special treatment for the last byte

we need that to reach full 64 bits, otherwise
we are short exactly one bit.

and in the 9th bit we already know we're going
to stop reading anyway.

src/6model/serialization.c

@@ -212,11 +212,14 @@ static size_t write_varint128(char *buffer, size_t offset, int64_t value) {
     size_t position;
     size_t needed_bytes = varintsize(value);
 
-    for (position = 0; position < needed_bytes; position++) {
+    for (position = 0; position < needed_bytes && position != 8; position++) {
         buffer[offset + position] = value & 0x7f;
         if (position != needed_bytes - 1) buffer[offset + position] = buffer[offset + position] | 0x80;
         value = value >> 7;
     }
+    if (position == 8) {
+        buffer[offset + position] = value;
+    }
     return needed_bytes;
 }
 
@@ -1197,7 +1200,7 @@ static size_t read_varint128(char *buffer, size_t offset, int64_t *value) {
     int64_t negation_mask = 0;
     *value = 0;
     int read_on = !!(buffer[offset] & 0x80) + 1;
-    while (read_on) {
+    while (read_on && inner_offset != 8) {
         *value = *value | ((buffer[offset + inner_offset] & 0x7f) << shift_amount);
         negation_mask = negation_mask | (0b1111111 << shift_amount);
         if (read_on == 1 && buffer[offset + inner_offset] & 0x80) {
@@ -1207,6 +1210,12 @@ static size_t read_varint128(char *buffer, size_t offset, int64_t *value) {
         inner_offset++;
         shift_amount += 7;
     }
+    // our last byte will be a full byte, so that we reach the full 64 bits
+    if (inner_offset == 8) {
+        shift_amount += 1;
+        *value = *value | (buffer[offset + inner_offset] << shift_amount);
+        negation_mask = negation_mask | (0b11111111 << shift_amount);
+    }
     negation_mask = negation_mask >> 1;
     // do we have a negative number so far?
     if (*value & ~negation_mask) {