From 7fef3c0d7cdad433fbf614ad4b5c30b7f99814c8 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Wed, 22 Apr 2020 06:42:32 -0700
Subject: parser: batched read operation for speed.

As a result of this change, the startup time is reduced.
The command txr -e '(compile-toplevel nil)' shows a 54%
speedup: around 110 milliseconds down from around 170.

Programs that read large amounts of TXR Lisp data will
benefit.

* parser.l (YY_INPUT): Use new get_bytes function instead of
get_byte to read a buffer at a time.

* stream.c (get_bytes): New function.

* stream.h (get_bytes): Declared.
---
 parser.l | 12 +++++-------
 stream.c |  8 ++++++++
 stream.h |  1 +
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/parser.l b/parser.l
index 87215221..52f30f2f 100644
--- a/parser.l
+++ b/parser.l
@@ -52,13 +52,11 @@
 #include "parser.h"
 #include "txr.h"
 
-#define YY_INPUT(buf, result, max_size)           \
-  do {                                            \
-    val c = get_byte(yyextra->stream);            \
-    int n = 0;                                    \
-    if (c)                                        \
-      buf[n++] = convert(char, c_num(c));         \
-    result = n;                                   \
+#define YY_INPUT(buf, result, max_size)                                 \
+  do {                                                                  \
+    val n = get_bytes(lit("parser"), yyextra->stream,                   \
+                      convert(mem_t *,  buf), max_size);                \
+    result = c_num(n);                                                  \
   } while (0)
 
 #define YY_DECL \
diff --git a/stream.c b/stream.c
index 7120fd78..d264da16 100644
--- a/stream.c
+++ b/stream.c
@@ -2972,6 +2972,14 @@ val get_byte(val stream_in)
   return ops->get_byte(stream);
 }
 
+val get_bytes(val self, val stream_in, mem_t *ptr, ucnum len)
+{
+  val stream = default_arg(stream_in, std_input);
+  struct strm_ops *ops = coerce(struct strm_ops *,
+                                cobj_ops(self, stream, stream_s));
+  return unum(ops->fill_buf(stream, ptr, len, 0));
+}
+
 val unget_char(val ch, val stream_in)
 {
   val self = lit("unget-char");
diff --git a/stream.h b/stream.h
index ba905871..197be303 100644
--- a/stream.h
+++ b/stream.h
@@ -194,6 +194,7 @@ val clear_error(val stream);
 val get_line(val);
 val get_char(val);
 val get_byte(val);
+val get_bytes(val self, val, mem_t *ptr, ucnum len);
 val unget_char(val ch, val stream);
 val unget_byte(val byte, val stream);
 val put_buf(val buf, val pos, val stream);
-- 
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