Function DecodeUnsignedLeb128

Bcore/src/main/cpp/base/leb128.h:33–56

Reads an unsigned LEB128 value, updating the given pointer to point just past the end of the read value. This function tolerates non-zero high-order bits in the fifth encoded byte.

// just past the end of the read value. This function tolerates
// non-zero high-order bits in the fifth encoded byte.
static inline uint32_t DecodeUnsignedLeb128(const uint8_t** data) {
  const uint8_t* ptr = *data;
  int result = *(ptr++);
  if (UNLIKELY(result > 0x7f)) {
    int cur = *(ptr++);
    result = (result & 0x7f) | ((cur & 0x7f) << 7);
    if (cur > 0x7f) {
      cur = *(ptr++);
      result |= (cur & 0x7f) << 14;
      if (cur > 0x7f) {
        cur = *(ptr++);
        result |= (cur & 0x7f) << 21;
        if (cur > 0x7f) {
          // Note: We don't check to see if cur is out of range here,
          // meaning we tolerate garbage in the four high-order bits.
          cur = *(ptr++);
          result |= cur << 28;
        }
      }
    }
  }
  *data = ptr;
  return static_cast<uint32_t>(result);
}

static inline uint32_t DecodeUnsignedLeb128WithoutMovingCursor(const uint8_t* data) {
  return DecodeUnsignedLeb128(&data);