AbstractCharInputReader throws ArrayIndexOutOfBoundsException when buffer starts with whitespace

[arun1ram]

Description

When parsing a CSV file, AbstractCharInputReader throws ArrayIndexOutOfBoundsException when buffer starts with whitespace and the parsing fails with the error below:

Exception in thread "main" com.univocity.parsers.common.TextParsingException: java.lang.ArrayIndexOutOfBoundsException - Index -1 out of bounds for length 128
Parser Configuration: CsvParserSettings:
	Auto configuration enabled=true
	Auto-closing enabled=true
	Autodetect column delimiter=false
	Autodetect quotes=false
	Column reordering enabled=true
	Delimiters for detection=[]
	Empty value=
	Escape unquoted values=false
	Header extraction enabled=false
	Headers=[null]
	Ignore leading whitespaces=false
	Ignore leading whitespaces in quotes=false
	Ignore trailing whitespaces=true
	Ignore trailing whitespaces in quotes=false
	Input buffer size=128
	Input reading on separate thread=false
	Keep escape sequences=false
	Keep quotes=false
	Length of content displayed on error=1000
	Line separator detection enabled=false
	Maximum number of characters per column=-1
	Maximum number of columns=20480
	Normalize escaped line separators=true
	Null value=null
	Number of records to read=all
	Processor=none
	Restricting data in exceptions=false
	RowProcessor error handler=null
	Selected fields=none
	Skip bits as whitespace=true
	Skip empty lines=true
	Unescaped quote handling=STOP_AT_DELIMITERFormat configuration:
	CsvFormat:
		Comment character=#
		Field delimiter=,
		Line separator (normalized)=\n
		Line separator sequence=\r\n
		Quote character="
		Quote escape character="
		Quote escape escape character=null
Internal state when error was thrown: line=1, column=34, record=1, charIndex=641, headers=[null]
	at com.univocity.parsers.common.AbstractParser.handleException(AbstractParser.java:402)
	at com.univocity.parsers.common.AbstractParser.parseNext(AbstractParser.java:623)
	at com.univocity.parsers.common.AbstractParser.internalParseAll(AbstractParser.java:552)
	at com.univocity.parsers.common.AbstractParser.parseAll(AbstractParser.java:545)
	at com.univocity.parsers.common.AbstractParser.parseAll(AbstractParser.java:532)
	at com.example.univocitytest.UnivocityTestApplication.main(UnivocityTestApplication.java:114)
Caused by: java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 128
	at com.univocity.parsers.common.input.AbstractCharInputReader.getString(AbstractCharInputReader.java:482)
	at com.univocity.parsers.csv.CsvParser.parseSingleDelimiterRecord(CsvParser.java:186)
	at com.univocity.parsers.csv.CsvParser.parseRecord(CsvParser.java:109)
	at com.univocity.parsers.common.AbstractParser.parseNext(AbstractParser.java:581)
	... 4 more

Reproducing the problem

The problem can only be reproduced with the attached CSV file
bad_file_bug.csv
because the data in the file and the input buffer size configuration causes the issue.
Create a simple java application with the main method as below:

    public static void main(String[] args) throws FileNotFoundException {
        CsvParserSettings settings = new CsvParserSettings();
        settings.setAutoConfigurationEnabled(true);
        settings.setAutoClosingEnabled(true);
        settings.setDelimiterDetectionEnabled(false);
        settings.setQuoteDetectionEnabled(false);
        settings.setColumnReorderingEnabled(true);
        settings.setEmptyValue("");
        settings.setEscapeUnquotedValues(false);
        settings.setHeaderExtractionEnabled(false);
        settings.setHeaders((String) null);
        settings.setIgnoreLeadingWhitespaces(false);
        settings.setIgnoreLeadingWhitespacesInQuotes(false);
        settings.setIgnoreTrailingWhitespaces(true);
        settings.setIgnoreTrailingWhitespacesInQuotes(false);
        settings.setInputBufferSize(128);
        settings.setReadInputOnSeparateThread(false);
        settings.setKeepEscapeSequences(false);
        settings.setKeepQuotes(false);
        settings.setErrorContentLength(1000);
        //settings.setLineSeparatorDetectionEnabled(true);
        settings.setMaxCharsPerColumn(-1);
        settings.setMaxColumns(20480);
        settings.setNormalizeLineEndingsWithinQuotes(true); //?
        settings.setNullValue("null");
        settings.setSkipBitsAsWhitespace(true);
        settings.setSkipEmptyLines(true);
        settings.setUnescapedQuoteHandling(UnescapedQuoteHandling.STOP_AT_DELIMITER);

        settings.getFormat().setComment('#');
        settings.getFormat().setDelimiter(',');
        settings.getFormat().setLineSeparator("\r\n");
        settings.getFormat().setQuote('"');
        settings.getFormat().setQuoteEscape('"');

        // Create a CSV parser
        CsvParser parser = new CsvParser(settings);

        // Parse all rows from a CSV file
        List<String[]> allRows = parser.parseAll(new FileReader("**path/to/the/attached/csv/file**"));

        // Print all rows
        for (String[] row : allRows) {
            for (String column : row) {
                System.out.print(column + "||");
            }
            System.out.println();
        }
    }

Use the attached csv file as input to the FIleReader constructor which is given as input to CsvParser.parseAll() method.
Running the above application reproduces the error mentioned in the description.

Root Cause

The problem occurs in the case when the input buffer size specified in configuration (in this case 128 ) makes it such that the first character in the buffer is a whitespace character. When getString() method of AbstractCharInputCharReader class is trying to trim the trailing whitespaces by walking back on the buffer until a non-whitespace character is seen. However, if the first character in the buffer is a whitepace character, the code tries to decrement variable i one more time and access the buffer with an index of -1. This causes the exception.

	public final String getString(char ch, char stop, boolean trim, String nullValue, int maxLength) {
		if (i == 0) {
			return null;
		}
		int i = this.i;
		for (; ch != stop; ch = buffer[i++]) {
			if (i >= length) {
				return null;
			}
			if (lineSeparator1 == ch && (lineSeparator2 == '\0' || lineSeparator2 == buffer[i])) {
				break;
			}
		}

		int pos = this.i - 1;
		int len = i - this.i;
		if (maxLength != -1 && len > maxLength) { //validating before trailing whitespace handling so this behaves as an appender.
			return null;
		}

		this.i = i - 1;

		if (trim) {
			i = i - 2;
			while (buffer[i] <= ' ' && whitespaceRangeStart < buffer[i]) {
				len--;
				i--;
			}
		}

		String out;
		if (len <= 0) {
			out = nullValue;
		} else {
			out = new String(buffer, pos, len);
		}

		nextChar();

		return out;
	}```