HpackDynamicTable Class — netty Architecture

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/HpackDynamicTable.java lines 37–201

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("Index " + index + " out of bounds for length " + length());
        }
        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 += headerSize;
        if (head == hpackHeaderFields.length) {
            head = 0;
        }
    }