streams: fill_buf for string byte input streams.

* stream.c (byte_in_fill_buf): New function.
(byte_in_ops): Wire byte_in_fill_buf in place of
generic_fill_buf.

1 files changed, 20 insertions, 1 deletions

diff --git a/stream.c b/stream.c
index e7558c91..4fd134e0 100644
--- a/stream.c
+++ b/stream.c
@@ -2161,6 +2161,25 @@ static val byte_in_unget_byte(val stream, int byte)
   return num_fast(byte);
 }
 
+static ucnum byte_in_fill_buf(val stream, mem_t *ptr, ucnum len, ucnum pos)
+{
+  val self = lit("fill-buf");
+  struct byte_input *bi = coerce(struct byte_input *, stream->co.handle);
+
+  if (convert(size_t, len) != len || len > INT_PTR_MAX)
+    uw_throwf(error_s, lit("~a: buffer too large"), self, nao);
+  if (pos >= len) {
+    return len;
+  } else {
+    size_t room = len - pos;
+    size_t avail = bi->size - bi->index;
+    size_t copy = min(room, avail);
+    memcpy(ptr + pos, bi->buf + bi->index, copy);
+    bi->index += copy;
+    return pos + copy;
+  }
+}
+
 static val byte_in_get_error(val stream)
 {
   struct byte_input *bi = coerce(struct byte_input *, stream->co.handle);
@@ -2186,7 +2205,7 @@ static struct strm_ops byte_in_ops =
                 byte_in_unget_char,
                 byte_in_unget_byte,
                 0,
-                generic_fill_buf,
+                byte_in_fill_buf,
                 0, 0, 0, 0, 0, 0,
                 byte_in_get_error,
                 byte_in_get_error_str,