QpackDecoderDynamicTable Class — netty Architecture

Source Code

codec-http3/src/main/java/io/netty/handler/codec/http3/QpackDecoderDynamicTable.java lines 27–170

final class QpackDecoderDynamicTable {
    private static final QpackException GET_ENTRY_ILLEGAL_INDEX_VALUE =
            QpackException.newStatic(QpackDecoderDynamicTable.class, "getEntry(...)",
                    "QPACK - illegal decoder dynamic table index value");
    private static final QpackException HEADER_TOO_LARGE =
            QpackException.newStatic(QpackDecoderDynamicTable.class, "add(...)", "QPACK - header entry too large.");

    // a circular queue of header fields
    private QpackHeaderField[] fields;
    private int head;
    private int tail;
    private long size;
    private long capacity = -1; // ensure setCapacity creates the array
    private int insertCount;

    int length() {
        return head < tail ? fields.length - tail + head : head - tail;
    }

    long size() {
        return size;
    }

    int insertCount() {
        return insertCount;
    }

    QpackHeaderField getEntry(int index) throws QpackException {
        if (index < 0 || fields == null || index >= fields.length) {
            throw GET_ENTRY_ILLEGAL_INDEX_VALUE;
        }
        QpackHeaderField entry = fields[index];
        if (entry == null) {
            throw GET_ENTRY_ILLEGAL_INDEX_VALUE;
        }
        return entry;
    }

    QpackHeaderField getEntryRelativeEncodedField(int index) throws QpackException {
        // https://www.rfc-editor.org/rfc/rfc9204.html#name-relative-indexing
        return getEntry(moduloIndex(index));
    }

    QpackHeaderField getEntryRelativeEncoderInstructions(int index) throws QpackException {
        // https://www.rfc-editor.org/rfc/rfc9204.html#name-relative-indexing
        // Name index is the relative index, relative to the last added entry.
        return getEntry(index > tail ? fields.length - index + tail : tail - index);
    }

    void add(QpackHeaderField header) throws QpackException {
        long headerSize = header.size();
        if (headerSize > capacity) {
            throw HEADER_TOO_LARGE;
        }
        while (capacity - size < headerSize) {
            remove();
        }
        insertCount++;
        fields[getAndIncrementHead()] = header;
        size += headerSize;
    }

    private void remove() {
        QpackHeaderField removed = fields[tail];
        if (removed == null) {
            return;
        }
        size -= removed.size();
        fields[getAndIncrementTail()] = null;
    }

    void clear() {
        if (fields != null) {
            Arrays.fill(fields, null);
        }
        head = 0;
        tail = 0;
        size = 0;
    }

    void setCapacity(long capacity) throws QpackException {