Improve escaping performance

src/main/java/com/samskivert/mustache/Escapers.java

@@ -4,11 +4,17 @@
 
 package com.samskivert.mustache;
 
+import java.io.IOException;
+import java.io.UncheckedIOException;
+
 /**
  * Defines some standard {@link Mustache.Escaper}s.
  */
 public class Escapers
 {
+    // TODO for 2.0 this class should be final and have a private constructor but that
+    // would break semver on the off chance someone did extend it.
+
     /** Escapes HTML entities. */
     public static final Mustache.Escaper HTML = simple(new String[][] {
         { "&",  "&" },
@@ -30,6 +36,11 @@ public class Escapers
     /** Returns an escaper that replaces a list of text sequences with canned replacements.
      * @param repls a list of {@code (text, replacement)} pairs. */
     public static Mustache.Escaper simple (final String[]... repls) {
+        String[] lookupTable = Lookup7bitEscaper.createTable(repls);
+        if (lookupTable != null) {
+            return new Lookup7bitEscaper(lookupTable);
+        }
+        // our lookup replacements are not 7 bit ascii.
         return new Mustache.Escaper() {
             @Override public String escape (String text) {
                 for (String[] escape : repls) {
@@ -39,4 +50,98 @@ public class Escapers
             }
         };
     }
+    // This is based on benchmarking: https://github.com/jstachio/escape-benchmark
+    private static class Lookup7bitEscaper implements Mustache.Escaper {
+        /*
+         * This only works for replacing the lower 7 bit ascii
+         * characters
+         */
+        private final String[] lookupTable;
+
+        private Lookup7bitEscaper(
+                String[] lookupTable) {
+            super();
+            this.lookupTable = lookupTable;
+        }
+
+        static /* @Nullable */ String[] createTable (String[][] mappings) {
+            String[] table = new String[128];
+            for (String[] entry : mappings) {
+                String key = entry[0];
+                String value = entry[1];
+                if (key.length() != 1) {
+                    return null;
+                }
+                char k = key.charAt(0);
+                if (k > 127) {
+                    return null;
+                }
+                table[k] = value;
+            }
+            return table;
+        }
+
+        @Override
+        public void escape (Appendable a, CharSequence raw) throws IOException {
+            int end = raw.length();
+            for (int i = 0, start = 0; i < end; i++) {
+                char c = raw.charAt(i);
+                String found = escapeChar(lookupTable, c);
+                /*
+                 * While this could be done with one loop it appears through
+                 * benchmarking that by having the first loop assume the string
+                 * to be not changed creates a fast path for strings with no escaping needed.
+                 */
+                if (found != null) {
+                    a.append(raw, 0, i);
+                    a.append(found);
+                    start = i = i + 1;
+                    for (; i < end; i++) {
+                        c = raw.charAt(i);
+                        found = escapeChar(lookupTable, c);
+                        if (found != null) {
+                            a.append(raw, start, i);
+                            a.append(found);
+                            start = i + 1;
+                        }
+                    }
+                    a.append(raw, start, end);
+                    return;
+                }
+            }
+            a.append(raw);
+        }
+
+        private static /* @Nullable */ String escapeChar (String[] lookupTable, char c) {
+            if (c > 127) {
+                return null;
+            }
+            return lookupTable[c];
+        }
+
+        @Override
+        public String escape (String raw) {
+            StringBuilder sb = new StringBuilder(raw.length());
+            try {
+                escape(sb, raw);
+            } catch (IOException e) {
+                throw new UncheckedIOException(e);
+            }
+            return sb.toString();
+        }
+
+        @Override
+        public String toString () {
+            StringBuilder sb = new StringBuilder();
+            sb.append("Escaper[");
+            for(char i = 0; i < lookupTable.length; i++) {
+                String value = lookupTable[i];
+                if (value != null) {
+                    sb.append("{'").append(i).append("', '").append(value).append("'},");
+                }
+            }
+            sb.append("]");
+            return sb.toString();
+        }
+    }
 }

src/main/java/com/samskivert/mustache/Mustache.java

@@ -317,6 +317,17 @@ public class Mustache {
         default CharSequence escape (CharSequence raw) {
             return escape(raw.toString());
         }
+
+        /**
+          * Escapes the raw characters with escape sequeneces if needed and appends to the appendable.
+          * The default implementation calls {@link #escape(CharSequence)}.
+          * @param a the stream like to append to.
+          * @param raw input string.
+          * @throws IOException if an error happens while writing to the appendable.
+          */
+        default void escape (Appendable a, CharSequence raw) throws IOException {
+            a.append(escape(raw));
+        }
     }
 
     /** Handles loading partial templates. */
@@ -1317,7 +1328,7 @@ public class Mustache {
                     "No key, method or field with name '" + _name + "' on line " + _line;
                 throw new MustacheException.Context(msg, _name, _line);
             }
-            write(out, _escaper.escape(_formatter.format(value)));
+            escape(out, _formatter.format(value), _escaper);
         }
         @Override public void decompile (Delims delims, StringBuilder into) {
             delims.addTag(' ', _name, into);

src/main/java/com/samskivert/mustache/Template.java

@@ -433,6 +433,14 @@ public class Template {
                 throw new MustacheException(ioe);
             }
         }
+
+        protected static void escape (Appendable out, CharSequence data, Mustache.Escaper escape) {
+            try {
+                escape.escape(out, data);
+            } catch (IOException ioe) {
+                throw new MustacheException(ioe);
+            }
+        }
     }
 
     /** Used to cache variable fetchers for a given context class, name combination. */