X-Git-Url: http://git.indexdata.com/?p=idzebra-moved-to-github.git;a=blobdiff_plain;f=isamb%2Fisamb.c;h=e4b87ca66dd42f5df1ee4a5e40b39cb000bccd06;hp=460b8ad7eb25dbd04862b483e1f9c238b612124e;hb=0e56fa84bb4a5985c19a21926e86862c08d84689;hpb=dbf15c09e6ad1986b914c695c161f81f774e9f39

diff --git a/isamb/isamb.c b/isamb/isamb.c
index 460b8ad..e4b87ca 100644
--- a/isamb/isamb.c
+++ b/isamb/isamb.c
@@ -1,5 +1,5 @@
-/* $Id: isamb.c,v 1.24 2003-03-17 20:22:54 adam Exp $
-   Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002,2003
+/* $Id: isamb.c,v 1.61 2004-12-08 14:02:36 adam Exp $
+   Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002,2003,2004
    Index Data Aps
 
 This file is part of the Zebra server.
@@ -22,27 +22,45 @@ Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 
 #include <string.h>
 #include <yaz/xmalloc.h>
-#include <yaz/log.h>
-#include <isamb.h>
+#include <yaz/ylog.h>
+#include <idzebra/isamb.h>
 #include <assert.h>
 
+#ifndef ISAMB_DEBUG
+#define ISAMB_DEBUG 0
+#endif
+
+#define ISAMB_MAJOR_VERSION 2
+#define ISAMB_MINOR_VERSION 0
+
 struct ISAMB_head {
-    int first_block;
-    int last_block;
+    zint first_block;
+    zint last_block;
+    zint free_list;
+    zint no_items;
     int block_size;
     int block_max;
-    int free_list;
+    int block_offset;
 };
 
-#define ISAMB_DATA_OFFSET 3
-
+/* maximum size of encoded buffer */
 #define DST_ITEM_MAX 256
 
-/* approx 2*4 K + max size of item */
-#define DST_BUF_SIZE 8448
+#define ISAMB_MAX_LEVEL 10
+/* approx 2*max page + max size of item */
+#define DST_BUF_SIZE 16840
 
 #define ISAMB_CACHE_ENTRY_SIZE 4096
 
+/* CAT_MAX: _must_ be power of 2 */
+#define CAT_MAX 4
+#define CAT_MASK (CAT_MAX-1)
+/* CAT_NO: <= CAT_MAX */
+#define CAT_NO 4
+
+/* ISAMB_PTR_CODEC=1 var, =0 fixed */
+#define ISAMB_PTR_CODEC 1
+
 struct ISAMB_cache_entry {
     ISAMB_P pos;
     unsigned char *buf;
@@ -51,7 +69,6 @@ struct ISAMB_cache_entry {
     struct ISAMB_cache_entry *next;
 };
 
-
 struct ISAMB_file {
     BFile bf;
     int head_dirty;
@@ -61,13 +78,17 @@ struct ISAMB_file {
 
 struct ISAMB_s {
     BFiles bfs;
-    ISAMC_M method;
+    ISAMC_M *method;
 
     struct ISAMB_file *file;
     int no_cat;
     int cache; /* 0=no cache, 1=use cache, -1=dummy isam (for testing only) */
     int log_io;        /* log level for bf_read/bf_write calls */
     int log_freelist;  /* log level for freelist handling */
+    zint skipped_numbers; /* on a leaf node */
+    zint returned_numbers; 
+    zint skipped_nodes[ISAMB_MAX_LEVEL]; /* [0]=skipped leaves, 1=higher etc */
+    zint accessed_nodes[ISAMB_MAX_LEVEL]; /* nodes we did not skip */
 };
 
 struct ISAMB_block {
@@ -78,7 +99,9 @@ struct ISAMB_block {
     int dirty;
     int deleted;
     int offset;
+    zint no_items;  /* number of nodes in this + children */
     char *bytes;
+    char *cbuf;
     unsigned char *buf;
     void *decodeClientData;
     int log_rw;
@@ -88,41 +111,87 @@ struct ISAMB_PP_s {
     ISAMB isamb;
     ISAMB_P pos;
     int level;
-    int total_size;
-    int no_blocks;
+    int maxlevel; /* total depth */
+    zint total_size;
+    zint no_blocks;
+    zint skipped_numbers; /* on a leaf node */
+    zint returned_numbers; 
+    zint skipped_nodes[ISAMB_MAX_LEVEL]; /* [0]=skipped leaves, 1=higher etc */
+    zint accessed_nodes[ISAMB_MAX_LEVEL]; /* nodes we did not skip */
     struct ISAMB_block **block;
+    int scope;  /* on what level we forward */
 };
 
-void encode_ptr (char **dst, int pos)
+
+#if ISAMB_PTR_CODEC
+static void encode_ptr (char **dst, zint pos)
 {
-    memcpy (*dst, &pos, sizeof(pos));
+    unsigned char *bp = (unsigned char*) *dst;
+
+    while (pos > 127)
+    {
+         *bp++ = 128 | (pos & 127);
+         pos = pos >> 7;
+    }
+    *bp++ = pos;
+    *dst = (char *) bp;
+}
+#else
+static void encode_ptr (char **dst, zint pos)
+{
+    memcpy(*dst, &pos, sizeof(pos));
     (*dst) += sizeof(pos);
 }
+#endif
 
-void decode_ptr (char **src, int *pos)
+#if ISAMB_PTR_CODEC
+static void decode_ptr (const char **src1, zint *pos)
 {
-    memcpy (pos, *src, sizeof(*pos));
-    (*src) += sizeof(*pos);
+    const unsigned char **src = (const unsigned char **) src1;
+    zint d = 0;
+    unsigned char c;
+    unsigned r = 0;
+
+    while (((c = *(*src)++) & 128))
+    {
+        d += ((zint) (c & 127) << r);
+	r += 7;
+    }
+    d += ((zint) c << r);
+    *pos = d;
 }
+#else
+static void decode_ptr (const char **src, zint *pos)
+{
+     memcpy (pos, *src, sizeof(*pos));
+     (*src) += sizeof(*pos);
+}
+#endif
 
-ISAMB isamb_open (BFiles bfs, const char *name, int writeflag, ISAMC_M method,
+ISAMB isamb_open (BFiles bfs, const char *name, int writeflag, ISAMC_M *method,
                   int cache)
 {
     ISAMB isamb = xmalloc (sizeof(*isamb));
     int i, b_size = 32;
 
     isamb->bfs = bfs;
-    isamb->method = (ISAMC_M) xmalloc (sizeof(*method));
+    isamb->method = (ISAMC_M *) xmalloc (sizeof(*method));
     memcpy (isamb->method, method, sizeof(*method));
-    isamb->no_cat = 4;
+    isamb->no_cat = CAT_NO;
     isamb->log_io = 0;
+    isamb->log_freelist = 0;
     isamb->cache = cache;
+    isamb->skipped_numbers=0;
+    isamb->returned_numbers=0;
+    for (i=0;i<ISAMB_MAX_LEVEL;i++)
+      isamb->skipped_nodes[i]= isamb->accessed_nodes[i]=0;
 
     assert (cache == 0);
     isamb->file = xmalloc (sizeof(*isamb->file) * isamb->no_cat);
-    for (i = 0; i<isamb->no_cat; i++)
+    for (i = 0; i < isamb->no_cat; i++)
     {
         char fname[DST_BUF_SIZE];
+	char hbuf[DST_BUF_SIZE];
         isamb->file[i].cache_entries = 0;
         isamb->file[i].head_dirty = 0;
         sprintf (fname, "%s%c", name, i+'A');
@@ -132,21 +201,68 @@ ISAMB isamb_open (BFiles bfs, const char *name, int writeflag, ISAMC_M method,
         else
             isamb->file[i].bf = bf_open (bfs, fname, b_size, writeflag);
 
