m05：该合的合，该分的分

std::string Server::handleGet() {
    if (args_.size() != 2) return "ERR wrong number of arguments for 'get'";
    const std::string& key = args_[1];
    if (key.size() > kMaxKeyLength) return "ERR key too long";
    ...
}
std::string Server::handleAppend() {
    if (args_.size() != 2 || rawValue_.empty()) return "ERR wrong number ...";
    const std::string& key = args_[1];
    // (键长检查漏掉了)
    ...
}
std::string Server::handleGetRange() {
    ...
    start = std::stoll(args_[2]);   // "1x" 被当成 1
    end = std::stoll(args_[3]);

struct Command {
    Handler handler;
    size_t minArgs;
    size_t maxArgs;
    bool firstIsKey;   // args[0] is a key and must be at most kMaxKeyLength bytes
    bool restOfLine;   // the last argument is the rest of the line, spaces included
};
//                         handler                  min max  key?   rest of line?
commands_["SET"]      = {&Server::handleSet,      2, 2, true,  true};
commands_["GET"]      = {&Server::handleGet,      1, 1, true,  false};
commands_["APPEND"]   = {&Server::handleAppend,   2, 2, true,  true};
commands_["GETRANGE"] = {&Server::handleGetRange, 3, 3, true,  false};
...
// in handle():
if (args.size() < cmd.minArgs || args.size() > cmd.maxArgs)
    return "ERR wrong number of arguments for '" + toLower(name) + "'";
if (cmd.firstIsKey && args[0].size() > kMaxKeyLength) return "ERR key too long";
return (this->*cmd.handler)(args);

void Server::tokenize(const std::string& line) {
    ...
        if (args_.size() == 2) {
            std::string cmd = toUpper(args_[0]);
            if (cmd == "SET" || cmd == "APPEND") {
                ...
                rawValue_ = line.substr(i);   // 只有这两个命令读它
                return;
            }
        }
}
std::string Server::handleSet() {
    if (args_.size() != 2 || rawValue_.empty()) ...   // 为什么是 2？

// Splits `text` into words separated by runs of whitespace. If `maxWords` is
// not 0 and the text has more words than that, the last word returned is
// everything from the start of word number `maxWords` to the end of the
// text, whitespace included.
std::vector<std::string> splitWords(const std::string& text, size_t maxWords);

// in handle():
Args args;
if (nameAndRest.size() == 2)
    args = splitWords(nameAndRest[1], cmd.restOfLine ? cmd.maxArgs : 0);

std::string Server::handleSet(const Args& args) {
    try {
        db_.set(args[0], args[1], writeOptions_);
        return "OK";
    } ...