[jira] Commented: (LANG-505) Rewrite StringEscapeUtils

    [ https://issues.apache.org/jira/browse/LANG-505?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12716850#action_12716850 ]

Henri Yandell commented on LANG-505:
------------------------------------

Worked on this some more. The notion of passing in CharSequences works well, with a codepoint version to ease coding (and currently a char version but it may be pointless as codepoints feel like chars). I ignored the idea of having a query as to whether an escape will happen and then a second invocation to do the escape. It's not needed as yet.

escapeJava looks like:

{code:java}
    public static void escapeJava(String input, Writer out) throws IOException {
        AggregateEscaper escapers = new AggregateEscaper(
            new LookupTranslator(
                      new String[][] {
                            {"\"", "\\\""},
                            {"\\", "\\\\"}
                      }),
            new EscapeLowAsciiAsUnicode(),
            new EscapeNonAsciiAsUnicode()
        );
         
        escape(input, escapers, out);
    }
{code}

ie) despite the API change, much the same as the above. I went ahead and stopped the Escaper extending FilterWriter so that's why the out variable stops getting repeated everywhere.

The core algorithm itself now looks like:

{code:java}
    public static void escape(CharSequence input, CharSequenceEscaper escaper, Writer out) throws IOException {
        if (out == null) {
            throw new IllegalArgumentException("The Writer must not be null");
        }
        if (input == null) {
            return;
        }
        if (escaper == null) {
            throw new IllegalArgumentException("The CharSequenceEscaper must not be null. " +
                                               "Use NullEscaper if you expected this to mean a no-operation");
        }
        int sz = Character.codePointCount(input, 0, input.length());
        for (int i = 0; i < sz; i++) {

            // consumed is the number of codepoints consumed
            int consumed = escaper.escape(input, i, out);

            if(consumed == 0) {
                out.write( Character.toChars( Character.codePointAt(input, i) ) );
            } else {
                // contract with escapers is that they have to understand codepoints and they just took care of a surrogate pair
                for(int j=0; j<consumed; j++) {
                    if(i < sz - 2) {
                        // for loop will increment 1 anyway, so remove 1 from the end charCount
                        i += Character.charCount( Character.codePointAt(input, i) ) - 1;
                    }
                }
            }
        }
    }
{code}

This should be able to implement unescape as well as it is now a simple general purpose text translation API that can handle escaping n->m changes in characters. ie) a plugin can choose to consume 3 characters and turn them into 5, and vice versa.

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