-        
-        if (!bf_read (isamb->file[i].bf, 0, 0, sizeof(struct ISAMB_head),
-                      &isamb->file[i].head))
+        /* fill-in default values (for empty isamb) */
+	isamb->file[i].head.first_block = ISAMB_CACHE_ENTRY_SIZE/b_size+1;
+	isamb->file[i].head.last_block = isamb->file[i].head.first_block;
+	isamb->file[i].head.block_size = b_size;
+	if (i == isamb->no_cat-1 || b_size > 128)
+	    isamb->file[i].head.block_offset = 8;
+	else
+	    isamb->file[i].head.block_offset = 4;
+	isamb->file[i].head.block_max =
+	    b_size - isamb->file[i].head.block_offset;
+	isamb->file[i].head.free_list = 0;
+	if (bf_read (isamb->file[i].bf, 0, 0, 0, hbuf))
 	{
-            isamb->file[i].head.first_block = ISAMB_CACHE_ENTRY_SIZE/b_size+1;
-            isamb->file[i].head.last_block = isamb->file[i].head.first_block;
-            isamb->file[i].head.block_size = b_size;
-            isamb->file[i].head.block_max = b_size - ISAMB_DATA_OFFSET;
-            isamb->file[i].head.free_list = 0;
+	    /* got header assume "isamb"major minor len can fit in 16 bytes */
+	    zint zint_tmp;
+	    int major, minor, len, pos = 0;
+	    int left;
+	    const char *src = 0;
+	    if (memcmp(hbuf, "isamb", 5))
+	    {
+		yaz_log(YLOG_WARN, "bad isamb header for file %s", fname);
+		return 0;
+	    }
+	    if (sscanf(hbuf+5, "%d %d %d", &major, &minor, &len) != 3)
+	    {
+		yaz_log(YLOG_WARN, "bad isamb header for file %s", fname);
+		return 0;
+	    }
+	    if (major != ISAMB_MAJOR_VERSION)
+	    {
+		yaz_log(YLOG_WARN, "bad major version for file %s %d, must be %d",
+		     fname, major, ISAMB_MAJOR_VERSION);
+		return 0;
+	    }
+	    for (left = len - b_size; left > 0; left = left - b_size)
+	    {
+		pos++;
+		if (!bf_read (isamb->file[i].bf, pos, 0, 0, hbuf + pos*b_size))
+		{
+		    yaz_log(YLOG_WARN, "truncated isamb header for " 
+			 "file=%s len=%d pos=%d",
+			 fname, len, pos);
+		    return 0;
+		}
+	    }
+	    src = hbuf + 16;
+	    decode_ptr(&src, &isamb->file[i].head.first_block);
+	    decode_ptr(&src, &isamb->file[i].head.last_block);
+	    decode_ptr(&src, &zint_tmp);
+	    isamb->file[i].head.block_size = zint_tmp;
+	    decode_ptr(&src, &zint_tmp);
+	    isamb->file[i].head.block_max = zint_tmp;
+	    decode_ptr(&src, &isamb->file[i].head.free_list);
 	}
-        assert (isamb->file[i].head.block_size >= ISAMB_DATA_OFFSET);
+        assert (isamb->file[i].head.block_size >= isamb->file[i].head.block_offset);
         isamb->file[i].head_dirty = 0;
         assert(isamb->file[i].head.block_size == b_size);
         b_size = b_size * 4;
     }
+#if ISAMB_DEBUG
+    yaz_log(YLOG_WARN, "isamb debug enabled. Things will be slower than usual");
+#endif
     return isamb;
 }
 
@@ -169,11 +285,11 @@ static void flush_blocks (ISAMB b, int cat)
 
 static int get_block (ISAMB b, ISAMC_P pos, char *userbuf, int wr)
 {
-    int cat = pos&3;
-    int off = ((pos/4) & 
+    int cat = (int) (pos&CAT_MASK);
+    int off = (int) (((pos/CAT_MAX) & 
                (ISAMB_CACHE_ENTRY_SIZE / b->file[cat].head.block_size - 1))
-        * b->file[cat].head.block_size;
-    int norm = pos / (4*ISAMB_CACHE_ENTRY_SIZE / b->file[cat].head.block_size);
+        * b->file[cat].head.block_size);
+    zint norm = pos / (CAT_MASK*ISAMB_CACHE_ENTRY_SIZE / b->file[cat].head.block_size);
     int no = 0;
     struct ISAMB_cache_entry **ce, *ce_this = 0, **ce_last = 0;
 
@@ -243,13 +359,46 @@ static int get_block (ISAMB b, ISAMC_P pos, char *userbuf, int wr)
 void isamb_close (ISAMB isamb)
 {
     int i;
+    for (i=0;isamb->accessed_nodes[i];i++)
+        yaz_log(YLOG_DEBUG,"isamb_close  level leaf-%d: "ZINT_FORMAT" read, "
+			ZINT_FORMAT" skipped",
+             i, isamb->accessed_nodes[i], isamb->skipped_nodes[i]);
+    yaz_log(YLOG_DEBUG,"isamb_close returned "ZINT_FORMAT" values, "
+		   "skipped "ZINT_FORMAT,
+         isamb->skipped_numbers, isamb->returned_numbers);
     for (i = 0; i<isamb->no_cat; i++)
     {
         flush_blocks (isamb, i);
         if (isamb->file[i].head_dirty)
-            bf_write (isamb->file[i].bf, 0, 0,
-                      sizeof(struct ISAMB_head), &isamb->file[i].head);
-        
+	{
+	    char hbuf[DST_BUF_SIZE];
+	    int major = ISAMB_MAJOR_VERSION;
+	    int minor = ISAMB_MINOR_VERSION;
+	    int len = 16;
+	    char *dst = hbuf + 16;
+	    int pos = 0, left;
+	    int b_size = isamb->file[i].head.block_size;
+
+	    encode_ptr(&dst, isamb->file[i].head.first_block);
+	    encode_ptr(&dst, isamb->file[i].head.last_block);
+	    encode_ptr(&dst, isamb->file[i].head.block_size);
+	    encode_ptr(&dst, isamb->file[i].head.block_max);
+	    encode_ptr(&dst, isamb->file[i].head.free_list);
+	    memset(dst, '\0', b_size); /* ensure no random bytes are written */
+
+	    len = dst - hbuf;
+
+	    /* print exactly 16 bytes (including trailing 0) */
+	    sprintf(hbuf, "isamb%02d %02d %02d\r\n", major, minor, len);
+
+            bf_write (isamb->file[i].bf, pos, 0, 0, hbuf);
+
+	    for (left = len - b_size; left > 0; left = left - b_size)
+	    {
+		pos++;
+		bf_write (isamb->file[i].bf, pos, 0, 0, hbuf + pos*b_size);
+	    }
+	}
         bf_close (isamb->file[i].bf);
     }
     xfree (isamb->file);
@@ -257,40 +406,56 @@ void isamb_close (ISAMB isamb)
     xfree (isamb);
 }
 
