Convert libc to C.

libc/stdlib/getenv.c

@@ -0,0 +1,61 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2014.
+
+    This file is part of the Sortix C Library.
+
+    The Sortix C Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    The Sortix C Library is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
+
+    stdlib/getenv.c
+    Get an environment variable.
+
+*******************************************************************************/
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static inline
+bool matches_environment_variable(const char* what,
+                                  const char* name, size_t name_length)
+{
+	return !strncmp(what, name, name_length) && what[name_length] == '=';
+}
+
+char* getenv(const char* name)
+{
+	if ( !name )
+		return errno = EINVAL, (char*) NULL;
+
+	if ( !name[0] )
+		return errno = EINVAL, (char*) NULL;
+
+	// Verify the name doesn't contain a '=' character.
+	size_t name_length = 0;
+	while ( name[name_length] )
+		if ( name[name_length++] == '=' )
+			return errno = EINVAL, (char*) NULL;
+
+	if ( !environ )
+		return NULL;
+
+	// Find the environment variable with the given name.
+	for ( size_t i = 0; environ[i]; i++ )
+		if ( matches_environment_variable(environ[i], name, name_length) )
+			return environ[i] + name_length + 1;
+
+	return NULL;
+}