From d0e6dc755604526646dd6ba3b53021bf1ffff54c Mon Sep 17 00:00:00 2001
From: Vasilij Schneidermann <mail@vasilij.de>
Date: Sun, 17 Mar 2024 19:47:30 +0100
Subject: [PATCH 1/4] Avoid needless allocation in read-bytevector!

This change switches the implementation strategy to basing
read-bytevector on top of read-bytevector! rather than the other way
around.
---
 lib/scheme/extras.scm | 33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index 98b4f3c3..b87ce396 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -136,15 +136,8 @@
       #u8()
       (let ((in (if (pair? o) (car o) (current-input-port)))
             (res (make-bytevector n)))
-        (let lp ((i 0))
-          (if (>= i n)
-              res
-              (let ((x (read-u8 in)))
-                (cond ((eof-object? x)
-                       (if (zero? i) x (subbytes res 0 i)))
-                      (else
-                       (bytevector-u8-set! res i x)
-                       (lp (+ i 1))))))))))
+        (read-bytevector! res in)
+        res)))
 
 (define (read-bytevector! vec . o)
   (let* ((in (if (pair? o) (car o) (current-input-port)))
@@ -152,19 +145,19 @@
          (start (if (pair? o) (car o) 0))
          (end (if (and (pair? o) (pair? (cdr o)))
                   (cadr o)
-                  (bytevector-length vec))))
+                  (bytevector-length vec)))
+         (n (- end start)))
     (if (>= start end)
         0
-        (let ((res (read-bytevector (- end start) in)))
-          (cond
-           ((eof-object? res)
-            res)
-           (else
-            (let ((len (bytevector-length res)))
-              (do ((i 0 (+ i 1)))
-                  ((>= i len) len)
-                (bytevector-u8-set! vec (+ i start) (bytevector-u8-ref res i))
-                ))))))))
+        (let lp ((i 0))
+          (if (>= i n)
+              i
+              (let ((x (read-u8 in)))
+                (cond ((eof-object? x)
+                       (if (zero? i) x i))
+                      (else
+                       (bytevector-u8-set! vec (+ i start) x)
+                       (lp (+ i 1))))))))))
 
 (define (write-bytevector vec . o)
   (let* ((out (if (pair? o) (car o) (current-output-port)))

From 1b1e8b311b87bbe7aadb0f7ab4f5f590a5558ba0 Mon Sep 17 00:00:00 2001
From: Vasilij Schneidermann <mail@vasilij.de>
Date: Mon, 18 Mar 2024 02:06:27 +0100
Subject: [PATCH 2/4] Correct read-bytevector logic for small reads

---
 lib/scheme/extras.scm | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index b87ce396..9796a0e1 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -135,9 +135,11 @@
   (if (zero? n)
       #u8()
       (let ((in (if (pair? o) (car o) (current-input-port)))
-            (res (make-bytevector n)))
-        (read-bytevector! res in)
-        res)))
+            (vec (make-bytevector n))
+            (res (read-bytevector! vec in)))
+        (cond ((eof-object? res) res)
+              ((< res n) (subbytes vec 0 i))
+              (else res)))))
 
 (define (read-bytevector! vec . o)
   (let* ((in (if (pair? o) (car o) (current-input-port)))

From c837c7110f670bc40a01dd0d31fe8de565bf1800 Mon Sep 17 00:00:00 2001
From: Vasilij Schneidermann <mail@vasilij.de>
Date: Mon, 18 Mar 2024 02:48:48 +0100
Subject: [PATCH 3/4] Correct let to let*

---
 lib/scheme/extras.scm | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index 9796a0e1..a9279464 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -134,9 +134,9 @@
 (define (read-bytevector n . o)
   (if (zero? n)
       #u8()
-      (let ((in (if (pair? o) (car o) (current-input-port)))
-            (vec (make-bytevector n))
-            (res (read-bytevector! vec in)))
+      (let* ((in (if (pair? o) (car o) (current-input-port)))
+             (vec (make-bytevector n))
+             (res (read-bytevector! vec in)))
         (cond ((eof-object? res) res)
               ((< res n) (subbytes vec 0 i))
               (else res)))))

From 0fd351e0b587ea80070f4affa4624d006b730c1c Mon Sep 17 00:00:00 2001
From: Vasilij Schneidermann <mail@vasilij.de>
Date: Mon, 18 Mar 2024 03:15:39 +0100
Subject: [PATCH 4/4] Fix read-bytevector logic

---
 lib/scheme/extras.scm | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index a9279464..304db168 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -138,8 +138,8 @@
              (vec (make-bytevector n))
              (res (read-bytevector! vec in)))
         (cond ((eof-object? res) res)
-              ((< res n) (subbytes vec 0 i))
-              (else res)))))
+              ((< res n) (subbytes vec 0 res))
+              (else vec)))))
 
 (define (read-bytevector! vec . o)
   (let* ((in (if (pair? o) (car o) (current-input-port)))