/*
* Copyright 2015 The Netty Project
*
* The Netty Project 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.
*/
/*
* Copyright 2014 Twitter, Inc.
*
* Licensed 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 io.netty.handler.codec.http2;
import static io.netty.handler.codec.http2.Http2CodecUtil.MAX_HEADER_TABLE_SIZE;
import static io.netty.handler.codec.http2.Http2CodecUtil.MIN_HEADER_TABLE_SIZE;
final class HpackDynamicTable {
// a circular queue of header fields
HpackHeaderField[] hpackHeaderFields;
int head;
int tail;
private long size;
private long capacity = -1; // ensure setCapacity creates the array
/**
* Creates a new dynamic table with the specified initial capacity.
*/
HpackDynamicTable(long initialCapacity) {
setCapacity(initialCapacity);
}
/**
* Return the number of header fields in the dynamic table.
*/
public int length() {
int length;
if (head < tail) {
length = hpackHeaderFields.length - tail + head;
} else {
length = head - tail;
}
return length;
}
/**
* Return the current size of the dynamic table. This is the sum of the size of the entries.
*/
public long size() {
return size;
}
/**
* Return the maximum allowable size of the dynamic table.
*/
public long capacity() {
return capacity;
}
/**
* Return the header field at the given index. The first and newest entry is always at index 1,
* and the oldest entry is at the index length().
*/
public HpackHeaderField getEntry(int index) {
if (index <= 0 || index > length()) {
throw new IndexOutOfBoundsException();
}
int i = head - index;
if (i < 0) {
return hpackHeaderFields[i + hpackHeaderFields.length];
} else {
return hpackHeaderFields[i];
}
}
/**
* Add the header field to the dynamic table. Entries are evicted from the dynamic table until
* the size of the table and the new header field is less than or equal to the table's capacity.
* If the size of the new entry is larger than the table's capacity, the dynamic table will be
* cleared.
*/
public void add(HpackHeaderField header) {
int headerSize = header.size();
if (headerSize > capacity) {
clear();
return;
}
while (capacity - size < headerSize) {
remove();
}
hpackHeaderFields[head++] = header;
size += header.size();
if (head == hpackHeaderFields.length) {
head = 0;
}
}
/**
* Remove and return the oldest header field from the dynamic table.
*/
public HpackHeaderField remove() {
HpackHeaderField removed = hpackHeaderFields[tail];
if (removed == null) {
return null;
}
size -= removed.size();
hpackHeaderFields[tail++] = null;
if (tail == hpackHeaderFields.length) {
tail = 0;
}
return removed;
}
/**
* Remove all entries from the dynamic table.
*/
public void clear() {
while (tail != head) {
hpackHeaderFields[tail++] = null;
if (tail == hpackHeaderFields.length) {
tail = 0;
}
}
head = 0;
tail = 0;
size = 0;
}
/**
* Set the maximum size of the dynamic table. Entries are evicted from the dynamic table until
* the size of the table is less than or equal to the maximum size.
*/
public void setCapacity(long capacity) {
if (capacity < MIN_HEADER_TABLE_SIZE || capacity > MAX_HEADER_TABLE_SIZE) {
throw new IllegalArgumentException("capacity is invalid: " + capacity);
}
// initially capacity will be -1 so init won't return here
if (this.capacity == capacity) {
return;
}
this.capacity = capacity;
if (capacity == 0) {
clear();
} else {
// initially size will be 0 so remove won't be called
while (size > capacity) {
remove();
}
}
int maxEntries = (int) (capacity / HpackHeaderField.HEADER_ENTRY_OVERHEAD);
if (capacity % HpackHeaderField.HEADER_ENTRY_OVERHEAD != 0) {
maxEntries++;
}
// check if capacity change requires us to reallocate the array
if (hpackHeaderFields != null && hpackHeaderFields.length == maxEntries) {
return;
}
HpackHeaderField[] tmp = new HpackHeaderField[maxEntries];
// initially length will be 0 so there will be no copy
int len = length();
int cursor = tail;
for (int i = 0; i < len; i++) {
HpackHeaderField entry = hpackHeaderFields[cursor++];
tmp[i] = entry;
if (cursor == hpackHeaderFields.length) {
cursor = 0;
}
}
tail = 0;
head = tail + len;
hpackHeaderFields = tmp;
}
}