hpack/src/main/java/com/twitter/hpack/Encoder.java
public void encodeHeader(OutputStream out, byte[] name, byte[] value, boolean sensitive) throws IOException {

    // If the header value is sensitive then it must never be indexed
    if (sensitive) {
      int nameIndex = getNameIndex(name);
      encodeLiteral(out, name, value, IndexType.NEVER, nameIndex);
      return;
    }

    // If the peer will only use the static table
    if (capacity == 0) {
      int staticTableIndex = StaticTable.getIndex(name, value);
      if (staticTableIndex == -1) {
        int nameIndex = StaticTable.getIndex(name);
        encodeLiteral(out, name, value, IndexType.NONE, nameIndex);
      } else {
        encodeInteger(out, 0x80, 7, staticTableIndex);
      }
      return;
    }

    int headerSize = HeaderField.sizeOf(name, value);

    // If the headerSize is greater than the max table size then it must be encoded literally
    if (headerSize > capacity) {
      int nameIndex = getNameIndex(name);
      encodeLiteral(out, name, value, IndexType.NONE, nameIndex);
      return;
    }

    HeaderEntry headerField = getEntry(name, value);
    if (headerField != null) {
      int index = getIndex(headerField.index) + StaticTable.length;
      // Section 6.1. Indexed Header Field Representation
      encodeInteger(out, 0x80, 7, index);
    } else {
      int staticTableIndex = StaticTable.getIndex(name, value);
      if (staticTableIndex != -1) {
        // Section 6.1. Indexed Header Field Representation
        encodeInteger(out, 0x80, 7, staticTableIndex);
      } else {
        int nameIndex = getNameIndex(name);
        if (useIndexing) {
          ensureCapacity(headerSize);
        }
        IndexType indexType = useIndexing ? IndexType.INCREMENTAL : IndexType.NONE;
        encodeLiteral(out, name, value, indexType, nameIndex);
        if (useIndexing) {
          add(name, value);
        }
      }
    }
  }
public void encodeHeader(OutputStream out, byte[] name, byte[] value, boolean sensitive) throws IOException {

    // If the header value is sensitive then it must never be indexed
    if (sensitive) {
      int nameIndex = getNameIndex(name);
      encodeLiteral(out, name, value, IndexType.NEVER, nameIndex);
      return;
    }

    // If the peer will only use the static table
    if (capacity == 0) {
      int staticTableIndex = StaticTable.getIndex(name, value);
      if (staticTableIndex == -1) {
        int nameIndex = StaticTable.getIndex(name);
        encodeLiteral(out, name, value, IndexType.NONE, nameIndex);
      } else {
        encodeInteger(out, 0x80, 7, staticTableIndex);
      }
      return;
    }

    int headerSize = HeaderField.sizeOf(name, value);

    // If the headerSize is greater than the max table size then it must be encoded literally
    if (headerSize > capacity) {
      int nameIndex = getNameIndex(name);
      encodeLiteral(out, name, value, IndexType.NONE, nameIndex);
      return;
    }

    HeaderEntry headerField = getEntry(name, value);
    if (headerField != null) {
      int index = getIndex(headerField.index) + StaticTable.length;
      // Section 6.1. Indexed Header Field Representation
      encodeInteger(out, 0x80, 7, index);
    } else {
      int staticTableIndex = StaticTable.getIndex(name, value);
      if (staticTableIndex != -1) {
        // Section 6.1. Indexed Header Field Representation
        encodeInteger(out, 0x80, 7, staticTableIndex);
      } else {
        int nameIndex = getNameIndex(name);
        if (useIndexing) {
          ensureCapacity(headerSize);
        }
        IndexType indexType = useIndexing ? IndexType.INCREMENTAL : IndexType.NONE;
        encodeLiteral(out, name, value, indexType, nameIndex);
        if (useIndexing) {
          add(name, value);
        }
      }
    }
  }
Encode the header field into the header block.