vendor/snap/src/varint.rs

   1 /// https://developers.google.com/protocol-buffers/docs/encoding#varints
   2 pub fn write_varu64(data: &mut [u8], mut n: u64) -> usize {
   3     let mut i = 0;
   4     while n >= 0b1000_0000 {
   5         data[i] = (n as u8) | 0b1000_0000;
   6         n >>= 7;
   7         i += 1;
   8     }
   9     data[i] = n as u8;
  10     i + 1
  11 }
  12
  13 /// https://developers.google.com/protocol-buffers/docs/encoding#varints
  14 pub fn read_varu64(data: &[u8]) -> (u64, usize) {
  15     let mut n: u64 = 0;
  16     let mut shift: u32 = 0;
  17     for (i, &b) in data.iter().enumerate() {
  18         if b < 0b1000_0000 {
  19             return match (b as u64).checked_shl(shift) {
  20                 None => (0, 0),
  21                 Some(b) => (n | b, i + 1),
  22             };
  23         }
  24         match ((b as u64) & 0b0111_1111).checked_shl(shift) {
  25             None => return (0, 0),
  26             Some(b) => n |= b,
  27         }
  28         shift += 7;
  29     }
  30     (0, 0)
  31 }