add bresenham line algo, lfutility and Point struct

src/lfinput.c

@@ -71,8 +71,10 @@ int *get_ints(const char *path, size_t *sz) {
         const char *errstr;
         n = (int) strtonum(lines[idx], INT_MIN, INT_MAX, &errstr);
         if (errstr) {
-            printf("Failed to convert %s to int. Returning NULL\n", lines[idx]);
-            exit(1);
+            fprintf(stderr, "Failed to convert %s to int. Returning NULL\n", lines[idx]);
+            free(i);
+            del_lines(lines);
+            return NULL;
         }
         i[idx] = n;
     }

src/lfmath.c

@@ -1,4 +1,5 @@
 #include <string.h>
+#include <stdlib.h>
 
 #include "lfmath.h"
 
@@ -35,3 +36,40 @@ int binstr_to_int(const char *s) {
     }
     return n;
 }
+
+Point *bresenham(int x0, int y0, int x1, int y1, size_t *sz) {
+    Point *line = NULL;
+    size_t n = 0;
+    *sz = 0;
+
+    int dx = abs(x1 - x0), sx = x0 < x1 ? 1 : -1;
+    int dy = abs(y1 - y0), sy = y0 < y1 ? 1 : -1;
+    int err = (dx > dy ? dx : -dy) / 2, e2;
+
+    for (;;) {
+        line = realloc(line, sizeof(Point) * ++n);
+        ++*sz;
+        line[n - 1].x = x0;
+        line[n - 1].y = y0;
+
+        if (x0 == x1 && y0 == y1) {
+            break;
+        }
+
+        e2 = err;
+        if (e2 > -dx) {
+            err -= dy;
+            x0 += sx;
+        }
+        if (e2 < dy) {
+            err += dx;
+            y0 += sy;
+        }
+    }
+
+    return line;
+}
+
+Point *bresenham_p(Point p1, Point p2, size_t *sz) {
+    return bresenham(p1.x, p1.y, p2.x, p2.y, sz);
+}