adds first version of the expanded as assembler from mikko

lib/elf/symbol_table_section.rb

@@ -0,0 +1,77 @@
+module Elf
+  class SymbolTableSection < Section
+    def initialize(name, strtab)
+      super(name)
+
+      @strtab = strtab
+
+      @symbols = []
+    end
+
+    def add_func_symbol(name, value, text_section, linkage)
+      @strtab.add_string name
+      arr = [name, value, text_section, linkage]
+      if (linkage == Elf::Constants::STB_LOCAL)
+        @symbols.unshift arr
+      else
+        @symbols.push arr
+      end
+    end
+
+    def index_for_name(name)
+      @symbols.each_with_index { |sym, idx|
+        if (sym[0] == name)
+          return idx
+        end
+      }
+      nil
+    end
+
+    def type
+      Elf::Constants::SHT_SYMTAB
+    end
+
+    def ent_size
+      16
+    end
+
+    def link
+      @strtab.index
+    end
+
+    def info
+      i = -1
+      @symbols.each_with_index { |sym, idx|
+        if (sym[4] == Elf::Constants::STB_LOCAL)
+          i = idx
+        end
+      }
+      i + 1
+    end
+
+    def write(io)
+      # write undefined symbol
+      io.write_uint32 0
+      io.write_uint32 0
+      io.write_uint32 0
+      io.write_uint8 Elf::Constants::STB_LOCAL << 4
+      io.write_uint8 0
+      io.write_uint16 0
+
+      # write other symbols
+      @symbols.each { |sym|
+        io.write_uint32 @strtab.index_for(sym[0])
+        io.write_uint32 sym[1]
+        io.write_uint32 0
+        io.write_uint8((sym[3] << 4) + 0)
+        io.write_uint8 0
+        if (sym[2])
+          io.write_uint16 sym[2].index
+        else
+          # undefined symbol
+          io.write_uint16 0
+        end
+      }
+    end
+  end
+end