-
-struct ISAMB_block *open_block (ISAMB b, ISAMC_P pos)
+/* open_block: read one block at pos.
+   Decode leading sys bytes .. consisting of
+   Offset:Meaning
+   0: leader byte, != 0 leaf, == 0, non-leaf
+   1-2: used size of block
+   3-7*: number of items and all children
+   
+   * Reserve 5 bytes for large block sizes. 1 for small ones .. Number
+   of items. We can thus have at most 2^40 nodes. 
+*/
+static struct ISAMB_block *open_block (ISAMB b, ISAMC_P pos)
 {
-    int cat = pos&3;
+    int cat = (int) (pos&CAT_MASK);
+    const char *src;
+    int offset = b->file[cat].head.block_offset;
     struct ISAMB_block *p;
     if (!pos)
         return 0;
     p = xmalloc (sizeof(*p));
     p->pos = pos;
-    p->cat = pos & 3;
+    p->cat = (int) (pos & CAT_MASK);
     p->buf = xmalloc (b->file[cat].head.block_size);
+    p->cbuf = 0;
 
     if (!get_block (b, pos, p->buf, 0))
     {
         yaz_log (b->log_io, "bf_read: open_block");
-        if (!bf_read (b->file[cat].bf, pos/4, 0, 0, p->buf))
+        if (!bf_read (b->file[cat].bf, pos/CAT_MAX, 0, 0, p->buf))
         {
-            yaz_log (LOG_FATAL, "read failure for pos=%ld block=%ld",
-                     (long) pos, (long) pos/4);
+            yaz_log (YLOG_FATAL, "isamb: read fail for pos=%ld block=%ld",
+                     (long) pos, (long) pos/CAT_MAX);
             abort();
         }
     }
-    p->bytes = p->buf + ISAMB_DATA_OFFSET;
+    p->bytes = p->buf + offset;
     p->leaf = p->buf[0];
-    p->size = (p->buf[1] + 256 * p->buf[2]) - ISAMB_DATA_OFFSET;
+    p->size = (p->buf[1] + 256 * p->buf[2]) - offset;
     if (p->size < 0)
     {
-        fprintf (stderr, "pos=%d\n", pos);
+        yaz_log (YLOG_FATAL, "Bad block size %d in pos=" ZINT_FORMAT "\n",
+		 p->size, pos);
     }
     assert (p->size >= 0);
+    src = p->buf + 3;
+    decode_ptr(&src, &p->no_items);
+
     p->offset = 0;
     p->dirty = 0;
     p->deleted = 0;
-    p->decodeClientData = (*b->method->code_start)(ISAMC_DECODE);
+    p->decodeClientData = (*b->method->codec.start)();
     return p;
 }
 
@@ -303,38 +468,39 @@ struct ISAMB_block *new_block (ISAMB b, int leaf, int cat)
 
     if (!b->file[cat].head.free_list)
     {
-        int block_no;
+        zint block_no;
         block_no = b->file[cat].head.last_block++;
-        p->pos = block_no * 4 + cat;
+        p->pos = block_no * CAT_MAX + cat;
     }
     else
     {
         p->pos = b->file[cat].head.free_list;
-        assert((p->pos & 3) == cat);
+        assert((p->pos & CAT_MASK) == cat);
         if (!get_block (b, p->pos, p->buf, 0))
         {
             yaz_log (b->log_io, "bf_read: new_block");
-            if (!bf_read (b->file[cat].bf, p->pos/4, 0, 0, p->buf))
+            if (!bf_read (b->file[cat].bf, p->pos/CAT_MAX, 0, 0, p->buf))
             {
-                yaz_log (LOG_FATAL, "read failure for pos=%ld block=%ld",
-                         (long) p->pos/4, (long) p->pos/4);
+                yaz_log (YLOG_FATAL, "isamb: read fail for pos=%ld block=%ld",
+                         (long) p->pos/CAT_MAX, (long) p->pos/CAT_MAX);
                 abort ();
             }
         }
-        yaz_log (b->log_freelist, "got block %d from freelist %d:%d", p->pos,
-                 cat, p->pos/4);
+        yaz_log (b->log_freelist, "got block " ZINT_FORMAT " from freelist %d:" ZINT_FORMAT, p->pos,
+                 cat, p->pos/CAT_MAX);
         memcpy (&b->file[cat].head.free_list, p->buf, sizeof(int));
     }
     p->cat = cat;
     b->file[cat].head_dirty = 1;
     memset (p->buf, 0, b->file[cat].head.block_size);
-    p->bytes = p->buf + ISAMB_DATA_OFFSET;
+    p->bytes = p->buf + b->file[cat].head.block_offset;
     p->leaf = leaf;
     p->size = 0;
     p->dirty = 1;
     p->deleted = 0;
     p->offset = 0;
-    p->decodeClientData = (*b->method->code_start)(ISAMC_DECODE);
+    p->no_items = 0;
+    p->decodeClientData = (*b->method->codec.start)();
     return p;
 }
 
@@ -351,6 +517,7 @@ struct ISAMB_block *new_int (ISAMB b, int cat)
 
 static void check_block (ISAMB b, struct ISAMB_block *p)
 {
+    assert(b); /* mostly to make the compiler shut up about unused b */
     if (p->leaf)
     {
         ;
@@ -359,20 +526,23 @@ static void check_block (ISAMB b, struct ISAMB_block *p)
     {
         /* sanity check */
         char *startp = p->bytes;
-        char *src = startp;
+        const char *src = startp;
         char *endp = p->bytes + p->size;
-        int pos;
+        ISAMB_P pos;
             
         decode_ptr (&src, &pos);
-        assert ((pos&3) == p->cat);
+        assert ((pos&CAT_MASK) == p->cat);
         while (src != endp)
         {
-            int item_len;
+            zint item_len;
             decode_ptr (&src, &item_len);
-            assert (item_len > 0 && item_len < 30);
+            assert (item_len > 0 && item_len < 80);
             src += item_len;
             decode_ptr (&src, &pos);
-            assert ((pos&3) == p->cat);
+	    if ((pos&CAT_MASK) != p->cat)
+	    {
+		assert ((pos&CAT_MASK) == p->cat);
+	    }
         }
     }
 }
@@ -383,55 +553,62 @@ void close_block (ISAMB b, struct ISAMB_block *p)
         return;
     if (p->deleted)
     {
-        yaz_log (b->log_freelist, "release block %d from freelist %d:%d",
-                 p->pos, p->cat, p->pos/4);
+        yaz_log (b->log_freelist, "release block " ZINT_FORMAT " from freelist %d:" ZINT_FORMAT,
+                 p->pos, p->cat, p->pos/CAT_MAX);
         memcpy (p->buf, &b->file[p->cat].head.free_list, sizeof(int));
         b->file[p->cat].head.free_list = p->pos;
         if (!get_block (b, p->pos, p->buf, 1))
         {
             yaz_log (b->log_io, "bf_write: close_block (deleted)");
-            bf_write (b->file[p->cat].bf, p->pos/4, 0, 0, p->buf);
+            bf_write (b->file[p->cat].bf, p->pos/CAT_MAX, 0, 0, p->buf);
         }
     }
     else if (p->dirty)
     {
-        int size = p->size + ISAMB_DATA_OFFSET;
+	int offset = b->file[p->cat].head.block_offset;
+        int size = p->size + offset;
+	char *dst =  p->buf + 3;
         assert (p->size >= 0);
+	
+	/* memset becuase encode_ptr usually does not write all bytes */
+	memset(p->buf, 0, b->file[p->cat].head.block_offset);
         p->buf[0] = p->leaf;
         p->buf[1] = size & 255;
         p->buf[2] = size >> 8;
+	encode_ptr(&dst, p->no_items);
         check_block(b, p);
         if (!get_block (b, p->pos, p->buf, 1))
         {
             yaz_log (b->log_io, "bf_write: close_block");
-            bf_write (b->file[p->cat].bf, p->pos/4, 0, 0, p->buf);
+            bf_write (b->file[p->cat].bf, p->pos/CAT_MAX, 0, 0, p->buf);
         }
     }
-    (*b->method->code_stop)(ISAMC_DECODE, p->decodeClientData);
+    (*b->method->codec.stop)(p->decodeClientData);
     xfree (p->buf);
     xfree (p);
 }
 
 int insert_sub (ISAMB b, struct ISAMB_block **p,
                 void *new_item, int *mode,
-                ISAMC_I stream,
+                ISAMC_I *stream,
                 struct ISAMB_block **sp,
                 void *sub_item, int *sub_size,
-                void *max_item);
+                const void *max_item);
 
 int insert_int (ISAMB b, struct ISAMB_block *p, void *lookahead_item,
                 int *mode,
-                ISAMC_I stream, struct ISAMB_block **sp,
-                void *split_item, int *split_size, void *last_max_item)
+                ISAMC_I *stream, struct ISAMB_block **sp,
+                void *split_item, int *split_size, const void *last_max_item)
 {
     char *startp = p->bytes;
-    char *src = startp;
+    const char *src = startp;
     char *endp = p->bytes + p->size;
-    int pos;
+    ISAMB_P pos;
     struct ISAMB_block *sub_p1 = 0, *sub_p2 = 0;
     char sub_item[DST_ITEM_MAX];
     int sub_size;
-    int more;
+    int more = 0;
+    zint diff_terms = 0;
 
