Change meaning of 'b' field values

RabbitMQ prior to version 3.3.0 treated the 'b' field value as
unsigned; however, the specification and most clients treat it as
signed.

lib/codec.js

@@ -156,13 +156,13 @@ function encodeFieldValue(buffer, value, offset) {
             buffer.writeDoubleBE(val, offset);
             offset += 8;
         }
-        else { // only signed values are used in tables by RabbitMQ,
-               // except for 'byte's which are only unsigned. (The
-               // errata on the RabbitMQ website is wrong on this --
-               // see rabbit_binary_generator.erl)
-            if (val < 256 && val >= 0) {
+        else { // only signed values are used in tables by
+               // RabbitMQ. It *used* to (< v3.3.0) treat the byte 'b'
+               // type as unsigned, but most clients (and the spec)
+               // think it's signed, and now RabbitMQ does too.
+            if (val < 128 && val >= -128) {
                 tag('b');
-                buffer.writeUInt8(val, offset); offset++;
+                buffer.writeInt8(val, offset); offset++;
             }
             else if (val >= -0x8000 && val < 0x8000) { //  short
                 tag('s');
@@ -215,7 +215,7 @@ function decodeFields(slice) {
         var tag = String.fromCharCode(slice[offset]); offset++;
         switch (tag) {
         case 'b':
-            val = slice.readUInt8(offset); offset++;
+            val = slice.readInt8(offset); offset++;
             break;
         case 'S':
             len = slice.readUInt32BE(offset); offset += 4;

test/codec.js

@@ -13,11 +13,11 @@ var forAll = C.forAll;
 
 var testCases = [
     // integers
-    ['byte', {byte: 127}, [4,98,121,116,101,98,127]],
-    ['byte max value', {byte: 255}, [4,98,121,116,101,98,255]],
-    ['byte min value', {byte: 0}, [4,98,121,116,101,98,0]],
-    ['< 0 promoted to signed short', {short: -1}, [5,115,104,111,114,116,115,255,255]],
-    ['> 255 promoted to short', {short: 256}, [5,115,104,111,114,116,115,1,0]],
+    ['byte', {byte: 112}, [4,98,121,116,101,98,112]],
+    ['byte max value', {byte: 127}, [4,98,121,116,101,98,127]],
+    ['byte min value', {byte: -128}, [4,98,121,116,101,98,128]],
+    ['< -128 promoted to signed short', {short: -129}, [5,115,104,111,114,116,115,255,127]],
+    ['> 127 promoted to short', {short: 128}, [5,115,104,111,114,116,115,0,128]],
     ['< 2^15 still a short', {short: 0x7fff}, [5,115,104,111,114,116,115,127,255]],
     ['-2^15 still a short', {short: -0x8000}, [5,115,104,111,114,116,115,128,0]],
     ['>= 2^15 promoted to int', {int: 0x8000}, [3,105,110,116,73,0,0,128,0]],