Userspace: Implement basic cp

This does not support any meaningful command line arguments but
is a good start.

userspace/CMakeLists.txt

@@ -5,6 +5,7 @@ project(userspace CXX)
 set(USERSPACE_PROJECTS
 	cat
 	cat-mmap
+	cp
 	dd
 	echo
 	id

userspace/cp/CMakeLists.txt

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(cp CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(cp ${SOURCES})
+target_compile_options(cp PUBLIC -O2 -g)
+target_link_libraries(cp PUBLIC libc ban)
+
+add_custom_target(cp-install
+	COMMAND sudo cp ${CMAKE_CURRENT_BINARY_DIR}/cp ${BANAN_BIN}/
+	DEPENDS cp
+	USES_TERMINAL
+)

userspace/cp/main.cpp

@@ -0,0 +1,143 @@
+#include <BAN/String.h>
+#include <BAN/Vector.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#define STR_STARTS_WITH(str, arg) (strncmp(str, arg, sizeof(arg) - 1) == 0)
+#define STR_EQUAL(str, arg) (strcmp(str, arg) == 0)
+
+bool copy_file(const BAN::String& source, BAN::String destination)
+{
+	struct stat st;
+	if (stat(source.data(), &st) == -1)
+	{
+		fprintf(stderr, "%s: ", source.data());
+		perror("stat");
+		return false;
+	}
+	if (!S_ISREG(st.st_mode))
+	{
+		fprintf(stderr, "%s: not a directory\n", source.data());
+		return false;
+	}
+
+	if (stat(destination.data(), &st) != -1 && S_ISDIR(st.st_mode))
+	{
+		MUST(destination.push_back('/'));
+		MUST(destination.append(MUST(source.sv().split('/')).back()));
+	}
+
+	int src_fd = open(source.data(), O_RDONLY);
+	if (src_fd == -1)
+	{
+		fprintf(stderr, "%s: ", source.data());
+		perror("open");
+		return false;
+	}
+
+	int dest_fd = open(destination.data(), O_CREAT | O_TRUNC | O_WRONLY, 0644);
+	if (dest_fd == -1)
+	{
+		fprintf(stderr, "%s: ", destination.data());
+		perror("open");
+		close(src_fd);
+		return false;
+	}
+
+	bool ret = true;
+	char buffer[1024];
+	while (ssize_t nread = read(src_fd, buffer, sizeof(buffer)))
+	{
+		if (nread < 0)
+		{
+			fprintf(stderr, "%s: ", source.data());
+			perror("read");
+			ret = false;
+			break;
+		}
+
+		size_t written = 0;
+		while (written < nread)
+		{
+			ssize_t nwrite = write(dest_fd, buffer, nread - written);
+			if (nwrite < 0)
+			{
+				fprintf(stderr, "%s: ", destination.data());
+				perror("write");
+				ret = false;
+			}
+			if (nwrite == 0)
+				break;
+			written += nwrite;
+		}
+
+		if (written < nread)
+			break;
+	}
+
+	close(src_fd);
+	close(dest_fd);
+	return ret;
+}
+
+bool copy_file_to_directory(const BAN::String& source, const BAN::String& destination)
+{
+	auto temp = destination;
+	MUST(temp.append(MUST(source.sv().split('/')).back()));
+	return copy_file(source, destination);
+}
+
+void usage(const char* argv0, int ret)
+{
+	FILE* out = (ret == 0) ? stdout : stderr;
+	fprintf(out, "usage: %s [OPTIONS]... SOURCE... DEST\n", argv0);
+	fprintf(out, "Copies files SOURCE... to DEST\n");
+	fprintf(out, "OPTIONS:\n");
+	fprintf(out, "    -h, --help\n");
+	fprintf(out, "        Show this message and exit\n");
+	exit(ret);
+}
+
+int main(int argc, char** argv)
+{
+	BAN::Vector<BAN::StringView> src;
+	BAN::StringView dest;
+
+	int i = 1;
+	for (; i < argc; i++)
+	{
+		if (STR_EQUAL(argv[i], "-h") || STR_EQUAL(argv[i], "--help"))
+		{
+			usage(argv[0], 0);
+		}
+		else if (argv[i][0] == '-')
+		{
+			fprintf(stderr, "Unknown argument %s\n", argv[i]);
+			usage(argv[0], 1);
+		}
+		else
+		{
+			break;
+		}
+	}
+
+	for (; i < argc - 1; i++)
+		MUST(src.push_back(argv[i]));
+	dest = argv[argc - 1];
+
+	if (src.empty())
+	{
+		fprintf(stderr, "Missing destination operand\n");
+		usage(argv[0], 1);
+	}
+
+	int ret = 0;
+	for (auto file_path : src)
+		if (!copy_file(file_path, dest))
+			ret = 1;
+
+	return ret;
+}