuf = is->files[cat].alloc_buf;
+    zint block = is->files[cat].head.freelist;
+
+    (is->files[cat].no_released)++;
+
+    if (block && !is->files[cat].alloc_entries_num) /* must read block */
+    {
+	bf_read (is->files[cat].bf, block, 0, 0, abuf);
+	memcpy (&is->files[cat].alloc_entries_num, abuf,
+		sizeof(is->files[cat].alloc_entries_num));
+	assert (is->files[cat].alloc_entries_num > 0);
+    }
+    assert (is->files[cat].alloc_entries_num <= is->files[cat].alloc_entries_max);
+    if (is->files[cat].alloc_entries_num == is->files[cat].alloc_entries_max)
+    {
+	assert (block);
+	memcpy (abuf, &is->files[cat].alloc_entries_num, sizeof(int));
+	bf_write (is->files[cat].bf, block, 0, 0, abuf);
+	is->files[cat].alloc_entries_num = 0;
+    }
+    if (!is->files[cat].alloc_entries_num) /* make new buffer? */
+    {
+	memcpy (abuf + sizeof(int), &block, sizeof(zint));
+	is->files[cat].head.freelist = pos;
+	is->files[cat].head_is_dirty = 1;
+    }
+    else
+    {
+	memcpy (abuf + sizeof(int) +
+		is->files[cat].alloc_entries_num*sizeof(zint),
+		&pos, sizeof(zint));
+    }
+    is->files[cat].alloc_entries_num++;
+}
+#else
+static void flush_block (ISAMC is, int cat)
+{
+}
+
+static zint alloc_block (ISAMC is, int cat)
+{
+    zint block;
+    char buf[sizeof(zint)];
 
     is->files[cat].head_is_dirty = 1;
     (is->files[cat].no_allocated)++;
     if ((block = is->files[cat].head.freelist))
     {
-        bf_read (is->files[cat].bf, block, 0, sizeof(int), buf);
-        memcpy (&is->files[cat].head.freelist, buf, sizeof(int));
+        bf_read (is->files[cat].bf, block, 0, sizeof(zint), buf);
+        memcpy (&is->files[cat].head.freelist, buf, sizeof(zint));
     }
     else
         block = (is->files[cat].head.lastblock)++;
     return block;
 }
 
-int isc_alloc_block (ISAMC is, int cat)
+static void release_block (ISAMC is, int cat, zint pos)
+{
+    char buf[sizeof(zint)];
+
+    (is->files[cat].no_released)++;
+    is->files[cat].head_is_dirty = 1;
+    memcpy (buf, &is->files[cat].head.freelist, sizeof(zint));
+    is->files[cat].head.freelist = pos;
+    bf_write (is->files[cat].bf, pos, 0, sizeof(zint), buf);
+}
+#endif
+
+zint isamc_alloc_block (ISAMC is, int cat)
 {
-    int block = 0;
+    zint block = 0;
 
     if (is->files[cat].fc_list)
     {
-        int j, nb;
+        int j;
+	zint nb;
         for (j = 0; j < is->files[cat].fc_max; j++)
             if ((nb = is->files[cat].fc_list[j]) && (!block || nb < block))
             {
                 is->files[cat].fc_list[j] = 0;
+		block = nb;
                 break;
             }
     }
     if (!block)
         block = alloc_block (is, cat);
     if (is->method->debug > 3)
-        logf (LOG_LOG, "isc: alloc_block in cat %d: %d", cat, block);
+        yaz_log (YLOG_LOG, "isc: alloc_block in cat %d: " ZINT_FORMAT, cat, block);
     return block;
 }
 
