Added support for compound indices.

[didex.git] / didex / index.py

diff --git a/didex/index.py b/didex/index.py
index 4d42506..cdd4069 100644 (file)
--- a/didex/index.py
+++ b/didex/index.py
@@ -2,6 +2,8 @@ import struct, contextlib, math
 from . import db, lib
 from .db import bd, txnfun
 
+__all__ = ["maybe", "t_int", "t_uint", "t_float", "t_str", "ordered"]
+
 deadlock = bd.DBLockDeadlockError
 notfound = bd.DBNotFoundError
 
@@ -47,6 +49,45 @@ class maybe(object):
         else:
             return self.bk.compare(a[1:], b[1:])
 
+class compound(object):
+    def __init__(self, *parts):
+        self.parts = parts
+
+    def encode(self, obs):
+        if len(obs) != len(self.parts):
+            raise ValueError("invalid length of compound data: " + str(len(obs)) + ", rather than " + len(self.parts))
+        buf = bytearray()
+        for ob, part in zip(obs, self.parts):
+            dat = part.encode(ob)
+            if len(dat) < 128:
+                buf.append(0x80 | len(dat))
+                buf.extend(dat)
+            else:
+                buf.extend(struct.pack(">i", len(dat)))
+                buf.extend(dat)
+        return bytes(buf)
+    def decode(self, dat):
+        ret = []
+        off = 0
+        for part in self.parts:
+            if dat[off] & 0x80:
+                ln = dat[off] & 0x7f
+                off += 1
+            else:
+                ln = struct.unpack(">i", dat[off:off + 4])[0]
+                off += 4
+            ret.append(part.decode(dat[off:off + len]))
+            off += len
+        return tuple(ret)
+    def compare(self, al, bl):
+        if (len(al) != len(self.parts)) or (len(bl) != len(self.parts)):
+            raise ValueError("invalid length of compound data: " + str(len(al)) + ", " + str(len(bl)) + ", rather than " + len(self.parts))
+        for a, b, part in zip(al, bl, self.parts):
+            c = part.compare(a, b)
+            if c != 0:
+                return c
+        return 0
+
 def floatcmp(a, b):
     if math.isnan(a) and math.isnan(b):
         return 0