1 files changed, 39 insertions, 0 deletions
diff --git a/lib/bob/u8strgrow.c b/lib/bob/u8strgrow.c
new file mode 100644
index 0000000..f1f86d3
--- /dev/null
+++ b/lib/bob/u8strgrow.c
@@ -0,0 +1,39 @@
+#include <stdlib.h>
+
+#include "bob.h"
+
+static size_t nextpow2(size_t);
+
+struct u8str *
+u8strgrow(struct u8str *b, size_t n)
+{
+	if (n > b->cap) {
+		b->cap = nextpow2(n);
+		if (!(b->p = realloc(b->p, b->cap)))
+			return nullptr;
+	}
+	return b;
+}
+
+size_t
+nextpow2(size_t x)
+{
+#if defined(__has_builtin) && __has_builtin(__builtin_clzl)
+	x = x <= 1 ? 1 : 1 << (64 - __builtin_clzl(x - 1));
+#else
+	if (x) {
+		x--;
+		x |= x >> 1;
+		x |= x >> 2;
+		x |= x >> 4;
+		x |= x >> 8;
+		if (sizeof(size_t) >= 4)
+			x |= x >> 16;
+		if (sizeof(size_t) >= 8)
+			x |= x >> 32;
+	}
+	x++;
+#endif
+
+	return x;
+}