Use the environ table over the environment library

lenviron.c

@@ -0,0 +1,115 @@
+/***
+ * Getting and setting environment variables.
+ * @module environ
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+
+#include <lua.h>
+#include <lauxlib.h>
+
+#include "lcallisto.h"
+
+
+extern char **environ;
+
+/***
+ * Table enabling easy access to environment
+ * variables.
+ *
+ * Has metamethods *\_\_index* and *\_\_newindex*,
+ * which allow for the table to be indexed with a
+ * string to get values of environment variables,
+ * or for fields to be set to set an environment
+ * variable.
+ *
+ * @table environ
+ * @usage
+-- Print the value of an environment variable:
+print(environ["MYVAR"])
+-- Set an environment variable:
+environ["MYVAR"] = 1
+ */
+
+/*
+ * Returns the value of the given environment variable.
+ */
+static int
+environ_index(lua_State *L)
+{
+	const char *variable; /* parameter 2 (string) */
+	char *ret;
+
+	variable = luaL_checkstring(L, 2);
+	ret = getenv(variable);
+
+	if (ret == NULL) /* no environment variable? */
+		lua_pushnil(L);
+	else
+		lua_pushstring(L, ret); /* push variable value */
+
+	return 1;
+}
+
+/*
+ * Sets the value of the given environment variable.
+ */
+static int
+environ_newindex(lua_State *L)
+{
+	int ret;
+	const char *variable; /* parameter 2 (string) */
+	const char *value;    /* parameter 3 (string) */
+
+	variable = luaL_checkstring(L, 2);
+
+	if (lua_isnil(L, 3)) {
+		ret = unsetenv(variable); /* remove variable from environ */
+		if (ret == 0) /* did unsetenv succeed? */
+			return 0;
+
+		/* if unsetenv didn't succeed:
+		 * (unsetenv only sets errno to EINVAL on error) */
+		return luaL_error(L, "invalid input string");
+	}
+
+	value = luaL_checkstring(L, 3);
+	ret	= setenv(variable, value, 1);
+
+	if (ret == 0) /* did setenv succeed? */
+		return 0;
+
+	switch (errno) {
+		case EINVAL:
+			return luaL_error(L, "invalid input string");
+			break;
+		case ENOMEM:
+			return luaL_error(L, "insufficient memory");
+			break;
+	}
+
+	return 0;
+}
+
+static const luaL_Reg mt[] = {
+	{"__index", environ_index},
+	{"__newindex", environ_newindex},
+	{NULL, NULL}
+};
+
+int
+callistoopen_environ(lua_State *L)
+{
+	const luaL_Reg *lib;
+
+	lua_newtable(L);
+	luaL_newmetatable(L, CALLISTO_ENVIRON);  /* metatable for environ */
+
+	for (lib = mt; lib->func; lib++) {
+		lua_pushcfunction(L, lib->func);
+		lua_setfield(L, -2, lib->name);
+	}
+	lua_setmetatable(L, -2);
+	return 1;
+}