feat(examples): add the C++ benchmark and three test targets

A C++ consumer of the C archives, plus maths, scene and image tests driven by
meowc test.

examples/raytracer/tests/image_test.c

@@ -0,0 +1,91 @@
+#include "rt_config.h"
+#include "rt_image.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static int failures = 0;
+
+static void check(const char *what, int cond) {
+    if (!cond) {
+        fprintf(stderr, "  %s: failed\n", what);
+        failures++;
+    }
+}
+
+static long read_all(const char *path, unsigned char **out) {
+    FILE *f = fopen(path, "rb");
+    if (!f) return -1;
+    fseek(f, 0, SEEK_END);
+    long n = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    unsigned char *buf = malloc((size_t)n);
+    if (!buf || fread(buf, 1u, (size_t)n, f) != (size_t)n) {
+        free(buf);
+        fclose(f);
+        return -1;
+    }
+    fclose(f);
+    *out = buf;
+    return n;
+}
+
+static unsigned long be32(const unsigned char *p) {
+    return ((unsigned long)p[0] << 24) | ((unsigned long)p[1] << 16) | ((unsigned long)p[2] << 8) | p[3];
+}
+
+int main(void) {
+    image *im = image_new(17, 11);
+    check("the image allocates", im != NULL);
+    if (!im) return 1;
+
+    check("width is kept", im->width == 17);
+    check("the buffer starts black", im->rgb[0] == 0 && im->rgb[17 * 11 * 3 - 1] == 0);
+
+    for (int y = 0; y < im->height; y++)
+        for (int x = 0; x < im->width; x++) {
+            unsigned char *px = im->rgb + ((size_t)y * 17 + (size_t)x) * 3;
+            px[0] = (unsigned char)(x * 15);
+            px[1] = (unsigned char)(y * 23);
+            px[2] = 128;
+        }
+
+    check("a zero sized image is refused", image_new(0, 4) == NULL);
+
+    const char *ppm = "test-out.ppm";
+    check("ppm writes", image_write_ppm(im, ppm) == 0);
+    unsigned char *buf = NULL;
+    long n = read_all(ppm, &buf);
+    check("ppm has a header and every pixel", n == (long)(strlen("P6\n17 11\n255\n") + 17 * 11 * 3));
+    check("ppm starts with the magic", n > 2 && buf[0] == 'P' && buf[1] == '6');
+    free(buf);
+    remove(ppm);
+
+#ifdef HAVE_ZLIB
+    const char *png = "test-out.png";
+    check("png writes", image_write_png(im, png) == 0);
+    n = read_all(png, &buf);
+    check("png is not empty", n > 8);
+    if (n > 8) {
+        static const unsigned char sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
+        check("png signature", memcmp(buf, sig, 8) == 0);
+        check("first chunk is IHDR", memcmp(buf + 12, "IHDR", 4) == 0);
+        check("IHDR carries the width", be32(buf + 16) == 17);
+        check("IHDR carries the height", be32(buf + 20) == 11);
+        check("eight bits per channel", buf[24] == 8);
+        check("truecolour", buf[25] == 2);
+        check("last chunk is IEND", memcmp(buf + n - 8, "IEND", 4) == 0);
+    }
+    free(buf);
+    remove(png);
+    check("the default extension follows zlib", strcmp(image_default_extension(), "png") == 0);
+#else
+    check("without zlib the default is ppm", strcmp(image_default_extension(), "ppm") == 0);
+#endif
+
+    image_free(im);
+    image_free(NULL); /* must tolerate a null pointer */
+
+    if (failures == 0) printf("  image: every assertion held\n");
+    return failures == 0 ? 0 : 1;
+}