diff --git a/updater/Android.mk b/updater/Android.mk
index 4762664..46c56f4 100644
--- a/updater/Android.mk
+++ b/updater/Android.mk
@@ -56,6 +56,7 @@
 LOCAL_MODULE := libupdater
 
 LOCAL_SRC_FILES := \
+    commands.cpp \
     install.cpp \
     blockimg.cpp
 
diff --git a/updater/blockimg.cpp b/updater/blockimg.cpp
index 4a70b98..5d6da6c 100644
--- a/updater/blockimg.cpp
+++ b/updater/blockimg.cpp
@@ -57,6 +57,7 @@
 #include "otautil/paths.h"
 #include "otautil/print_sha1.h"
 #include "otautil/rangeset.h"
+#include "private/commands.h"
 #include "updater/install.h"
 #include "updater/updater.h"
 
@@ -546,8 +547,8 @@
 struct CommandParameters {
     std::vector<std::string> tokens;
     size_t cpos;
-    const char* cmdname;
-    const char* cmdline;
+    std::string cmdname;
+    std::string cmdline;
     std::string freestash;
     std::string stashbase;
     bool canwrite;
@@ -1496,23 +1497,13 @@
   return 0;
 }
 
-// Definitions for transfer list command functions
-typedef int (*CommandFunction)(CommandParameters&);
+using CommandFunction = std::function<int(CommandParameters&)>;
 
-struct Command {
-    const char* name;
-    CommandFunction f;
-};
-
-// args:
-//    - block device (or file) to modify in-place
-//    - transfer list (blob)
-//    - new data stream (filename within package.zip)
-//    - patch stream (filename within package.zip, must be uncompressed)
+using CommandMap = std::unordered_map<Command::Type, CommandFunction>;
 
 static Value* PerformBlockImageUpdate(const char* name, State* state,
                                       const std::vector<std::unique_ptr<Expr>>& argv,
-                                      const Command* commands, size_t cmdcount, bool dryrun) {
+                                      const CommandMap& command_map, bool dryrun) {
   CommandParameters params = {};
   params.canwrite = !dryrun;
 
@@ -1532,6 +1523,11 @@
     return nullptr;
   }
 
+  // args:
+  //   - block device (or file) to modify in-place
+  //   - transfer list (blob)
+  //   - new data stream (filename within package.zip)
+  //   - patch stream (filename within package.zip, must be uncompressed)
   const std::unique_ptr<Value>& blockdev_filename = args[0];
   const std::unique_ptr<Value>& transfer_list_value = args[1];
   const std::unique_ptr<Value>& new_data_fn = args[2];
@@ -1707,16 +1703,6 @@
     skip_executed_command = false;
   }
 
-  // Build a map of the available commands
-  std::unordered_map<std::string, const Command*> cmd_map;
-  for (size_t i = 0; i < cmdcount; ++i) {
-    if (cmd_map.find(commands[i].name) != cmd_map.end()) {
-      LOG(ERROR) << "Error: command [" << commands[i].name << "] already exists in the cmd map.";
-      return StringValue("");
-    }
-    cmd_map[commands[i].name] = &commands[i];
-  }
-
   int rc = -1;
 
   static constexpr size_t kTransferListHeaderLines = 4;
@@ -1728,36 +1714,35 @@
     size_t cmdindex = i - kTransferListHeaderLines;
     params.tokens = android::base::Split(line, " ");
     params.cpos = 0;
-    params.cmdname = params.tokens[params.cpos++].c_str();
-    params.cmdline = line.c_str();
+    params.cmdname = params.tokens[params.cpos++];
+    params.cmdline = line;
     params.target_verified = false;
 
-    if (cmd_map.find(params.cmdname) == cmd_map.end()) {
+    Command::Type cmd_type = Command::ParseType(params.cmdname);
+    if (cmd_type == Command::Type::LAST) {
       LOG(ERROR) << "unexpected command [" << params.cmdname << "]";
       goto pbiudone;
     }
 
-    const Command* cmd = cmd_map[params.cmdname];
+    const CommandFunction& performer = command_map.at(cmd_type);
 
     // Skip the command if we explicitly set the corresponding function pointer to nullptr, e.g.
     // "erase" during block_image_verify.
-    if (cmd->f == nullptr) {
+    if (performer == nullptr) {
       LOG(DEBUG) << "skip executing command [" << line << "]";
       continue;
     }
 
-    std::string cmdname = std::string(params.cmdname);
-
     // Skip all commands before the saved last command index when resuming an update, except for
     // "new" command. Because new commands read in the data sequentially.
     if (params.canwrite && skip_executed_command && cmdindex <= saved_last_command_index &&
-        cmdname != "new") {
+        cmd_type != Command::Type::NEW) {
       LOG(INFO) << "Skipping already executed command: " << cmdindex
                 << ", last executed command for previous update: " << saved_last_command_index;
       continue;
     }
 
