Remove "buf" field from port buffers

* libguile/ports-internal.h (scm_port_buffer_reset_end): New helper.
  (scm_port_buffer_putback): New helper.
* libguile/ports.h (scm_t_port_buffer): Remove "buf" field.
  (scm_get_byte_or_eof_unlocked, scm_peek_byte_or_eof_unlocked): Adapt.
* libguile/ports.c (scm_c_make_port_buffer): No more "buf" field.
  (scm_i_unget_bytes_unlocked): Use helper.
* libguile/read.c (scm_i_scan_for_encoding): No more "buf" field.

libguile/ports-internal.h

@@ -22,6 +22,8 @@
 #ifndef SCM_PORTS_INTERNAL
 #define SCM_PORTS_INTERNAL
 
+#include <assert.h>
+
 #include "libguile/_scm.h"
 #include "libguile/ports.h"
 
@@ -37,6 +39,12 @@ scm_port_buffer_reset (scm_t_port_buffer *buf)
   buf->cur = buf->end = 0;
 }
 
+static inline void
+scm_port_buffer_reset_end (scm_t_port_buffer *buf)
+{
+  buf->cur = buf->end = scm_port_buffer_size (buf);
+}
+
 static inline size_t
 scm_port_buffer_can_take (scm_t_port_buffer *buf)
 {
@@ -96,6 +104,18 @@ scm_port_buffer_put (scm_t_port_buffer *buf, const scm_t_uint8 *src,
   return count;
 }
 
+static inline void
+scm_port_buffer_putback (scm_t_port_buffer *buf, const scm_t_uint8 *src,
+                         size_t count)
+{
+  assert (count <= buf->cur);
+
+  /* Sometimes used to move around data within a buffer, so we must use
+     memmove.  */
+  buf->cur -= count;
+  memmove (SCM_BYTEVECTOR_CONTENTS (buf->bytevector) + buf->cur, src, count);
+}
+
 enum scm_port_encoding_mode {
   SCM_PORT_ENCODING_MODE_UTF8,
   SCM_PORT_ENCODING_MODE_LATIN1,

libguile/ports.c

@@ -518,7 +518,6 @@ scm_c_make_port_buffer (size_t size)
   scm_t_port_buffer *ret = scm_gc_typed_calloc (scm_t_port_buffer);
 
   ret->bytevector = scm_c_make_bytevector (size);
-  ret->buf = (scm_t_uint8 *) SCM_BYTEVECTOR_CONTENTS (ret->bytevector);
   ret->has_eof_p = SCM_BOOL_F;
 
   return ret;
@@ -1998,11 +1997,9 @@ scm_i_unget_bytes_unlocked (const scm_t_uint8 *buf, size_t len, SCM port)
         {
           /* But they would fit if we shift the not-yet-read bytes from
              the read_buf right.  Let's do that.  */
-          memmove (read_buf->buf + (size - buffered),
-                   scm_port_buffer_take_pointer (read_buf),
-                   buffered);
-          read_buf->end = size;
-          read_buf->cur = read_buf->end - buffered;
+          const scm_t_uint8 *to_shift = scm_port_buffer_take_pointer (read_buf);
+          scm_port_buffer_reset_end (read_buf);
+          scm_port_buffer_putback (read_buf, to_shift, buffered);
         }
       else
         {
@@ -2013,18 +2010,16 @@ scm_i_unget_bytes_unlocked (const scm_t_uint8 *buf, size_t len, SCM port)
             size *= 2;
 
           new_buf = scm_c_make_port_buffer (size);
-          new_buf->end = size;
-          new_buf->cur = new_buf->end - buffered;
+          scm_port_buffer_reset_end (new_buf);
           new_buf->has_eof_p = read_buf->has_eof_p;
-          memcpy (new_buf->buf + new_buf->cur, read_buf->buf + read_buf->cur,
-                  buffered);
-
+          scm_port_buffer_putback (new_buf,
+                                   scm_port_buffer_take_pointer (read_buf),
+                                   buffered);
           pt->read_buf = read_buf = new_buf;
         }
     }
 
-  read_buf->cur -= len;
-  memcpy (read_buf->buf + read_buf->cur, buf, len);
+  scm_port_buffer_putback (read_buf, buf, len);
 }
 #undef FUNC_NAME
 

libguile/ports.h

@@ -29,6 +29,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#include "libguile/bytevectors.h"
 #include "libguile/gc.h"
 #include "libguile/tags.h"
 #include "libguile/error.h"
@@ -73,8 +74,8 @@ struct scm_port_internal;
 
 typedef struct
 {
-  /* Start of the buffer.  Never changed.  */
-  scm_t_uint8 *buf;
+  /* The port buffer. */
+  SCM bytevector;
 
   /* Offsets into the buffer.  Invariant: cur <= end <= size(buf).  */
   size_t cur;
@@ -86,8 +87,6 @@ typedef struct
      peek-u8 should still return EOF.  */
   SCM has_eof_p;
 
-  /* Bytevector whose contents are [BUF, BUF + SIZE). */
-  SCM bytevector;
 } scm_t_port_buffer;
 
 
@@ -430,13 +429,16 @@ SCM_INLINE_IMPLEMENTATION int
 scm_get_byte_or_eof_unlocked (SCM port)
 {
   scm_t_port_buffer *buf = SCM_PTAB_ENTRY (port)->read_buf;
+  scm_t_uint8 *ptr;
 
+  ptr = (scm_t_uint8 *) SCM_BYTEVECTOR_CONTENTS (buf->bytevector);
   if (SCM_LIKELY (buf->cur < buf->end))
-    return buf->buf[buf->cur++];
+    return ptr[buf->cur++];
 
   buf = scm_fill_input_unlocked (port);
+  ptr = (scm_t_uint8 *) SCM_BYTEVECTOR_CONTENTS (buf->bytevector);
   if (buf->cur < buf->end)
-    return buf->buf[buf->cur++];
+    return ptr[buf->cur++];
 
   /* The next peek or get should cause the read() function to be called
      to see if we still have EOF.  */
@@ -448,15 +450,15 @@ scm_get_byte_or_eof_unlocked (SCM port)
 SCM_INLINE_IMPLEMENTATION int
 scm_peek_byte_or_eof_unlocked (SCM port)
 {
-  scm_t_port *pt = SCM_PTAB_ENTRY (port);
-  scm_t_port_buffer *buf = pt->read_buf;
+  scm_t_port_buffer *buf = SCM_PTAB_ENTRY (port)->read_buf;
+  scm_t_uint8 *ptr = (scm_t_uint8 *) SCM_BYTEVECTOR_CONTENTS (buf->bytevector);
 
   if (SCM_LIKELY (buf->cur < buf->end))
-    return buf->buf[buf->cur];
+    return ptr[buf->cur];
 
   buf = scm_fill_input_unlocked (port);
   if (buf->cur < buf->end)
-    return buf->buf[buf->cur];
+    return ptr[buf->cur];
 
   return EOF;
 }

libguile/read.c

@@ -2086,7 +2086,7 @@ scm_i_scan_for_encoding (SCM port)
         /* An unbuffered port -- don't scan.  */
         return NULL;
 
-      memcpy (header, buf->buf + buf->cur, bytes_read);
+      memcpy (header, scm_port_buffer_take_pointer (buf), bytes_read);
       header[bytes_read] = '\0';
     }
   else