date mutated in libcouchbase's send buffer

while true
set 1000 json document to couchbase-server
get 1000 json documents from couchbase-server
some of them may become invalid json document

the test code is here https://github.com/killgxlin/libcouchbase_testcode
i think it may be a bug of libcouchbase. if not it may be a bug of myself ,please point out and mail me
killgxlin@hotmail.com please.

broken document is in attachment
key_*.base64 is the broken document saved in couchbase-server
key_*.json is a broken json which decoded from key_*base64,
key_.hexdump is a hexdumped text from broken key_.json

by watch key_*.hexdump i could see that the past of the document is overwroted by a network msgof couchbase which head is 80 01 PROTOCOL_BINARY_REQ PROTOCOL_BINARY_CMD_SET