     *sp = 0;
 
@@ -439,18 +616,20 @@ int insert_int (ISAMB b, struct ISAMB_block *p, void *lookahead_item,
     decode_ptr (&src, &pos);
     while (src != endp)
     {
-        int item_len;
+        zint item_len;
         int d;
-        char *src0 = src;
+        const char *src0 = src;
         decode_ptr (&src, &item_len);
         d = (*b->method->compare_item)(src, lookahead_item);
         if (d > 0)
         {
             sub_p1 = open_block (b, pos);
             assert (sub_p1);
+	    diff_terms -= sub_p1->no_items;
             more = insert_sub (b, &sub_p1, lookahead_item, mode,
                                stream, &sub_p2, 
                                sub_item, &sub_size, src);
+	    diff_terms += sub_p1->no_items;
             src = src0;
             break;
         }
@@ -461,8 +640,17 @@ int insert_int (ISAMB b, struct ISAMB_block *p, void *lookahead_item,
     {
         sub_p1 = open_block (b, pos);
         assert (sub_p1);
+	diff_terms -= sub_p1->no_items;
         more = insert_sub (b, &sub_p1, lookahead_item, mode, stream, &sub_p2, 
                            sub_item, &sub_size, last_max_item);
+	diff_terms += sub_p1->no_items;
+    }
+    if (sub_p2)
+	diff_terms += sub_p2->no_items;
+    if (diff_terms)
+    {
+	p->dirty = 1;
+	p->no_items += diff_terms;
     }
     if (sub_p2)
     {
@@ -470,7 +658,7 @@ int insert_int (ISAMB b, struct ISAMB_block *p, void *lookahead_item,
         char dst_buf[DST_BUF_SIZE];
         char *dst = dst_buf;
 
-        assert (sub_size < 30 && sub_size > 1);
+        assert (sub_size < 80 && sub_size > 1);
 
         memcpy (dst, startp, src - startp);
                 
@@ -489,37 +677,62 @@ int insert_int (ISAMB b, struct ISAMB_block *p, void *lookahead_item,
         }
         p->size = dst - dst_buf;
         assert (p->size >= 0);
+
+
         if (p->size <= b->file[p->cat].head.block_max)
         {
             memcpy (startp, dst_buf, dst - dst_buf);
         }
         else
         {
+	    struct ISAMB_block *sub_p3;
+	    zint split_size_tmp;
+	    zint no_items_first_half = 0;
             int p_new_size;
-            char *half;
+            const char *half;
             src = dst_buf;
             endp = dst;
 
             half = src + b->file[p->cat].head.block_size/2;
             decode_ptr (&src, &pos);
+
+	    /* read sub block so we can get no_items for it */
+	    sub_p3 = open_block(b, pos);
+	    no_items_first_half += sub_p3->no_items;
+	    close_block(b, sub_p3);
+
             while (src <= half)
             {
-                decode_ptr (&src, split_size);
+                decode_ptr (&src, &split_size_tmp);
+		*split_size = (int) split_size_tmp;
+
                 src += *split_size;
                 decode_ptr (&src, &pos);
+
+		/* read sub block so we can get no_items for it */
+		sub_p3 = open_block(b, pos);
+		no_items_first_half += sub_p3->no_items;
+		close_block(b, sub_p3);
             }
+	    /*  p is first half */
             p_new_size = src - dst_buf;
             memcpy (p->bytes, dst_buf, p_new_size);
 
-            decode_ptr (&src, split_size);
+	    decode_ptr (&src, &split_size_tmp);
+	    *split_size = (int) split_size_tmp;
             memcpy (split_item, src, *split_size);
             src += *split_size;
 
+	    /*  *sp is second half */
             *sp = new_int (b, p->cat);
             (*sp)->size = endp - src;
             memcpy ((*sp)->bytes, src, (*sp)->size);
 
             p->size = p_new_size;
+
+	    /*  adjust no_items in first&second half */
+	    (*sp)->no_items = p->no_items - no_items_first_half;
+	    p->no_items = no_items_first_half;
         }
         p->dirty = 1;
         close_block (b, sub_p2);
@@ -528,26 +741,30 @@ int insert_int (ISAMB b, struct ISAMB_block *p, void *lookahead_item,
     return more;
 }
 
-
 int insert_leaf (ISAMB b, struct ISAMB_block **sp1, void *lookahead_item,
-                 int *lookahead_mode, ISAMC_I stream, struct ISAMB_block **sp2,
+                 int *lookahead_mode, ISAMC_I *stream,
+		 struct ISAMB_block **sp2,
                  void *sub_item, int *sub_size,
-                 void *max_item)
+                 const void *max_item)
 {
     struct ISAMB_block *p = *sp1;
-    char *src = 0, *endp = 0;
+    char *endp = 0;
+    const char *src = 0;
     char dst_buf[DST_BUF_SIZE], *dst = dst_buf;
     int new_size;
-    void *c1 = (*b->method->code_start)(ISAMC_DECODE);
-    void *c2 = (*b->method->code_start)(ISAMC_ENCODE);
+    void *c1 = (*b->method->codec.start)();
+    void *c2 = (*b->method->codec.start)();
     int more = 1;
     int quater = b->file[b->no_cat-1].head.block_max / 4;
-    char *cut = dst_buf + quater * 2;
+    char *mid_cut = dst_buf + quater * 2;
+    char *tail_cut = dst_buf + quater * 3;
     char *maxp = dst_buf + b->file[b->no_cat-1].head.block_max;
     char *half1 = 0;
     char *half2 = 0;
     char cut_item_buf[DST_ITEM_MAX];
     int cut_item_size = 0;
+    int no_items = 0;    /* number of items (total) */
+    int no_items_1 = 0;  /* number of items (first half) */
 
     if (p && p->size)
     {
@@ -556,63 +773,93 @@ int insert_leaf (ISAMB b, struct ISAMB_block **sp1, void *lookahead_item,
             
         src = p->bytes;
         endp = p->bytes + p->size;
-        (*b->method->code_item)(ISAMC_DECODE, c1, &file_item, &src);
+        (*b->method->codec.decode)(c1, &file_item, &src);
         while (1)
         {
-            char *dst_item = 0;
-            char *dst_0 = dst;
+            const char *dst_item = 0; /* resulting item to be inserted */
             char *lookahead_next;
             int d = -1;
             
             if (lookahead_item)
                 d = (*b->method->compare_item)(file_item_buf, lookahead_item);
             
