libc: Partially support environment variables

libc/generic/ansi/src/stdlib-stubs.cpp

@@ -3,8 +3,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
-#include <frg/random.hpp>
 
+#include <frg/random.hpp>
+#include <frigg/debug.hpp>
 #include <mlibc/ensure.h>
 
 extern "C" int __cxa_atexit(void (*function)(void *), void *argument, void *dso_tag);
@@ -177,10 +178,7 @@ void exit(int status) {
 	_Exit(status);
 }
 // _Exit() is provided by the platform
-char *getenv(const char *name) {
-	// TODO: should be provided by the POSIX sublibrary based on environ
-	return nullptr;
-}
+// getenv() is provided by POSIX
 void quick_exit(int status) {
 	__ensure(!"Not implemented");
 	__builtin_unreachable();

libc/generic/posix/include/mlibc/posix_stdlib.h

@@ -8,6 +8,8 @@ extern "C" {
 
 long random(void);
 
+int putenv(const char *);
+
 #ifdef __cplusplus
 }
 #endif

libc/generic/posix/src/environment.cpp

@@ -1,5 +1,49 @@
 
-char *__emptyEnviron[] = { nullptr };
+#include <stdlib.h>
 
-char **environ = __emptyEnviron;
+#include <frigg/string.hpp>
+#include <frigg/vector.hpp>
+#include <mlibc/ensure.h>
+#include <mlibc/frigg-alloc.hpp>
+
+static char *emptyEnvironment[] = { nullptr };
+
+char **environ = emptyEnvironment;
+
+char *getenv(const char *name) {
+	for(auto it = environ; *it; it++) {
+		frigg::StringView view{*it};
+
+		size_t s = view.findFirst('=');
+		if(s == size_t(-1)) {
+			frigg::infoLogger() << "\e[35mmlibc: getenv() environment string '"
+					<< view << "' does not contain the '=' sign\e[39m" << frigg::endLog;
+			continue;
+		}
+		if(view.subString(0, s) != name)
+			continue;
+
+		return const_cast<char *>(view.data() + s + 1);
+	}
+	return nullptr;
+}
+
+// Environment vector that is mutated by putenv() and setenv().
+static frigg::Vector<char *, MemoryAllocator> mutEnvironment{getAllocator()};
+
+int putenv(const char *string) {
+	// If the environ variable was changed, we copy the environment.
+	if(environ != mutEnvironment.data()) {
+		// TODO: Actually copy the entries.
+		__ensure(!*environ);
+		mutEnvironment.push(nullptr);
+	}
+
+	// TODO: Replace the entry instead of adding it.
+	__ensure(!mutEnvironment.back());
+	mutEnvironment.back() = const_cast<char *>(string);
+	mutEnvironment.push(nullptr);
+	environ = mutEnvironment.data();
+	return 0;
+}