feat: hash command hscan

src/base_cmd.h

@@ -69,6 +69,7 @@ const std::string kCmdNameHGetAll = "hgetall";
 const std::string kCmdNameHKeys = "hkeys";
 const std::string kCmdNameHLen = "hlen";
 const std::string kCmdNameHStrLen = "hstrlen";
+const std::string kCmdNameHScan = "hscan";
 
 // set cmd
 const std::string kCmdNameSIsMember = "sismember";

src/client.cc

@@ -129,6 +129,9 @@ void CmdRes::SetRes(CmdRes::CmdRet _ret, const std::string& content) {
       AppendStringRaw(content);
       AppendStringRaw(CRLF);
       break;
+    case kInvalidCursor:
+      AppendStringRaw("-ERR invalid cursor");
+      break;
     default:
       break;
   }

src/client.h

@@ -47,6 +47,7 @@ class CmdRes {
     kInconsistentHashTag,
     kErrOther,
     KIncrByOverFlow,
+    kInvalidCursor,
   };
 
   CmdRes() = default;

src/cmd_hash.cc

@@ -9,6 +9,7 @@
 
 #include <config.h>
 
+#include "pstd/pstd_string.h"
 #include "store.h"
 
 namespace pikiwidb {
@@ -227,4 +228,59 @@ void HStrLenCmd::DoCmd(PClient* client) {
   }
 }
 
+HScanCmd::HScanCmd(const std::string& name, int16_t arity)
+    : BaseCmd(name, arity, kCmdFlagsReadonly, kAclCategoryRead | kAclCategoryHash) {}
+
+bool HScanCmd::DoInitial(PClient* client) {
+  if (auto size = client->argv_.size(); size != 3 && size != 5 && size != 7) {
+    client->SetRes(CmdRes::kSyntaxErr);
+    return false;
+  }
+  client->SetKey(client->argv_[1]);
+  return true;
+}
+
+void HScanCmd::DoCmd(PClient* client) {
+  const auto& argv = client->argv_;
+  // parse arguments
+  int64_t cursor{};
+  int64_t count{10};
+  std::string pattern{"*"};
+  if (pstd::String2int(argv[2], &cursor) == 0) {
+    client->SetRes(CmdRes::kInvalidCursor);
+    return;
+  }
+  for (size_t i = 3; i < argv.size(); i += 2) {
+    if (auto lower = pstd::StringToLower(argv[i]); kMatchSymbol == lower) {
+      pattern = argv[i + 1];
+    } else if (kCountSymbol == lower) {
+      if (pstd::String2int(argv[i + 1], &count) == 0) {
+        client->SetRes(CmdRes::kInvalidInt, kCmdNameHScan);
+        return;
+      }
+    } else {
+      client->SetRes(CmdRes::kErrOther, kCmdNameHScan);
+      return;
+    }
+  }
+
+  // execute command
+  std::vector<storage::FieldValue> fvs;
+  int64_t next_cursor{};
+  auto status = PSTORE.GetBackend()->HScan(client->Key(), cursor, pattern, count, &fvs, &next_cursor);
+  if (!status.ok() && !status.IsNotFound()) {
+    client->SetRes(CmdRes::kErrOther, status.ToString());
+    return;
+  }
+
+  // reply to client
+  client->AppendArrayLen(2);
+  client->AppendString(std::to_string(next_cursor));
+  client->AppendArrayLenUint64(fvs.size() * 2);
+  for (const auto& [field, value] : fvs) {
+    client->AppendString(field);
+    client->AppendString(value);
+  }
+}
+
 }  // namespace pikiwidb

src/cmd_hash.h

@@ -99,4 +99,18 @@ class HStrLenCmd : public BaseCmd {
   void DoCmd(PClient *client) override;
 };
 
+class HScanCmd : public BaseCmd {
+ public:
+  HScanCmd(const std::string &name, int16_t arity);
+
+ protected:
+  bool DoInitial(PClient *client) override;
+
+ private:
+  void DoCmd(PClient *client) override;
+
+  static constexpr const char *kMatchSymbol = "match";
+  static constexpr const char *kCountSymbol = "count";
+};
+
 }  // namespace pikiwidb

src/cmd_table_manager.cc

@@ -73,6 +73,7 @@ void CmdTableManager::InitCmdTable() {
   ADD_COMMAND(HKeys, 2);
   ADD_COMMAND(HLen, 2);
   ADD_COMMAND(HStrLen, 3);
+  ADD_COMMAND(HScan, -3);
 
   // set
   ADD_COMMAND(SIsMember, 3);