Function formatImpl

src/tinyformat.h:888–951

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//------------------------------------------------------------------------------
inline void formatImpl(std::ostream& out, const char* fmt,
                       const detail::FormatArg* args,
                       int numArgs)
{
    // Saved stream state
    std::streamsize origWidth = out.width();
    std::streamsize origPrecision = out.precision();
    std::ios::fmtflags origFlags = out.flags();
    char origFill = out.fill();

    // "Positional mode" means all format specs should be of the form "%n$..."
    // with `n` an integer. We detect this in `streamStateFromFormat`.
    bool positionalMode = false;
    int argIndex = 0;
    while (true) {
        fmt = printFormatStringLiteral(out, fmt);
        if (*fmt == '\0') {
            if (!positionalMode && argIndex < numArgs) {
                TINYFORMAT_ERROR("tinyformat: Not enough conversion specifiers in format string");
            }
            break;
        }
        bool spacePadPositive = false;
        int ntrunc = -1;
        const char* fmtEnd = streamStateFromFormat(out, positionalMode, spacePadPositive, ntrunc, fmt,
                                                   args, argIndex, numArgs);
        // NB: argIndex may be incremented by reading variable width/precision
        // in `streamStateFromFormat`, so do the bounds check here.
        if (argIndex >= numArgs) {
            TINYFORMAT_ERROR("tinyformat: Too many conversion specifiers in format string");
            return;
        }
        const FormatArg& arg = args[argIndex];
        // Format the arg into the stream.
        if (!spacePadPositive) {
            arg.format(out, fmt, fmtEnd, ntrunc);
        }
        else {
            // The following is a special case with no direct correspondence
            // between stream formatting and the printf() behaviour.  Simulate
            // it crudely by formatting into a temporary string stream and
            // munging the resulting string.
            std::ostringstream tmpStream;
            tmpStream.copyfmt(out);
            tmpStream.setf(std::ios::showpos);
            arg.format(tmpStream, fmt, fmtEnd, ntrunc);
            std::string result = tmpStream.str(); // allocates... yuck.
            for (size_t i = 0, iend = result.size(); i < iend; ++i) {
                if (result[i] == '+')
                    result[i] = ' ';
            }
            out << result;
        }
        if (!positionalMode)
            ++argIndex;
        fmt = fmtEnd;
    }