Improve support searching indexes (#36)

Author: Schamper

dissect/esedb/btree.py

@@ -0,0 +1,166 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from dissect.esedb.exceptions import KeyNotFoundError, NoNeighbourPageError
+
+if TYPE_CHECKING:
+    from dissect.esedb.esedb import EseDB
+    from dissect.esedb.page import Node, Page
+
+
+class BTree:
+    """A simple implementation for searching the ESE B+Trees.
+
+    This is a stateful interactive class that moves an internal cursor to a position within the BTree.
+
+    Args:
+        esedb: An instance of :class:`~dissect.esedb.esedb.EseDB`.
+        page: The page to open the :class:`BTree` on.
+    """
+
+    def __init__(self, esedb: EseDB, root: int | Page):
+        self.esedb = esedb
+
+        if isinstance(root, int):
+            page_num = root
+            root = esedb.page(page_num)
+        else:
+            page_num = root.num
+
+        self.root = root
+
+        self._page = root
+        self._page_num = page_num
+        self._node_num = 0
+
+    def reset(self) -> None:
+        """Reset the internal state to the root of the BTree."""
+        self._page = self.root
+        self._page_num = self._page.num
+        self._node_num = 0
+
+    def node(self) -> Node:
+        """Return the node the BTree is currently on.
+
+        Returns:
+            A :class:`~dissect.esedb.page.Node` object of the current node.
+        """
+        return self._page.node(self._node_num)
+
+    def next(self) -> Node:
+        """Move the BTree to the next node and return it.
+
+        Can move the BTree to the next page as a side effect.
+
+        Returns:
+            A :class:`~dissect.esedb.page.Node` object of the next node.
+        """
+        if self._node_num + 1 > self._page.node_count - 1:
+            self.next_page()
+        else:
+            self._node_num += 1
+
+        return self.node()
+
+    def next_page(self) -> None:
+        """Move the BTree to the next page in the tree.
+
+        Raises:
+            NoNeighbourPageError: If the current page has no next page.
+        """
+        if self._page.next_page:
+            self._page = self.esedb.page(self._page.next_page)
+            self._node_num = 0
+        else:
+            raise NoNeighbourPageError(f"{self._page} has no next page")
+
+    def prev(self) -> Node:
+        """Move the BTree to the previous node and return it.
+
+        Can move the BTree to the previous page as a side effect.
+
+        Returns:
+            A :class:`~dissect.esedb.page.Node` object of the previous node.
+        """
+        if self._node_num - 1 < 0:
+            self.prev_page()
+        else:
+            self._node_num -= 1
+
+        return self.node()
+
+    def prev_page(self) -> None:
+        """Move the BTree to the previous page in the tree.
+
+        Raises:
+            NoNeighbourPageError: If the current page has no previous page.
+        """
+        if self._page.previous_page:
+            self._page = self.esedb.page(self._page.previous_page)
+            self._node_num = self._page.node_count - 1
+        else:
+            raise NoNeighbourPageError(f"{self._page} has no previous page")
+
+    def search(self, key: bytes, exact: bool = True) -> Node:
+        """Search the tree for the given ``key``.
+
+        Moves the BTree to the matching node, or on the last node that is less than the requested key.
+
+        Args:
+            key: The key to search for.
+            exact: Whether to only return successfully on an exact match.
+
+        Raises:
+            KeyNotFoundError: If an ``exact`` match was requested but not found.
+        """
+        page = self._page
+        while True:
+            node = find_node(page, key)
+
+            if page.is_branch:
+                page = self.esedb.page(node.child)
+            else:
+                self._page = page
+                self._page_num = page.num
+                self._node_num = node.num
+                break
+
+        if exact and key != node.key:
+            raise KeyNotFoundError(f"Can't find key: {key}")
+
+        return self.node()
+
+
+def find_node(page: Page, key: bytes) -> Node:
+    """Search a page for a node matching ``key``.
+
+    Args:
+        page: The page to search.
+        key: The key to search.
+    """
+    first_node_idx = 0
+    last_node_idx = page.node_count - 1
+
+    node = None
+    while first_node_idx < last_node_idx:
+        node_idx = (first_node_idx + last_node_idx) // 2
+        node = page.node(node_idx)
+
+        # It turns out that the way BTree keys are compared matches 1:1 with how Python compares bytes
+        # First compare data, then length
+        if key < node.key:
+            last_node_idx = node_idx
+        elif key == node.key:
+            if page.is_branch:
+                # If there's an exact match on a key on a branch page, the actual leaf nodes are in the next branch
+                # Page keys for branch pages appear to be non-inclusive upper bounds
+                node_idx = min(node_idx + 1, page.node_count - 1)
+                node = page.node(node_idx)
+
+            return node
+        else:
+            first_node_idx = node_idx + 1
+
+    # We're at the last node
+    return page.node(first_node_idx)

dissect/esedb/c_esedb.py

@@ -426,6 +426,34 @@
     DotNetGuid              = 0x00040000,           // index over GUID column according to .Net GUID sort order
     ImmutableStructure      = 0x00080000,           // Do not write to the input structures during a JetCreateIndexN call.
 };
+
+flag IDBFLAG : uint16 {
+    Unique                  = 0x0001,               // Duplicate keys not allowed
+    AllowAllNulls           = 0x0002,               // Make entries for NULL keys (all segments are null)
+    AllowFirstNull          = 0x0004,               // First index column NULL allowed in index
+    AllowSomeNulls          = 0x0008,               // Make entries for keys with some null segments
+    NoNullSeg               = 0x0010,               // Don't allow a NULL key segment
+    Primary                 = 0x0020,               // Index is the primary index
+    LocaleSet               = 0x0040,               // Index locale information (locale name) is set (JET_bitIndexUnicode was specified).
+    Multivalued             = 0x0080,               // Has a multivalued segment
+    TemplateIndex           = 0x0100,               // Index of a template table
+    DerivedIndex            = 0x0200,               // Index derived from template table
+                                                    //   Note that this flag is persisted, but
+                                                    //   never used in an in-memory IDB, because
+                                                    //   we use the template index IDB instead.
+    LocalizedText           = 0x0400,               // Has a unicode text column? (code page is 1200)
+    SortNullsHigh           = 0x0800,               // NULL sorts after data
+    // Jan 2012: MSU is being removed. fidbUnicodeFixupOn should no longer be referenced.
+    UnicodeFixupOn_Deprecated   = 0x1000,           // Track entries with undefined Unicode codepoints
+    CrossProduct            = 0x2000,               // all combinations of multi-valued columns are indexed
+    DisallowTruncation      = 0x4000,               // fail update rather than allow key truncation
+    NestedTable             = 0x8000,               // combinations of multi-valued columns of same itagSequence are indexed
+};
+
+flag IDXFLAG : uint16 {
+    ExtendedColumns         = 0x0001,               // IDXSEGs are comprised of JET_COLUMNIDs, not FIDs
+    DotNetGuid              = 0x0002,               // GUIDs sort according to .Net rules
+};
 """  # noqa E501
 
 c_esedb = cstruct().load(esedb_def)
@@ -444,6 +472,8 @@
 TAGFLD_HEADER = c_esedb.TAGFLD_HEADER
 CODEPAGE = c_esedb.CODEPAGE
 COMPRESSION_SCHEME = c_esedb.COMPRESSION_SCHEME
+IDBFLAG = c_esedb.IDBFLAG
+IDXFLAG = c_esedb.IDXFLAG
 
 CODEPAGE_MAP = {
     CODEPAGE.UNICODE: "utf-16-le",