stream: move decoder to stream and rename as codec

Since every stream will need to pass through a codec to code/decode to
and from textual data, the former 'decoder' attribute is now moved to
Stream and renamed to better reflect its use.

Signed-off-by: Lucas Bajolet <lucas.bajolet@gmail.com>

diff --git a/lib/core/stream.nit b/lib/core/stream.nit
index 61b59dd..d077a73 100644 (file)
--- a/lib/core/stream.nit
+++ b/lib/core/stream.nit
@@ -29,6 +29,51 @@ end
 
 # Any kind of stream to read/write/both to or from a source
 abstract class Stream
+       # Codec used to transform raw data to text
+       #
+       # Note: defaults to UTF-8
+       var codec: Codec = utf8_codec is protected writable(set_codec)
+
+       # Lookahead buffer for codecs
+       #
+       # Since some codecs are multibyte, a lookahead may be required
+       # to store the next bytes and consume them only if a valid character
+       # is read.
+       protected var lookahead: CString is noinit
+
+       # Capacity of the lookahead
+       protected var lookahead_capacity = 0
+
+       # Current occupation of the lookahead
+       protected var lookahead_length = 0
+
+       # Buffer for writing data to a stream
+       protected var write_buffer: CString is noinit
+
+       init do
+               var lcap = codec.max_lookahead
+               lookahead = new CString(lcap)
+               write_buffer = new CString(lcap)
+               lookahead_length = 0
+               lookahead_capacity = lcap
+       end
+
+       # Change the codec for this stream.
+       fun codec=(c: Codec) do
+               if c.max_lookahead > lookahead_capacity then
+                       var lcap = codec.max_lookahead
+                       var lk = new CString(lcap)
+                       var llen = lookahead_length
+                       if llen > 0 then
+                               lookahead.copy_to(lk, llen, 0, 0)
+                       end
+                       lookahead = lk
+                       lookahead_capacity = lcap
+                       write_buffer = new CString(lcap)
+               end
+               set_codec(c)
+       end
+
        # Error produced by the file stream
        #
        #     var ifs = new FileReader.open("donotmakethisfile.binx")
@@ -65,9 +110,6 @@ end
 abstract class Reader
        super Stream
 
-       # Decoder used to transform input bytes to UTF-8
-       var decoder: Codec = utf8_codec is writable
-
        # Reads a character. Returns `null` on EOF or timeout
        fun read_char: nullable Char is abstract
 
@@ -409,9 +451,6 @@ end
 abstract class Writer
        super Stream
 
-       # The coder from a nit UTF-8 String to the output file
-       var coder: Codec = utf8_codec is writable
-
        # Writes bytes from `s`
        fun write_bytes(s: Bytes) is abstract