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https://issues.apache.org/jira/browse/LANG-877?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Henri Yandell updated LANG-877:
-------------------------------
Fix Version/s: Patch Needed
> Performance improvements for StringEscapeUtils
> ----------------------------------------------
>
> Key: LANG-877
> URL: https://issues.apache.org/jira/browse/LANG-877
> Project: Commons Lang
> Issue Type: Improvement
> Components: lang.text.translate.*
> Affects Versions: 3.1
> Reporter: Henri Yandell
> Fix For: Patch Needed
>
>
> An email on the list from Lawrence Angrave:
> Hi,
> Some comments that are relevant to Apache3 UnicodeEscaper and Apache2's
> StringEscapeUtils.java
> Summary-
> * I noticed the current Apache code creates three String objects each
> time it writes a unicode hexadecimal value.
> * Apache3 can also create a char[] array per character translation
> (but I do not include a fix for that)
> * This is a easy-to-fix performance bottleneck when writing many
> non-ascii characters.
> * The logic to test for unicode values of different magnitudes can
> also be simplified.
> * Benchmark and code fixes for Apache2 and Apache 3 are included. I do
> not have time to become an Apache maintainer. use or ignore at your
> choice.
> * I'm not interested in being a developer for Commons Lang Use it or
> not - that's a choice for Commons Lang developers.
> A simple fix more than doubles the string escape speed (40 ms v 100ms to
> translate all unicode characters) for Apache3.
> The older Apache2-style implementation can now translate all unicode
> characters in 8ms.
> The existing Apache3/Apache2 write unicode hex values like this-
> if (codepoint > 0xfff) {
> out.write("\\u" + hex(codepoint));
> } else if (codepoint > 0xff) {
> out.write("\\u0" + hex(codepoint));
> } else if (codepoint > 0xf) {
> out.write("\\u00" + hex(codepoint));
> } else {
> out.write("\\u000" + hex(codepoint));
> }
> The hex() function,
> //hex(): return Integer.toHexString(codepoint).toUpperCase(Locale.ENGLISH);
> also creates two string objects, so we have 3 objects per unicode hex value.
> FIX:
> The padding logic can be simplified and per-character object creation can be
> eliminated by writing hex digits directly
> out.write("\\u");
> out.write(HEX_DIGIT[(codepoint >> 12) & 15]);
> out.write(HEX_DIGIT[(codepoint >> 8) & 15]);
> out.write(HEX_DIGIT[(codepoint >> 4) & 15]);
> out.write(HEX_DIGIT[(codepoint) & 15]);
> where HEX_DIGIT is
> public static final char[] HEX_DIGIT = "0123456789ABCDEF".toCharArray();
> I believe this is safe for all Locales.
> When benchmarked it was disconcerting that Apache3 is still five times slower
> (40ms instead of 8ms) than my rewritten Apache2 version (included below).
> My guess is that there are other unnecessary per-character object creation
> issues still lurking Here's one example -
> CharSequenceTranslator.translate(CharSequence input, Writer out) :
> char[] c = *Character.toChars*(Character.codePointAt(input, pos))
> For better performance this should use toChars(int codePoint, char[] dst,
> int dstIndex) , which can re-use the dst char array
> The benchmark, my version of a Apache2-style escapeJavaStyleString
> implementation and the code fix for UnicodeEscaper.java are included below.
> I hope this email does not go into a blackhole... Feel free to forward it to
> the relevant maintainers.
> Regards,
> Lawrence.
> public static final char[] HEX_DIGIT = "0123456789ABCDEF".toCharArray();
> public static final char[] CONTROL_CHARS; // non-zero entries for special
> case control characters
> static {
> CONTROL_CHARS = new char[32];
> CONTROL_CHARS['\b'] = 'b';
> CONTROL_CHARS['\n'] = 'n';
> CONTROL_CHARS['\t'] = 't';
> CONTROL_CHARS['\f'] = 'f';
> CONTROL_CHARS['\r'] = 'r';
> }
> public static void escapeJavaStyleString(Writer out, String s, boolean
> escapeSingleQuote) throws IOException {
> // Apache2 makes the following checks, so we will too-
> if(out==null) throw new IllegalArgumentException("The Writer must not be
> null");
> if(s == null) return;
> final int len = s.length();
> for(int i =0; i < len;i++)
> escapeChar(out,s.charAt(i), escapeSingleQuote);
> }
> public static void escapeChar(Writer out, char c, boolean
> escapeSingleQuote)
> throws IOException {
> // Most common case
> if (c >= 32 && c < 127) {
> if (c == '\\' || c == '"' || (c == '\'' && escapeSingleQuote))
> out.write('\\');
> out.write(c);
> return;
> }
> out.write('\\');
> if (c < 32 && CONTROL_CHARS[c] != 0) {
> out.write(CONTROL_CHARS[c]);
> return;
> }
> // Fast 4 digit uppercase hexadecimal without object creation
> out.write('u');
> out.write(HEX_DIGIT[(c >> 12) & 15]);
> out.write(HEX_DIGIT[(c >> 8) & 15]);
> out.write(HEX_DIGIT[(c >> 4) & 15]);
> out.write(HEX_DIGIT[(c) & 15]);
> }
> FYI The benchmark test just writes all possible unicode characters into a
> null writer:
> Writer nullWriter = new Writer() {
> public void write(String s) {
> };
> public void write(int c) {
> }
> public void close() throws IOException {
> }
> public void flush() throws IOException {
> }
> public void write(char[] cbuf, int off, int len) throws
> IOException {
> }
> };
> StringBuilder sb = new StringBuilder(0x10000);
> for (int i = 0; i <= 0xffff; i++)
> sb.append((char) i);
> String allChars = sb.toString();
> long t1 = System.currentTimeMillis();
> StringEscaper.escapeJavaStyleString(nullWriter, allChars, true);
> long t2 = System.currentTimeMillis();
> System.out.println(t2 - t1);
> long t3 = System.currentTimeMillis();
> CharSequenceTranslator translator = StringEscapeUtils.ESCAPE_JAVA;
> translator.translate(allChars, nullWriter);
> long t4 = System.currentTimeMillis();
> System.out.println(t4 - t3);
> The modification to Apache3 UnicodeEscaper :
> if (codepoint > 0xffff) {
> // TODO: Figure out what to do. Output as two Unicodes?
> // Does this make this a Java-specific output class?
> out.write("\\u" + hex(codepoint));
> } else if (1 == 0) { //*OLD SLOW CODE* (can be removed)
> *if (codepoint > 0xfff) {
> out.write("\\u" + hex(codepoint));
> } else if (codepoint > 0xff) {
> out.write("\\u0" + hex(codepoint));
> } else if (codepoint > 0xf) {
> out.write("\\u00" + hex(codepoint));
> } else {
> out.write("\\u000" + hex(codepoint));
> }*
> } else { // *NEW FAST CODE*
> * out.write("\\u");
> out.write(HEX_DIGIT[(codepoint >> 12) & 15]);
> out.write(HEX_DIGIT[(codepoint >> 8) & 15]);
> out.write(HEX_DIGIT[(codepoint >> 4) & 15]);
> out.write(HEX_DIGIT[(codepoint) & 15]);*
> }
> *and add public static final char[] HEX_DIGIT =
> "0123456789ABCDEF".toCharArray();**
> *
> ps.
> The home page for Commons lang
> http://commons.apache.org/proper/commons-lang/)
> has the following 404 link on the left
> Contributing Patches
> http://commons.apache.org/proper/patches.html
> (I believe the 'proper' is unnecessary)
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