聊聊claudb的list command

序

本文主要研究一下claudb的list command

LeftPushCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/LeftPushCommand.java

@Command(&34;)@ParamLength(2)@ParamType(DataType.LIST)public class LeftPushCommand implements DBCommand { @Override public RedisToken execute(Database db, Request request) {   ImmutableList<SafeString> values = request.getParams().asList().tail().reverse();​   DatabaseValue result = db.merge(safeKey(request.getParam(0)), list(values),       (oldValue, newValue) -> list(newValue.getList().appendAll(oldValue.getList())));​   return RedisToken.integer(result.size()); }}

• LeftPushCommand實現了DBCommand接口，其execute方法提取values，然後執行db.merge，在newValue.getList()之後追加上oldValue.getList()

LeftPopCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/LeftPopCommand.java

@Command(&34;)@ParamLength(1)@ParamType(DataType.LIST)public class LeftPopCommand implements DBCommand {​ @Override public RedisToken execute(Database db, Request request) {   List<SafeString> removed = new LinkedList<>();   db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,       (oldValue, newValue) -> {         ImmutableList<SafeString> list = oldValue.getList();         list.head().stream().forEach(removed::add);         return list(list.tail());       });​   if (removed.isEmpty()) {     return nullString();   } else {     return string(removed.remove(0));   } }}

• LeftPopCommand實現了DBCommand接口，其execute方法執行db.merge，它先獲取oldValue.getList()，然後取出head添加到removed中，然後再通過list.tail()丟棄head作為新的結果

RightPushCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/RightPushCommand.java

@Command(&34;)@ParamLength(2)@ParamType(DataType.LIST)public class RightPushCommand implements DBCommand {​ @Override public RedisToken execute(Database db, Request request) {   ImmutableList<SafeString> values = request.getParams().asList().tail();​   DatabaseValue result = db.merge(safeKey(request.getParam(0)), list(values),       (oldValue, newValue) -> list(oldValue.getList().appendAll(newValue.getList())));​   return integer(result.size()); }}

• RightPushCommand實現了DBCommand接口，其execute方法提取values，然後執行db.merge，在oldValue.getList()之後追加上newValue.getList()

RightPopCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/RightPopCommand.java

@Command(&34;)@ParamLength(1)@ParamType(DataType.LIST)public class RightPopCommand implements DBCommand {​ @Override public RedisToken execute(Database db, Request request) {   List<SafeString> removed = new LinkedList<>();   db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,       (oldValue, newValue) -> {         ImmutableList<SafeString> list = oldValue.getList();         list.reverse().head().stream().forEach(removed::add);         return list(list.reverse().tail().reverse());       });​   if (removed.isEmpty()) {     return nullString();   } else {     return string(removed.remove(0));   } }}

• RightPopCommand實現了DBCommand接口，其execute方法執行db.merge，它先獲取oldValue.getList()，然後取出list倒數的head添加到removed中，然後再通過list.reverse().tail()丟棄head再reverse作為新的結果

ListLengthCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListLengthCommand.java

@ReadOnly@Command(&34;)@ParamLength(1)@ParamType(DataType.LIST)public class ListLengthCommand implements DBCommand {​ @Override public RedisToken execute(Database db, Request request) {   ImmutableList<SafeString> list = db.getList(request.getParam(0));   return integer(list.size()); }}

• ListLengthCommand實現了DBCommand接口，其execute方法先通過db.getList(request.getParam(0))獲取list，然後返回integer(list.size())

ListRangeCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListRangeCommand.java

@ReadOnly@Command(&34;)@ParamLength(3)@ParamType(DataType.LIST)public class ListRangeCommand implements DBCommand {​ @Override public RedisToken execute(Database db, Request request) {   try {     DatabaseValue value = db.getOrDefault(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST);     ImmutableList<SafeString> list = value.getList();​     int from = Integer.parseInt(request.getParam(1).toString());     if (from < 0) {       from = list.size() + from;     }     int to = Integer.parseInt(request.getParam(2).toString());     if (to < 0) {       to = list.size() + to;     }​     int min = Math.min(from, to);     int max = Math.max(from, to);​     // TODO: use Array     ImmutableList<SafeString> result = ImmutableList.from(list.stream().skip(min).limit((max - min) + 1));​     return convert(result);   } catch (NumberFormatException e) {     return error(&34;);   } }}

• ListRangeCommand實現了DBCommand接口，其execute方法先獲取list，之後修正min及max，然後取ImmutableList.from(list.stream().skip(min).limit((max - min) + 1))

ListIndexCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListIndexCommand.java

@ReadOnly@Command(&34;)@ParamLength(2)@ParamType(DataType.LIST)public class ListIndexCommand implements DBCommand {​ @Override public RedisToken execute(Database db, Request request) {   try {     ImmutableList<SafeString> list = db.getList(request.getParam(0));​     int index = Integer.parseInt(request.getParam(1).toString());     if (index < 0) {       index = list.size() + index;     }​     // TODO: fix asArray     return string(list.asArray().get(index));   } catch (NumberFormatException e) {     return error(&34;);   } catch (IndexOutOfBoundsException e) {     return nullString();   } }}

• ListIndexCommand實現了DBCommand接口，其execute方法先獲取list，然後返回string(list.asArray().get(index))

ListSetCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListSetCommand.java

@Command(&34;)@ParamLength(3)@ParamType(DataType.LIST)public class ListSetCommand implements DBCommand {​ @Override public RedisToken execute(Database db, Request request) {   try {     int index = Integer.parseInt(request.getParam(1).toString());     db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,         (oldValue, newValue) -> {           ImmutableList<SafeString> oldList = oldValue.getList();           // TODO: use Array           List<SafeString> array = new ArrayList<>(oldList.toList());           array.set(index > -1 ? index : array.size() + index, request.getParam(2));           return list(array);         });     return status(&34;);   } catch (NumberFormatException e) {     return error(&34;);   } catch (IndexOutOfBoundsException e) {     return error(&34;);   } }}

• ListSetCommand實現了DBCommand接口，其execute方法先讀取index參數，然後執行db.merge，它讀取oldList，然後執行array.set(index > -1 ? index : array.size() + index, request.getParam(2))，最後返回list(array)

小結

claudb list相關的command有LeftPushCommand、LeftPopCommand、RightPushCommand、RightPopCommand、ListLengthCommand、ListRangeCommand、ListIndexCommand、ListSetCommand

doc

• command/list