`init`: implement a working tar driver

3 files changed, 88 insertions, 51 deletions

diff --git a/src/init/main.c b/src/init/main.c
index aef6410..c81f789 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -12,8 +12,8 @@ extern char _initrd;
 
 int tty_fd;
 
+void read_file(const char *path, size_t len);
 void fs_test(void);
-void fs_server(handle_t back);
 
 __attribute__((section(".text.startup")))
 int main(void) {
@@ -25,66 +25,43 @@ int main(void) {
 		_syscall_exit(argify("couldn't open tty"));
 
 	fs_test();
-	tar_driver(&_initrd);
 
 	_syscall_exit(argify("my job here is done."));
 }
 
-void fs_test(void) {
-	handle_t front, back, file;
-	front = _syscall_fs_create(&back);
+void read_file(const char *path, size_t len) {
+	int fd = _syscall_open(path, len);
+	static char buf[64];
+	int buf_len = 64;
 
-	if (_syscall_fork()) {
-		// child: is the fs server
-		fs_server(back);
+	_syscall_write(tty_fd, path, len);
+	log(": ");
+	if (fd < 0) {
+		log("couldn't open.\n");
 		return;
 	}
 
-	// parent: accesses the fs
-	_syscall_mount(front, argify("/mnt"));
-	log("requesting file. ");
-	file = _syscall_open(argify("/mnt/tty"));
-	log("open returned. ");
-	_syscall_write(file, argify("hello"));
+	buf_len = _syscall_read(fd, buf, buf_len);
+	_syscall_write(tty_fd, buf, buf_len);
 
-	// try reading
-	char buf[8];
-	int len = 8;
-	for (int i = 0; i < 8; i++)
-		buf[i] = '.';
-	len = _syscall_read(file, buf, len);
-	_syscall_write(tty_fd, buf, len + 1); // read 1 byte past, should be a dot
+	_syscall_close(fd);
 }
 
-void fs_server(handle_t back) {
-	static char buf[64];
-	int len, id;
-	for (;;) {
-		len = 64;
-		switch (_syscall_fs_wait(back, buf, &len, &id)) {
-			case VFSOP_OPEN:
-				_syscall_write(tty_fd, buf, len);
-				log(" was opened. ");
-				_syscall_fs_respond(NULL, 32); // doesn't check the path yet
-				break;
-
-			case VFSOP_READ:
-				// all reads output "world"
-				_syscall_fs_respond("world", 5);
-				break;
-
-			case VFSOP_WRITE:
-				// uppercase the buffer
-				for (int i = 0; i < len; i++) buf[i] &= ~id; // id == 32
-				// and passthrough to tty
-				_syscall_write(tty_fd, buf, len);
-				_syscall_fs_respond(NULL, len); // return the amt of bytes written
-				break;
+void fs_test(void) {
+	handle_t front, back, file;
+	front = _syscall_fs_create(&back);
 
-			default:
-				log("fuck");
-				break;
-		}
+	if (_syscall_fork()) {
+		// child: is the fs server
+		tar_driver(back, &_initrd);
+		return;
 	}
 
+	// parent: accesses the fs
+	log("\n");
+	_syscall_mount(front, argify("/init"));
+	read_file(argify("/init/fake.txt"));
+	read_file(argify("/init/1.txt"));
+	read_file(argify("/init/2.txt"));
+	read_file(argify("/init/dir/3.txt"));
 }
diff --git a/src/init/tar.c b/src/init/tar.c
index a2b03df..d25b8a5 100644
--- a/src/init/tar.c
+++ b/src/init/tar.c
@@ -1,12 +1,38 @@
 #include <init/stdlib.h>
+#include <shared/flags.h>
 #include <shared/syscalls.h>
 #include <stdint.h>
 
 extern int tty_fd;
 
+// TODO struct tar
+static int tar_open(const char *path, int len, void *base, size_t base_len);
+static int tar_size(void *sector);
+static void *tar_find(const char *path, size_t path_len, void *base, size_t base_len);
 static int oct_parse(char *str, size_t len);
 
-void tar_driver(void *base) {
+void tar_driver(handle_t back, void *base) {
+	static char buf[64];
+	int len;
+	void *id; // IDs usually are integers, but here i'm using them as pointers
+	          // to the metadata sectors
+	for (;;) {
+		len = 64;
+		switch (_syscall_fs_wait(back, buf, &len, (int*)&id)) {
+			case VFSOP_OPEN:
+				_syscall_fs_respond(NULL, tar_open(buf, len, base, ~0));
+				break;
+
+			case VFSOP_READ:
+				_syscall_fs_respond(id + 512, tar_size(id));
+				break;
+
+			default:
+				_syscall_fs_respond(NULL, -1); // unsupported
+				break;
+		}
+	}
+
 	// iterate over all sectors, printing filenames
 	while (0 == memcmp(base + 257, "ustar", 5)) {
 		int size = oct_parse(base + 124, 12);
@@ -21,6 +47,39 @@ void tar_driver(void *base) {
 	_syscall_write(tty_fd, "done.", 5);
 }
 
+static int tar_open(const char *path, int len, void *base, size_t base_len) {
+	void *ptr;
+
+	if (len <= 1) return -1;
+	path += 1; // skip the leading slash
+	len  -= 1;
+
+	ptr = tar_find(path, len, base, ~0);
+	if (!ptr) return -1;
+	return (int)ptr;
+}
+
+static int tar_size(void *sector) {
+	return oct_parse(sector + 124, 12);
+}
+
+static void *tar_find(const char *path, size_t path_len, void *base, size_t base_len) {
+	int size;
+	if (path_len > 100) return NULL; // illegal path
+
+	for (size_t off = 0; off < base_len;) {
+		if (0 != memcmp(base + off + 257, "ustar", 5))
+			break; // not a metadata sector
+		if (0 == memcmp(base + off, path, path_len))
+			return base + off; // file found, quit
+
+		size = tar_size(base + off);
+		off += 512;                 // skip this metadata sector
+		off += (size + 511) & ~511; // skip the data sectors
+	}
+	return NULL;
+}
+
 static int oct_parse(char *str, size_t len) {
 	int res = 0;
 	for (size_t i = 0; i < len; i++) {
diff --git a/src/init/tar.h b/src/init/tar.h
index 77141b4..71c30fe 100644
--- a/src/init/tar.h
+++ b/src/init/tar.h
@@ -1,3 +1,4 @@
 #pragma once
+#include <shared/types.h>
 
-void tar_driver(void *base);
+_Noreturn void tar_driver(handle_t back, void *base);