Implement msgpack-rpc helper module

Still missing the `msgpack_rpc_dispatch` function which will be automatically
generated by a script

src/msgpack_rpc.c

@@ -0,0 +1,156 @@
+#include <msgpack.h>
+
+#include "msgpack_rpc.h"
+#include "vim.h"
+#include "memory.h"
+
+
+bool msgpack_rpc_call(msgpack_object *req, msgpack_packer *res)
+{
+  // Validate the basic structure of the msgpack-rpc payload
+  if (req->type != MSGPACK_OBJECT_ARRAY) {
+    return msgpack_rpc_error(req, res, "Request is not an array");
+  }
+
+  if (req->via.array.size != 4) {
+    char error_msg[256];
+    snprintf(error_msg,
+             sizeof(error_msg),
+             "Request array size is %u, it should be 4",
+             req->via.array.size);
+    return msgpack_rpc_error(req, res, error_msg);
+  }
+
+  if (req->via.array.ptr[0].type != MSGPACK_OBJECT_POSITIVE_INTEGER) {
+    return msgpack_rpc_error(req, res, "Message type must be an integer");
+  }
+
+  if (req->via.array.ptr[0].via.u64 != 0) {
+    return msgpack_rpc_error(req, res, "Message type must be 0");
+  }
+
+  if (req->via.array.ptr[1].type != MSGPACK_OBJECT_POSITIVE_INTEGER) {
+    return msgpack_rpc_error(req, res, "Id must be a positive integer");
+  }
+
+  if (req->via.array.ptr[2].type != MSGPACK_OBJECT_POSITIVE_INTEGER) {
+    return msgpack_rpc_error(req, res, "Method id must be a positive integer");
+  }
+
+  if (req->via.array.ptr[3].type != MSGPACK_OBJECT_ARRAY) {
+    return msgpack_rpc_error(req, res, "Paremeters must be an array");
+  }
+
+  // dispatch the message
+  return msgpack_rpc_dispatch(req, res);
+}
+
+void msgpack_rpc_response(msgpack_object *req, msgpack_packer *res)
+{
+  // Array of size 4
+  msgpack_pack_array(res, 4);
+  // Response type is 1
+  msgpack_pack_int(res, 1);
+  // Msgid is the same as the request
+  msgpack_pack_int(res, req->via.array.ptr[1].via.u64);
+}
+
+void msgpack_rpc_success(msgpack_object *req, msgpack_packer *res)
+{
+  msgpack_rpc_response(req, res);
+  // Nil error
+  msgpack_pack_nil(res);
+}
+
+bool msgpack_rpc_error(msgpack_object *req, msgpack_packer *res, char *msg)
+{
+  size_t len = strlen(msg);
+
+  msgpack_rpc_response(req, res);
+  msgpack_pack_raw(res, len);
+  msgpack_pack_raw_body(res, msg, len);
+  // Nil result
+  msgpack_pack_nil(res);
+
+  return false;
+}
+
+char **msgpack_rpc_array_argument(msgpack_object *obj)
+{
+  uint32_t i;
+  char **rv = xmalloc(obj->via.array.size + 1);
+
+  for (i = 0; i < obj->via.array.size; i++) {
+    rv[i] = msgpack_rpc_raw_argument(obj->via.array.ptr + i);
+  }
+
+  rv[i] = NULL;
+
+  return rv;
+}
+
+char *msgpack_rpc_raw_argument(msgpack_object *obj)
+{
+  char *rv = xmalloc(obj->via.raw.size + 1);
+  memcpy(rv, obj->via.raw.ptr, obj->via.raw.size);
+  rv[obj->via.raw.size] = NUL;
+
+  return rv;
+}
+
+uint32_t msgpack_rpc_integer_argument(msgpack_object *obj)
+{
+  return obj->via.u64;
+}
+
+bool msgpack_rpc_array_result(char **result,
+                              msgpack_object *req,
+                              msgpack_packer *res)
+{
+  char **ptr;
+  uint32_t array_size;
+
+  // Count number of items in the array
+  for (ptr = result; *ptr != NULL; ptr++) continue;
+
+  msgpack_rpc_success(req, res);
+  // Subtract 1 to exclude the NULL slot
+  array_size = ptr - result - 1;
+  msgpack_pack_array(res, array_size);
+
+  // push each string to the array
+  for (ptr = result; *ptr != NULL; ptr++) {
+    size_t raw_size = strlen(*ptr);
+    msgpack_pack_raw(res, raw_size);
+    msgpack_pack_raw_body(res, *ptr, raw_size);
+  }
+
+  return true;
+}
+
+bool msgpack_rpc_raw_result(char *result,
+                            msgpack_object *req,
+                            msgpack_packer *res)
+{
+  size_t raw_size = strlen(result);
+  msgpack_rpc_success(req, res);
+  msgpack_pack_raw(res, raw_size);
+  msgpack_pack_raw_body(res, result, raw_size);
+  return true;
+}
+
+bool msgpack_rpc_integer_result(uint32_t result,
+                                msgpack_object *req,
+                                msgpack_packer *res)
+{
+  msgpack_rpc_success(req, res);
+  msgpack_pack_int(res, result);
+  return true;
+}
+
+bool msgpack_rpc_void_result(msgpack_object *req, msgpack_packer *res)
+{
+  msgpack_rpc_success(req, res);
+  msgpack_pack_nil(res);
+  return true;
+}

src/msgpack_rpc.h

@@ -0,0 +1,30 @@
+#ifndef NEOVIM_MSGPACK_RPC_H
+#define NEOVIM_MSGPACK_RPC_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <msgpack.h>
+
+bool msgpack_rpc_call(msgpack_object *req, msgpack_packer *res);
+bool msgpack_rpc_dispatch(msgpack_object *req, msgpack_packer *res);
+void msgpack_rpc_response(msgpack_object *req, msgpack_packer *res);
+void msgpack_rpc_success(msgpack_object *req, msgpack_packer *res);
+bool msgpack_rpc_error(msgpack_object *req, msgpack_packer *res, char *msg);
+char **msgpack_rpc_array_argument(msgpack_object *obj);
+char *msgpack_rpc_raw_argument(msgpack_object *obj);
+uint32_t msgpack_rpc_integer_argument(msgpack_object *obj);
+bool msgpack_rpc_array_result(char **result,
+                              msgpack_object *req,
+                              msgpack_packer *res);
+bool msgpack_rpc_raw_result(char *result,
+                            msgpack_object *req,
+                            msgpack_packer *res);
+bool msgpack_rpc_integer_result(uint32_t result,
+                                msgpack_object *req,
+                                msgpack_packer *res);
+bool msgpack_rpc_void_result(msgpack_object *req, msgpack_packer *res);
+
+
+#endif // NEOVIM_MSGPACK_RPC_H
+