Shell: Move builtin commands to a hash map

This allows accessing builtin commands outside of `execute_builtin`

userspace/programs/Shell/main.cpp

@@ -1,5 +1,5 @@
+#include <BAN/HashMap.h>
 #include <BAN/Optional.h>
-#include <BAN/ScopeGuard.h>
 #include <BAN/String.h>
 #include <BAN/Vector.h>
 
@@ -52,6 +52,12 @@ struct CommandList
 	BAN::Vector<Command> commands;
 };
 
+struct BuiltinCommand
+{
+	int (*function)(const SingleCommand&, FILE* fout, int fd_in, int fd_out);
+};
+static BAN::HashMap<BAN::String, BuiltinCommand> s_builtin_commands;
+
 static BAN::StringView strip_whitespace(BAN::StringView sv)
 {
 	size_t leading = 0;
@@ -374,6 +380,10 @@ static BAN::Optional<int> execute_builtin(const SingleCommand& command, int fd_i
 	if (command.arguments.empty())
 		return 0;
 
+	auto it = s_builtin_commands.find(command.arguments.front());
+	if (it == s_builtin_commands.end())
+		return {};
+
 	FILE* fout = stdout;
 	bool should_close = false;
 	if (fd_out != STDOUT_FILENO)
@@ -386,14 +396,28 @@ static BAN::Optional<int> execute_builtin(const SingleCommand& command, int fd_i
 			ERROR_RETURN("fdopen", 1);
 		should_close = true;
 	}
-	BAN::ScopeGuard _([fout, should_close] { if (should_close) fclose(fout); });
 
-	if (command.arguments.front() == "clear"_sv)
+	int ret = it->value.function(command, fout, fd_in, fd_out);
-	{
+
-		fprintf(fout, "\e[H\e[2J");
+	if (should_close)
-		fflush(fout);
+		fclose(fout);
+
+	return ret;
 }
-	else if (command.arguments.front() == "exit"_sv)
+
+static void install_builtin_commands()
+{
+	MUST(s_builtin_commands.emplace("clear"_sv,
+		[](const SingleCommand&, FILE* fout, int, int) -> int
+		{
+			fprintf(fout, "\e[H\e[3J");
+			fflush(fout);
+			return 0;
+		}
+	));
+
+	MUST(s_builtin_commands.emplace("exit"_sv,
+		[](const SingleCommand& command, FILE*, int, int) -> int
 		{
 			int exit_code = 0;
 			if (command.arguments.size() > 1)
@@ -403,8 +427,12 @@ static BAN::Optional<int> execute_builtin(const SingleCommand& command, int fd_i
 					exit_code = (exit_code * 10) + (exit_string[i] - '0');
 			}
 			exit(exit_code);
+			ASSERT_NOT_REACHED();
 		}
-	else if (command.arguments.front() == "export"_sv)
+	));
+
+	MUST(s_builtin_commands.emplace("export"_sv,
+		[](const SingleCommand& command, FILE*, int, int) -> int
 		{
 			bool first = false;
 			for (const auto& argument : command.arguments)
@@ -422,8 +450,12 @@ static BAN::Optional<int> execute_builtin(const SingleCommand& command, int fd_i
 				if (setenv(BAN::String(split[0]).data(), BAN::String(split[1]).data(), true) == -1)
 					ERROR_RETURN("setenv", 1);
 			}
+			return 0;
 		}
-	else if (command.arguments.front() == "source"_sv)
+	));
+
+	MUST(s_builtin_commands.emplace("source"_sv,
+		[](const SingleCommand& command, FILE* fout, int, int) -> int
 		{
 			if (command.arguments.size() != 2)
 			{
@@ -432,13 +464,20 @@ static BAN::Optional<int> execute_builtin(const SingleCommand& command, int fd_i
 			}
 			return source_script(command.arguments[1]);
 		}
-	else if (command.arguments.front() == "env"_sv)
+	));
+
+	MUST(s_builtin_commands.emplace("env"_sv,
+		[](const SingleCommand&, FILE* fout, int, int) -> int
 		{
 			char** current = environ;
-		while (*current)
+			while (current && *current)
 				fprintf(fout, "%s\n", *current++);
+			return 0;
 		}
-	else if (command.arguments.front() == "cd"_sv)
+	));
+
+	MUST(s_builtin_commands.emplace("cd"_sv,
+		[](const SingleCommand& command, FILE* fout, int, int) -> int
 		{
 			if (command.arguments.size() > 2)
 			{
@@ -460,13 +499,18 @@ static BAN::Optional<int> execute_builtin(const SingleCommand& command, int fd_i
 
 			if (chdir(path.data()) == -1)
 				ERROR_RETURN("chdir", 1);
+
+			return 0;
 		}
-	else if (command.arguments.front() == "time"_sv)
+	));
+
+	MUST(s_builtin_commands.emplace("time"_sv,
+		[](const SingleCommand& command, FILE* fout, int fd_in, int fd_out) -> int
 		{
 			SingleCommand timed_command;
 			MUST(timed_command.arguments.reserve(command.arguments.size() - 1));
 			for (size_t i = 1; i < command.arguments.size(); i++)
-			timed_command.arguments[i - 1] = command.arguments[i];
+				MUST(timed_command.arguments.emplace_back(command.arguments[i]));
 
 			timespec start, end;
 
@@ -489,22 +533,23 @@ static BAN::Optional<int> execute_builtin(const SingleCommand& command, int fd_i
 
 			return ret;
 		}
-	else if (command.arguments.front() == "start-gui"_sv)
+	));
+
+	MUST(s_builtin_commands.emplace("start-gui"_sv,
+		[](const SingleCommand&, FILE*, int, int) -> int
 		{
-		pid_t pid = fork();
+			const pid_t pid = fork();
+			if (pid == -1)
+				return 1;
 			if (pid == 0)
 				execl("/bin/WindowServer", "WindowServer", NULL);
 			if (fork() == 0)
 				execl("/bin/Terminal", "Terminal", NULL);
 			waitpid(pid, nullptr, 0);
-	}
-	else
-	{
-		return {};
-	}
-
 			return 0;
 		}
+	));
+}
 
 static pid_t execute_command_no_wait(const SingleCommand& command, int fd_in, int fd_out, pid_t pgrp)
 {
@@ -930,6 +975,8 @@ int main(int argc, char** argv)
 
 	atexit([]() { tcsetattr(0, TCSANOW, &old_termios); });
 
+	install_builtin_commands();
+
 	for (int i = 1; i < argc; i++)
 	{
 		if (argv[i][0] != '-')