libifupdown: add environment management routines

Makefile

@@ -15,7 +15,8 @@ LIBIFUPDOWN_SRC = \
 	libifupdown/interface-file.c \
 	libifupdown/fgetline.c \
 	libifupdown/version.c \
-	libifupdown/state.c
+	libifupdown/state.c \
+	libifupdown/environment.c
 
 LIBIFUPDOWN_OBJ = ${LIBIFUPDOWN_SRC:.c=.o}
 LIBIFUPDOWN_LIB = libifupdown.a

libifupdown/environment.c

@@ -0,0 +1,57 @@
+/*
+ * libifupdown/environment.c
+ * Purpose: environment variable management
+ *
+ * Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "libifupdown/environment.h"
+
+bool
+lif_environment_push(char **env[], const char *name, const char *val)
+{
+	char buf[4096];
+
+	snprintf(buf, sizeof buf, "%s=%s", name, val);
+
+	/* create an initial envp: {"foo=bar", NULL} */
+	if (*env == NULL)
+	{
+		*env = calloc(1, sizeof (**env));
+		**env = strdup(buf);
+
+		return true;
+	}
+
+	size_t nelems;
+	for (nelems = 0; *env[nelems] != NULL; nelems++)
+		;
+
+	nelems += 1;
+	*env = realloc(*env, (nelems * sizeof (**env)));
+
+	*env[nelems] = strdup(buf);
+	*env[nelems + 1] = NULL;
+
+	return true;
+}
+
+void
+lif_environment_free(char **env[])
+{
+	size_t nelems;
+
+	for (nelems = 0; *env[nelems] != NULL; nelems++)
+		free(*env[nelems]);
+}

libifupdown/environment.h

@@ -0,0 +1,24 @@
+/*
+ * libifupdown/environment.h
+ * Purpose: environment variable management
+ *
+ * Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#ifndef LIBIFUPDOWN_ENVIRONMENT_H__GUARD
+#define LIBIFUPDOWN_ENVIRONMENT_H__GUARD
+
+#include <stdbool.h>
+
+extern bool lif_environment_push(char **env[], const char *name, const char *val);
+extern void lif_environment_free(char **env[]);
+
+#endif

libifupdown/libifupdown.h

@@ -23,5 +23,6 @@
 #include "libifupdown/fgetline.h"
 #include "libifupdown/version.h"
 #include "libifupdown/state.h"
+#include "libifupdown/environment.h"
 
 #endif