+	    /* d now holds comparison between existing file item and
+	       lookahead item 
+	       d = 0: equal
+               d > 0: lookahead before file
+	       d < 0: lookahead after file
+	    */
             if (d > 0)
             {
+		/* lookahead must be inserted */
                 dst_item = lookahead_item;
-                assert (*lookahead_mode);
+		/* if this is not an insertion, it's really bad .. */
+                if (!*lookahead_mode)
+                {
+                    yaz_log (YLOG_WARN, "isamb: Inconsistent register (1)");
+                    assert (*lookahead_mode);
+                }
             }
             else
                 dst_item = file_item_buf;
+
+	       
             if (!*lookahead_mode && d == 0)
             {
+		/* it's a deletion and they match so there is nothing to be
+		   inserted anyway .. But mark the thing bad (file item
+		   was part of input.. The item will not be part of output */
                 p->dirty = 1;
             }
-            else if (!half1 && dst > cut)
+            else if (!half1 && dst > mid_cut)
             {
-                char *dst_item_0 = dst_item;
+		/* we have reached the splitting point for the first time */
+                const char *dst_item_0 = dst_item;
                 half1 = dst; /* candidate for splitting */
-                
-                (*b->method->code_item)(ISAMC_ENCODE, c2, &dst, &dst_item);
+
+		/* encode the resulting item */
+                (*b->method->codec.encode)(c2, &dst, &dst_item);
                 
                 cut_item_size = dst_item - dst_item_0;
+		assert(cut_item_size > 0);
                 memcpy (cut_item_buf, dst_item_0, cut_item_size);
                 
                 half2 = dst;
+		no_items_1 = no_items;
+		no_items++;
             }
             else
-                (*b->method->code_item)(ISAMC_ENCODE, c2, &dst, &dst_item);
+	    {
+		/* encode the resulting item */
+                (*b->method->codec.encode)(c2, &dst, &dst_item);
+		no_items++;
+	    }
+
+	    /* now move "pointers" .. result has been encoded .. */
             if (d > 0)  
             {
+		/* we must move the lookahead pointer */
+
                 if (dst > maxp)
-                {
-                    dst = dst_0;
+		    /* no more room. Mark lookahead as "gone".. */
                     lookahead_item = 0;
-                }
                 else
                 {
+		    /* move it really.. */
                     lookahead_next = lookahead_item;
                     if (!(*stream->read_item)(stream->clientData,
                                               &lookahead_next,
                                               lookahead_mode))
                     {
+			/* end of stream reached: no "more" and no lookahead */
                         lookahead_item = 0;
                         more = 0;
                     }
                     if (lookahead_item && max_item &&
                         (*b->method->compare_item)(max_item, lookahead_item) <= 0)
                     {
-                        /* max_item 1 */
+			/* the lookahead goes beyond what we allow in this
+			   leaf. Mark it as "gone" */
                         lookahead_item = 0;
                     }
                     
@@ -621,6 +868,8 @@ int insert_leaf (ISAMB b, struct ISAMB_block **sp1, void *lookahead_item,
             }
             else if (d == 0)
             {
+		/* exact match .. move both pointers */
+
                 lookahead_next = lookahead_item;
                 if (!(*stream->read_item)(stream->clientData,
                                           &lookahead_next, lookahead_mode))
@@ -629,56 +878,66 @@ int insert_leaf (ISAMB b, struct ISAMB_block **sp1, void *lookahead_item,
                     more = 0;
                 }
                 if (src == endp)
-                    break;
-                file_item = file_item_buf;
-                (*b->method->code_item)(ISAMC_DECODE, c1, &file_item, &src);
+                    break;  /* end of file stream reached .. */
+                file_item = file_item_buf; /* move file pointer */
+                (*b->method->codec.decode)(c1, &file_item, &src);
             }
             else
             {
+		/* file pointer must be moved */
                 if (src == endp)
                     break;
                 file_item = file_item_buf;
-                (*b->method->code_item)(ISAMC_DECODE, c1, &file_item, &src);
+                (*b->method->codec.decode)(c1, &file_item, &src);
             }
         }
     }
     maxp = dst_buf + b->file[b->no_cat-1].head.block_max + quater;
+    /* this loop runs when we are "appending" to a leaf page. That is
+       either it's empty (new) or all file items have been read in
+       previous loop */
     while (lookahead_item)
     {
-        char *dst_item = lookahead_item;
+        char *dst_item;
+	const char *src = lookahead_item;
         char *dst_0 = dst;
         
+	/* compare lookahead with max item */
         if (max_item &&
             (*b->method->compare_item)(max_item, lookahead_item) <= 0)
         {
-            /* max_item 2 */
+            /* stop if we have reached the value of max item */
             break;
         }
         if (!*lookahead_mode)
         {
-            yaz_log (LOG_WARN, "Inconsistent register (2)");
+	    /* this is append. So a delete is bad */
+            yaz_log (YLOG_WARN, "isamb: Inconsistent register (2)");
             abort();
         }
-        else if (!half1 && dst > cut)   
+        else if (!half1 && dst > tail_cut)
         {
-            char *dst_item_0 = dst_item;
+            const char *src_0 = src;
             half1 = dst; /* candidate for splitting */
             
-            (*b->method->code_item)(ISAMC_ENCODE, c2, &dst, &dst_item);
+            (*b->method->codec.encode)(c2, &dst, &src);
             
-            cut_item_size = dst_item - dst_item_0;
-            memcpy (cut_item_buf, dst_item_0, cut_item_size);
+            cut_item_size = src - src_0;
+	    assert(cut_item_size > 0);
+            memcpy (cut_item_buf, src_0, cut_item_size);
             
+	    no_items_1 = no_items;
             half2 = dst;
         }
         else
-            (*b->method->code_item)(ISAMC_ENCODE, c2, &dst, &dst_item);
+            (*b->method->codec.encode)(c2, &dst, &src);
 
         if (dst > maxp)
         {
             dst = dst_0;
             break;
         }
+	no_items++;
         if (p)
             p->dirty = 1;
         dst_item = lookahead_item;
@@ -712,27 +971,31 @@ int insert_leaf (ISAMB b, struct ISAMB_block **sp1, void *lookahead_item,
     if (new_size > b->file[p->cat].head.block_max)
     {
         char *first_dst;
-        char *cut_item = cut_item_buf;
+        const char *cut_item = cut_item_buf;
 
         assert (half1);
         assert (half2);
 
-       /* first half */
+	assert(cut_item_size > 0);
+	
+	/* first half */
         p->size = half1 - dst_buf;
         memcpy (p->bytes, dst_buf, half1 - dst_buf);
+	p->no_items = no_items_1;
 
         /* second half */
         *sp2 = new_leaf (b, p->cat);
 
-        (*b->method->code_reset)(c2);
+        (*b->method->codec.reset)(c2);
 
         first_dst = (*sp2)->bytes;
 
-        (*b->method->code_item)(ISAMC_ENCODE, c2, &first_dst, &cut_item);
+        (*b->method->codec.encode)(c2, &first_dst, &cut_item);
 
         memcpy (first_dst, half2, dst - half2);
 
         (*sp2)->size = (first_dst - (*sp2)->bytes) + (dst - half2);
+	(*sp2)->no_items = no_items - no_items_1;
         (*sp2)->dirty = 1;
         p->dirty = 1;
         memcpy (sub_item, cut_item_buf, cut_item_size);
@@ -742,19 +1005,20 @@ int insert_leaf (ISAMB b, struct ISAMB_block **sp1, void *lookahead_item,
     {
         memcpy (p->bytes, dst_buf, dst - dst_buf);
         p->size = new_size;
+	p->no_items = no_items;
     }
-    (*b->method->code_stop)(ISAMC_DECODE, c1);
-    (*b->method->code_stop)(ISAMC_ENCODE, c2);
+    (*b->method->codec.stop)(c1);
+    (*b->method->codec.stop)(c2);
     *sp1 = p;
     return more;
 }
 
 int insert_sub (ISAMB b, struct ISAMB_block **p, void *new_item,
                 int *mode,
-                ISAMC_I stream,
+                ISAMC_I *stream,
                 struct ISAMB_block **sp,
                 void *sub_item, int *sub_size,
-                void *max_item)
+                const void *max_item)
 {
     if (!*p || (*p)->leaf)
         return insert_leaf (b, p, new_item, mode, stream, sp, sub_item, 
@@ -764,12 +1028,42 @@ int insert_sub (ISAMB b, struct ISAMB_block **p, void *new_item,
                            sub_size, max_item);
 }
 
