refactor(api): use a unpacker based on libmpack instead of msgpack-c

Currently this is more or less a straight off reimplementation,
but this allow further optimizations down the line, especially
for avoiding memory allocations of rpc objects.

Current score for "make functionaltest; make oldtest" on a -DEXITFREE build:

is 117 055 352 xfree(ptr != NULL) calls (that's NUMBERWANG!).

1 files changed, 40 insertions, 0 deletions

diff --git a/src/nvim/msgpack_rpc/unpacker.h b/src/nvim/msgpack_rpc/unpacker.h
new file mode 100644
index 0000000000..bbd6b1ef4f
--- /dev/null
+++ b/src/nvim/msgpack_rpc/unpacker.h
@@ -0,0 +1,40 @@
+#ifndef NVIM_MSGPACK_RPC_UNPACKER_H
+#define NVIM_MSGPACK_RPC_UNPACKER_H
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include "mpack/mpack_core.h"
+#include "mpack/object.h"
+#include "nvim/api/private/dispatch.h"
+#include "nvim/api/private/helpers.h"
+
+typedef struct {
+  mpack_parser_t parser;
+  mpack_tokbuf_t reader;
+
+  const char *read_ptr;
+  size_t read_size;
+
+#define MAX_EXT_LEN 9  // byte + 8-byte integer
+  char ext_buf[MAX_EXT_LEN];
+
+  int state;
+  MessageType type;
+  uint32_t request_id;
+  size_t method_name_len;
+  MsgpackRpcRequestHandler handler;
+  Object error;  // error return
+  Object result;  // arg list or result
+  Error unpack_error;
+} Unpacker;
+
+// unrecovareble error. unpack_error should be set!
+#define unpacker_closed(p) ((p)->state < 0)
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "msgpack_rpc/unpacker.h.generated.h"
+#endif
+
+#endif  // NVIM_MSGPACK_RPC_UNPACKER_H