Add disk extraction tools

1 files changed, 145 insertions, 0 deletions

diff --git a/eumel.py b/eumel.py
new file mode 100644
index 0000000..0434b35
--- /dev/null
+++ b/eumel.py
@@ -0,0 +1,145 @@
+"""
+EUMEL utility functions, including:
+
+"""
+
+import logging
+import codecs
+
+# EUMEL character map. See “Benutzerhandbuch 1.7”, page 107.
+# map eumel character to unicode codepoint
+eumel2unicodemap = dict (
+    [(10, '\n'), (13, '\r')] +
+    # first part is same as ascii
+    [(i, chr (i)) for i in range (32, 126)] + 
+    [(126, '~')] +
+    [(214, 'Ä'), (215, 'Ö'), (216, 'Ü'), (217, 'ä'), (218, 'ö'), (219, 'ü'), (220, 'k'), (221, '-'), (222, '#'), (223, ' ')] +
+    [(251, 'ß')])
+
+def decode (input, errors='strict'):
+    ret = []
+    pos = 0
+    for pos in range (len (input)):
+        c = input[pos]
+        m = eumel2unicodemap.get (c, None)
+        if m:
+            ret.append (m)
+        else:
+            if errors == 'strict':
+                raise UnicodeError ('unknown char {}'.format (c))
+            elif errors == 'ignore':
+                pass
+            elif errors == 'replace':
+                ret.append ('\uFFFD')
+            else:
+                break
+    return (''.join (ret), pos)
+
+def lookup (name):
+    if name == 'eumel':
+        return codecs.CodecInfo(None, decode)
+    return None
+
+codecs.register (lookup)
+
+# Dataspace utilities
+import struct, os
+
+class DataspaceTypeMismatch (ValueError):
+    pass
+
+class Dataspace:
+    # Expected type
+    TYPE = None
+
+    def __init__ (self, fd):
+        self.fd = fd
+        self.lastaddr, self.firstaddr, self.type, _ = self._parseHeader ()
+        if self.TYPE is not None and self.type != self.TYPE:
+            raise DataspaceTypeMismatch ()
+        self.heap = {}
+
+    def _parseHeader (self):
+        """
+        :return: (last heap address, first heap address, dataspace type, unknown)
+        """
+        buf = self.fd.read (8)
+        return struct.unpack ('<HHHH', buf)
+
+    def parseText (self):
+        """
+        Parse TEXT datatype, which can either be embedded (up to 13? chars) or in the heap (i.e. address)
+        """
+        buf = self.fd.read (16)
+        address, length = struct.unpack ('<HB', buf[:3])
+        if length <= 13:
+            r = buf[3:3+length]
+        else:
+            length, = struct.unpack ('<H', buf[3:5])
+            r = HeapReference (self.heap, address, length)
+        return r
+
+    def parseInt (self, count=1):
+        if count == 1:
+            return struct.unpack ('<H', self.fd.read (1*intsize))[0]
+        else:
+            return [self.parseInt () for i in range (count)]
+
+    def parseHeap (self):
+        heapaddr = self.firstaddr
+        maxaddr = 2**(intsize*8)-1
+        while True:
+            head = self.fd.read (2)
+            # XXX: not sure how to find its offset
+            if head == b'\xff\xff':
+                continue
+            if not head or len (head) < 2:
+                break
+            length, = struct.unpack ('<H', head)
+            self.heap[heapaddr] = self.fd.read (length)
+            logging.debug ('got heap entry {:x} = ({}) {}'.format (heapaddr, length, self.heap[heapaddr]))
+            heapaddr = (heapaddr+2+length) % maxaddr
+
+    def skip (self, n):
+        self.fd.seek (n, os.SEEK_CUR)
+
+    def seek (self, pos):
+        self.fd.seek (pos, os.SEEK_SET)
+
+class HeapReference:
+    def __init__ (self, heap, address, length):
+        self.heap = heap
+        self.address = address
+        self.length = length
+        self._item = None
+
+    def __bytes__ (self):
+        return self.item[:self.length]
+
+    def __len__ (self):
+        return self.length
+
+    def __getitem__ (self, key):
+        return self.item[key]
+
+    def __repr__ (self):
+        return '<HeapReference to {:x} length {}>'.format (self.address, self.length)
+    
+    @property
+    def item (self):
+        if self._item:
+            return self._item
+        elif self.address in self.heap:
+            self._item = self.heap[self.address]
+            return self._item
+        else:
+            raise HeapReferenceUnresolved (self.address, self.length)
+
+class HeapReferenceUnresolved (Exception):
+    def __init__ (self, address, length):
+        Exception.__init__ (self, 'addr: {:x}, len: {}'.format (address, length))
+
+# Machine constants
+intsize = 2
+pagesize = 512
+