/*

* Licensed to the Apache Software Foundation (ASF) under one or more

* contributor license agreements. See the NOTICE file distributed with

* this work for additional information regarding copyright ownership.

* The ASF licenses this file to You under the Apache License, Version 2.0

* (the "License"); you may not use this file except in compliance with

* the License. You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*/

package org.apache.coyote.http2;

import java.nio.ByteBuffer;

import org.apache.tomcat.util.res.StringManager;

final class Hpack {

protected static final StringManager sm = StringManager.getManager(Hpack.class);

private static final byte LOWER_DIFF = 'a' - 'A';

static final int DEFAULT_TABLE_SIZE = 4096;

private static final int MAX_INTEGER_OCTETS = 8; //not sure what a good value for this is, but the spec says we need to provide an upper bound

/**

* table that contains powers of two,

* used as both bitmask and to quickly calculate 2^n

*/

private static final int[] PREFIX_TABLE;

static final HeaderField[] STATIC_TABLE;

static final int STATIC_TABLE_LENGTH;

static {

PREFIX_TABLE = new int[32];

for (int i = 0; i < 32; ++i) {

int n = 0;

for (int j = 0; j < i; ++j) {

n = n << 1;

n |= 1;

}

PREFIX_TABLE[i] = n;

}

HeaderField[] fields = new HeaderField[62];

//note that zero is not used

fields[1] = new HeaderField(":authority", null);

fields[2] = new HeaderField(":method", "GET");

fields[3] = new HeaderField(":method", "POST");

fields[4] = new HeaderField(":path", "/");

fields[5] = new HeaderField(":path", "/index.html");

fields[6] = new HeaderField(":scheme", "http");

fields[7] = new HeaderField(":scheme", "https");

fields[8] = new HeaderField(":status", "200");

fields[9] = new HeaderField(":status", "204");

fields[10] = new HeaderField(":status", "206");

fields[11] = new HeaderField(":status", "304");

fields[12] = new HeaderField(":status", "400");

fields[13] = new HeaderField(":status", "404");

fields[14] = new HeaderField(":status", "500");

fields[15] = new HeaderField("accept-charset", null);

fields[16] = new HeaderField("accept-encoding", "gzip, deflate");

fields[17] = new HeaderField("accept-language", null);

fields[18] = new HeaderField("accept-ranges", null);

fields[19] = new HeaderField("accept", null);

fields[20] = new HeaderField("access-control-allow-origin", null);

fields[21] = new HeaderField("age", null);

fields[22] = new HeaderField("allow", null);

fields[23] = new HeaderField("authorization", null);

fields[24] = new HeaderField("cache-control", null);

fields[25] = new HeaderField("content-disposition", null);

fields[26] = new HeaderField("content-encoding", null);

fields[27] = new HeaderField("content-language", null);

fields[28] = new HeaderField("content-length", null);

fields[29] = new HeaderField("content-location", null);

fields[30] = new HeaderField("content-range", null);

fields[31] = new HeaderField("content-type", null);

fields[32] = new HeaderField("cookie", null);

fields[33] = new HeaderField("date", null);

fields[34] = new HeaderField("etag", null);

fields[35] = new HeaderField("expect", null);

fields[36] = new HeaderField("expires", null);

fields[37] = new HeaderField("from", null);

fields[38] = new HeaderField("host", null);

fields[39] = new HeaderField("if-match", null);

fields[40] = new HeaderField("if-modified-since", null);

fields[41] = new HeaderField("if-none-match", null);

fields[42] = new HeaderField("if-range", null);

fields[43] = new HeaderField("if-unmodified-since", null);

fields[44] = new HeaderField("last-modified", null);

fields[45] = new HeaderField("link", null);

fields[46] = new HeaderField("location", null);

fields[47] = new HeaderField("max-forwards", null);

fields[48] = new HeaderField("proxy-authenticate", null);

fields[49] = new HeaderField("proxy-authorization", null);

fields[50] = new HeaderField("range", null);

fields[51] = new HeaderField("referer", null);

fields[52] = new HeaderField("refresh", null);

fields[53] = new HeaderField("retry-after", null);

fields[54] = new HeaderField("server", null);

fields[55] = new HeaderField("set-cookie", null);

fields[56] = new HeaderField("strict-transport-security", null);

fields[57] = new HeaderField("transfer-encoding", null);

fields[58] = new HeaderField("user-agent", null);

fields[59] = new HeaderField("vary", null);

fields[60] = new HeaderField("via", null);

fields[61] = new HeaderField("www-authenticate", null);

STATIC_TABLE = fields;

STATIC_TABLE_LENGTH = STATIC_TABLE.length - 1;

}

static class HeaderField {

final String name;

final String value;

final int size;

HeaderField(String name, String value) {

this.name = name;

this.value = value;

if (value != null) {

this.size = 32 + name.length() + value.length();

} else {

this.size = -1;

}

}

}

/**

* Decodes an integer in the HPACK prefex format. If the return value is -1

* it means that there was not enough data in the buffer to complete the decoding

* sequence.

* <p/>

* If this method returns -1 then the source buffer will not have been modified.

*

* @param source The buffer that contains the integer

* @param n The encoding prefix length

* @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];

int i = mask & source.get();

int b;

if (i < PREFIX_TABLE[n]) {

return i;

} 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();

i = i + (b & 127) * (PREFIX_TABLE[m] + 1);

m += 7;

} while ((b & 128) == 128);

}

return i;

}

/**

* Encodes an integer in the HPACK prefix format.

* <p/>

* This method assumes that the buffer has already had the first 8-n bits filled.

* As such it will modify the last byte that is already present in the buffer, and

* potentially add more if required

*

* @param source The buffer that contains the integer

* @param value The integer to encode

* @param n The encoding prefix length

*/

static void encodeInteger(ByteBuffer source, int value, int n) {

int twoNminus1 = PREFIX_TABLE[n];

int pos = source.position() - 1;

if (value < twoNminus1) {

source.put(pos, (byte) (source.get(pos) | value));

} else {

source.put(pos, (byte) (source.get(pos) | twoNminus1));

value = value - twoNminus1;

while (value >= 128) {

source.put((byte) (value % 128 + 128));

value = value / 128;

}

source.put((byte) value);

}

}

static byte toLower(byte b) {

if (b >= 'A' && b <= 'Z') {

return (byte) (b + LOWER_DIFF);

}

return b;

}

private Hpack() {}

}