plugin_manager adapt session_manager API and rewrite plugin_manger gtest

sdk/example/http_plugin.cpp

@@ -0,0 +1,70 @@
+#include <stdlib.h>
+
+#include "session.h"
+
+static char *g_handler = NULL;
+
+struct session_ctx
+{
+	char data[64];
+};
+
+static struct session_ctx *session_ctx_create()
+{
+	struct session_ctx *ctx = (struct session_ctx *)calloc(1, sizeof(struct session_ctx));
+	return ctx;
+}
+
+static void session_ctx_destory(struct session_ctx *ctx)
+{
+	if (ctx)
+	{
+		free(ctx);
+		ctx = NULL;
+	}
+}
+
+extern "C" void http_plugin_entry(struct stellar_session *session, enum session_state state, int thread_id, void **ctx)
+{
+	struct session_ctx **sctx = (struct session_ctx **)ctx;
+
+	if (state & SESSION_STATE_OPENING)
+	{
+		if (*sctx == NULL)
+		{
+			struct session_ctx *cur_ctx = session_ctx_create();
+			memcpy(cur_ctx->data, "http_plugin_entry", 17);
+			*sctx = *&cur_ctx;
+		}
+	}
+
+	if (state & SESSION_STATE_ACTIVE)
+	{
+		// TODO
+	}
+
+	if (state & SESSION_STATE_CLOSING)
+	{
+		session_ctx_destory(*sctx);
+		*sctx = NULL;
+	}
+}
+
+extern "C" int http_plugin_init(void)
+{
+	if (g_handler == NULL)
+	{
+		g_handler = (char *)malloc(1024);
+	}
+
+	return 0;
+}
+
+extern "C" void http_plugin_exit(void)
+{
+	if (g_handler)
+	{
+		free(g_handler);
+		g_handler = NULL;
+	}
+}