`init`: start work on the tar driver

3 files changed, 49 insertions, 1 deletions

diff --git a/src/init/main.c b/src/init/main.c
index db94d4a..683d0ca 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -1,3 +1,4 @@
+#include <init/tar.h>
 #include <init/types.h>
 #include <shared/flags.h>
 #include <shared/syscalls.h>
@@ -25,8 +26,8 @@ int main(void) {
 		_syscall_exit(argify("couldn't open tty"));
 
 	fs_test();
+	tar_driver(&_initrd);
 
-	_syscall_write(tty_fd, &_initrd, 23);
 	_syscall_exit(argify("my job here is done."));
 }
 
diff --git a/src/init/tar.c b/src/init/tar.c
new file mode 100644
index 0000000..22e4785
--- /dev/null
+++ b/src/init/tar.c
@@ -0,0 +1,44 @@
+#include <init/types.h>
+#include <shared/syscalls.h>
+#include <stdint.h>
+
+extern int tty_fd;
+
+static int oct_parse(char *str, size_t len);
+int memcmp(const void *s1, const void *s2, size_t n); // TODO move to a dedicated file
+
+
+void tar_driver(void *base) {
+	// iterate over all sectors, printing filenames
+	while (0 == memcmp(base + 257, "ustar", 5)) {
+		int size = oct_parse(base + 124, 12);
+
+		_syscall_write(tty_fd, base, 100);
+		_syscall_write(tty_fd, " ", 1);
+
+		base += 512;                 // skip metadata sector
+		base += (size + 511) & ~511; // skip file (size rounded up to 512)
+		// TODO might pagefault if the last sector was at a page boundary
+	}
+	_syscall_write(tty_fd, "done.", 5);
+}
+
+static int oct_parse(char *str, size_t len) {
+	int res = 0;
+	for (size_t i = 0; i < len; i++) {
+		res *= 8;
+		res += str[i] - '0'; // no format checking
+	}
+	return res;
+}
+
+int memcmp(const void *s1, const void *s2, size_t n) {
+	const unsigned char *c1 = s1, *c2 = s2;
+	for (size_t i = 0; i < n; i++) {
+		if (c1[i] != c2[i]) {
+			if (c1[i] < c2[i])  return -1;
+			else                return 1;
+		}
+	}
+	return 0;
+}
diff --git a/src/init/tar.h b/src/init/tar.h
new file mode 100644
index 0000000..77141b4
--- /dev/null
+++ b/src/init/tar.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void tar_driver(void *base);