Coding-Library/fast IO.cpp at master · zyrch/Coding-Library · GitHub

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// template by neal
namespace IO {
    const int BUFFER_SIZE = 1 << 15;

    char input_buffer[BUFFER_SIZE];
    size_t input_pos = 0, input_len = 0;

    char output_buffer[BUFFER_SIZE];
    int output_pos = 0;

    char number_buffer[100];
    uint8_t lookup[100];

    void _update_input_buffer() {
        input_len = fread(input_buffer, sizeof(char), BUFFER_SIZE, stdin);
        input_pos = 0;

        if (input_len == 0)
            input_buffer[0] = EOF;
    }

    inline char next_char(bool advance = true) {
        if (input_pos >= input_len)
            _update_input_buffer();

        return input_buffer[advance ? input_pos++ : input_pos];
    }

    inline bool isspace(char c) {
        return (unsigned char) (c - '\t') < 5 || c == ' ';
    }

    inline void read_char(char &c) {
        while (isspace(next_char(false)))
            next_char();

        c = next_char();
    }

    template<typename T>
    inline void read_int(T &number) {
        bool negative = false;
        number = 0;

        while (!isdigit(next_char(false)))
            if (next_char() == '-')
                negative = true;

        do {
            number = 10 * number + (next_char() - '0');
        } while (isdigit(next_char(false)));

        if (negative)
            number = -number;
    }

    template<typename T, typename... Args>
    inline void read_int(T &number, Args &... args) {
        read_int(number);
        read_int(args...);
    }

    inline void read_str(string &str) {
        while (isspace(next_char(false)))
            next_char();

        str.clear();

        do {
            str += next_char();
        } while (!isspace(next_char(false)));
    }

    void _flush_output() {
        fwrite(output_buffer, sizeof(char), output_pos, stdout);
        output_pos = 0;
    }

    inline void write_char(char c) {
        if (output_pos == BUFFER_SIZE)
            _flush_output();

        output_buffer[output_pos++] = c;
    }

    template<typename T>
    inline void write_int(T number, char after = '\0') {
        if (number < 0) {
            write_char('-');
            number = -number;
        }

        int length = 0;

        while (number >= 10) {
            uint8_t lookup_value = lookup[number % 100];
            number /= 100;
            number_buffer[length++] = char((lookup_value & 15) + '0');
            number_buffer[length++] = char((lookup_value >> 4) + '0');
        }

        if (number != 0 || length == 0)
            write_char(char(number + '0'));

        for (int i = length - 1; i >= 0; i--)
            write_char(number_buffer[i]);

        if (after)
            write_char(after);
    }

    inline void write_str(const string &str, char after = '\0') {
        for (char c : str)
            write_char(c);

        if (after)
            write_char(after);
    }

    void init() {
        // Make sure _flush_output() is called at the end of the program.
        bool exit_success = atexit(_flush_output) == 0;
        assert(exit_success);

        for (int i = 0; i < 100; i++)
            lookup[i] = uint8_t((i / 10 << 4) + i % 10);
    }
}