initial raytracing experiment

[dosdemo] / src / darray.c

diff --git a/src/darray.c b/src/darray.c
new file mode 100644 (file)
index 0000000..66c0715
--- /dev/null
+++ b/src/darray.c
@@ -0,0 +1,122 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "darray.h"
+#include "util.h"
+
+
+/* The array descriptor keeps auxilliary information needed to manipulate
+ * the dynamic array. It's allocated adjacent to the array buffer.
+ */
+struct arrdesc {
+       int nelem, szelem;
+       int max_elem;
+       int bufsz;      /* not including the descriptor */
+};
+
+#define DESC(x)                ((struct arrdesc*)((char*)(x) - sizeof(struct arrdesc)))
+
+void *darr_alloc(int elem, int szelem)
+{
+       struct arrdesc *desc;
+
+       desc = malloc_nf(elem * szelem + sizeof *desc);
+       desc->nelem = desc->max_elem = elem;
+       desc->szelem = szelem;
+       desc->bufsz = elem * szelem;
+       return (char*)desc + sizeof *desc;
+}
+
+void darr_free(void *da)
+{
+       if(da) {
+               free(DESC(da));
+       }
+}
+
+void *darr_resize_impl(void *da, int elem)
+{
+       int newsz;
+       struct arrdesc *desc;
+
+       if(!da) return 0;
+       desc = DESC(da);
+
+       newsz = desc->szelem * elem;
+       desc = realloc_nf(desc, newsz + sizeof *desc);
+
+       desc->nelem = desc->max_elem = elem;
+       desc->bufsz = newsz;
+       return (char*)desc + sizeof *desc;
+}
+
+int darr_empty(void *da)
+{
+       return DESC(da)->nelem ? 0 : 1;
+}
+
+int darr_size(void *da)
+{
+       return DESC(da)->nelem;
+}
+
+
+void *darr_clear_impl(void *da)
+{
+       return darr_resize_impl(da, 0);
+}
+
+/* stack semantics */
+void *darr_push_impl(void *da, void *item)
+{
+       struct arrdesc *desc;
+       int nelem;
+
+       desc = DESC(da);
+       nelem = desc->nelem;
+
+       if(nelem >= desc->max_elem) {
+               /* need to resize */
+               int newsz = desc->max_elem ? desc->max_elem * 2 : 1;
+
+               da = darr_resize_impl(da, newsz);
+               desc = DESC(da);
+               desc->nelem = nelem;
+       }
+
+       if(item) {
+               memcpy((char*)da + desc->nelem * desc->szelem, item, desc->szelem);
+       }
+       desc->nelem++;
+       return da;
+}
+
+void *darr_pop_impl(void *da)
+{
+       struct arrdesc *desc;
+       int nelem;
+
+       desc = DESC(da);
+       nelem = desc->nelem;
+
+       if(!nelem) return da;
+
+       if(nelem <= desc->max_elem / 3) {
+               /* reclaim space */
+               int newsz = desc->max_elem / 2;
+
+               da = darr_resize_impl(da, newsz);
+               desc = DESC(da);
+               desc->nelem = nelem;
+       }
+       desc->nelem--;
+
+       return da;
+}
+
+void *darr_finalize(void *da)
+{
+       struct arrdesc *desc = DESC(da);
+       memmove(desc, da, desc->bufsz);
+       return desc;
+}