-int isamb_merge (ISAMB b, ISAMC_P pos, ISAMC_I stream)
+int isamb_unlink (ISAMB b, ISAMC_P pos)
+{
+    struct ISAMB_block *p1;
+
+    if (!pos)
+	return 0;
+    p1 = open_block(b, pos);
+    p1->deleted = 1;
+    if (!p1->leaf)
+    {
+	zint sub_p;
+	zint item_len;
+	const char *src = p1->bytes + p1->offset;
+
+	decode_ptr(&src, &sub_p);
+	isamb_unlink(b, sub_p);
+	
+	while (src != p1->bytes + p1->size)
+	{
+	    decode_ptr(&src, &item_len);
+	    src += item_len;
+	    decode_ptr(&src, &sub_p);
+	    isamb_unlink(b, sub_p);
+	}
+    }
+    close_block(b, p1);
+    return 0;
+}
+
+ISAMB_P isamb_merge (ISAMB b, ISAMC_P pos, ISAMC_I *stream)
 {
     char item_buf[DST_ITEM_MAX];
     char *item_ptr;
     int i_mode;
     int more;
+    int must_delete = 0;
 
     if (b->cache < 0)
     {
@@ -793,67 +1087,88 @@ int isamb_merge (ISAMB b, ISAMC_P pos, ISAMC_I stream)
         if (pos)
             p = open_block (b, pos);
         more = insert_sub (b, &p, item_buf, &i_mode, stream, &sp,
-                            sub_item, &sub_size, 0);
+			   sub_item, &sub_size, 0);
         if (sp)
         {    /* increase level of tree by one */
             struct ISAMB_block *p2 = new_int (b, p->cat);
             char *dst = p2->bytes + p2->size;
             
             encode_ptr (&dst, p->pos);
-            assert (sub_size < 20);
+            assert (sub_size < 40);
             encode_ptr (&dst, sub_size);
             memcpy (dst, sub_item, sub_size);
             dst += sub_size;
             encode_ptr (&dst, sp->pos);
             
             p2->size = dst - p2->bytes;
+	    p2->no_items = p->no_items + sp->no_items;
             pos = p2->pos;  /* return new super page */
             close_block (b, sp);
             close_block (b, p2);
         }
         else
+	{
             pos = p->pos;   /* return current one (again) */
+	}
+	if (p->no_items == 0)
+	    must_delete = 1;
+	else
+	    must_delete = 0;
         close_block (b, p);
     }
+    if (must_delete)
+    {
+	isamb_unlink(b, pos);
+	return 0;
+    }
     return pos;
 }
 
-ISAMB_PP isamb_pp_open_x (ISAMB isamb, ISAMB_P pos, int *level)
+ISAMB_PP isamb_pp_open_x (ISAMB isamb, ISAMB_P pos, int *level, int scope)
 {
     ISAMB_PP pp = xmalloc (sizeof(*pp));
+    int i;
 
     pp->isamb = isamb;
-    pp->block = xmalloc (10 * sizeof(*pp->block));
+    pp->block = xmalloc (ISAMB_MAX_LEVEL * sizeof(*pp->block));
 
     pp->pos = pos;
     pp->level = 0;
+    pp->maxlevel=0;
     pp->total_size = 0;
     pp->no_blocks = 0;
+    pp->skipped_numbers=0;
+    pp->returned_numbers=0;
+    pp->scope=scope;
+    for (i=0;i<ISAMB_MAX_LEVEL;i++)
+        pp->skipped_nodes[i] = pp->accessed_nodes[i]=0;
     while (1)
     {
         struct ISAMB_block *p = open_block (isamb, pos);
-        char *src = p->bytes + p->offset;
+        const char *src = p->bytes + p->offset;
         pp->block[pp->level] = p;
 
         pp->total_size += p->size;
         pp->no_blocks++;
-
         if (p->leaf)
             break;
 
+                                        
         decode_ptr (&src, &pos);
         p->offset = src - p->bytes;
         pp->level++;
+        pp->accessed_nodes[pp->level]++; 
     }
     pp->block[pp->level+1] = 0;
+    pp->maxlevel=pp->level;
     if (level)
         *level = pp->level;
     return pp;
 }
 
-ISAMB_PP isamb_pp_open (ISAMB isamb, ISAMB_P pos)
+ISAMB_PP isamb_pp_open (ISAMB isamb, ISAMB_P pos, int scope)
 {
-    return isamb_pp_open_x (isamb, pos, 0);
+    return isamb_pp_open_x (isamb, pos, 0, scope);
 }
 
 void isamb_pp_close_x (ISAMB_PP pp, int *size, int *blocks)
@@ -861,6 +1176,21 @@ void isamb_pp_close_x (ISAMB_PP pp, int *size, int *blocks)
     int i;
     if (!pp)
         return;
+    yaz_log(YLOG_DEBUG,"isamb_pp_close lev=%d returned "ZINT_FORMAT" values," 
+		    "skipped "ZINT_FORMAT,
+        pp->maxlevel, pp->skipped_numbers, pp->returned_numbers);
+    for (i=pp->maxlevel;i>=0;i--)
+        if ( pp->skipped_nodes[i] || pp->accessed_nodes[i])
+            yaz_log(YLOG_DEBUG,"isamb_pp_close  level leaf-%d: "
+			    ZINT_FORMAT" read, "ZINT_FORMAT" skipped", i,
+                 pp->accessed_nodes[i], pp->skipped_nodes[i]);
+    pp->isamb->skipped_numbers += pp->skipped_numbers;
+    pp->isamb->returned_numbers += pp->returned_numbers;
+    for (i=pp->maxlevel;i>=0;i--)
+    {
+        pp->isamb->accessed_nodes[i] += pp->accessed_nodes[i];
+        pp->isamb->skipped_nodes[i] += pp->skipped_nodes[i];
+    }
     if (size)
         *size = pp->total_size;
     if (blocks)
@@ -883,64 +1213,434 @@ void isamb_pp_close (ISAMB_PP pp)
     isamb_pp_close_x (pp, 0, 0);
 }
 
+/* simple recursive dumper .. */
+static void isamb_dump_r (ISAMB b, ISAMB_P pos, void (*pr)(const char *str),
+			  int level)
+{
+    char buf[1024];
+    char prefix_str[1024];
+    if (pos)
+    {
+	struct ISAMB_block *p = open_block (b, pos);
+	sprintf(prefix_str, "%*s " ZINT_FORMAT " cat=%d size=%d max=%d items="
+		ZINT_FORMAT, level*2, "",
+		pos, p->cat, p->size, b->file[p->cat].head.block_max,
+		p->no_items);
+	(*pr)(prefix_str);
+	sprintf(prefix_str, "%*s " ZINT_FORMAT, level*2, "", pos);
+	if (p->leaf)
+	{
+	    while (p->offset < p->size)
+	    {
+		const char *src = p->bytes + p->offset;
+		char *dst = buf;
+		(*b->method->codec.decode)(p->decodeClientData, &dst, &src);
+		(*b->method->log_item)(YLOG_DEBUG, buf, prefix_str);
+		p->offset = src - (char*) p->bytes;
+	    }
+	    assert(p->offset == p->size);
+	}
+	else
+	{
+	    const char *src = p->bytes + p->offset;
+	    ISAMB_P sub;
+	    zint item_len;
+
+	    decode_ptr (&src, &sub);
+	    p->offset = src - (char*) p->bytes;
+
+	    isamb_dump_r(b, sub, pr, level+1);
+	    
+	    while (p->offset < p->size)
+	    {
+		decode_ptr (&src, &item_len);
+		(*b->method->log_item)(YLOG_DEBUG, src, prefix_str);
+		src += item_len;
+		decode_ptr (&src, &sub);
+		
+		p->offset = src - (char*) p->bytes;
+		
+		isamb_dump_r(b, sub, pr, level+1);
+	    }		
+	}
+	close_block(b,p);
+    }
+}
+
+void isamb_dump (ISAMB b, ISAMB_P pos, void (*pr)(const char *str))
+{
+    isamb_dump_r(b, pos, pr, 0);
+}
+
 int isamb_pp_read (ISAMB_PP pp, void *buf)
 {
-    char *dst = buf;
-    char *src;
-    struct ISAMB_block *p = pp->block[pp->level];
-    if (!p)
-        return 0;
+    return isamb_pp_forward(pp, buf, 0);
+}
 
