Initial scaffoldingjd/mix-pool-bytes-comparison

1 files changed, 30 insertions, 0 deletions

diff --git a/widelfsr.c b/widelfsr.c
new file mode 100644
index 0000000..088ec7e
--- /dev/null
+++ b/widelfsr.c
@@ -0,0 +1,30 @@
+#include <linux/kernel.h>
+
+enum poolinfo {
+	POOL_WORDS = 128,
+	POOL_WORDMASK = POOL_WORDS - 1,
+	POOL_BITS = POOL_WORDS * sizeof(u32) * 8,
+};
+
+static u32 input_pool_data[POOL_WORDS];
+
+static struct {
+	u16 add_ptr;
+} input_pool = { 0 };
+
+void mix_widelfsr(const void *in, int nbytes)
+{
+	unsigned long i = input_pool.add_ptr;
+	const u8 *src = in;
+
+	/* Mix one byte at a time to simplify size handling and churn faster. */
+	while (nbytes--) {
+		input_pool_data[(i+0)&127] = rol32(input_pool_data[(i+0)&127], 4) ^
+					     (input_pool_data[(i+126)&127] << 7) ^
+					     rol32(input_pool_data[(i+127)&127],12) ^
+					     rol32(input_pool_data[(i+127)&127],21) ^
+					     *src++;
+		i = (i+1)&127;
+	}
+	input_pool.add_ptr = i;
+}