private void pauseCapture() {
        int end = current == -1 ? index : index - 1;
        captureBuffer.append(buffer, captureStart, end - captureStart);
        captureStart = -1;
    }
Reads the entire input from the given reader and parses it as JSON. The input must contain a
valid JSON value, optionally padded with whitespace.
<p>
Characters are read in chunks into an input buffer of the given size. Hence, wrapping a reader
in an additional <code>BufferedReader</code> likely won't improve reading performance.
</p>

@param reader the reader to read the input from
@param buffersize the size of the input buffer in chars
@throws IOException if an I/O error occurs in the reader
@throws ModelSyntaxException if the input is not valid JSON
smithy-model/src/main/java/software/amazon/smithy/model/node/internal/JsonParser.java