Adding LUA tutorials: lua_calls_C1 - lua_calls_C5

Adding blinker demo: lua_blink_led

lua/examples/lua_calls_C2/Makefile

@@ -0,0 +1,23 @@
+CC       = mipsel-openwrt-linux-gcc
+CXX      =  mipsel-openwrt-linux-g++
+OPENWRT_BUILD_DIR = /home/cain/Embedded/ingenic/sakc/build/openwrt-xburst/staging_dir/target-mipsel_uClibc-0.9.30.1
+INCLUDE  = -I. -I$(OPENWRT_BUILD_DIR)/usr/include/
+WARNINGS = -Wcast-align -Wpacked -Wpadded -Wall 
+CCFLAGS  = ${INCLUDE} ${DEBUG} ${WARNINGS} -std=c99 -fPIC
+LDFLAGS  =
+DEBUG    = -O3 -g0
+NANO_PATH = root@192.168.254.101:
+TARGET   = luapassing
+
+$(TARGET): $(TARGET)
+	$(CC)  $(CCFLAGS) -o $(TARGET).so -shared $(TARGET).c
+
+.c.o:
+	$(CC) -c $(CCFLAGS) -o $@
+
+upload: $(TARGET)
+	scp $(TARGET).so top2.lua $(NANO_PATH)
+
+
+clean:
+	rm -f *.o $(TARGET).so

lua/examples/lua_calls_C2/README

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+Examples from http://www.wellho.net/mouth/1844_Calling-functions-in-C-from-your-Lua-script-a-first-HowTo.html
+
+
+The code is very similar, but you'll notice six additions - in the Lua:
+
+a) We have added a parameter to the call to dothis in the Lua
+b) We have added an assignment to collect a return value from the C
+
+summat = cstuff.dothis(value)
+
+c) We have printed out these values
+print ("Values in Lua now",value, summat)
+
+
+and in the C:
+
+d) We have used lua_tonumber to collect a numeric value that was passed from the Lua to the C; you'll note that all such numbers are treated as doubles. The parameter "1" indicates 1 down - i.e. top of - the state stack.
+
+  double trouble = lua_tonumber(L, 1);
+
+e) We have performed a calculation (representative of something being done in the C code) and pushed the result of this back onto the Lua state stack so that it can be picked up once we have returned from the C to the Lua
+
+  lua_pushnumber(L, 16.0 - trouble);
+
+f) We have changed return 0 into return 1 to indicate that one result is being returned.
+
+  return 1; }
+
+

lua/examples/lua_calls_C2/luapassing.c

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+#include "lua.h"
+#include "lualib.h"
+#include "lauxlib.h"
+#include <stdio.h>
+
+
+static int myCfunc ( lua_State *L) {
+  printf ("lua SIE's test\n");
+  double trouble = lua_tonumber(L, 1);
+  lua_pushnumber(L, 16.0 - trouble);
+  return 1; }
+
+
+int luaopen_luapassing ( lua_State *L) {
+  static const luaL_reg Map [] = {
+    {"dothis", myCfunc},
+    {NULL,NULL} } ;
+  luaL_register(L, "cstuff", Map);
+  return 1; }

lua/examples/lua_calls_C2/top2.lua

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+package.cpath = "./?.so"
+require "luapassing"
+print("hello")
+value = 10
+summat = cstuff.dothis(value)
+print ("It's run da C code!")
+print ("Values in Lua now",value, summat)