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authorMattes D <github@xoft.cz>2019-08-23 16:17:05 +0200
committerMattes D <github@xoft.cz>2019-08-24 12:03:38 +0200
commit02fbf1686565ace00df5af938d95fbe18783fc37 (patch)
treee109749b5823f758d605dd2a8f5d2c8b8b22878b /src
parentUpgrade Appveyor's MSVC (diff)
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Diffstat (limited to '')
-rw-r--r--src/BlockState.cpp167
-rw-r--r--src/BlockState.h90
-rw-r--r--src/CMakeLists.txt2
3 files changed, 259 insertions, 0 deletions
diff --git a/src/BlockState.cpp b/src/BlockState.cpp
new file mode 100644
index 000000000..4e2607bd3
--- /dev/null
+++ b/src/BlockState.cpp
@@ -0,0 +1,167 @@
+#include "Globals.h"
+#include "BlockState.h"
+
+
+
+
+
+BlockState::BlockState():
+ mChecksum(initializeChecksum())
+{
+ // Nothing needed yet
+}
+
+
+
+
+
+BlockState::BlockState(const AString & aKey, const AString & aValue):
+ mState({{aKey, aValue}}),
+ mChecksum(initializeChecksum())
+{
+}
+
+
+
+
+
+BlockState::BlockState(std::initializer_list<std::pair<const AString, AString>> aKeysAndValues):
+ mState(aKeysAndValues),
+ mChecksum(initializeChecksum())
+{
+}
+
+
+
+
+
+BlockState::BlockState(const std::map<AString, AString> & aKeysAndValues):
+ mState(aKeysAndValues),
+ mChecksum(initializeChecksum())
+{
+}
+
+
+
+
+
+BlockState::BlockState(std::map<AString, AString> && aKeysAndValues):
+ mState(std::move(aKeysAndValues)),
+ mChecksum(initializeChecksum())
+{
+}
+
+
+
+
+
+BlockState::BlockState(const BlockState & aCopyFrom, std::initializer_list<std::pair<const AString, AString>> aAdditionalKeysAndValues):
+ mState(aCopyFrom.mState)
+{
+ for (const auto & kav: aAdditionalKeysAndValues)
+ {
+ mState[kav.first] = kav.second;
+ }
+ mChecksum = initializeChecksum();
+}
+
+
+
+
+
+BlockState::BlockState(const BlockState & aCopyFrom, const std::map<AString, AString> & aAdditionalKeysAndValues):
+ mState(aCopyFrom.mState)
+{
+ for (const auto & kav: aAdditionalKeysAndValues)
+ {
+ mState[kav.first] = kav.second;
+ }
+ mChecksum = initializeChecksum();
+}
+
+
+
+
+
+bool BlockState::operator ==(const BlockState & aOther) const
+{
+ // Fast-fail if the checksums differ or differrent counts:
+ if ((mChecksum != aOther.mChecksum) || (mState.size() != aOther.mState.size()))
+ {
+ return false;
+ }
+
+ // Slow-check everything if the checksums match:
+ return std::equal(mState.begin(), mState.end(), aOther.mState.begin());
+}
+
+
+
+
+
+const AString & BlockState::value(const AString & aKey) const
+{
+ auto itr = mState.find(aKey);
+ if (itr == mState.end())
+ {
+ static AString empty;
+ return empty;
+ }
+ return itr->second;
+}
+
+
+
+
+
+UInt32 BlockState::initializeChecksum()
+{
+ removeEmptyKeys();
+
+ // Calculate the checksum as a XOR of all mState keys' and values' checksums
+ // This way we don't depend on the std::map's ordering
+ UInt32 res = 0;
+ for (const auto & kv: mState)
+ {
+ auto partial = partialChecksum(kv.first) ^ partialChecksum(kv.second);
+ res = res ^ partial;
+ }
+ return res;
+}
+
+
+
+
+
+void BlockState::removeEmptyKeys()
+{
+ for (auto itr = mState.begin(); itr != mState.end();)
+ {
+ if (itr->second.empty())
+ {
+ itr = mState.erase(itr);
+ }
+ else
+ {
+ ++itr;
+ }
+ }
+}
+
+
+
+
+
+UInt32 BlockState::partialChecksum(const AString & aString)
+{
+ UInt32 shift = 0;
+ UInt32 res = 0;
+ for (auto ch: aString)
+ {
+ UInt32 v = static_cast<UInt8>(ch);
+ v = v << shift;
+ shift = (shift + 1) % 24;
+ res = res ^ v;
+ }
+ return res;
+}
diff --git a/src/BlockState.h b/src/BlockState.h
new file mode 100644
index 000000000..3b0575f0e
--- /dev/null
+++ b/src/BlockState.h
@@ -0,0 +1,90 @@
+#pragma once
+
+#include <initializer_list>
+
+
+
+
+
+/** Represents the state of a single block (previously known as "block meta").
