94 lines
3.7 KiB
C++
94 lines
3.7 KiB
C++
#pragma once
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#include <initializer_list>
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/** Represents the state of a single block (previously known as "block meta").
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The state consists of a map of string -> string, plus a mechanism for fast equality checks between two BlockState instances.
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Once a BlockState instance is created, it is then immutable - there's no way of changing it, only by creating a (modified) copy.
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A BlockState instance can be created from hard-coded data or from dynamic data:
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BlockState bs({{"key1", "value1"}, {key2", "value2"}}); // Hard-coded
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- or -
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std::map<AString, AString> map({{"key1", "value1"}, {key2", "value2"}});
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map["key3"] = "value3";
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BlockState bs(map); // From dynamic data
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*/
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class BlockState
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{
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public:
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/** Creates a new instance with an empty map. */
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BlockState();
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/** Creates a new instance consisting of a single key-value pair.
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If the value is empty, it is not stored wihin the map. */
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BlockState(const AString & aKey, const AString & aValue);
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/** Creates a new instance initialized with several (hard-coded) key-value pairs.
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Any key with an empty value is not stored within the map. */
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BlockState(std::initializer_list<std::pair<const AString, AString>> aKeysAndValues);
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/** Creates a new instance initialized with several (dynamic) key-value pairs.
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Makes a copy of aKeysAndValues for this object.
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Any key with an empty value is not stored within the map. */
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BlockState(const std::map<AString, AString> & aKeysAndValues);
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/** Creates a new instance initialized with several (dynamic) key-value pairs.
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Any key with an empty value is not stored within the map. */
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BlockState(std::map<AString, AString> && aKeysAndValues);
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/** Creates a copy of the specified BlockState with the (hard-coded) additional keys and values added to it.
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Any key in aAdditionalKeysAndValues that is already present in aCopyFrom is overwritten with the aAdditionalKeysAndValues' one.
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Any key with an empty value is not stored in the map.
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(it's possible to erase a key from aCopyFrom by setting it to empty string in aAdditionalKeysAndValues). */
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BlockState(const BlockState & aCopyFrom, std::initializer_list<std::pair<const AString, AString>> aAdditionalKeysAndValues);
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/** Creates a copy of the specified BlockState with the (dynamic) additional keys and values added to it.
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Any key in aAdditionalKeysAndValues that is already present in aCopyFrom is overwritten with the aAdditionalKeysAndValues' one.
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Any key with an empty value is not stored in the map.
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(it's possible to erase a key from aCopyFrom by setting it to empty string in aAdditionalKeysAndValues). */
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BlockState(const BlockState & aCopyFrom, const std::map<AString, AString> & aAdditionalKeysAndValues);
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/** Less-than comparison. */
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bool operator <(const BlockState & aOther) const;
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/** Fast equality check. */
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bool operator ==(const BlockState & aOther) const;
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/** Fast inequality check. */
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bool operator !=(const BlockState & aOther) const
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{
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return !(operator ==(aOther));
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}
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/** Returns the value at the specified key.
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If the key is not present, returns an empty string. */
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const AString & value(const AString & aKey) const;
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protected:
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/** The state, represented as a string->string map. */
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std::map<AString, AString> mState;
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/** The checksum used for the fast equality check.
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This is calculated upon creation. */
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UInt32 mChecksum;
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/** Normalizes mState and calculates the checksum from it.
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Removes all the empty values from mState.
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Used only from constructors. */
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UInt32 initializeChecksum();
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/** Removes all the keys from mState that have an empty value. */
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void removeEmptyKeys();
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/** Calculates the partial checksum of a single string.
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Used from within initializeChecksum(). */
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UInt32 partialChecksum(const AString & aString);
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};
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