ParagonIE_Sodium_Core32_Poly1305_State::update

    public function update($message = '')
    {
        $bytes = self::strlen($message);

        /* handle leftover */
        if ($this->leftover) {
            /** @var int $want */
            $want = ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE - $this->leftover;
            if ($want > $bytes) {
                $want = $bytes;
            }
            for ($i = 0; $i < $want; ++$i) {
                $mi = self::chrToInt($message[$i]);
                $this->buffer[$this->leftover + $i] = $mi;
            }
            // We snip off the leftmost bytes.
            $message = self::substr($message, $want);
            $bytes = self::strlen($message);
            $this->leftover += $want;
            if ($this->leftover < ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE) {
                // We still don't have enough to run $this->blocks()
                return $this;
            }

            $this->blocks(
                self::intArrayToString($this->buffer),
                ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE
            );
            $this->leftover = 0;
        }

        /* process full blocks */
        if ($bytes >= ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE) {
            /** @var int $want */
            $want = $bytes & ~(ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE - 1);
            if ($want >= ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE) {
                /** @var string $block */
                $block = self::substr($message, 0, $want);
                if (self::strlen($block) >= ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE) {
                    $this->blocks($block, $want);
                    $message = self::substr($message, $want);
                    $bytes = self::strlen($message);
                }
            }
        }

        /* store leftover */
        if ($bytes) {
            for ($i = 0; $i < $bytes; ++$i) {
                $mi = self::chrToInt($message[$i]);
                $this->buffer[$this->leftover + $i] = $mi;
            }
            $this->leftover = (int) $this->leftover + $bytes;
        }
        return $this;
    }