From 8759cc51f11ca1750cab66374026befafed71238 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 15 Feb 2024 08:35:35 -0500
Subject: image: jpeg: Use bytestruct for header data.

---
 chickadee/image/jpeg.scm | 45 +++++++++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/chickadee/image/jpeg.scm b/chickadee/image/jpeg.scm
index 98a7189..c19fa6c 100644
--- a/chickadee/image/jpeg.scm
+++ b/chickadee/image/jpeg.scm
@@ -21,6 +21,7 @@
 
 (define-module (chickadee image jpeg)
   #:use-module (chickadee config)
+  #:use-module (chickadee data bytestruct)
   #:use-module (ice-9 binary-ports)
   #:use-module (ice-9 exceptions)
   #:use-module (ice-9 format)
@@ -82,6 +83,14 @@
 ;;; High-level bindings
 ;;;
 
+(define-byterecord-type <header>
+  (make-header)
+  header?
+  (width int header-width)
+  (height int header-height)
+  (jpeg-subsamp int header-jpeg-subsamp)
+  (jpeg-colorspace int header-jpeg-colorspace))
+
 (define (display-tjhandle handle port)
   (display "#<tjhandle>" port))
 
@@ -103,19 +112,18 @@
   (tj-destroy (unwrap-tjhandle handle)))
 
 (define (decompress-headers handle buffer)
-  (let ((result (make-s32vector 4)))
-    (unless (zero? (tj-decompress-header3 (unwrap-tjhandle handle)
-                                          (bytevector->pointer buffer)
-                                          (bytevector-length buffer)
-                                          (bytevector->pointer result)
-                                          (bytevector->pointer result 4)
-                                          (bytevector->pointer result 8)
-                                          (bytevector->pointer result 12)))
+  (let ((header (bytestruct-alloc <header>)))
+    (unless (zero?
+             (tj-decompress-header3
+              (unwrap-tjhandle handle)
+              (bytevector->pointer buffer)
+              (bytevector-length buffer)
+              (bytestruct-&ref <header> (width) header)
+              (bytestruct-&ref <header> (height) header)
+              (bytestruct-&ref <header> (jpeg-subsamp) header)
+              (bytestruct-&ref <header> (jpeg-colorspace) header)))
       (check-error handle))
-    (values (s32vector-ref result 0)
-            (s32vector-ref result 1)
-            (s32vector-ref result 2)
-            (s32vector-ref result 3))))
+    header))
 
 (define (decompress handle buffer width pitch height pixel-format flags)
   (let ((bv (make-bytevector (* pitch height))))
@@ -134,12 +142,13 @@
         (dynamic-wind
           (lambda () #t)
           (lambda ()
-            (let-values (((width height subsamples color-space)
-                          (decompress-headers handle buffer)))
-              (let ((pitch (* width 4)))
-                (values (decompress handle buffer width pitch height
-                                    TJPF_RGBA 0) ; TJFLAG_BOTTOMUP
-                        width height))))
+            (let* ((header (decompress-headers handle buffer))
+                   (width (header-width header))
+                   (height (header-height header))
+                   (pitch (* width 4)))
+              (values (decompress handle buffer width pitch height
+                                  TJPF_RGBA 0) ; TJFLAG_BOTTOMUP
+                      width height)))
           (lambda ()
             (destroy-handle handle))))
       (raise-exception
-- 
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