From c28a0f45dc285224c5b7a910c5c9df7b45b651f4 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 12 Feb 2019 09:50:02 -0700
Subject: [PATCH] io: (mostly) keep fast path when line counting is enabled

---
 racket/src/io/demo.rkt                    |  5 +++--
 racket/src/io/port/bytes-port.rkt         | 24 ++++++++---------------
 racket/src/io/port/peek-via-read-port.rkt | 17 ++++++++--------
 racket/src/io/port/pipe.rkt               |  4 ++--
 racket/src/io/port/port.rkt               |  3 ---
 racket/src/io/port/read-and-peek.rkt      |  4 ++++
 6 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/racket/src/io/demo.rkt b/racket/src/io/demo.rkt
index 797ea3a02b..e0678b6e11 100644
--- a/racket/src/io/demo.rkt
+++ b/racket/src/io/demo.rkt
@@ -779,6 +779,7 @@
        (loop (sub1 j))))))
 
 (define read-byte-buffer-mode 'block)
+(define count-lines? #t)
 
 'read-byte/host
 (time
@@ -787,7 +788,7 @@
      (let ()
        (define p (host:open-input-file "compiled/io.rktl"))
        (host:file-stream-buffer-mode p read-byte-buffer-mode)
-       (host:port-count-lines! p)
+       (when count-lines? (host:port-count-lines! p))
        (let loop ()
          (unless (eof-object? (host:read-byte p))
            (loop)))
@@ -801,7 +802,7 @@
      (let ()
        (define p (open-input-file "compiled/io.rktl"))
        (file-stream-buffer-mode p read-byte-buffer-mode)
-       (port-count-lines! p)
+       (when count-lines? (port-count-lines! p))
        (let loop ()
          (unless (eof-object? (read-byte p))
            (loop)))
diff --git a/racket/src/io/port/bytes-port.rkt b/racket/src/io/port/bytes-port.rkt
index 4f4068d1b4..332c74e030 100644
--- a/racket/src/io/port/bytes-port.rkt
+++ b/racket/src/io/port/bytes-port.rkt
@@ -73,14 +73,10 @@
          [(i . < . len)
           (define amt (min (- end start) (fx- len i)))
           (define new-pos (fx+ i amt))
-          (cond
-            [(not count)
-             ;; Keep/resume fast mode
-             (set! buffer-pos new-pos)
-             (set! offset 0)
-             (set! buffer bstr)]
-            [else
-             (set! pos new-pos)])
+          ;; Keep/resume fast mode
+          (set! buffer-pos new-pos)
+          (set! offset 0)
+          (set! buffer bstr)
           (bytes-copy! dest-bstr start bstr i new-pos)
           (progress!)
           amt]
@@ -128,14 +124,10 @@
           (let ([amt (min amt (- len i))])
             (define dest-bstr (make-bytes amt))
             (bytes-copy! dest-bstr 0 bstr i (+ i amt))
-            (cond
-              [(not count)
-               ;; Keep/resume fast mode
-               (set! buffer-pos (fx+ i amt))
-               (set! buffer bstr)
-               (set! offset 0)]
-              [else
-               (set! pos (fx+ i amt))])
+            ;; Keep/resume fast mode
+            (set! buffer-pos (fx+ i amt))
+            (set! buffer bstr)
+            (set! offset 0)
             (progress!)
             (finish dest-bstr)))))]
 
diff --git a/racket/src/io/port/peek-via-read-port.rkt b/racket/src/io/port/peek-via-read-port.rkt
index c7b9d73fd2..4ffa902513 100644
--- a/racket/src/io/port/peek-via-read-port.rkt
+++ b/racket/src/io/port/peek-via-read-port.rkt
@@ -87,15 +87,14 @@
 
     ;; in atomic mode
     [fast-mode!
-     (lambda (amt) ; amt = not yet added to `count`
-       (unless count
-         (set! buffer bstr)
-         (define s pos)
-         (set! buffer-pos s)
-         (set! buffer-end end-pos)
-         (define o offset)
-         (when o
-           (set! offset (- (+ o amt) s)))))]
+     (lambda (amt) ; amt = not yet added to `offset`
+       (set! buffer bstr)
+       (define s pos)
+       (set! buffer-pos s)
+       (set! buffer-end end-pos)
+       (define o offset)
+       (when o
+         (set! offset (- (+ o amt) s))))]
 
     ;; in atomic mode
     [slow-mode!
diff --git a/racket/src/io/port/pipe.rkt b/racket/src/io/port/pipe.rkt
index 5e3ef973ee..6c2111b307 100644
--- a/racket/src/io/port/pipe.rkt
+++ b/racket/src/io/port/pipe.rkt
@@ -127,8 +127,8 @@
 
   (private
     [fast-mode!
-     (lambda (amt) ; amt = not yet added to `count`
-       (unless (or count buffer)
+     (lambda (amt) ; amt = not yet added to `offset`
+       (unless buffer
          (with-object pipe-data d
            (define s start)
            (define e end)
diff --git a/racket/src/io/port/port.rkt b/racket/src/io/port/port.rkt
index 1a19f4e635..12161770a7 100644
--- a/racket/src/io/port/port.rkt
+++ b/racket/src/io/port/port.rkt
@@ -29,9 +29,6 @@
    ;;
    ;; A non-#f `buffer` further implies that `buffer-pos` should be
    ;; added to `offset` to get the true offset.
-   ;;
-   ;; Shortcut mode must be disabled when line counting is enabled,
-   ;; since shortcut mode skips explicit count.
    [buffer #f]
    [buffer-pos 0]   ; if < `buffer-end`, allows direct read/write on `buffer`
    [buffer-end 0]
diff --git a/racket/src/io/port/read-and-peek.rkt b/racket/src/io/port/read-and-peek.rkt
index aeccf20290..4da9075bb2 100644
--- a/racket/src/io/port/read-and-peek.rkt
+++ b/racket/src/io/port/read-and-peek.rkt
@@ -67,6 +67,8 @@
           (define new-pos (fx+ buf-pos v))
           (bytes-copy! bstr start (core-port-buffer in) buf-pos new-pos)
           (set-core-port-buffer-pos! in new-pos)
+          (when (core-port-count in)
+            (port-count! in v bstr start))
           (end-atomic)
           v]
          [else
@@ -208,6 +210,8 @@
     [(pos . fx< . (core-port-buffer-end in))
      (define b (bytes-ref (core-port-buffer in) pos))
      (set-core-port-buffer-pos! in (fx+ pos 1))
+     (when (core-port-count in)
+       (port-count-byte! in b))
      (end-atomic)
      b]
     [else