-    if (cmd->f(params) == -1) {
+    if (performer(params) == -1) {
       LOG(ERROR) << "failed to execute command [" << line << "]";
       goto pbiudone;
     }
@@ -1767,7 +1752,8 @@
     // that we will resume the update from the first command in the transfer list.
     if (!params.canwrite && skip_executed_command && cmdindex <= saved_last_command_index) {
       // TODO(xunchang) check that the cmdline of the saved index is correct.
-      if ((cmdname == "move" || cmdname == "bsdiff" || cmdname == "imgdiff") &&
+      if ((cmd_type == Command::Type::MOVE || cmd_type == Command::Type::BSDIFF ||
+           cmd_type == Command::Type::IMGDIFF) &&
           !params.target_verified) {
         LOG(WARNING) << "Previously executed command " << saved_last_command_index << ": "
                      << params.cmdline << " doesn't produce expected target blocks.";
@@ -1775,6 +1761,7 @@
         DeleteLastCommandFile();
       }
     }
+
     if (params.canwrite) {
       if (ota_fsync(params.fd) == -1) {
         failure_type = kFsyncFailure;
@@ -1911,38 +1898,42 @@
  */
 Value* BlockImageVerifyFn(const char* name, State* state,
                           const std::vector<std::unique_ptr<Expr>>& argv) {
-    // Commands which are not tested are set to nullptr to skip them completely
-    const Command commands[] = {
-        { "bsdiff",     PerformCommandDiff  },
-        { "erase",      nullptr             },
-        { "free",       PerformCommandFree  },
-        { "imgdiff",    PerformCommandDiff  },
-        { "move",       PerformCommandMove  },
-        { "new",        nullptr             },
-        { "stash",      PerformCommandStash },
-        { "zero",       nullptr             }
-    };
+  // Commands which are not allowed are set to nullptr to skip them completely.
+  const CommandMap command_map{
+    // clang-format off
+    { Command::Type::BSDIFF,  PerformCommandDiff },
+    { Command::Type::ERASE,   nullptr },
+    { Command::Type::FREE,    PerformCommandFree },
+    { Command::Type::IMGDIFF, PerformCommandDiff },
+    { Command::Type::MOVE,    PerformCommandMove },
+    { Command::Type::NEW,     nullptr },
+    { Command::Type::STASH,   PerformCommandStash },
+    { Command::Type::ZERO,    nullptr },
+    // clang-format on
+  };
+  CHECK_EQ(static_cast<size_t>(Command::Type::LAST), command_map.size());
 
-    // Perform a dry run without writing to test if an update can proceed
-    return PerformBlockImageUpdate(name, state, argv, commands,
-                sizeof(commands) / sizeof(commands[0]), true);
+  // Perform a dry run without writing to test if an update can proceed.
+  return PerformBlockImageUpdate(name, state, argv, command_map, true);
 }
 
 Value* BlockImageUpdateFn(const char* name, State* state,
                           const std::vector<std::unique_ptr<Expr>>& argv) {
-    const Command commands[] = {
-        { "bsdiff",     PerformCommandDiff  },
-        { "erase",      PerformCommandErase },
-        { "free",       PerformCommandFree  },
-        { "imgdiff",    PerformCommandDiff  },
-        { "move",       PerformCommandMove  },
-        { "new",        PerformCommandNew   },
-        { "stash",      PerformCommandStash },
-        { "zero",       PerformCommandZero  }
-    };
+  const CommandMap command_map{
+    // clang-format off
+    { Command::Type::BSDIFF,  PerformCommandDiff },
+    { Command::Type::ERASE,   PerformCommandErase },
+    { Command::Type::FREE,    PerformCommandFree },
+    { Command::Type::IMGDIFF, PerformCommandDiff },
+    { Command::Type::MOVE,    PerformCommandMove },
+    { Command::Type::NEW,     PerformCommandNew },
+    { Command::Type::STASH,   PerformCommandStash },
+    { Command::Type::ZERO,    PerformCommandZero },
+    // clang-format on
+  };
+  CHECK_EQ(static_cast<size_t>(Command::Type::LAST), command_map.size());
 
-    return PerformBlockImageUpdate(name, state, argv, commands,
-                sizeof(commands) / sizeof(commands[0]), false);
+  return PerformBlockImageUpdate(name, state, argv, command_map, false);
 }
 
 Value* RangeSha1Fn(const char* name, State* state, const std::vector<std::unique_ptr<Expr>>& argv) {
diff --git a/updater/commands.cpp b/updater/commands.cpp
new file mode 100644
index 0000000..f798c6a
--- /dev/null
+++ b/updater/commands.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "private/commands.h"
+
+#include <string>
+
+#include <android-base/logging.h>
+
+Command::Type Command::ParseType(const std::string& type_str) {
+  if (type_str == "zero") {
+    return Type::ZERO;
+  } else if (type_str == "new") {
+    return Type::NEW;
+  } else if (type_str == "erase") {
+    return Type::ERASE;
+  } else if (type_str == "move") {
+    return Type::MOVE;
+  } else if (type_str == "bsdiff") {
+    return Type::BSDIFF;
+  } else if (type_str == "imgdiff") {
+    return Type::IMGDIFF;
+  } else if (type_str == "stash") {
+    return Type::STASH;
+  } else if (type_str == "free") {
+    return Type::FREE;
+  }
+  LOG(ERROR) << "Invalid type: " << type_str;
+  return Type::LAST;
+};
diff --git a/updater/include/private/commands.h b/updater/include/private/commands.h
new file mode 100644
index 0000000..b360000
--- /dev/null
+++ b/updater/include/private/commands.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <string>
+
+struct Command {
+  enum class Type {
+    ZERO,
+    NEW,
+    ERASE,
+    MOVE,
+    BSDIFF,
+    IMGDIFF,
+    STASH,
+    FREE,
+    LAST,  // Not a valid type.
+  };
+
+  static Type ParseType(const std::string& type_str);
+};