Pathname: add Mach-O module

The MachO module contains methods for learning about Mach-O binaries,
and can be used where one might normally shell out to file(1).

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

1 files changed, 93 insertions, 0 deletions

diff --git a/Library/Homebrew/mach.rb b/Library/Homebrew/mach.rb
new file mode 100644
index 000000000..e24cc1bc5
--- /dev/null
+++ b/Library/Homebrew/mach.rb
@@ -0,0 +1,93 @@
+module MachO
+  # Mach-O binary methods, see:
+  # /usr/include/mach-o/loader.h
+  # /usr/include/mach-o/fat.h
+
+  def mach_data
+    @mach_data ||= begin
+      offsets = []
+      mach_data = []
+
+      header = read(8).unpack("N2")
+      case header[0]
+      when 0xcafebabe # universal
+        header[1].times do |i|
+          # header[1] is the number of struct fat_arch in the file.
+          # Each struct fat_arch is 20 bytes, and the 'offset' member
+          # begins 8 bytes into the struct, with an additional 8 byte
+          # offset due to the struct fat_header at the beginning of
+          # the file.
+          offsets << read(4, 20*i + 16).unpack("N")[0]
+        end
+      when 0xcefaedfe, 0xcffaedfe, 0xfeedface, 0xfeedfacf # Single arch
+        offsets << 0
+      else
+        raise "Not a Mach-O binary."
+      end
+
+      offsets.each do |offset|
+        arch = case read(8, offset).unpack("N2")
+          when [0xcefaedfe, 0x07000000] then :i386
+          when [0xcffaedfe, 0x07000001] then :x86_64
+          when [0xfeedface, 0x00000012] then :ppc7400
+          when [0xfeedfacf, 0x01000012] then :ppc64
+          else :dunno
+          end
+
+        type = case read(4, offset + 12).unpack("N")[0]
+         when 0x00000002, 0x02000000 then :executable
+         when 0x00000006, 0x06000000 then :dylib
+         else :dunno
+         end
+
+        mach_data << { :arch => arch, :type => type }
+      end
+      mach_data
+    rescue
+      # read() will raise if it sees EOF, which should only happen if the
+      # file is < 8 bytes. Otherwise, we raise if the file is not a Mach-O 
+      # binary. In both cases, we want to return an empty array.
+      []
+    end
+  end
+
+  def archs
+    mach_data.map{ |m| m.fetch :arch }
+  end
+
+  def arch
+    case archs.length
+    when 0 then :dunno
+    when 1 then archs.first
+    else :universal
+    end
+  end
+
+  def universal?
+    arch == :universal
+  end
+
+  def i386?
+    arch == :i386
+  end
+
+  def x86_64?
+    arch == :x86_64
+  end
+
+  def ppc7400?
+    arch == :ppc7400
+  end
+
+  def ppc64?
+    arch == :ppc64
+  end
+
+  def dylib?
+    mach_data.map{ |m| m.fetch :type }.include? :dylib
+  end
+
+  def mach_o_executable?
+    mach_data.map{ |m| m.fetch :type }.include? :executable
+  end
+end