Moved core extensions to Net::BER. Documented.

lib/net/ber/core_ext/fixnum.rb

@@ -0,0 +1,63 @@
+module Net::BER::Extensions::Fixnum
+  ##
+  # Converts the fixnum to BER format.
+  def to_ber
+    "\002#{to_ber_internal}"
+  end
+
+  ##
+  # Converts the fixnum to BER enumerated format.
+  def to_ber_enumerated
+    "\012#{to_ber_internal}"
+  end
+
+  ##
+  # Converts the fixnum to BER length encodining format.
+  def to_ber_length_encoding
+    if self <= 127
+      [self].pack('C')
+    else
+      i = [self].pack('N').sub(/^[\0]+/,"")
+      [0x80 + i.length].pack('C') + i
+    end
+  end
+
+  ##
+  # Generate a BER-encoding for an application-defined INTEGER. Examples of
+  # such integers are SNMP's Counter, Gauge, and TimeTick types.
+  def to_ber_application(tag)
+    [0x40 + tag].pack("C") + to_ber_internal
+  end
+
+  ##
+  # Used to BER-encode the length and content bytes of a Fixnum. Callers
+  # must prepend the tag byte for the contained value.
+  def to_ber_internal
+    # CAUTION: Bit twiddling ahead. You might want to shield your eyes or
+    # something.
+
+    # Looks for the first byte in the fixnum that is not all zeroes. It does
+    # this by masking one byte after another, checking the result for bits
+    # that are left on.
+    size = Net::BER::MAX_FIXNUM_SIZE
+    while size > 1
+      break if (self & (0xff << (size - 1) * 8)) > 0
+      size -= 1
+    end
+
+    # Store the size of the fixnum in the result
+    result = [size]
+
+    # Appends bytes to result, starting with higher orders first. Extraction
+    # of bytes is done by right shifting the original fixnum by an amount
+    # and then masking that with 0xff.
+    while size > 0
+      # right shift size - 1 bytes, mask with 0xff
+      result << ((self >> ((size - 1) * 8)) & 0xff)
+      size -= 1
+    end
+
+    result.pack('C*')
+  end
+  private :to_ber_internal
+end