Use the environ table over the environment library

Makefile

@@ -5,8 +5,8 @@ CFLAGS   = -std=c99 -pedantic -fpic -O2 -Wall -Wextra -Wno-override-init -I. -Il
 CPPFLAGS = -D_DEFAULT_SOURCE -DLUA_USE_READLINE
 LDFLAGS = -lm -lreadline
 
-OBJS = csto.o lcallisto.o lcl.o lenvironment.o lextra.o \
+OBJS = csto.o lcallisto.o lcl.o lenviron.o lextra.o lfile.o \
-	   lfile.o ljson.o lmath.o los.o lprocess.o lsocket.o util.o
+	   ljson.o lmath.o los.o lprocess.o lsocket.o util.o
 LIBS = liblua.a cjson.a socket.a
 
 all: csto libcallisto.so
@@ -25,7 +25,7 @@ csto.o: csto.c lcallisto.h
 lcallisto.o: lcallisto.c lcallisto.h
 lcl.o: lcl.c lcallisto.h
 lextra.o: lextra.c lcallisto.h
-lenvironment.o: lenvironment.c lcallisto.h
+lenviron.o: lenviron.c lcallisto.h
 lfile.o: lfile.c lcallisto.h
 ljson.o: ljson.c lcallisto.h
 lmath.o: lmath.c lcallisto.h

lcallisto.c

@@ -11,7 +11,7 @@
 
 static const luaL_Reg loadedlibs[] = {
 	{CALLISTO_CLLIBNAME,   callistoopen_cl},
-	{CALLISTO_ENVLIBNAME,  callistoopen_environment},
+	{CALLISTO_ENVLIBNAME,  callistoopen_environ},
 	{CALLISTO_EXTLIBNAME,  callistoopen_extra},
 	{CALLISTO_FILELIBNAME, callistoopen_file},
 	{CALLISTO_JSONLIBNAME, callistoopen_json},

lcallisto.h

@@ -16,7 +16,7 @@
 #define CALLISTO_COPYRIGHT	CALLISTO_VERSION " (" LUA_RELEASE ")  Copyright (C) 1994-2022 Lua.org, PUC-Rio"
 
 #define CALLISTO_CLLIBNAME   "cl"
-#define CALLISTO_ENVLIBNAME  "environment"
+#define CALLISTO_ENVLIBNAME  "environ"
 #define CALLISTO_EXTLIBNAME  "_G" /* global table */
 #define CALLISTO_FILELIBNAME "file"
 #define CALLISTO_JSONLIBNAME "json"
@@ -25,8 +25,10 @@
 #define CALLISTO_PROCLIBNAME "process"
 #define CALLISTO_SOCKLIBNAME "socket"
 
+#define CALLISTO_ENVIRON "environ"
+
 int callistoopen_cl(lua_State *);
-int callistoopen_environment(lua_State *);
+int callistoopen_environ(lua_State *);
 int callistoopen_extra(lua_State *);
 int callistoopen_file(lua_State *);
 int callistoopen_json(lua_State *);

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;
+}

lenvironment.c

@@ -1,148 +0,0 @@
-/***
- * Getting and setting
- * environment variables.
- * @module environment
- */
-
-#include <stdlib.h>
-#include <errno.h>
-#ifdef BSD
-#	include <string.h>
-#endif
-
-#include <lua.h>
-#include <lauxlib.h>
-
-#include "lcallisto.h"
-#include "util.h"
-
-
-extern char **environ;
-
-/***
- * Returns the value of the given environment
- * variable.
- *
- * If *var* does not exist in the environment
- * and *defaultvalue* is not nil,
- * *defaultvalue* will be returned.
- *
- * @function get
- * @usage environment.get("HOME", "/root")
- * @tparam       string var The environment variable to get.
- * @param[opt] defaultvalue The value to return in case the environment variable was not found.
- */
-static int
-environment_get(lua_State *L)
-{
-	const char *variable;
-	char *ret;
-
-	variable = luaL_checkstring(L, 1);
-	ret = getenv(variable);
-
-	if (ret == NULL)
-		if (!lua_isnoneornil(L, 2))
-			lua_pushvalue(L, 2);
-		else
-			lua_pushnil(L);
-	else
-		lua_pushstring(L, ret);
-	return 1;
-}
-
-/***
- * Sets the value of the given environment variable.
- *
- * This function will throw an error if the value of
- * *var* is invalid for the name of an environment
- * variable, or if there is insufficient memory
- * available to perform the operation.
- *
- * @function set
- * @usage environment.set("MYVAR", "1")
- * @tparam string   var The environment variable to set.
- * @tparam string value The value to set for *var*.
- */
-static int
-environment_set(lua_State *L)
-{
-	int ret;
-	const char *variable;
-	const char *value;
-
-	variable = luaL_checkstring(L, 1);
-	value    = luaL_checkstring(L, 2);
-
-	ret	= setenv(variable, value, 1);
-
-	if (ret == 0)
-		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;
-}
-
-/***
- * Clears the environment.
- *
- * If *var* is not nil, only clears the value of that
- * environment variable (not the whole environment).
- *
- * This function will throw an error if the value of
- * *var* is invalid for the name of an environment
- * variable, or if there is insufficient memory
- * available to perform the operation.
- *
- * @function clear
- * @usage environment.clear("MYVAR")
- * @tparam[opt] string var The environment variable to clear.
- */
-static int
-environment_clear(lua_State *L)
-{
-	const char *variable;
-	int ret;
-
-	if (lua_isnoneornil(L, 1)) {
-		environ = NULL;
-		return 0;
-	}
-
-	variable = luaL_checkstring(L, 1);
-	ret = unsetenv(variable);
-
-	if (ret == 0)
-		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 envlib[] = {
-	{"get",   environment_get},
-	{"set",   environment_set},
-	{"clear", environment_clear},
-	{NULL, NULL}
-};
-
-int
-callistoopen_environment(lua_State *L)
-{
-	luaL_newlib(L, envlib);
-	return 1;
-}