-    while (p->offset == p->size)
+
+static int isamb_pp_on_right_node(ISAMB_PP pp, int level, const void *untilbuf)
+{ /* looks one node higher to see if we should be on this node at all */
+  /* useful in backing off quickly, and in avoiding tail descends */
+  /* call with pp->level to begin with */
+    struct ISAMB_block *p;
+    int cmp;
+    const char *src;
+    zint item_len;
+    assert(level>=0);
+    if ( level == 0) {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_on_right returning true for root");
+#endif
+        return 1; /* we can never skip the root node */
+    }
+    level--;
+    p=pp->block[level];
+    assert(p->offset <= p->size);
+    if (p->offset < p->size )
     {
-        int pos, item_len;
-        while (p->offset == p->size)
-        {
-            if (pp->level == 0)
-                return 0;
-            close_block (pp->isamb, pp->block[pp->level]);
-            pp->block[pp->level] = 0;
-            (pp->level)--;
-            p = pp->block[pp->level];
-            assert (!p->leaf);  /* must be int */
+        assert(p->offset>0); 
+        src=p->bytes + p->offset;
+        decode_ptr(&src, &item_len);
+#if ISAMB_DEBUG
+        (*pp->isamb->method->codec.log_item)(YLOG_DEBUG,untilbuf,"on_leaf: until");
+        (*pp->isamb->method->codec.log_item)(YLOG_DEBUG,src,"on_leaf: value");
+#endif
+        cmp=(*pp->isamb->method->compare_item)(untilbuf,src);
+        if (cmp<pp->scope) {  /* cmp<2 */
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_on_right returning true "
+                            "cmp=%d lev=%d ofs=%d",cmp,level,p->offset);
+#endif
+            return 1; 
         }
-        src = p->bytes + p->offset;
-        
-        decode_ptr (&src, &item_len);
-        src += item_len;
-        decode_ptr (&src, &pos);
-        
-        p->offset = src - (char*) p->bytes;
+        else {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_on_right returning false "
+                            "cmp=%d lev=%d ofs=%d",cmp,level,p->offset);
+#endif
+            return 0; 
+        }
+    }
+    else {
+#if ISAMB_DEBUG
+        yaz_log(YLOG_DEBUG,"isamb_pp_on_right at tail, looking higher "
+                        "lev=%d",level);
+#endif
+        return isamb_pp_on_right_node(pp, level, untilbuf);
+    }
+} /* isamb_pp_on_right_node */
 
-        ++(pp->level);
-        
-        while (1)
-        {
-            pp->block[pp->level] = p = open_block (pp->isamb, pos);
+static int isamb_pp_read_on_leaf(ISAMB_PP pp, void *buf)
+{ /* reads the next item on the current leaf, returns 0 if end of leaf*/
+    struct ISAMB_block *p = pp->block[pp->level];
+    char *dst;
+    const char *src;
+    assert(pp);
+    assert(buf);
+    if (p->offset == p->size) {
+#if ISAMB_DEBUG
+        yaz_log(YLOG_DEBUG,"isamb_pp_read_on_leaf returning 0 on node %d",p->pos);
+#endif
+        return 0; /* at end of leaf */
+    }
+    src=p->bytes + p->offset;
+    dst=buf;
+    (*pp->isamb->method->codec.decode)(p->decodeClientData,&dst, &src);
+    p->offset = src - (char*) p->bytes;
+#if ISAMB_DEBUG
+    (*pp->isamb->method->codec.log_item)(YLOG_DEBUG, buf, "read_on_leaf returning 1");
+#endif
+    pp->returned_numbers++;
+    return 1;
+} /* read_on_leaf */
+
+static int isamb_pp_forward_on_leaf(ISAMB_PP pp, void *buf, const void *untilbuf)
+{ /* forwards on the current leaf, returns 0 if not found */
+    int cmp;
+    int skips=0;
+    while (1){
+        if (!isamb_pp_read_on_leaf(pp,buf))
+            return 0;
+        /* FIXME - this is an extra function call, inline the read? */
+        cmp=(*pp->isamb->method->compare_item)(untilbuf,buf);
+        if (cmp <pp->scope){  /* cmp<2  found a good one */
+#if ISAMB_DEBUG
+            if (skips)
+                yaz_log(YLOG_DEBUG, "isam_pp_fwd_on_leaf skipped %d items",skips);
+#endif
+            pp->returned_numbers++;
+            return 1;
+        }
+        if (!skips)
+            if (!isamb_pp_on_right_node(pp, pp->level, untilbuf))
+                return 0; /* never mind the rest of this leaf */
+        pp->skipped_numbers++;
+        skips++;
+    }
+} /* forward_on_leaf */
 
-            pp->total_size += p->size;
-            pp->no_blocks++;
+static int isamb_pp_climb_level(ISAMB_PP pp, ISAMB_P *pos)
+{ /* climbs higher in the tree, until finds a level with data left */
+  /* returns the node to (consider to) descend to in *pos) */
+    struct ISAMB_block *p = pp->block[pp->level];
+    const char *src;
+    zint item_len;
+#if ISAMB_DEBUG
+    yaz_log(YLOG_DEBUG,"isamb_pp_climb_level starting "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+    assert(pp->level >= 0);
+    assert(p->offset <= p->size);
+    if (pp->level==0)
+    {
+#if ISAMB_DEBUG
+        yaz_log(YLOG_DEBUG,"isamb_pp_climb_level returning 0 at root");
+#endif
+        return 0;
+    }
+    assert(pp->level>0); 
+    close_block(pp->isamb, pp->block[pp->level]);
+    pp->block[pp->level]=0;
+    (pp->level)--;
+    p=pp->block[pp->level];
+#if ISAMB_DEBUG
+    yaz_log(YLOG_DEBUG,"isamb_pp_climb_level climbed to level %d node %d ofs=%d",
+                    pp->level, p->pos, p->offset);
+#endif
+    assert(!p->leaf);
+    assert(p->offset <= p->size);
+    if (p->offset == p->size ) {
+        /* we came from the last pointer, climb on */
+        if (!isamb_pp_climb_level(pp,pos))
+            return 0;
+        p=pp->block[pp->level];
+    }
+    else
+    {
+        /* skip the child we just came from */
+#if ISAMB_DEBUG
+        yaz_log(YLOG_DEBUG,"isam_pp_climb_level: skipping lev=%d ofs=%d sz=%d", 
+                        pp->level, p->offset, p->size);
+#endif
+        assert (p->offset < p->size );
+        src=p->bytes + p->offset;
+        decode_ptr(&src, &item_len);
+        src += item_len;
+        decode_ptr(&src, pos);
+        p->offset=src - (char *)p->bytes;
             
