Port buffer cur/next pointers are Scheme values

* libguile/ports.h (scm_t_port_buffer): Change "cur" and "end" members
  to be SCM values, in preparation for changing port buffers to be
  Scheme vectors.
  (scm_get_byte_or_eof_unlocked, scm_peek_byte_or_eof_unlocked): Adapt.
* libguile/ports.c (scm_c_make_port_buffer): Initialize cur and end
  members.
  (looking_at_bytes): Use helper instead of incrementing cur.
  (scm_i_read_unlocked): Adapt to end type change.
  (CONSUME_PEEKED_BYTE): Use helper instead of incrementing cur.
  (scm_i_unget_bytes_unlocked): Use helper instead of comparing cur.
  (scm_i_write_unlocked): Fix for changing end/cur types.
* libguile/read.c (scm_i_scan_for_encoding): Use helpers instead of
  addressing cursors directly.
* libguile/rw.c (scm_write_string_partial): Likewise.
* libguile/ports-internal.h (scm_port_buffer_reset):
  (scm_port_buffer_reset_end, scm_port_buffer_can_take):
  (scm_port_buffer_can_put, scm_port_buffer_can_putback):
  (scm_port_buffer_did_take, scm_port_buffer_did_put):
  (scm_port_buffer_take_pointer, scm_port_buffer_put_pointer):
  (scm_port_buffer_putback): Adapt to data types.

1 files changed, 2 insertions, 2 deletions

diff --git a/libguile/read.c b/libguile/read.c
index a4357d179..bc5c3c179 100644
--- a/libguile/read.c
+++ b/libguile/read.c
@@ -2074,11 +2074,11 @@ scm_i_scan_for_encoding (SCM port)
       pt->rw_active = SCM_PORT_READ;
     }
 
-  if (buf->cur == buf->end)
+  if (scm_port_buffer_can_take (buf) == 0)
     {
       /* We can use the read buffer, and thus avoid a seek. */
       buf = scm_fill_input_unlocked (port);
-      bytes_read = buf->end - buf->cur;
+      bytes_read = scm_port_buffer_can_take (buf);
       if (bytes_read > SCM_ENCODING_SEARCH_SIZE)
         bytes_read = SCM_ENCODING_SEARCH_SIZE;