initial commit of wasm worker for sla rendering

wasm/kiri-sla.c

@@ -0,0 +1,112 @@
+#include <emscripten.h>
+#include <string.h>
+
+typedef unsigned char Uint8;
+typedef unsigned short Uint16;
+typedef unsigned int Uint32;
+
+struct info {
+    Uint16 width;  // image width
+    Uint16 height; // image height
+    Uint16 polys;  // total number of polygons to render
+};
+
+struct poly {
+    Uint16 length; // offset to end of record in bytes
+    Uint16 inners; // number of inner polygons
+    Uint16 points; // number of points in polygon
+};
+
+struct point {
+    float x;
+    float y;
+};
+
+extern void last(float a, float b);
+extern void report(int a, int b);
+
+Uint32 readoff; // read position offset
+
+Uint8 check_cross(Uint32 x, Uint32 y, struct point *p1, struct point *p2) {
+    return (
+        ((p1->y >= y) != (p2->y >= y)) &&
+        (x < (p2->x - p1->x) * (y - p1->y) / (p2->y - p1->y) + p1->x)
+    ) ? 1 : 0;
+}
+
+Uint8 check_inside(Uint32 x, Uint32 y, unsigned char *p) {
+    struct poly *poly = (struct poly *)(p + readoff);
+
+    Uint32 nextpoly = readoff + poly->length;
+    Uint8 side = 0; // 0=outside, 1=inside
+    Uint8 psize = sizeof(struct point);
+
+    // skip post header
+    readoff += sizeof(struct poly);
+
+    // save pointer to first point or last comparison
+    struct point *pf = (struct point *)(p + readoff);
+    struct point *p1 = pf;
+    struct point *p2;
+
+    // skip past first point
+    readoff += psize;
+
+    // read and check point pairs updating `side`
+    for (Uint16 i=1; i<poly->points; i++) {
+        p2 = (struct point *)(p + readoff);
+        // increment read pointe
+        readoff += psize;
+        // check current/previous point crossing
+        if (check_cross(x, y, p1, p2)) {
+            side = 1 - side;
+        }
+        p1 = p2;
+    }
+
+    // check last/first point crossing
+    if (check_cross(x, y, p1, pf)) {
+        side = 1 - side;
+    }
+
+    // check inner polygons only if inside the outer polygon
+    if (side)
+    for (Uint16 i=0; i<poly->inners; i++) {
+        // if inside an inner, then actually outside poly and term
+        if (check_inside(x, y, p + readoff)) {
+            side = 0;
+            break;
+        }
+    }
+
+    // update pointer to next polygon
+    readoff = nextpoly;
+
+    return side;
+}
+
+EMSCRIPTEN_KEEPALIVE
+Uint32 render(unsigned char *m, Uint32 i, Uint32 o) {
+    struct info *info = (struct info *)(m + i);
+    Uint32 impos;
+    Uint8 inside;
+    Uint32 maxpos = 0;
+    Uint32 polypos = (sizeof (struct info)) + i;
+
+    memset(m+o, 0, info->width * info->height);
+
+    for (Uint32 x=0; x<info->width; x++) {
+        for (Uint32 y=0; y<info->height; y++) {
+            inside = 0;
+            impos = y + (x * info->height);
+            readoff = polypos;
+            for (Uint32 p=0; p<info->polys; p++) {
+                inside = inside | check_inside(x, y, m);
+            }
+            if (inside) (m + o)[impos] = 255;
+            if (impos > maxpos) maxpos = impos;
+        }
+    }
+
+    return maxpos;
+}

wasm/makefile

@@ -0,0 +1,5 @@
+kiri-sla.wasm: kiri-sla.c
+	emcc kiri-sla.c -o kiri-sla.wasm -O3 -s ERROR_ON_UNDEFINED_SYMBOLS=0
+
+clean: *.wasm
+	rm *.wasm