-static void release_block (ISAMC is, int cat, int pos)
-{
-    char buf[sizeof(int)];
-   
-    (is->files[cat].no_released)++;
-    is->files[cat].head_is_dirty = 1; 
-    memcpy (buf, &is->files[cat].head.freelist, sizeof(int));
-    is->files[cat].head.freelist = pos;
-    bf_write (is->files[cat].bf, pos, 0, sizeof(int), buf);
-}
-
-void isc_release_block (ISAMC is, int cat, int pos)
+void isamc_release_block (ISAMC is, int cat, zint pos)
 {
     if (is->method->debug > 3)
-        logf (LOG_LOG, "isc: release_block in cat %d: %d", cat, pos);
+        yaz_log (YLOG_LOG, "isc: release_block in cat %d:" ZINT_FORMAT, cat, pos);
     if (is->files[cat].fc_list)
     {
-        int b, j;
+        int j;
         for (j = 0; j<is->files[cat].fc_max; j++)
             if (!is->files[cat].fc_list[j])
             {
@@ -263,16 +433,18 @@ void isc_release_block (ISAMC is, int cat, int pos)
 static void init_fc (ISAMC is, int cat)
 {
     int j = 100;
-        
+
     is->files[cat].fc_max = j;
-    is->files[cat].fc_list = xmalloc (sizeof(*is->files[0].fc_list) * j);
+    is->files[cat].fc_list = (zint *)
+	xmalloc (sizeof(*is->files[0].fc_list) * j);
     while (--j >= 0)
         is->files[cat].fc_list[j] = 0;
 }
 
 static void release_fc (ISAMC is, int cat)
 {
-    int b, j = is->files[cat].fc_max;
+    int j = is->files[cat].fc_max;
+    zint b;
 
     while (--j >= 0)
         if ((b = is->files[cat].fc_list[j]))
@@ -282,72 +454,146 @@ static void release_fc (ISAMC is, int cat)
         }
 }
 
-void isc_pp_close (ISAMC_PP pp)
+void isamc_pp_close (ISAMC_PP pp)
 {
     ISAMC is = pp->is;
 
-    (*is->method->code_stop)(ISAMC_DECODE, pp->decodeClientData);
+    (*is->method->codec.stop)(pp->decodeClientData);
     xfree (pp->buf);
     xfree (pp);
 }
 
-ISAMC_PP isc_pp_open (ISAMC is, ISAMC_P ipos)
+ISAMC_PP isamc_pp_open (ISAMC is, ISAM_P ipos)
 {
-    ISAMC_PP pp = xmalloc (sizeof(*pp));
+    ISAMC_PP pp = (ISAMC_PP) xmalloc (sizeof(*pp));
     char *src;
-   
-    pp->cat = isc_type(ipos);
-    pp->next = isc_block(ipos); 
 
-    src = pp->buf = xmalloc (is->method->filecat[pp->cat].bsize);
+    pp->cat = (int) isamc_type(ipos);
+    pp->pos = isamc_block(ipos);
+
+    src = pp->buf = (char *) xmalloc (is->method->filecat[pp->cat].bsize);
 
-    pp->pos = 0;    
+    pp->next = 0;
     pp->size = 0;
     pp->offset = 0;
     pp->is = is;
-    pp->decodeClientData = (*is->method->code_start)(ISAMC_DECODE);
+    pp->decodeClientData = (*is->method->codec.start)();
     pp->deleteFlag = 0;
+    pp->numKeys = 0;
+
+    if (pp->pos)
+    {
+        src = pp->buf;
+        isamc_read_block (is, pp->cat, pp->pos, src);
+        memcpy (&pp->next, src, sizeof(pp->next));
+        src += sizeof(pp->next);
+        memcpy (&pp->size, src, sizeof(pp->size));
+        src += sizeof(pp->size);
+        memcpy (&pp->numKeys, src, sizeof(pp->numKeys));
+        src += sizeof(pp->numKeys);
+	if (pp->next == pp->pos)
+	{
+	    yaz_log(YLOG_FATAL|YLOG_LOG, "pp->next = " ZINT_FORMAT, pp->next);
+	    yaz_log(YLOG_FATAL|YLOG_LOG, "pp->pos = " ZINT_FORMAT, pp->pos);
+	    assert (pp->next != pp->pos);
+	}
+        pp->offset = src - pp->buf;
+        assert (pp->offset == ISAMC_BLOCK_OFFSET_1);
+        if (is->method->debug > 2)
+            yaz_log (YLOG_LOG, "isc: read_block size=%d %d " ZINT_FORMAT " next="
+		  ZINT_FORMAT, pp->size, pp->cat, pp->pos, pp->next);
+    }
     return pp;
 }
 
