Optimize `peek-char'.

This makes `peek-char' 40x faster on a port whose encoding is
faster on a UTF-8 port containing multi-byte codepoints.

The `xml->sxml' procedure is 4x faster on a 2.7 MiB XML file.

* libguile/ports.c (get_codepoint): New procedure, moved here from
  `scm_getc', with the additional BUF and LEN parameters.
  (scm_getc): Use it.
  (scm_peek_char): Use it instead of the `scm_getc'/`scm_ungetc'
  sequence.

* test-suite/tests/ports.test ("string ports")["peek-char [latin-1]",
  "peek-char [utf-8]"]: New tests.

* benchmark-suite/Makefile.am (SCM_BENCHMARKS): Add
  `benchmarks/ports.bm'.

* benchmark-suite/benchmarks/ports.bm: New file.

2 files changed, 68 insertions, 0 deletions

diff --git a/benchmark-suite/Makefile.am b/benchmark-suite/Makefile.am
index 9f49f2aad..e2aad9148 100644
--- a/benchmark-suite/Makefile.am
+++ b/benchmark-suite/Makefile.am
@@ -4,6 +4,7 @@ SCM_BENCHMARKS = benchmarks/0-reference.bm		\
 		 benchmarks/continuations.bm		\
                  benchmarks/if.bm			\
                  benchmarks/logand.bm			\
+		 benchmarks/ports.bm			\
 		 benchmarks/read.bm			\
 		 benchmarks/srfi-1.bm			\
 		 benchmarks/srfi-13.bm			\
diff --git a/benchmark-suite/benchmarks/ports.bm b/benchmark-suite/benchmarks/ports.bm
new file mode 100644
index 000000000..917a7ddbe
--- /dev/null
+++ b/benchmark-suite/benchmarks/ports.bm
@@ -0,0 +1,67 @@
+;;; ports.bm --- Port I/O.         -*- mode: scheme; coding: utf-8; -*-
+;;;
+;;; Copyright (C) 2010 Free Software Foundation, Inc.
+;;;
+;;; This program is free software; you can redistribute it and/or
+;;; modify it under the terms of the GNU Lesser General Public License
+;;; as published by the Free Software Foundation; either version 3, or
+;;; (at your option) any later version.
+;;;
+;;; This program is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU Lesser General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Lesser General Public
+;;; License along with this software; see the file COPYING.LESSER.  If
+;;; not, write to the Free Software Foundation, Inc., 51 Franklin
+;;; Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+(define-module (benchmarks ports)
+  #:use-module (benchmark-suite lib))
+
+(define %latin1-port
+  (with-fluids ((%default-port-encoding #f))
+    (open-input-string "hello, world")))
+
+(define %utf8/ascii-port
+  (with-fluids ((%default-port-encoding "UTF-8"))
+    (open-input-string "hello, world")))
+
+(define %utf8/wide-port
+  (with-fluids ((%default-port-encoding "UTF-8"))
+    (open-input-string "안녕하세요")))
+
+
+(with-benchmark-prefix "peek-char"
+
+  (benchmark "latin-1 port" 700000
+    (peek-char %latin1-port))
+
+  (benchmark "utf-8 port, ascii character" 700000
+    (peek-char %utf8/ascii-port))
+
+  (benchmark "utf-8 port, Korean character" 700000
+    (peek-char %utf8/wide-port)))
+
+(with-benchmark-prefix "read-char"
+
+  (benchmark "latin-1 port" 10000000
+    (read-char %latin1-port))
+
+  (benchmark "utf-8 port, ascii character" 10000000
+    (read-char %utf8/ascii-port))
+
+  (benchmark "utf-8 port, Korean character" 10000000
+    (read-char %utf8/wide-port)))
+
+(with-benchmark-prefix "char-ready?"
+
+  (benchmark "latin-1 port" 10000000
+    (char-ready? %latin1-port))
+
+  (benchmark "utf-8 port, ascii character" 10000000
+    (char-ready? %utf8/ascii-port))
+
+  (benchmark "utf-8 port, Korean character" 10000000
+    (char-ready? %utf8/wide-port)))