[PROTON-1988] [cpp] streamable message support

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: proton-c-0.26.0
• Component/s: cpp-binding
• Assignee: Unassigned
• Reporter: Alan Conway
• Created: 07/Jan/19 16:57
• Updated: 05/Mar/19 21:39

Description

C++ API support for streaming large messages in chunks  (too large to fit entire message in memory)

The C link-level API does support streaming messages in chunks, but the C message encoder/decoder and the proton::message type do. Provide an alternative (or extended) C++ message type with a byte-stream API to send/receive the body data in chunks, without every requiring the entire body to be held in memory.

Use cases:

1. Only the message body need be streamed. Properties are encoded/decode as a unit before sending/receiving any of the body. Most client/endpoint applications would work this way.
2. The entire message, headers, properties and all, need to be streamed, with support for partial decoding of an incoming message and efficient pass thru (incoming to outgoing without decode/re-encode). Only advanced intermediaries are likely to need this (e.g. this is what dispatch router does.)