Allow opening archive from IO instance

lib/ffi-libarchive/archive.rb

@@ -294,6 +294,10 @@ def self.read_open_fd(fd, command = nil, &block)
     Reader.open_fd fd, command, &block
   end
 
+  def self.read_open_io(io, command = nil, &block)
+    Reader.open_io io, command, &block
+  end
+
   def self.read_open_memory(string, command = nil, &block)
     Reader.open_memory string, command, &block
   end

lib/ffi-libarchive/reader.rb

@@ -28,6 +28,19 @@ def self.open_fd(fd, command = nil, strip_components: 0)
       end
     end
 
+    def self.open_io(io, command = nil, strip_components: 0)
+      if block_given?
+        reader = open_io io, command, strip_components: strip_components
+        begin
+          yield reader
+        ensure
+          reader.close
+        end
+      else
+        new io: io, command: command, strip_components: strip_components
+      end
+    end
+
     def self.open_memory(string, command = nil)
       if block_given?
         reader = open_memory string, command
@@ -81,6 +94,15 @@ def initialize(params = {})
         raise Error, @archive if C.archive_read_open_filename(archive, params[:file_name], 1024) != C::OK
       when params[:fd]
         raise Error, @archive if C.archive_read_open_fd(archive, params[:fd], 1024) != C::OK
+      when params[:io]
+        # Hold a reference to the IO so Ruby understands we're using it while this object is alive
+        @io = params[:io]
+        raise ArgumentError, "Expected io to respond to #fileno" unless @io.respond_to?(:fileno)
+
+        fd = @io.fileno
+        raise ArgumentError, "Expected io.fileno to return an fd but got nil" if fd.nil?
+
+        raise Error, @archive if C.archive_read_open_fd(archive, fd, 1024) != C::OK
       when params[:memory]
         str = params[:memory]
         @data = FFI::MemoryPointer.new(str.bytesize + 1)

test/sets/ts_read.rb

@@ -1,4 +1,5 @@
 require "ffi-libarchive"
+require "stringio"
 require "tmpdir"
 require "test/unit"
 
@@ -75,6 +76,46 @@ def test_read_tar_gz_from_fd_with_external_gunzip
     end
   end
 
+  def test_read_tar_gz_from_io
+    return if windows?
+
+    File.open("data/test.tar.gz", "r") do |f|
+      Archive.read_open_io(f) do |ar|
+        verify_content(ar)
+      end
+    end
+  end
+
+  def test_read_tar_gz_from_io_with_external_gunzip
+    return if windows?
+
+    File.open("data/test.tar.gz", "r") do |f|
+      Archive.read_open_io(f, "gunzip") do |ar|
+        verify_content(ar)
+      end
+    end
+  end
+
+  def test_read_tar_gz_from_io_no_fileno
+    return if windows?
+
+    string = File.read("data/test.tar.gz")
+
+    assert_raise ArgumentError, "Expected io to respond to #fileno" do
+      Archive.read_open_io(string)
+    end
+  end
+
+  def test_read_tar_gz_from_string_io
+    return if windows?
+
+    io = StringIO.new(File.read("data/test.tar.gz"))
+
+    assert_raise ArgumentError, "Expected io.fileno to return an fd but got nil" do
+      Archive.read_open_io(io)
+    end
+  end
+
   def test_read_tar_gz_from_memory
     return if windows?