block.rb in bio-bgzf-0.2.0

- old
+ new

@@ -1,32 +1,38 @@
 module Bio::BGZF
 
+  class FormatError < StandardError
+  end
+
+  class NotBGZFError < FormatError
+  end
+
   def read_bgzf_block(f)
     hstart = f.read(12)
     return nil if hstart == nil # EOF?
     magic, gzip_extra_length = hstart.unpack('Vxxxxxxv')
-    raise 'wrong BGZF magic' unless magic == 0x04088B1F
+    raise NotBGZFError, "wrong BGZF magic: #{sprintf('%08x', magic)}" unless magic == 0x04088B1F
 
     len = 0
     bsize = nil
     while len < gzip_extra_length do
       si1, si2, slen = f.read(4).unpack('CCv')
       if si1 == 66 and si2 == 67 then
-        raise "BC subfield length is #{slen} but must be 2" if slen != 2
-        raise 'duplicate field with block size' unless bsize.nil?
+        raise FormatError, "BC subfield length is #{slen} but must be 2" if slen != 2
+        raise FormatError, 'duplicate field with block size' unless bsize.nil?
         bsize = f.read(2).unpack('v')[0]
         f.seek(slen - 2, IO::SEEK_CUR)
       else
         f.seek(slen, IO::SEEK_CUR)
       end
       len += 4 + slen
     end
 
     if len != gzip_extra_length then
-      raise "total length of subfields is #{len} bytes but must be #{gzip_extra_length}"
+      raise FormatError, "total length of subfields is #{len} bytes but must be #{gzip_extra_length}"
     end
-    raise 'block size was not found in any subfield' if bsize.nil?
+    raise NotBGZFError, 'block size was not found in any subfield' if bsize.nil?
 
     compressed_data = f.read(bsize - gzip_extra_length - 19)
     crc32, input_size = f.read(8).unpack('VV')
 
     return compressed_data, input_size, crc32
@@ -36,14 +42,14 @@
   def decompress_block(f)
     cdata, in_size, expected_crc = read_bgzf_block(f)
     return nil if cdata == nil
     data = unpack(cdata)
     if data.bytesize != in_size
-      raise "Expected #{in_size} bytes from BGZF block at #{pos}, but got #{data.bytesize} bytes!"
+      raise FormatError, "Expected #{in_size} bytes from BGZF block at #{pos}, but got #{data.bytesize} bytes!"
     end
     crc = Zlib.crc32(data, 0)
     if crc != expected_crc
-      raise "CRC error: expected #{expected_crc.to_s(16)}, got #{crc.to_s(16)}"
+      raise FormatError, "CRC error: expected #{expected_crc.to_s(16)}, got #{crc.to_s(16)}"
     end
     return data
   end
   module_function :decompress_block
 