Factor out QPACK absolute, relative, and post-base index conversion functions, and add new ones.
gfe-relnote: n/a, change to QUIC v99-only code. Protected by existing disabled gfe2_reloadable_flag_quic_enable_version_99.
PiperOrigin-RevId: 263421099
Change-Id: I762c3105da671f9d01ba5971c57a2f89f130ebbf
diff --git a/quic/core/qpack/qpack_index_conversions.h b/quic/core/qpack/qpack_index_conversions.h
new file mode 100644
index 0000000..f05a477
--- /dev/null
+++ b/quic/core/qpack/qpack_index_conversions.h
@@ -0,0 +1,65 @@
+// Copyright (c) 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Utility methods to convert between absolute indexing (used in the dynamic
+// table), relative indexing used on the encoder stream, and relative indexing
+// and post-base indexing used on request streams (in header blocks). See:
+// https://quicwg.org/base-drafts/draft-ietf-quic-qpack.html#indexing
+// https://quicwg.org/base-drafts/draft-ietf-quic-qpack.html#relative-indexing
+// https://quicwg.org/base-drafts/draft-ietf-quic-qpack.html#post-base
+
+#ifndef QUICHE_QUIC_CORE_QPACK_QPACK_INDEX_CONVERSIONS_H_
+#define QUICHE_QUIC_CORE_QPACK_QPACK_INDEX_CONVERSIONS_H_
+
+#include <cstdint>
+
+namespace quic {
+
+// Conversion functions used in the encoder do not check for overflow/underflow.
+// Since the maximum index is limited by maximum dynamic table capacity
+// (represented on uint64_t) divided by minimum header field size (defined to be
+// 32 bytes), overflow is not possible. The caller is responsible for providing
+// input that does not underflow.
+
+uint64_t QpackAbsoluteIndexToEncoderStreamRelativeIndex(
+ uint64_t absolute_index,
+ uint64_t inserted_entry_count);
+
+uint64_t QpackAbsoluteIndexToRequestStreamRelativeIndex(uint64_t absolute_index,
+ uint64_t base);
+
+// Conversion functions used in the decoder operate on input received from the
+// network. These functions return false on overflow or underflow.
+
+// TODO The encoder stream uses relative index (but different from the kind of
+// relative index used on a request stream). This method converts relative
+// index to absolute index (zero based). It returns true on success, or false
+// if conversion fails due to overflow/underflow.
+
+bool QpackEncoderStreamRelativeIndexToAbsoluteIndex(
+ uint64_t relative_index,
+ uint64_t inserted_entry_count,
+ uint64_t* absolute_index);
+
+// TODO The request stream can use relative index (but different from the kind
+// of relative index used on the encoder stream), and post-base index. These
+// methods convert relative index and post-base index to absolute index (one
+// based). They return true on success, or false if conversion fails due to
+// overflow/underflow.
+
+// On success, |*absolute_index| is guaranteed to be strictly less than
+// std::numeric_limits<uint64_t>::max().
+bool QpackRequestStreamRelativeIndexToAbsoluteIndex(uint64_t relative_index,
+ uint64_t base,
+ uint64_t* absolute_index);
+
+// On success, |*absolute_index| is guaranteed to be strictly less than
+// std::numeric_limits<uint64_t>::max().
+bool QpackPostBaseIndexToAbsoluteIndex(uint64_t post_base_index,
+ uint64_t base,
+ uint64_t* absolute_index);
+
+} // namespace quic
+
+#endif // QUICHE_QUIC_CORE_QPACK_QPACK_INDEX_CONVERSIONS_H_
