1 files changed, 108 insertions, 0 deletions

diff --git a/structutils.py b/structutils.py
new file mode 100644
index 0000000..26b0188
--- /dev/null
+++ b/structutils.py
@@ -0,0 +1,108 @@
+# vim: set filencoding=utf8
+"""
+Utilities for Manipulating Byte Streams
+
+@author: Mike Crute (mcrute@gmail.com)
+@organization: SoftGroup Interactive, Inc.
+@date: May 05, 2010
+"""
+
+import struct
+
+
+INT_FORMAT = struct.Struct('>I')
+
+
+def pack_string(string):
+    """
+    Pack a string into a network style byte array.
+    """
+    return pack_int(len(string)) + string
+
+
+def pack_int(integer):
+    """
+    Pack an integer into a byte array.
+    """
+    return INT_FORMAT.pack(integer)
+
+
+def pack_mp_int(mp_int):
+    """
+    Pack a multiple-percision integer into a byte array.
+    """
+    return pack_string(int_to_bytes(mp_int))
+
+
+def unpack_string(buf):
+    """
+    Unpack a string from a byte array buffer returning
+    the string and the remainder of the buffer.
+    """
+    length, = INT_FORMAT.unpack(buf[:4])
+    string = buf[4:4+length]
+    remainder = buf[4+length:]
+    return string, remainder
+
+
+def unpack_mp_int(buf):
+    """
+    Unpack a multiple-percision integer from a byte array
+    buffer returning the string and the remainder of the
+    buffer.
+    """
+    length, = INT_FORMAT.unpack(buf[:4])
+    remainder = buf[4+length:]
+
+    return bytes_to_int(buf[4:4+length]), remainder
+
+
+def unpack_int(buf):
+    """
+    Unpack an integer from a byte array buffer returning the
+    string and the remainder of the buffer.
+    """
+    integer, = INT_FORMAT.unpack(buf[:4])
+    remainder = buf[4:]
+    return integer, remainder
+
+
+def get_packed_mp_ints(buf, count=1):
+    """
+    Get a number of multiple-percision integers from a byte
+    array buffer but leaves them as network style mpints.
+    """
+    ints = []
+    for _ in range(count):
+        length, = INT_FORMAT.unpack(buf[:4])
+        ints.append(buf[:4+length]
+        buf = buf[4+length:]
+
+    return ints
+
+
+def int_to_bytes(integer):
+    """
+    Convert an integer or a long integer to an array of
+    bytes.
+    """
+    bytes = []
+
+    while integer > 0:
+        integer, chunk = divmod(integer, 256)
+        bytes.insert(0, chr(chunk))
+
+    return ''.join(bytes)
+
+
+def bytes_to_int(buf):
+    """
+    Convert an array of bytes into an integer or long
+    integer.
+    """
+    integer = 0
+    for byte in buf:
+        integer <<= 8
+        integer += ord(byte)
+
+    return integer