+The state consists of a map of string -> string, plus a mechanism for fast equality checks between two BlockState instances.
+Once a BlockState instance is created, it is then immutable - there's no way of changing it, only by creating a (modified) copy.
+A BlockState instance can be created from hard-coded data or from dynamic data:
+ BlockState bs({{"key1", "value1"}, {key2", "value2"}}); // Hard-coded
+ - or -
+ std::map<AString, AString> map({{"key1", "value1"}, {key2", "value2"}});
+ map["key3"] = "value3";
+ BlockState bs(map); // From dynamic data
+*/
+class BlockState
+{
+public:
+
+ /** Creates a new instance with an empty map. */
+ BlockState();
+
+ /** Creates a new instance consisting of a single key-value pair.
+ If the value is empty, it is not stored wihin the map. */
+ BlockState(const AString & aKey, const AString & aValue);
+
+ /** Creates a new instance initialized with several (hard-coded) key-value pairs.
+ Any key with an empty value is not stored within the map. */
+ BlockState(std::initializer_list<std::pair<const AString, AString>> aKeysAndValues);
+
+ /** Creates a new instance initialized with several (dynamic) key-value pairs.
+ Makes a copy of aKeysAndValues for this object.
+ Any key with an empty value is not stored within the map. */
+ BlockState(const std::map<AString, AString> & aKeysAndValues);
+
+ /** Creates a new instance initialized with several (dynamic) key-value pairs.
+ Any key with an empty value is not stored within the map. */
+ BlockState(std::map<AString, AString> && aKeysAndValues);
+
+ /** Creates a copy of the specified BlockState with the (hard-coded) additional keys and values added to it.
+ Any key in aAdditionalKeysAndValues that is already present in aCopyFrom is overwritten with the aAdditionalKeysAndValues' one.
+ Any key with an empty value is not stored in the map.
+ (it's possible to erase a key from aCopyFrom by setting it to empty string in aAdditionalKeysAndValues). */
+ BlockState(const BlockState & aCopyFrom, std::initializer_list<std::pair<const AString, AString>> aAdditionalKeysAndValues);
+
+ /** Creates a copy of the specified BlockState with the (dynamic) additional keys and values added to it.
+ Any key in aAdditionalKeysAndValues that is already present in aCopyFrom is overwritten with the aAdditionalKeysAndValues' one.
+ Any key with an empty value is not stored in the map.
+ (it's possible to erase a key from aCopyFrom by setting it to empty string in aAdditionalKeysAndValues). */
+ BlockState(const BlockState & aCopyFrom, const std::map<AString, AString> & aAdditionalKeysAndValues);
+
+ /** Fast equality check. */
+ bool operator ==(const BlockState & aOther) const;
+
+ /** Fast inequality check. */
+ bool operator !=(const BlockState & aOther) const
+ {
+ return !(operator ==(aOther));
+ }
+
+ /** Returns the value at the specified key.
+ If the key is not present, returns an empty string. */
+ const AString & value(const AString & aKey) const;
+
+
+protected:
+
+ /** The state, represented as a string->string map. */
+ std::map<AString, AString> mState;
+
+ /** The checksum used for the fast equality check.
+ This is calculated upon creation. */
+ UInt32 mChecksum;
+
+
+ /** Normalizes mState and calculates the checksum from it.
+ Removes all the empty values from mState.
+ Used only from constructors. */
+ UInt32 initializeChecksum();
+
+ /** Removes all the keys from mState that have an empty value. */
+ void removeEmptyKeys();
+
+ /** Calculates the partial checksum of a single string.
+ Used from within initializeChecksum(). */
+ UInt32 partialChecksum(const AString & aString);
+};
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d23fe388d..dd92a969c 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -17,6 +17,7 @@ SET (SRCS
BlockArea.cpp
BlockID.cpp
BlockInfo.cpp
+ BlockState.cpp
BlockTypeRegistry.cpp
BrewingRecipes.cpp
Broadcaster.cpp
@@ -84,6 +85,7 @@ SET (HDRS
BlockID.h
BlockInServerPluginInterface.h
BlockInfo.h
+ BlockState.h
BlockTracer.h
BlockTypeRegistry.h
BrewingRecipes.h