Start an asynchronous operation to read data into a dynamic buffer sequence, or into a streambuf, until it contains a delimiter, matches a regular expression, or a function object indicates a match.

template<
    typename AsyncReadStream,
    typename DynamicBuffer,
    typename ReadHandler>
DEDUCED async_read_until(
    AsyncReadStream & s,
    DynamicBuffer && buffers,
    char delim,
    ReadHandler && handler);
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template<
    typename AsyncReadStream,
    typename DynamicBuffer,
    typename ReadHandler>
DEDUCED async_read_until(
    AsyncReadStream & s,
    DynamicBuffer && buffers,
    string_view delim,
    ReadHandler && handler);
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