refactor object file somewhat

lib/elf/object_file.rb

@@ -18,55 +18,42 @@ module Elf
     end
 
     def write(io)
-      io << "\x7fELF"
-      io.write_uint8 @target[0]
-      io.write_uint8 @target[1]
-      io.write_uint8 EV_CURRENT
-      io.write_uint8 @target[2]
-      io << "\x00" * 8 # pad
+      write_preamble(io)
 
-      io.write_uint16 ET_REL
-      io.write_uint16 @target[3]
-      io.write_uint32 EV_CURRENT
-      io.write_uint32 0 # entry point
-      io.write_uint32 0 # no program header table
       sh_offset_pos = io.tell
-      io.write_uint32 0 # section header table offset
-      io.write_uint32 0 # no flags
-      io.write_uint16 52 # header length
-      io.write_uint16 0 # program header length
-      io.write_uint16 0 # program header count
-      io.write_uint16 40 # section header length
 
-      shstrtab = StringTableSection.new(".shstrtab")
-      @sections << shstrtab
-      @sections.each { |section|
-        shstrtab.add_string section.name
-      }
+      write_header(io)
+
+      string_table = write_string_table(io)
 
       io.write_uint16 @sections.length # section header count
 
       io.write_uint16 @sections.length-1 # section name string table index
 
-      # write sections
-
-      section_data = []
-      @sections.each { |section|
-        offset = io.tell
-        section.write(io)
-        size = io.tell - offset
-        section_data << {:section => section, :offset => offset,
-                         :size => size}
-      }
-
-      # write section headers
+      section_data = write_sections(io)
 
       sh_offset = io.tell
 
+      write_section_data(section_data, string_table , io)
+
+      io.seek sh_offset_pos
+      io.write_uint32 sh_offset
+    end
+
+    def write_string_table(io)
+      string_table = StringTableSection.new(".shstrtab")
+      @sections << string_table
+      @sections.each { |section|
+        string_table.add_string section.name
+      }
+      string_table
+    end
+
+    def write_section_data(section_data, string_table,io)
       section_data.each { |data|
         section, offset, size = data[:section], data[:offset], data[:size]
         # write header first
-        io.write_uint32 shstrtab.index_for(section.name)
+        io.write_uint32 string_table.index_for(section.name)
         io.write_uint32 section.type
         io.write_uint32 section.flags
         io.write_uint32 section.addr
@@ -84,9 +71,40 @@ module Elf
         io.write_uint32 section.alignment
         io.write_uint32 section.ent_size
       }
+    end
 
-      io.seek sh_offset_pos
-      io.write_uint32 sh_offset
+    def write_sections(io)
+      section_data = []
+      @sections.each { |section|
+        offset = io.tell
+        section.write(io)
+        size = io.tell - offset
+        section_data << {:section => section, :offset => offset, :size => size}
+      }
+      section_data
+    end
+
+    def write_header(io)
+      io.write_uint32 0 # section header table offset
+      io.write_uint32 0 # no flags
+      io.write_uint16 52 # header length
+      io.write_uint16 0 # program header length
+      io.write_uint16 0 # program header count
+      io.write_uint16 40 # section header length
+    end
+
+    def write_preamble(io)
+      io << "\x7fELF"
+      io.write_uint8 @target[0]
+      io.write_uint8 @target[1]
+      io.write_uint8 EV_CURRENT
+      io.write_uint8 @target[2]
+      io << "\x00" * 8 # pad
+      io.write_uint16 ET_REL
+      io.write_uint16 @target[3]
+      io.write_uint32 EV_CURRENT
+      io.write_uint32 0 # entry point
+      io.write_uint32 0 # no program header table
     end
   end
 end