 /* returns non-zero if item could be read; 0 otherwise */
-int isc_read_key (ISAMC_PP pp, void *buf)
+int isamc_pp_read (ISAMC_PP pp, void *buf)
 {
-    return isc_read_item (pp, (char **) &buf);
+    char *cp = buf;
+    return isamc_read_item (pp, &cp);
 }
 
-/* returns non-zero if item could be read; 0 otherwise */
-int isc_read_item (ISAMC_PP pp, char **dst)
+/* read one item from file - decode and store it in *dst.
+   Returns
+     0 if end-of-file
+     1 if item could be read ok and NO boundary
+     2 if item could be read ok and boundary */
+int isamc_read_item (ISAMC_PP pp, char **dst)
 {
     ISAMC is = pp->is;
-    char *src = pp->buf + pp->offset;
+    const char *src = pp->buf + pp->offset;
 
     if (pp->offset >= pp->size)
     {
+	if (!pp->next)
+	{
+	    pp->pos = 0;
+	    return 0; /* end of file */
+	}
+	if (pp->next > pp->pos)
+	{
+	    if (pp->next == pp->pos + 1)
+		is->files[pp->cat].no_next++;
+	    else
+	    {
+		is->files[pp->cat].no_forward++;
+		is->files[pp->cat].sum_forward += pp->next - pp->pos;
+	    }
+	}
+	else
+	{
+	    if (pp->next + 1 == pp->pos)
+		is->files[pp->cat].no_prev++;
+	    else
+	    {
+		is->files[pp->cat].no_backward++;
+		is->files[pp->cat].sum_backward += pp->pos - pp->next;
+	    }
+	}
+	/* out new block position */
         pp->pos = pp->next;
-        if (!pp->pos)
-            return 0;
         src = pp->buf;
-        isc_read_block (is, pp->cat, pp->pos, src);
+	/* read block and save 'next' and 'size' entry */
+        isamc_read_block (is, pp->cat, pp->pos, pp->buf);
         memcpy (&pp->next, src, sizeof(pp->next));
         src += sizeof(pp->next);
         memcpy (&pp->size, src, sizeof(pp->size));
         src += sizeof(pp->size);
         /* assume block is non-empty */
-        assert (pp->next != pp->pos);
+        assert (src - pp->buf == ISAMC_BLOCK_OFFSET_N);
+
+	if (pp->next == pp->pos)
+	{
+	    yaz_log(YLOG_FATAL|YLOG_LOG, "pp->next = " ZINT_FORMAT, pp->next);
+	    yaz_log(YLOG_FATAL|YLOG_LOG, "pp->pos = " ZINT_FORMAT, pp->pos);
+	    assert (pp->next != pp->pos);
+	}
+
         if (pp->deleteFlag)
-            isc_release_block (is, pp->cat, pp->pos);
-        (*is->method->code_item)(ISAMC_DECODE, pp->decodeClientData, dst, &src);
-        pp->offset = src - pp->buf; 
+            isamc_release_block (is, pp->cat, pp->pos);
+        (*is->method->codec.decode)(pp->decodeClientData, dst, &src);
+        pp->offset = src - pp->buf;
+        if (is->method->debug > 2)
+            yaz_log (YLOG_LOG, "isc: read_block size=%d %d " ZINT_FORMAT " next="
+		  ZINT_FORMAT, pp->size, pp->cat, pp->pos, pp->next);
         return 2;
     }
-    (*is->method->code_item)(ISAMC_DECODE, pp->decodeClientData, dst, &src);
-    pp->offset = src - pp->buf; 
+    (*is->method->codec.decode)(pp->decodeClientData, dst, &src);
+    pp->offset = src - pp->buf;
     return 1;
 }
 
-int isc_numkeys (ISAMC_PP pp)
+zint isamc_pp_num (ISAMC_PP pp)
 {
-    return 1;
+    return pp->numKeys;
 }
 
+/*
+ * Local variables:
+ * c-basic-offset: 4
+ * c-file-style: "Stroustrup"
+ * indent-tabs-mode: nil
+ * End:
+ * vim: shiftwidth=4 tabstop=8 expandtab
+ */
+