1 files changed, 54 insertions, 0 deletions
diff --git a/upb/pb/varint.c b/upb/pb/varint.c
new file mode 100644
index 0000000..45caec1
--- /dev/null
+++ b/upb/pb/varint.c
@@ -0,0 +1,54 @@
+/*
+ * upb - a minimalist implementation of protocol buffers.
+ *
+ * Copyright (c) 2011 Google Inc.  See LICENSE for details.
+ * Author: Josh Haberman <jhaberman@gmail.com>
+ */
+
+#include "upb/pb/varint.h"
+
+// Given an encoded varint v, returns an integer with a single bit set that
+// indicates the end of the varint.  Subtracting one from this value will
+// yield a mask that leaves only bits that are part of the varint.  Returns
+// 0 if the varint is unterminated.
+INLINE uint64_t upb_get_vstopbit(uint64_t v) {
+  uint64_t cbits = v | 0x7f7f7f7f7f7f7f7fULL;
+  return ~cbits & (cbits+1);
+}
+INLINE uint64_t upb_get_vmask(uint64_t v) { return upb_get_vstopbit(v) - 1; }
+
+upb_decoderet upb_vdecode_max8_massimino(upb_decoderet r) {
+  uint64_t b;
+  memcpy(&b, r.p, sizeof(b));
+  uint64_t stop_bit = upb_get_vstopbit(b);
+  b =  (b & 0x7f7f7f7f7f7f7f7fULL) & (stop_bit - 1);
+  b +=       b & 0x007f007f007f007fULL;
+  b +=  3 * (b & 0x0000ffff0000ffffULL);
+  b += 15 * (b & 0x00000000ffffffffULL);
+  if (stop_bit == 0) {
+    // Error: unterminated varint.
+    upb_decoderet err_r = {(void*)0, 0};
+    return err_r;
+  }
+  upb_decoderet my_r = {r.p + ((__builtin_ctzll(stop_bit) + 1) / 8),
+                        r.val | (b << 7)};
+  return my_r;
+}
+
+upb_decoderet upb_vdecode_max8_wright(upb_decoderet r) {
+  uint64_t b;
+  memcpy(&b, r.p, sizeof(b));
+  uint64_t stop_bit = upb_get_vstopbit(b);
+  b &= (stop_bit - 1);
+  b = ((b & 0x7f007f007f007f00) >> 1) | (b & 0x007f007f007f007f);
+  b = ((b & 0xffff0000ffff0000) >> 2) | (b & 0x0000ffff0000ffff);
+  b = ((b & 0xffffffff00000000) >> 4) | (b & 0x00000000ffffffff);
+  if (stop_bit == 0) {
+    // Error: unterminated varint.
+    upb_decoderet err_r = {(void*)0, 0};
+    return err_r;
+  }
+  upb_decoderet my_r = {r.p + ((__builtin_ctzll(stop_bit) + 1) / 8),
+                        r.val | (b << 14)};
+  return my_r;
+}