-            if (p->leaf) /* leaf */
-            {
-                break;
-            }
-            src = p->bytes + p->offset;
-            decode_ptr (&src, &pos);
-            p->offset = src - (char*) p->bytes;
-            pp->level++;
-        }
     }
-    assert (p->offset < p->size);
-    assert (p->leaf);
-    src = p->bytes + p->offset;
-    (*pp->isamb->method->code_item)(ISAMC_DECODE, p->decodeClientData,
-                                    &dst, &src);
-    p->offset = src - (char*) p->bytes;
+    return 1;
+} /* climb_level */
+
+
+static zint isamb_pp_forward_unode(ISAMB_PP pp, zint pos, const void *untilbuf)
+{ /* scans a upper node until it finds a child <= untilbuf */
+  /* pp points to the key value, as always. pos is the child read from */
+  /* the buffer */
+  /* if all values are too small, returns the last child in the node */
+  /* FIXME - this can be detected, and avoided by looking at the */
+  /* parent node, but that gets messy. Presumably the cost is */
+  /* pretty low anyway */
+    struct ISAMB_block *p = pp->block[pp->level];
+    const char *src=p->bytes + p->offset;
+    zint item_len;
+    int cmp;
+    zint nxtpos;
+#if ISAMB_DEBUG
+    int skips=0;
+    yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode starting "
+                   "at level %d node %d ofs=%di sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+    assert(!p->leaf);
+    assert(p->offset <= p->size);
+    if (p->offset == p->size) {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode returning at end "
+                   "at level %d node %d ofs=%di sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+        return pos; /* already at the end of it */
+    }
+    while(p->offset < p->size) {
+        decode_ptr(&src,&item_len);
+        cmp=(*pp->isamb->method->compare_item)(untilbuf,src);
+        src+=item_len;
+        decode_ptr(&src,&nxtpos);
+        if (cmp<pp->scope) /* cmp<2 */
+        {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode returning a hit "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+            return pos;
+        } /* found one */
+        pos=nxtpos;
+        p->offset=src-(char*)p->bytes;
+        (pp->skipped_nodes[pp->maxlevel - pp->level -1])++;
+#if ISAMB_DEBUG
+        skips++;
+#endif
+    }
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode returning at tail "
+                   "at level %d node %d ofs=%d sz=%d skips=%d",
+                    pp->level, p->pos, p->offset, p->size, skips);
+#endif
+    return pos; /* that's the last one in the line */
+    
+} /* forward_unode */
+
+static void isamb_pp_descend_to_leaf(ISAMB_PP pp, ISAMB_P pos, const void *untilbuf)
+{ /* climbs down the tree, from pos, to the leftmost leaf */
+    struct ISAMB_block *p = pp->block[pp->level];
+    const char *src;
+    assert(!p->leaf);
+#if ISAMB_DEBUG
+    yaz_log(YLOG_DEBUG,"isamb_pp_descend_to_leaf "
+                   "starting at lev %d node %d ofs=%d lf=%d u=%p", 
+                   pp->level, p->pos, p->offset, p->leaf, untilbuf);
+#endif
+    if (untilbuf)
+        pos=isamb_pp_forward_unode(pp,pos,untilbuf);
+    ++(pp->level);
+    assert(pos);
+    p=open_block(pp->isamb, pos);
+    pp->block[pp->level]=p;
+    ++(pp->accessed_nodes[pp->maxlevel-pp->level]);
+    ++(pp->no_blocks);
+#if ISAMB_DEBUG
+    yaz_log(YLOG_DEBUG,"isamb_pp_descend_to_leaf "
+                   "got lev %d node %d lf=%d", 
+                   pp->level, p->pos, p->leaf);
+#endif
+    if (p->leaf)
+        return;
+    assert (p->offset==0 );
+    src=p->bytes + p->offset;
+    decode_ptr(&src, &pos);
+    p->offset=src-(char*)p->bytes;
+    isamb_pp_descend_to_leaf(pp,pos,untilbuf);
+#if ISAMB_DEBUG
+    yaz_log(YLOG_DEBUG,"isamb_pp_descend_to_leaf "
+                   "returning at lev %d node %d ofs=%d lf=%d", 
+                   pp->level, p->pos, p->offset, p->leaf);
+#endif
+} /* descend_to_leaf */
+
+static int isamb_pp_find_next_leaf(ISAMB_PP pp)
+{ /* finds the next leaf by climbing up and down */
+    ISAMB_P pos;
+    if (!isamb_pp_climb_level(pp,&pos))
+        return 0;
+    isamb_pp_descend_to_leaf(pp, pos,0);
     return 1;
 }
 
-int isamb_pp_num (ISAMB_PP pp)
-{
+static int isamb_pp_climb_desc(ISAMB_PP pp,  const void *untilbuf)
+{ /* climbs up and descends to a leaf where values >= *untilbuf are found */
+    ISAMB_P pos;
+#if ISAMB_DEBUG
+    struct ISAMB_block *p = pp->block[pp->level];
+    yaz_log(YLOG_DEBUG,"isamb_pp_climb_desc starting "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+    if (!isamb_pp_climb_level(pp,&pos))
+        return 0;
+    /* see if it would pay to climb one higher */
+    if (!isamb_pp_on_right_node(pp, pp->level, untilbuf))
+        if (!isamb_pp_climb_level(pp,&pos))
+            return 0;
+    isamb_pp_descend_to_leaf(pp, pos,untilbuf);
+#if ISAMB_DEBUG
+    p = pp->block[pp->level];
+    yaz_log(YLOG_DEBUG,"isamb_pp_climb_desc done "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
     return 1;
+} /* climb_desc */
+
+int isamb_pp_forward (ISAMB_PP pp, void *buf, const void *untilbuf)
+{
+#if ISAMB_DEBUG
+    struct ISAMB_block *p = pp->block[pp->level];
+    assert(p->leaf);
+    yaz_log(YLOG_DEBUG,"isamb_pp_forward starting "
+                   "at level %d node %d ofs=%d sz=%d u=%p sc=%d",
+                    pp->level, p->pos, p->offset, p->size,untilbuf, scope);
+#endif
+    if (untilbuf) {
+        if (isamb_pp_forward_on_leaf( pp, buf, untilbuf)) {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward (f) returning (A) "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+            return 1;
+        }
+        if (! isamb_pp_climb_desc( pp, untilbuf)) {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward (f) returning notfound (B) "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+            return 0; /* could not find a leaf */
+        }
+        do{
+            if (isamb_pp_forward_on_leaf( pp, buf, untilbuf)) {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward (f) returning (C) "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+                return 1;
+            }
+        }while ( isamb_pp_find_next_leaf(pp));
+        return 0; /* could not find at all */
+    }
+    else { /* no untilbuf, a straight read */
+        /* FIXME - this should be moved
+         * directly into the pp_read */
+        /* keeping here now, to keep same
+         * interface as the old fwd */
+        if (isamb_pp_read_on_leaf( pp, buf)) {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward (read) returning (D) "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+            return 1;
+        }
+        if (isamb_pp_find_next_leaf(pp)) {
+#if ISAMB_DEBUG
+            yaz_log(YLOG_DEBUG,"isamb_pp_forward (read) returning (E) "
+                   "at level %d node %d ofs=%d sz=%d",
+                    pp->level, p->pos, p->offset, p->size);
+#endif
+            return isamb_pp_read_on_leaf(pp, buf);
+        }
+        else
+            return 0;
+    }
+} /* isam_pp_forward (new version) */
+
+void isamb_pp_pos( ISAMB_PP pp, double *current, double *total )
+{ /* return an estimate of the current position and of the total number of */
+  /* occureences in the isam tree, based on the current leaf */
+    struct ISAMB_block *p = pp->block[pp->level];
+    assert(total);
+    assert(current);
+    assert(p->leaf);
+
+    *total = pp->block[0]->no_items;
+    *current = (double) pp->returned_numbers;
+#if ISAMB_DEBUG
+    yaz_log(YLOG_LOG, "isamb_pp_pos returning: cur= %0.1f tot=%0.1f rn="
+	 ZINT_FORMAT, *current, *total, pp->returned_numbers);
+#endif
 }