ClickHouse/base/common/LineReader.cpp

#include <common/LineReader.h>

#include <iostream>
#include <string_view>

#include <string.h>
#include <unistd.h>

#ifdef OS_LINUX
/// We can detect if code is linked with one or another readline variants or open the library dynamically.
#   include <dlfcn.h>
extern "C"
{
    char * readline(const char *) __attribute__((__weak__));
    char * (*readline_ptr)(const char *) = readline;
}
#endif

namespace
{

/// Trim ending whitespace inplace
void trim(String & s)
{
    s.erase(std::find_if(s.rbegin(), s.rend(), [](int ch) { return !std::isspace(ch); }).base(), s.end());
}

/// Check if multi-line query is inserted from the paste buffer.
/// Allows delaying the start of query execution until the entirety of query is inserted.
bool hasInputData()
{
    timeval timeout = {0, 0};
    fd_set fds;
    FD_ZERO(&fds);
    FD_SET(STDIN_FILENO, &fds);
    return select(1, &fds, nullptr, nullptr, &timeout) == 1;
}

}

LineReader::Suggest::WordsRange LineReader::Suggest::getCompletions(const String & prefix, size_t prefix_length) const
{
    if (!ready)
        return std::make_pair(words.end(), words.end());

    std::string_view last_word;

    auto last_word_pos = prefix.find_last_of(word_break_characters);
    if (std::string::npos == last_word_pos)
        last_word = prefix;
    else
        last_word = std::string_view(prefix).substr(last_word_pos + 1, std::string::npos);

    /// last_word can be empty.

    return std::equal_range(
        words.begin(), words.end(), last_word, [prefix_length](std::string_view s, std::string_view prefix_searched)
        {
            return strncmp(s.data(), prefix_searched.data(), prefix_length) < 0;
        });
}

LineReader::LineReader(const String & history_file_path_, char extender_, char delimiter_)
    : history_file_path(history_file_path_), extender(extender_), delimiter(delimiter_)
{
    /// FIXME: check extender != delimiter
}

String LineReader::readLine(const String & first_prompt, const String & second_prompt)
{
    String line;
    bool is_multiline = false;

    while (auto status = readOneLine(is_multiline ? second_prompt : first_prompt))
    {
        if (status == RESET_LINE)
        {
            line.clear();
            is_multiline = false;
            continue;
        }

        if (input.empty())
        {
            if (!line.empty() && !delimiter && !hasInputData())
                break;
            else
                continue;
        }

        is_multiline = (input.back() == extender) || (delimiter && input.back() != delimiter) || hasInputData();

        if (input.back() == extender)
        {
            input = input.substr(0, input.size() - 1);
            trim(input);
            if (input.empty())
                continue;
        }

        line += (line.empty() ? "" : " ") + input;

        if (!is_multiline)
            break;
    }

    if (!line.empty() && line != prev_line)
    {
        addToHistory(line);
        prev_line = line;
    }

    return line;
}

LineReader::InputStatus LineReader::readOneLine(const String & prompt)
{
    input.clear();

#ifdef OS_LINUX
    if (!readline_ptr)
    {
        for (auto name : {"libreadline.so", "libreadline.so.0", "libeditline.so", "libeditline.so.0"})
        {
            void * dl_handle = dlopen(name, RTLD_LAZY);
            if (dl_handle)
            {
                readline_ptr = reinterpret_cast<char * (*)(const char *)>(dlsym(dl_handle, "readline"));
                if (readline_ptr)
                {
                    break;
                }
            }
        }
    }

    /// Minimal support for readline
    if (readline_ptr)
    {
        char * line_read = (*readline_ptr)(prompt.c_str());
        if (!line_read)
            return ABORT;
        input = line_read;
    }
    else
#endif
    {
        std::cout << prompt;
        std::getline(std::cin, input);
        if (!std::cin.good())
            return ABORT;
    }

    trim(input);
    return INPUT_LINE;
}