1 files changed, 54 insertions, 0 deletions
diff --git a/src/librandom/surf.c b/src/librandom/surf.c
new file mode 100644
index 0000000..1687df9
--- /dev/null
+++ b/src/librandom/surf.c
@@ -0,0 +1,54 @@
+/* ISC license. */
+
+#include <skalibs/uint32.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/surf.h>
+
+#define ROTATE(x, b) (((x) << (b)) | ((x) >> (32 - (b))))
+#define MUSH(i, b) x = t[i] += (((x ^ ctx->seed[i]) + sum) ^ ROTATE(x, b))
+
+static void surfit (SURFSchedule_ref ctx)
+{
+  uint32 t[12] ;
+  uint32 z[8] ;
+  uint32 x ;
+  uint32 sum = 0 ;
+  unsigned int i = 0, loop = 0 ; ;
+
+  if (!++ctx->in[0] && !++ctx->in[1] && !++ctx->in[2]) ++ctx->in[3] ;
+  for (; i < 12 ; i++) t[i] = ctx->in[i] ^ ctx->seed[12+i] ;
+  for (i = 0 ; i < 8 ; i++) z[i] = ctx->seed[24+i] ;
+  x = t[11] ;
+  for (; loop < 2 ; loop++)
+  {
+    for (i = 0 ; i < 16 ; i++)
+    {
+      sum += 0x9e3779b9 ;
+      MUSH(0, 5) ; MUSH(1, 7) ; MUSH(2, 9) ;  MUSH(3, 13) ;
+      MUSH(4, 5) ; MUSH(5, 7) ; MUSH(6, 9) ;  MUSH(7, 13) ;
+      MUSH(8, 5) ; MUSH(9, 7) ; MUSH(10, 9) ; MUSH(11, 13) ;
+    }
+    for (i = 0 ; i < 8 ; i++) z[i] ^= t[i+4] ;
+  }
+  for (i = 0 ; i < 8 ; i++) uint32_pack(ctx->out + (i<<2), z[i]) ;
+}
+
+void surf (SURFSchedule_ref ctx, char *s, unsigned int n)
+{
+  {
+    register unsigned int i = 32 - ctx->pos ;
+    if (n < i) i = n ;
+    byte_copy(s, i, ctx->out + ctx->pos) ;
+    s += i ; n -= i ; ctx->pos += i ;
+  }
+  while (n > 32)
+  {
+    surfit(ctx) ;
+    byte_copy(s, 32, ctx->out) ;
+    s += 32 ; n -= 32 ;
+  }
+  if (!n) return ;
+  surfit(ctx) ;
+  byte_copy(s, n, ctx->out) ;
+  ctx->pos = n ;
+}