Index: blimp/net/delta_encoding.h |
diff --git a/blimp/net/delta_encoding.h b/blimp/net/delta_encoding.h |
deleted file mode 100644 |
index e38751598d0107620beff3261f4fe47ef51224ca..0000000000000000000000000000000000000000 |
--- a/blimp/net/delta_encoding.h |
+++ /dev/null |
@@ -1,124 +0,0 @@ |
-// Copyright 2016 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. |
- |
-#ifndef BLIMP_NET_DELTA_ENCODING_H_ |
-#define BLIMP_NET_DELTA_ENCODING_H_ |
- |
-#include <algorithm> |
-#include <functional> |
-#include <utility> |
- |
-// This file contains utility functions to concisely compute and apply |
-// delta encodings of arbitrarily-typed sequences of values. Delta-encoded |
-// numeric values tend to be smaller in magnitude than their source values |
-// which, when combined with variable integer encoding (a la protobuf), results |
-// in a smaller wire size. |
-// |
-// e.g. DeltaEncode([4, 1, 5]) => [4, -3, 4] |
-// DeltaDecode([4, -3, 4]) => [4, 1, 5] |
-// |
-// If ordering doesn't matter, then the function SortAndDeltaEncode() |
-// can be used to compute a delta encoding with the smallest possible values. |
-// |
-// e.g. SortAndDeltaEncode([4, 1, 5]) => [1, 3, 1] |
-// DeltaDecode([1, 3, 1]) => [1, 4, 5] |
-// |
-// Delta encodings can also be computed for structured or non-numeric data |
-// types as well, so long as functions are provided for differencing and |
-// reconstituting the data. This can also be applied to delta encode or elide |
-// across fields of a struct, for example. |
- |
-namespace blimp { |
- |
-// Homogeneously-typed signature for functions that compute and apply deltas. |
-template <typename T> |
-using BinaryFunction = T (*)(const T&, const T&); |
- |
-// Uses the subtraction operator to compute the delta across two values. |
-template <typename T> |
-inline T default_compute_delta(const T& lhs, const T& rhs) { |
- return lhs - rhs; |
-} |
- |
-// Uses the addition operator to add a delta value to a base value. |
-template <typename T> |
-inline T default_apply_delta(const T& lhs, const T& rhs) { |
- return lhs + rhs; |
-} |
- |
-// Uses the less-than (<) operator to determine if |lhs| is less-than |rhs|. |
-template <typename T> |
-inline bool lessthan(const T& lhs, const T& rhs) { |
- return lhs < rhs; |
-} |
- |
-// Delta-encodes a iterated sequence of values in-place. |
-// |begin|: An iterator pointing to the beginning of the sequence. |
-// |end|: An iterator pointing to the end of the sequence. |
-// |default_compute_delta_fn|: Optional function which computes the delta |
-// between |
-// every element and its next successor. |
-template <typename I> |
-void DeltaEncode(I begin, |
- I end, |
- BinaryFunction<typename std::iterator_traits<I>::value_type> |
- default_compute_delta_fn = &default_compute_delta) { |
- if (begin == end) { |
- return; |
- } |
- |
- I current = begin; |
- typename std::iterator_traits<I>::value_type value = *current; |
- ++current; |
- for (; current != end; ++current) { |
- value = (*default_compute_delta_fn)(*current, value); |
- |
- // Put the delta in place and store the actual value into |value|, ready for |
- // the next iteration. |
- std::swap(*current, value); |
- } |
-} |
- |
-// Delta-decodes a iterated sequence of values in-place. |
-// |begin|: An iterator pointing to the beginning of the sequence. |
-// |end|: An iterator pointing to the end of the sequence. |
-// |apply_fn|: Optional binary function which combines the value of |
-// every element with that of its immediate predecessor. |
-template <typename I> |
-void DeltaDecode(I begin, |
- I end, |
- BinaryFunction<typename std::iterator_traits<I>::value_type> |
- apply_fn = &default_apply_delta) { |
- if (begin == end) { |
- return; |
- } |
- |
- I current = begin; |
- typename std::iterator_traits<I>::value_type previous_value = *current; |
- ++current; |
- for (; current != end; ++current) { |
- *current = apply_fn(previous_value, *current); |
- previous_value = *current; |
- } |
-} |
- |
-// Convenience function for sorting and delta-encoding a sequence of values. |
-// The value type must support std::sort(), either by natively supporting |
-// inequality comparison or with custom comparison function |comparison_fn|. |
-template <typename I> |
-inline void SortAndDeltaEncode( |
- I begin, |
- I end, |
- BinaryFunction<typename std::iterator_traits<I>::value_type> |
- default_compute_delta_fn = &default_compute_delta, |
- bool (*comparison_fn)(const typename std::iterator_traits<I>::value_type&, |
- const typename std::iterator_traits<I>::value_type&) = |
- lessthan<typename std::iterator_traits<I>::value_type>) { |
- std::sort(begin, end, comparison_fn); |
- DeltaEncode(begin, end, default_compute_delta_fn); |
-} |
- |
-} // namespace blimp |
- |
-#endif // BLIMP_NET_DELTA_ENCODING_H_ |