Merge pull request #55 from JuliaRobotics/tk/lcm_handle-allocs

 Avoid allocation in onresponse using UnsafeArrays.

Author: rdeits

REQUIRE

@@ -4,3 +4,4 @@ BinDeps 0.8
 CMakeWrapper 0.2
 StaticArrays 0.5
 FastIOBuffers 0.0.1
+UnsafeArrays 0.2.0

src/LCMCore.jl

@@ -2,6 +2,7 @@ module LCMCore
 
 using StaticArrays
 using FastIOBuffers
+using UnsafeArrays
 
 using Dates
 using FileWatching: poll_fd

src/core.jl

@@ -146,12 +146,14 @@ end
 
 function onresponse(rbuf::RecvBuf, channelptr::Ptr{UInt8}, opts::SubscriptionOptions{T}) where T
     check_channel_name(channelptr, opts)
-    msgdata = unsafe_wrap(Vector{UInt8}, rbuf.data, rbuf.data_size)
-    if T === Nothing
-        opts.handler(opts.channel, msgdata)
-    else
-        msg = decode(msgdata, opts.msgtype)
-        opts.handler(opts.channel, msg)
+    GC.@preserve rbuf begin
+        msgdata = UnsafeArray(rbuf.data, (Int(rbuf.data_size), ))
+        if T === Nothing
+            opts.handler(opts.channel, msgdata)
+        else
+            msg = decode(msgdata, opts.msgtype)
+            opts.handler(opts.channel, msg)
+        end
     end
     return nothing
 end

test/runtests.jl

@@ -214,6 +214,27 @@ end
     @test did_callback2
 end
 
+@testset "lcm_handle allocations" begin
+    data = UInt8[1,2,3,4,5]
+    channel = "CHANNEL_1"
+
+    # start listening
+    sublcm = LCM()
+    sub = subscribe(sublcm, channel, (c, d) -> nothing)
+    set_queue_capacity(sub, 2)
+
+    # publish two messages
+    publcm = LCM()
+    for _ = 1 : 2
+        publish(publcm, channel, data)
+    end
+
+    # check that handling doesn't allocate
+    LCMCore.lcm_handle(sublcm)
+    allocs = @allocated LCMCore.lcm_handle(sublcm)
+    @test allocs == 0
+end
+
 include("test_lcmtype.jl")
 include("test_readlog.jl")