add BigString amp argument to accommodate huge offer list

jmbase/bigstring.py

@@ -0,0 +1,64 @@
+try:
+    from cStringIO import StringIO
+except ImportError:
+    from StringIO import StringIO
+from itertools import count
+from twisted.protocols import amp
+
+CHUNK_MAX = 0xffff
+
+class BigString(amp.Argument):
+    """
+    A byte-string amp.Argument with no 65,535 length limit.
+
+    Each value for a key/value pair in an AMP box may not
+    exceed 65,535 bytes in length. So if we *really* want to
+    send potentially larger values, this class will implicitly
+    encode/decode them to/from an arbitrary additional
+    number of key/value pairs that are given automatic key
+    names by prefixing this Argument's key name to a counter.
+    """
+    def fromBox(self, name, strings, objects, proto):
+        value = StringIO()
+        value.write(strings.get(name))
+        for counter in count(2):
+            chunk = strings.get("%s.%d" % (name, counter))
+            if chunk is None:
+                break
+            value.write(chunk)
+        objects[name] = self.buildvalue(value.getvalue())
+
+    def buildvalue(self, value):
+        return value
+
+    def toBox(self, name, strings, objects, proto):
+        value = StringIO(self.fromvalue(objects[name]))
+        firstChunk = value.read(CHUNK_MAX)
+        strings[name] = firstChunk
+        counter = 2
+        while True:
+            nextChunk = value.read(CHUNK_MAX)
+            if not nextChunk:
+                break
+            strings["%s.%d" % (name, counter)] = nextChunk
+            counter += 1
+
+    def fromvalue(self, value):
+        return value
+
+class BigUnicode(BigString):
+    """
+    A unicode-string amp.Argument with no 65,535 length limit.
+
+    Each value for a key/value pair in an AMP box may not
+    exceed 65,535 bytes in length. So if we *really* want to
+    send potentially larger values, this class will implicitly
+    encode/decode them to/from an arbitrary additional
+    number of key/value pairs that are given automatic key
+    names by prefixing this Argument's key name to a counter.
+    """
+    def buildvalue(self, value):
+        return value.decode('utf-8')
+
+    def fromvalue(self, value):
+        return value.encode('utf-8')

jmbase/commands.py

@@ -5,6 +5,7 @@ messaging protocol (*not* Joinmarket p2p protocol).
 Used for AMP asynchronous messages.
 """
 from twisted.protocols.amp import Integer, String, Unicode, Boolean, Command
+from bigstring import BigString
 
 class DaemonNotReady(Exception):
     pass
@@ -78,7 +79,7 @@ class JMSetupDone(JMCommand):
     arguments = []
 
 class JMOffers(JMCommand):
-    arguments = [('orderbook', String())]
+    arguments = [('orderbook', BigString())]
 
 class JMFillResponse(JMCommand):
     arguments = [('success', Boolean()),