streams: sequence input stream follows the vector length

This is to allow working with sequence streams where the vector may change after
the stream has been created.

When the user specifies :END to be some fixed value, then we upkeep that
promise, but when :END is NIL, then we always consult the vector fillp.

src/c/streams/strm_sequence.d

@@ -315,7 +315,7 @@ make_sequence_input_stream(cl_object vector, cl_index istart, cl_index iend,
   }
   SEQ_STREAM_VECTOR(strm) = vector;
   SEQ_STREAM_POSITION(strm) = istart;
-  SEQ_INPUT_LIMIT(strm) = iend;
+  SEQ_INPUT_VECTOR_END(strm) = iend;
   return strm;
 }
 
@@ -324,11 +324,15 @@ make_sequence_input_stream(cl_object vector, cl_index istart, cl_index iend,
                                          (end ECL_NIL)
                                          (external_format ECL_NIL))
   cl_index_pair p;
+  cl_object strm;
   @
   p = ecl_vector_start_end(@[ext::make-sequence-input-stream],
                            vector, start, end);
-  @(return make_sequence_input_stream(vector, p.start, p.end,
-                                      external_format))
+  strm = make_sequence_input_stream(vector, p.start, p.end,
+                                    external_format);
+  if (Null(end))
+    strm->stream.flags |= ECL_STREAM_USE_VECTOR_FILLP;
+  @(return strm)
   @)
 
 /**********************************************************************

src/doc/manual/standards/streams.txi

@@ -318,6 +318,9 @@ bytes comprising the character in the given external format.
 @defun ext:make-sequence-input-stream vector &key (start 0) (end nil) (external-format nil)
 Create a sequence input stream with the subsequence bounded by
 @var{start} and @var{end} of the given vector.
+
+When @var{end} is @code{nil}, then the end bound is the vector's length.
+When the vector is adjusted the end bound is updated as well.
 @end defun
 @lspdef ext:make-sequence-output-stream
 @defun ext:make-sequence-output-stream vector &key (external-format nil)

src/h/internal.h

@@ -533,7 +533,13 @@ write_char_increment_column(cl_object strm, ecl_character c)
 #define SEQ_STREAM_ELT_TYPE(strm) (strm)->stream.object0
 #define SEQ_STREAM_VECTOR(strm) (strm)->stream.object1
 #define SEQ_STREAM_POSITION(strm) (strm)->stream.int0
-#define SEQ_INPUT_LIMIT(strm) (strm)->stream.int1
+
+#define SEQ_INPUT_VECTOR_END(strm) (strm)->stream.int1
+#define SEQ_INPUT_LIMIT(strm)                                           \
+        ((strm)->stream.flags & ECL_STREAM_USE_VECTOR_FILLP             \
+         ? SEQ_STREAM_VECTOR(strm)->vector.fillp                        \
+         : SEQ_INPUT_VECTOR_END(strm))
+
 
 #ifndef HAVE_FSEEKO
 #define ecl_off_t int

src/h/object.h

@@ -645,15 +645,19 @@ enum {
         ECL_STREAM_USER_FORMAT = 8,
         ECL_STREAM_US_ASCII = 10,
 #endif
+        /* External Format */
         ECL_STREAM_CR = 16,
         ECL_STREAM_LF = 32,
         ECL_STREAM_SIGNED_BYTES = 64,
         ECL_STREAM_LITTLE_ENDIAN = 128,
+        /* OS Streams */
         ECL_STREAM_C_STREAM = 256,
         ECL_STREAM_MIGHT_SEEK = 512,
-        ECL_STREAM_CLOSE_COMPONENTS = 1024,
-        ECL_STREAM_CLOSE_ON_EXEC = 2048,
-        ECL_STREAM_NONBLOCK = 4096
+        ECL_STREAM_CLOSE_ON_EXEC = 1024,
+        ECL_STREAM_NONBLOCK = 2048,
+        /* Lisp Streams */
+        ECL_STREAM_CLOSE_COMPONENTS = 4096,
+        ECL_STREAM_USE_VECTOR_FILLP = 8192
 };
 
 /* buffer points to an array of bytes ending at buffer_end. Decode one