varintsize.diff

iff --git a/src/6model/serialization.c b/src/6model/serialization.c
index ce3157e..9d1aec9 100644
--- a/src/6model/serialization.c
+++ b/src/6model/serialization.c
@@ -201,10 +201,25 @@ static void write_double(char *buffer, size_t offset, double value) {
 /* Writes an int64 into up to 128 bits of storage.
  * Returns how far to advance the offset. */
 static size_t varintsize(int64_t value) {
-    int8_t sign_nudge = value < 0 ? 0: 1;
-    size_t varlog = ceil(log(abs(value) + sign_nudge) / log(2));
-    size_t needed_bytes = floor((varlog) / 7) + 1;
-    return needed_bytes;
+    if(value < 0)
+        value = abs(value++);
+    if(value < 64) /* 7 bits */
+        return 1;
+    if(value < 8192) /* 14 bits */
+        return 2;
+    if(value < 1048576) /* 21 bits */
+        return 3;
+    if(value < 134217728) /* 28 bits */
+        return 4;
+    if(value < 17179869184) /* 35 bits */
+        return 5;
+    if(value < 2199023255552) /* 42 bits */
+        return 6;
+    if(value < 281474976710656) /* 49 bits */
+        return 7;
+    if(value < 36028797018963968) /* 56 bits */
+        return 8;
+    return 9;
 }
 
 static size_t write_varint9(MVMuint8 *buffer, size_t offset, int64_t value) {