Add DataUtils.getMapName() as faster alternative to parseMap().get("name")

h2/src/main/org/h2/mvstore/DataUtils.java

@@ -613,6 +613,40 @@ public final class DataUtils {
         }
     }
 
+    /**
+     * @param buff output buffer, should be empty
+     * @param s parsed string
+     * @param i offset to parse from
+     * @param size stop offset (exclusive)
+     * @return new offset
+     */
+    private static int parseMapValue(StringBuilder buff, String s, int i, int size) {
+        while (i < size) {
+            char c = s.charAt(i++);
+            if (c == ',') {
+                break;
+            } else if (c == '\"') {
+                while (i < size) {
+                    c = s.charAt(i++);
+                    if (c == '\\') {
+                        if (i == size) {
+                            throw DataUtils.newIllegalStateException(
+                                    DataUtils.ERROR_FILE_CORRUPT,
+                                    "Not a map: {0}", s);
+                        }
+                        c = s.charAt(i++);
+                    } else if (c == '\"') {
+                        break;
+                    }
+                    buff.append(c);
+                }
+            } else {
+                buff.append(c);
+            }
+        }
+        return i;
+    }
+
     /**
      * Parse a key-value pair list.
      *
@@ -622,6 +656,7 @@ public final class DataUtils {
      */
     public static HashMap<String, String> parseMap(String s) {
         HashMap<String, String> map = New.hashMap();
+        StringBuilder buff = new StringBuilder();
         for (int i = 0, size = s.length(); i < size;) {
             int startKey = i;
             i = s.indexOf(':', i);
@@ -630,7 +665,33 @@ public final class DataUtils {
                         DataUtils.ERROR_FILE_CORRUPT, "Not a map: {0}", s);
             }
             String key = s.substring(startKey, i++);
+            i = parseMapValue(buff, s, i, size);
+            map.put(key, buff.toString());
+            buff.setLength(0);
+        }
+        return map;
+    }
+
+    /**
+     * Parse a name from key-value pair list.
+     *
+     * @param s the list
+     * @return value of name item, or {@code null}
+     * @throws IllegalStateException if parsing failed
+     */
+    public static String getMapName(String s) {
+        for (int i = 0, size = s.length(); i < size;) {
+            int startKey = i;
+            i = s.indexOf(':', i);
+            if (i < 0) {
+                throw DataUtils.newIllegalStateException(
+                        DataUtils.ERROR_FILE_CORRUPT, "Not a map: {0}", s);
+            }
+            if (i++ - startKey == 4 && s.regionMatches(startKey, "name", 0, 4)) {
                 StringBuilder buff = new StringBuilder();
+                i = parseMapValue(buff, s, i, size);
+                return buff.toString();
+            } else {
                 while (i < size) {
                     char c = s.charAt(i++);
                     if (c == ',') {
@@ -648,15 +709,12 @@ public final class DataUtils {
                             } else if (c == '\"') {
                                 break;
                             }
-                        buff.append(c);
                         }
-                } else {
-                    buff.append(c);
                     }
                 }
-            map.put(key, buff.toString());
             }
-        return map;
+        }
+        return null;
     }
 
     /**

h2/src/main/org/h2/mvstore/MVStore.java

@@ -2462,7 +2462,7 @@ public final class MVStore {
     public synchronized String getMapName(int id) {
         checkOpen();
         String m = meta.get(MVMap.getMapKey(id));
-        return m == null ? null : DataUtils.parseMap(m).get("name");
+        return m == null ? null : DataUtils.getMapName(m);
     }
 
     /**

h2/src/test/org/h2/test/store/TestDataUtils.java

@@ -99,16 +99,34 @@ public class TestDataUtils extends TestBase {
         DataUtils.appendMap(buff,  "c", "1,2");
         DataUtils.appendMap(buff,  "d", "\"test\"");
         DataUtils.appendMap(buff,  "e", "}");
-        assertEquals(":,a:1,b:\",\",c:\"1,2\",d:\"\\\"test\\\"\",e:}", buff.toString());
+        DataUtils.appendMap(buff,  "name", "1:1\",");
+        String encoded = buff.toString();
+        assertEquals(":,a:1,b:\",\",c:\"1,2\",d:\"\\\"test\\\"\",e:},name:\"1:1\\\",\"", encoded);
 
-        HashMap<String, String> m = DataUtils.parseMap(buff.toString());
-        assertEquals(6, m.size());
+        HashMap<String, String> m = DataUtils.parseMap(encoded);
+        assertEquals(7, m.size());
         assertEquals("", m.get(""));
         assertEquals("1", m.get("a"));
         assertEquals(",", m.get("b"));
         assertEquals("1,2", m.get("c"));
         assertEquals("\"test\"", m.get("d"));
         assertEquals("}", m.get("e"));
+        assertEquals("1:1\",", m.get("name"));
+        assertEquals("1:1\",", DataUtils.getMapName(encoded));
+
+        buff.setLength(0);
+        DataUtils.appendMap(buff,  "1", "1");
+        DataUtils.appendMap(buff,  "name", "2");
+        DataUtils.appendMap(buff,  "3", "3");
+        encoded = buff.toString();
+        assertEquals("2", DataUtils.parseMap(encoded).get("name"));
+        assertEquals("2", DataUtils.getMapName(encoded));
+
+        buff.setLength(0);
+        DataUtils.appendMap(buff,  "name", "xx");
+        encoded = buff.toString();
+        assertEquals("xx", DataUtils.parseMap(encoded).get("name"));
+        assertEquals("xx", DataUtils.getMapName(encoded));
     }
 
     private void testMapRandomized() {