C++ Istream::readsome方法代码示例

void test_readsome (const charT *cbuf, const Traits*,
                    unsigned cbuf_size,
                    unsigned i,   // index into states
                    unsigned j,   // number of chars to read
                    unsigned k,   // when underflow() will fail
                    int      l,   // value returned from showmanyc()
                    unsigned m)   // how underflow should fail()
{
    typedef std::basic_istream<charT, Traits> Istream;

    static unsigned iter = 0;   // iteration counter

    // construct a stream buffer object and initialize its read
    // sequence with the character buffer
    Streambuf<charT, Traits> sb (cbuf, cbuf + cbuf_size - 1);

    sb.showmanyc_ = l;

    const char* err_type = 0;

    if (m < 1) {
        // have the stream buffer object's underflow() fail (by
        // throwing an exception if possible) after k characters
        // have been extracted (this object calls underflow() for
        // every char)
        sb.throw_after_ = k;
        err_type        = "threw";
    }
    else {
        // have the stream buffer object's underflow() fail by
        // returning eof after k characters have been extracted
        // (this object calls underflow() for every char)
        sb.fail_after_ = k;
        err_type       = "returned EOF";
    }

    // construct an istream object and initialize it with the user
    // defined streambuf object
    Istream is (&sb);

    // set the stream object's initial state
    is.setstate (states [i]);

    // the number of extracted whitespace characters expected to
    // be reported by gcount() must equal the number of successful
    // extractions computed by the the stream buffer overridden
    // underflow member function
    const int extract =
        is.good () ? j < k ? int (j) < l ? j
                                         : l < 0 ? 0 : l
                           : int (k) < l ? k
                                         : l < 0 ? 0 : l
                   : 0;

    charT buf [256] = { 0 };

    std::streamsize nread = -1;

    // format the FCALL environment variable so that it can be
    // conveniently used in diagnostics below
    rw_fprintf (0, "%u. %{$FCALL!:@}",
                iter,
                "%{$ISTREAM}(%{*Ac}).readsome(%p, %d)",
                int (sizeof *cbuf), cbuf, buf, j);

#ifndef _RWSTD_NO_EXCEPTIONS

    const char *caught = 0;

    // on every other iteration set badbit in exceptions to check
    // that the thrown object is propagated by the function
    if (k % 2 && !is.bad ())
        is.exceptions (std::ios_base::badbit);

    try {
        nread = is.readsome (buf, j);
    }
    catch (const char *s) {
        caught = s;
    }
    catch (...) {

        caught = "...";

        rw_assert (0, 0, __LINE__,
                   "%{$FCALL} threw an exception of unexpected type");
    }

    //////////////////////////////////////////////////////////////////
    // verify that the function propagates exceptions thrown from the
    // streambuf object only when badbit is set in the stream object's
    // exceptions()

    rw_assert (!caught || (k % 2), 0, __LINE__,
               "%{$FCALL} unexpectedly propagated an exception");

#else   // if defined (_RWSTD_NO_EXCEPTIONS)

    nread = is.readsome (buf, j);

//.........这里部分代码省略.........