X-Git-Url: https://git.stg.codes/stg.git/blobdiff_plain/b27841d687ec9e84983340b5581376dfb24010ea..b2b89723a2427bba8290bd6967a1ab39cbb630be:/libs/smux/asn_random_fill.c

diff --git a/libs/smux/asn_random_fill.c b/libs/smux/asn_random_fill.c
new file mode 100644
index 00000000..819cf700
--- /dev/null
+++ b/libs/smux/asn_random_fill.c
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2017 Lev Walkin <vlm@lionet.info>.
+ * All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#include <asn_internal.h>
+#include <asn_random_fill.h>
+#include <constr_TYPE.h>
+
+int
+asn_random_fill(const struct asn_TYPE_descriptor_s *td, void **struct_ptr,
+                size_t length) {
+
+    if(td && td->op->random_fill) {
+        asn_random_fill_result_t res =
+            td->op->random_fill(td, struct_ptr, 0, length);
+        return (res.code == ARFILL_OK) ? 0 : -1;
+    } else {
+        return -1;
+    }
+}
+
+static uintmax_t
+asn__intmax_range(intmax_t lb, intmax_t ub) {
+    assert(lb <= ub);
+    if((ub < 0) == (lb < 0)) {
+        return ub - lb;
+    } else if(lb < 0) {
+        return 1 + ((uintmax_t)ub + (uintmax_t)-(lb + 1));
+    } else {
+        assert(!"Unreachable");
+        return 0;
+    }
+}
+
+intmax_t
+asn_random_between(intmax_t lb, intmax_t rb) {
+    if(lb == rb) {
+        return lb;
+    } else {
+        const uintmax_t intmax_max = ((~(uintmax_t)0) >> 1);
+        uintmax_t range = asn__intmax_range(lb, rb);
+        uintmax_t value = 0;
+        uintmax_t got_entropy = 0;
+
+        assert(RAND_MAX > 0xffffff);    /* Seen 7ffffffd! */
+        assert(range < intmax_max);
+
+        for(; got_entropy < range;) {
+            got_entropy = (got_entropy << 24) | 0xffffff;
+            value = (value << 24) | (random() % 0xffffff);
+        }
+
+        return lb + (intmax_t)(value % (range + 1));
+    }
+}