Method decodeInteger

java/org/apache/coyote/http2/Hpack.java:155–192

Decodes an integer in the HPACK prefix format. If the return value is -1 it means that there was not enough data in the buffer to complete the decoding sequence. If this method returns -1 then the source buffer will not have been modified. @param source The buffer that contains the integer @pa

(ByteBuffer source, int n)

     * @return The encoded integer, or -1 if there was not enough data
     */
    static int decodeInteger(ByteBuffer source, int n) throws HpackException {
        if (source.remaining() == 0) {
            return -1;
        }
        int count = 1;
        int sp = source.position();
        int mask = PREFIX_TABLE[n];

        // Use long internally as the value may exceed Integer.MAX_VALUE
        long result = mask & source.get();
        int b;
        if (result < PREFIX_TABLE[n]) {
            // Casting is safe as result must be less than 255 at this point.
            return (int) result;
        } else {
            int m = 0;
            do {
                if (count++ > MAX_INTEGER_OCTETS) {
                    throw new HpackException(
                            sm.getString("hpack.integerEncodedOverTooManyOctets", Integer.valueOf(MAX_INTEGER_OCTETS)));
                }
                if (source.remaining() == 0) {
                    // we have run out of data
                    // reset
                    source.position(sp);
                    return -1;
                }
                b = source.get();
                result = result + (b & 127) * (PREFIX_TABLE[m] + 1L);
                if (result > Integer.MAX_VALUE) {
                    throw new HpackException(sm.getString("hpack.integerEncodedTooBig"));
                }
                m += 7;
            } while ((b & 128) == 128);
        }
        // Casting is safe as result must be less than Integer.MAX_VALUE at this point
        return (int) result;
    }

    /**
     * Encodes an integer in the HPACK prefix format.