[PATCH] Move slow path out of 'scm_get_byte_or_eof' et al

[Mark H Weaver]

Andy suggested this.  Okay to push to stable-2.0?

    Mark


>From 0b70eba61ee26654f442199e7cc49838c5b0030e Mon Sep 17 00:00:00 2001
From: Mark H Weaver <address@hidden>
Date: Tue, 2 Apr 2013 05:33:24 -0400
Subject: [PATCH] Move slow path out of 'scm_get_byte_or_eof' et al.

Suggested by Andy Wingo.

* libguile/inline.h (scm_get_byte_or_eof, scm_peek_byte_or_eof): Keep
  only the fast path here, with fallback to 'scm_i_get_byte_or_eof' and
  'scm_i_peek_byte_or_eof'.

* libguile/ports.c (scm_i_get_byte_or_eof, scm_i_peek_byte_or_eof): New
  internal functions.

* libguile/ports.h (scm_i_get_byte_or_eof, scm_i_peek_byte_or_eof): Add
  prototypes.
---
 libguile/inline.h |   44 ++++++++++----------------------------------
 libguile/ports.c  |   41 +++++++++++++++++++++++++++++++++++++++++
 libguile/ports.h  |    2 ++
 3 files changed, 53 insertions(+), 34 deletions(-)

diff --git a/libguile/inline.h b/libguile/inline.h
index 88ba7f7..17d8a0c 100644
--- a/libguile/inline.h
+++ b/libguile/inline.h
@@ -96,50 +96,26 @@ scm_is_string (SCM x)
 SCM_INLINE_IMPLEMENTATION int
 scm_get_byte_or_eof (SCM port)
 {
-  int c;
   scm_t_port *pt = SCM_PTAB_ENTRY (port);
 
-  if (pt->rw_active == SCM_PORT_WRITE)
-    /* may be marginally faster than calling scm_flush.  */
-    scm_ptobs[SCM_PTOBNUM (port)].flush (port);
-
-  if (pt->rw_random)
-    pt->rw_active = SCM_PORT_READ;
-
-  if (pt->read_pos >= pt->read_end)
-    {
-      if (SCM_UNLIKELY (scm_fill_input (port) == EOF))
-       return EOF;
-    }
-
-  c = *(pt->read_pos++);
-
-  return c;
+  if (SCM_LIKELY ((pt->rw_active == SCM_PORT_READ || !pt->rw_random)
+                  && pt->read_pos < pt->read_end))
+    return *pt->read_pos++;
+  else
+    return scm_i_get_byte_or_eof (port);
 }
 
 /* Like `scm_get_byte_or_eof' but does not change PORT's `read_pos'.  */
 SCM_INLINE_IMPLEMENTATION int
 scm_peek_byte_or_eof (SCM port)
 {
-  int c;
   scm_t_port *pt = SCM_PTAB_ENTRY (port);
 
-  if (pt->rw_active == SCM_PORT_WRITE)
-    /* may be marginally faster than calling scm_flush.  */
-    scm_ptobs[SCM_PTOBNUM (port)].flush (port);
-
-  if (pt->rw_random)
-    pt->rw_active = SCM_PORT_READ;
-
-  if (pt->read_pos >= pt->read_end)
-    {
-      if (SCM_UNLIKELY (scm_fill_input (port) == EOF))
-       return EOF;
-    }
-
-  c = *pt->read_pos;
-
-  return c;
+  if (SCM_LIKELY ((pt->rw_active == SCM_PORT_READ || !pt->rw_random)
+                  && pt->read_pos < pt->read_end))
+    return *pt->read_pos;
+  else
+    return scm_i_peek_byte_or_eof (port);
 }
 
 SCM_INLINE_IMPLEMENTATION void
diff --git a/libguile/ports.c b/libguile/ports.c
index becdbed..76ec83f 100644
--- a/libguile/ports.c
+++ b/libguile/ports.c
@@ -1439,6 +1439,47 @@ scm_fill_input (SCM port)
   return scm_ptobs[SCM_PTOBNUM (port)].fill_input (port);
 }
 
+/* Slow-path fallback for 'scm_get_byte_or_eof' in inline.h */
+int
+scm_i_get_byte_or_eof (SCM port)
+{
+  scm_t_port *pt = SCM_PTAB_ENTRY (port);
+
+  if (pt->rw_active == SCM_PORT_WRITE)
+    scm_flush (port);
+
+  if (pt->rw_random)
+    pt->rw_active = SCM_PORT_READ;
+
+  if (pt->read_pos >= pt->read_end)
+    {
+      if (SCM_UNLIKELY (scm_fill_input (port) == EOF))
+       return EOF;
+    }
+
+  return *pt->read_pos++;
+}
+
+/* Slow-path fallback for 'scm_peek_byte_or_eof' in inline.h */
+int
+scm_i_peek_byte_or_eof (SCM port)
+{
+  scm_t_port *pt = SCM_PTAB_ENTRY (port);
+
+  if (pt->rw_active == SCM_PORT_WRITE)
+    scm_flush (port);
+
+  if (pt->rw_random)
+    pt->rw_active = SCM_PORT_READ;
+
+  if (pt->read_pos >= pt->read_end)
+    {
+      if (SCM_UNLIKELY (scm_fill_input (port) == EOF))
+       return EOF;
+    }
+
+  return *pt->read_pos;
+}
 
 /* scm_lfwrite
  *
diff --git a/libguile/ports.h b/libguile/ports.h
index 53d5081..54bf595 100644
--- a/libguile/ports.h
+++ b/libguile/ports.h
@@ -328,6 +328,8 @@ scm_i_default_port_conversion_handler (void);
 /* Use HANDLER as the default conversion strategy for future ports.  */
 SCM_INTERNAL void
 scm_i_set_default_port_conversion_handler 
(scm_t_string_failed_conversion_handler);
+SCM_INTERNAL int scm_i_get_byte_or_eof (SCM port);
+SCM_INTERNAL int scm_i_peek_byte_or_eof (SCM port);
 
 SCM_API SCM scm_port_conversion_strategy (SCM port);
 SCM_API SCM scm_set_port_conversion_strategy_x (SCM port, SCM behavior);
-- 
1.7.10.4