[hackers] [blind] Improve performance of blind-transpose || Mattias Andrée

[git]

commit 94de8e2bd18743949bbb82d9e8cac109da4a15f3
Author:     Mattias Andrée <maand...@kth.se>
AuthorDate: Mon May 8 20:25:47 2017 +0200
Commit:     Mattias Andrée <maand...@kth.se>
CommitDate: Mon May 8 20:25:47 2017 +0200

    Improve performance of blind-transpose
    
    Signed-off-by: Mattias Andrée <maand...@kth.se>

diff --git a/src/blind-transpose.c b/src/blind-transpose.c
index d1b4e47..c2d2d11 100644
--- a/src/blind-transpose.c
+++ b/src/blind-transpose.c
@@ -13,31 +13,36 @@ int
 main(int argc, char *argv[])
 {
        struct stream stream;
-       char *buf, *image;
-       size_t n, imgw, srcw, srch, ps, x, y, i, b, dx;
+       char *buf, *row, *pix, *image, *imag, *img;
+       size_t n, srcw, srch, srcwps, srchps, ps, x, y, i;
 
        UNOFLAGS(argc);
 
        eopen_stream(&stream, NULL);
-       imgw = srch = stream.height;
+       srch = stream.height;
        stream.height = srcw = stream.width;
-       stream.width = imgw;
+       stream.width = srch;
        fprint_stream_head(stdout, &stream);
        efflush(stdout, "<stdout>");
 
        echeck_frame_size(stream.width, stream.height, stream.pixel_size, 0, 
stream.file);
-       n = stream.width * stream.height * (ps = stream.pixel_size);
+       n = stream.height * stream.width * (ps = stream.pixel_size);
        buf   = emalloc(n);
-       image = emalloc(n); /* TODO optimise to a frame row */
+       image = emalloc(n);
 
-       srch *= ps;
-       srcw *= dx = imgw * ps;
-       imgw *= ps;
+       srchps = srch * ps;
+       srcwps = srcw * ps;
        while (eread_frame(&stream, buf, n)) {
-               for (b = y = 0; y < srch; y += ps)
-                       for (x = 0; x < srcw; x += dx)
-                               for (i = 0; i < ps; i++, b++)
-                                       image[y + x + i] = buf[b];
+               for (y = 0; y < srchps; y += ps) {
+                       imag = image + y;
+                       row  = buf + y * srcw;
+                       for (x = 0; x < srcwps; x += ps) {
+                               img = imag + x * srch;
+                               pix = row + x;
+                               for (i = 0; i < ps; i++)
+                                       img[i] = pix[i];
+                       }
+               }
                ewriteall(STDOUT_FILENO, image, n, "<stdout>");
        }