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authorqrort <qrort@yandex-team.com>2022-11-30 23:47:12 +0300
committerqrort <qrort@yandex-team.com>2022-11-30 23:47:12 +0300
commit22f8ae0e3f5d68b92aecccdf96c1d841a0334311 (patch)
treebffa27765faf54126ad44bcafa89fadecb7a73d7 /library/cpp/erasure/codec.h
parent332b99e2173f0425444abb759eebcb2fafaa9209 (diff)
downloadydb-22f8ae0e3f5d68b92aecccdf96c1d841a0334311.tar.gz
validate canons without yatest_common
Diffstat (limited to 'library/cpp/erasure/codec.h')
-rw-r--r--library/cpp/erasure/codec.h80
1 files changed, 80 insertions, 0 deletions
diff --git a/library/cpp/erasure/codec.h b/library/cpp/erasure/codec.h
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+#pragma once
+
+#include "public.h"
+
+#include <optional>
+#include <vector>
+
+namespace NErasure {
+
+//! Describes a generic way to generate parity blocks from data blocks and
+//! to recover (repair) missing blocks.
+/*!
+ * Given N data blocks (numbered from 0 to N - 1) one can call #Encode to generate
+ * another M parity blocks (numbered from N to N + M - 1).
+ *
+ * If some of the resulting N + M blocks ever become missing one can attempt to
+ * repair the missing blocks by calling #Decode.
+ *
+ * Here N and M are fixed (codec-specific) parameters.
+ * Call #GetDataPartCount and #GetParityPartCount to figure out the
+ * the values for N and M, respectively.
+ *
+ */
+template <class TBlobType>
+struct ICodec {
+ //! Computes a sequence of parity blocks for given data blocks.
+ /*!
+ * The size of #blocks must be equal to #GetDataPartCount.
+ * The size of the returned array is equal to #GetParityPartCount.
+ */
+ virtual std::vector<TBlobType> Encode(const std::vector<TBlobType>& blocks) const = 0;
+
+ //! Decodes (repairs) missing blocks.
+ /*!
+ * #erasedIndices must contain the set of erased blocks indices.
+ * #blocks must contain known blocks (in the order specified by #GetRepairIndices).
+ * \returns The repaired blocks.
+ */
+ virtual std::vector<TBlobType> Decode(
+ const std::vector<TBlobType>& blocks,
+ const TPartIndexList& erasedIndices) const = 0;
+
+ //! Given a set of missing block indices, returns |true| if missing blocks can be repaired.
+ //! Due to performance reasons the elements of #erasedIndices must unique and sorted.
+ virtual bool CanRepair(const TPartIndexList& erasedIndices) const = 0;
+
+ //! Rapid version that works with set instead of list.
+ virtual bool CanRepair(const TPartIndexSet& erasedIndices) const = 0;
+
+ //! Given a set of missing block indices, checks if missing blocks can be repaired.
+ /*!
+ * \returns
+ * If repair is not possible, returns |std::nullopt|.
+ * Otherwise returns the indices of blocks (both data and parity) to be passed to #Decode
+ * (in this very order). Not all known blocks may be needed for repair.
+ */
+ virtual std::optional<TPartIndexList> GetRepairIndices(const TPartIndexList& erasedIndices) const = 0;
+
+ //! Returns the number of data blocks this codec can handle.
+ virtual int GetDataPartCount() const = 0;
+
+ //! Returns the number of parity blocks this codec can handle.
+ virtual int GetParityPartCount() const = 0;
+
+ //! Returns the maximum number of blocks that can always be repaired when missing.
+ virtual int GetGuaranteedRepairablePartCount() const = 0;
+
+ //! Every block passed to this codec must have size divisible by the result of #GetWordSize.
+ virtual int GetWordSize() const = 0;
+
+ // Extension methods
+
+ //! Returns the sum of #GetDataPartCount and #GetParityPartCount.
+ int GetTotalPartCount() const {
+ return GetDataPartCount() + GetParityPartCount();
+ }
+};
+
+} // namespace NErasure
+