File Sharing MVP

New Generic SendMessage function that does basic handle checking and
error reporting

@@ -0,0 +41,4 @@
+// DownloadFile given a profile, a conversation handle and a file sharing key, start off a download process
+// to downloadFilePath
+func (f *Functionality) DownloadFile(profile peer.CwtchPeer, handle string, downloadFilePath string, key string) {
+	profile.SetAttribute(attr.GetLocalScope(key), downloadFilePath)

@@ -0,0 +1,19 @@
+package model
+
+// MessageWrapper is the canonical Cwtch overlay wrapper
+type MessageWrapper struct {

@@ -0,0 +18,4 @@
+type Chunk []byte
+
+// DefaultChunkSize is the default value of a manifest chunk
+const DefaultChunkSize = 4096

@@ -0,0 +71,4 @@
+			break
+		}
+		hash := sha256.New()
+		hash.Write(buf[0:n])

@@ -0,0 +75,4 @@
+		rootHash.Write(buf[0:n])
+		chunkHash := hash.Sum(nil)
+		chunks = append(chunks, chunkHash)
+		fileSizeInBytes += uint64(n)

@@ -0,0 +102,4 @@
+	}
+
+	// Seek to Chunk
+	offset, err := m.openFd.Seek(int64(id*m.ChunkSizeInBytes), 0)

@@ -0,0 +127,4 @@
+	}
+
+	manifest, err := files.CreateManifest("cwtch.out.png")
+	if hex.EncodeToString(manifest.RootHash) != "8f0ed73bbb30db45b6a740b1251cae02945f48e4f991464d5f3607685c45dcd136a325dab2e5f6429ce2b715e602b20b5b16bf7438fb6235fefe912adcedb5fd" {

@@ -0,0 +134,4 @@
+	queueOracle.Shutdown()
+	app.Shutdown()
+	acn.Close()
+

@@ -0,0 +23,4 @@
+}
+
+// FunctionalityGate returns contact.Functionality always
+func FunctionalityGate(experimentMap map[string]bool) (*Functionality, error) {

@@ -7,3 +15,1 @@
-	"encoding/base64"
-	"encoding/json"
-	"errors"
+	model3 "cwtch.im/cwtch/protocol/model"

@@ -481,3 +510,2 @@
-				}
-			} else if numtokens < 5 {
+				// we failed to post, probably because we ran out of tokens... so make a payment
 				go tokenApp.MakePayment()

@@ -493,2 +530,3 @@
 	log.Debugf("New message from peer: %v %v", hostname, context)
-	if context == event.ContextGetVal {
+
+	if context == event.ContextAck {

@@ -2,3 +2,3 @@
 
 import (
-	"cwtch.im/cwtch/event"
+	model2 "cwtch.im/cwtch/protocol/model"

@@ -0,0 +63,4 @@
+
+	i := 0
+
+	for {

@@ -0,0 +287,4 @@
+		buf := make([]byte, m.ChunkSizeInBytes)
+		chunkI := 0
+		for {
+			n, err := reader.Read(buf)