Add symlink support, closes #8

lib/archive/tar/minitar/writer.rb

@@ -258,6 +258,28 @@ def mkdir(name, opts = {})
       nil
     end
 
+    # Creates a symbolic link entry in the tar.
+    def symlink(name, link_target, opts = {})
+      raise ClosedStream if @closed
+
+      raise FileNameTooLong if link_target.size > 100
+
+      name, prefix = split_name(name)
+      header = {
+        :name => name,
+        :mode => opts[:mode],
+        :typeflag => "2",
+        :size => 0,
+        :linkname => link_target,
+        :gid => opts[:gid],
+        :uid => opts[:uid],
+        :mtime => opts[:mtime],
+        :prefix => prefix
+      }
+      @io.write(PosixHeader.new(header))
+      nil
+    end
+
     # Passes the #flush method to the wrapped stream, used for buffered
     # streams.
     def flush

test/minitest_helper.rb

@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require "fileutils"
 require "minitar"

test/support/tar_test_helpers.rb

@@ -73,19 +73,24 @@ def tar_dir_header(name, prefix, mode)
     update_checksum(header("5", name, prefix, 0, mode))
   end
 
-  def header(type, fname, dname, length, mode)
+  def tar_symlink_header(name, prefix, mode, target)
+    update_checksum(header("2", name, prefix, 0, mode, target))
+  end
+
+  def header(type, fname, dname, length, mode, link_name = "")
     raw_header(type,
       asciiz(fname, 100),
       asciiz(dname, 155),
       z(to_oct(length, 11)),
-      z(to_oct(mode, 7)))
+      z(to_oct(mode, 7)),
+      asciiz(link_name, 100))
   end
 
-  def raw_header(type, fname, dname, length, mode)
+  def raw_header(type, fname, dname, length, mode, link_name = "")
     arr = [
       fname, mode, z(to_oct(nil, 7)), z(to_oct(nil, 7)),
       length, z(to_oct(0, 11)), BLANK_CHECKSUM, type,
-      NULL_100, USTAR, DOUBLE_ZERO, asciiz("", 32), asciiz("", 32),
+      asciiz(link_name, 100), USTAR, DOUBLE_ZERO, asciiz("", 32), asciiz("", 32),
       z(to_oct(nil, 7)), z(to_oct(nil, 7)), dname
     ]
 

test/test_tar_writer.rb

@@ -73,10 +73,9 @@ def test_write_operations_fail_after_closed
     @os.add_file_simple("sadd", :mode => 0o644, :size => 20) { |f| }
     @os.close
     assert_raises(Minitar::ClosedStream) { @os.flush }
-    assert_raises(Minitar::ClosedStream) {
-      @os.add_file("dfdsf", :mode => 0o644) {}
-    }
+    assert_raises(Minitar::ClosedStream) { @os.add_file("dfdsf", :mode => 0o644) {} }
     assert_raises(Minitar::ClosedStream) { @os.mkdir "sdfdsf", :mode => 0o644 }
+    assert_raises(Minitar::ClosedStream) { @os.symlink "a", "b", :mode => 0o644 }
   end
 
   def test_file_name_is_split_correctly
@@ -261,4 +260,19 @@ def test_file_size_is_checked
     end
     @os.add_file_simple("lib/foo/bar", :mode => 0o644, :size => 10) { |f| }
   end
+
+  def test_symlink
+    @dummyos.reset
+    @os.symlink("lib/foo/bar", "lib/foo/baz", :mode => 0o644)
+    @os.flush
+    assert_headers_equal(tar_dir_header("lib/foo", "", 0o644),
+      @dummyos.data[0, 512])
+  end
+
+  def test_symlink_target_size_is_checked
+    @dummyos.reset
+    assert_raises(Minitar::FileNameTooLong) do
+      @os.symlink("lib/foo/bar", "x" * 101)
+    end
+  end
 end