appendline.cpp

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/*******************************************************************************
 * tlx/string/appendline.cpp
 *
 * Part of tlx - http://panthema.net/tlx
 *
 * Copyright (C) 2019 Timo Bingmann <tb@panthema.net>
 *
 * All rights reserved. Published under the Boost Software License, Version 1.0
 ******************************************************************************/

#include <tlx/string/appendline.hpp>

#include <algorithm>

namespace tlx {

std::istream& appendline(std::istream& is, std::string& str, char delim) {
    size_t size = str.size();
    size_t capacity = str.capacity();
    std::streamsize rest = capacity - size;

    if (rest == 0) {
        // if rest is zero, already expand string
        capacity = std::max(static_cast<size_t>(8), capacity * 2);
        rest = capacity - size;
    }

    // give getline access to all of capacity
    str.resize(capacity);

    // get until delim or rest is filled
    is.getline(const_cast<char*>(str.data()) + size, rest, delim);

    // gcount includes the delimiter
    size_t new_size = size + is.gcount();

    // is failbit set?
    if (!is) {
        // if string ran out of space, expand, and retry
        if (is.gcount() + 1 == rest) {
            is.clear();
            str.resize(new_size);
            str.reserve(capacity * 2);
            return appendline(is, str, delim);
        }
        // else fall through and deliver error
    }
    else if (!is.eof()) {
        // subtract delimiter
        --new_size;
    }

    // resize string to fit its contents
    str.resize(new_size);
    return is;
}

} // namespace tlx

/******************************************************************************/