THRIFT-1681: Add Lua Support Patch: Dave Watson

Github Pull Request: This closes #92
diff --git a/lib/lua/src/luabpack.c b/lib/lua/src/luabpack.c
new file mode 100644
index 0000000..c936428
--- /dev/null
+++ b/lib/lua/src/luabpack.c
@@ -0,0 +1,162 @@
+//
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+//
+
+#include <lua.h>
+#include <lauxlib.h>
+#include <string.h>
+#include <inttypes.h>
+#include <netinet/in.h>
+
+extern int64_t lualongnumber_checklong(lua_State *L, int index);
+extern int64_t lualongnumber_pushlong(lua_State *L, int64_t *val);
+
+// host order to network order (64-bit)
+static int64_t T_htonll(uint64_t data) {
+  uint32_t d1 = htonl((uint32_t)data);
+  uint32_t d2 = htonl((uint32_t)(data >> 32));
+  return ((uint64_t)d1 << 32) + (uint64_t)d2;
+}
+
+// network order to host order (64-bit)
+static int64_t T_ntohll(uint64_t data) {
+  uint32_t d1 = ntohl((uint32_t)data);
+  uint32_t d2 = ntohl((uint32_t)(data >> 32));
+  return ((uint64_t)d1 << 32) + (uint64_t)d2;
+}
+
+/**
+ * bpack(type, data)
+ *  c - Signed Byte
+ *  s - Signed Short
+ *  i - Signed Int
+ *  l - Signed Long
+ *  d - Double
+ */
+static int l_bpack(lua_State *L) {
+  const char *code = luaL_checkstring(L, 1);
+  luaL_argcheck(L, code[1] == '\0', 0, "Format code must be one character.");
+  luaL_Buffer buf;
+  luaL_buffinit(L, &buf);
+
+  switch (code[0]) {
+    case 'c': {
+      int8_t data = luaL_checknumber(L, 2);
+      luaL_addlstring(&buf, (void*)&data, sizeof(data));
+      break;
+    }
+    case 's': {
+      int16_t data = luaL_checknumber(L, 2);
+      data = (int16_t)htons(data);
+      luaL_addlstring(&buf, (void*)&data, sizeof(data));
+      break;
+    }
+    case 'i': {
+      int32_t data = luaL_checkinteger(L, 2);
+      data = (int32_t)htonl(data);
+      luaL_addlstring(&buf, (void*)&data, sizeof(data));
+      break;
+    }
+    case 'l': {
+      int64_t data = lualongnumber_checklong(L, 2);
+      data = (int64_t)T_htonll(data);
+      luaL_addlstring(&buf, (void*)&data, sizeof(data));
+      break;
+    }
+    case 'd': {
+      double data = luaL_checknumber(L, 2);
+      luaL_addlstring(&buf, (void*)&data, sizeof(data));
+      break;
+    }
+    default:
+      luaL_argcheck(L, 0, 0, "Invalid format code.");
+  }
+
+  luaL_pushresult(&buf);
+  return 1;
+}
+
+/**
+ * bunpack(type, data)
+ *  c - Signed Byte
+ *  s - Signed Short
+ *  i - Signed Int
+ *  l - Signed Long
+ *  d - Double
+ */
+static int l_bunpack(lua_State *L) {
+  const char *code = luaL_checkstring(L, 1);
+  luaL_argcheck(L, code[1] == '\0', 0, "Format code must be one character.");
+  const char *data = luaL_checkstring(L, 2);
+  size_t len = lua_rawlen(L, 2);
+
+  switch (code[0]) {
+    case 'c': {
+      int8_t val;
+      luaL_argcheck(L, len == sizeof(val), 1, "Invalid input string size.");
+      memcpy(&val, data, sizeof(val));
+      lua_pushnumber(L, val);
+      break;
+    }
+    case 's': {
+      int16_t val;
+      luaL_argcheck(L, len == sizeof(val), 1, "Invalid input string size.");
+      memcpy(&val, data, sizeof(val));
+      val = (int16_t)ntohs(val);
+      lua_pushnumber(L, val);
+      break;
+    }
+    case 'i': {
+      int32_t val;
+      luaL_argcheck(L, len == sizeof(val), 1, "Invalid input string size.");
+      memcpy(&val, data, sizeof(val));
+      val = (int32_t)ntohl(val);
+      lua_pushnumber(L, val);
+      break;
+    }
+    case 'l': {
+      int64_t val;
+      luaL_argcheck(L, len == sizeof(val), 1, "Invalid input string size.");
+      memcpy(&val, data, sizeof(val));
+      val = (int64_t)T_ntohll(val);
+      lualongnumber_pushlong(L, &val);
+      break;
+    }
+    case 'd': {
+      double val;
+      luaL_argcheck(L, len == sizeof(val), 1, "Invalid input string size.");
+      memcpy(&val, data, sizeof(val));
+      lua_pushnumber(L, val);
+      break;
+    }
+    default:
+      luaL_argcheck(L, 0, 0, "Invalid format code.");
+  }
+  return 1;
+}
+
+static const struct luaL_Reg lua_bpack[] = {
+  {"bpack", l_bpack},
+  {"bunpack", l_bunpack},
+  {NULL, NULL}
+};
+
+int luaopen_libluabpack(lua_State *L) {
+  luaL_register(L, "libluabpack", lua_bpack);
+  return 1;
+}