Merge branch '2.12' into 2.13

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -36,6 +36,7 @@ JSON library.
   show content, include byte offset
 #700: Unable to ignore properties when deserializing. TokenFilter seems broken
  (reported by xiazuojie@github)
+#712: Optimize array allocation by `JsonStringEncoder`
 - Add `mvnw` wrapper
 
 2.12.4 (06-Jul-2021)

src/main/java/com/fasterxml/jackson/core/io/JsonStringEncoder.java

@@ -30,8 +30,14 @@ public final class JsonStringEncoder
     private final static int SURR2_FIRST = 0xDC00;
     private final static int SURR2_LAST = 0xDFFF;
 
-    private final static int INITIAL_CHAR_BUFFER_SIZE = 120;
-    private final static int INITIAL_BYTE_BUFFER_SIZE = 200;
+    // 18-Aug-2021, tatu: [core#712] Change to more dynamic allocation; try
+    //    to estimate ok initial encoding buffer, switch to segmented for
+    //    possible (but rare) big content
+
+    final static int MIN_CHAR_BUFFER_SIZE = 16;
+    final static int MAX_CHAR_BUFFER_SIZE = 32000; // use segments beyond
+    final static int MIN_BYTE_BUFFER_SIZE = 24;
+    final static int MAX_BYTE_BUFFER_SIZE = 32000; // use segments beyond
 
     /*
     /**********************************************************************
@@ -70,11 +76,11 @@ public static JsonStringEncoder getInstance() {
      */
     public char[] quoteAsString(String input)
     {
-        char[] outputBuffer = new char[INITIAL_CHAR_BUFFER_SIZE];
+        final int inputLen = input.length();
+        char[] outputBuffer = new char[_initialCharBufSize(inputLen)];
         final int[] escCodes = CharTypes.get7BitOutputEscapes();
         final int escCodeCount = escCodes.length;
         int inPtr = 0;
-        final int inputLen = input.length();
         TextBuffer textBuffer = null;
         int outPtr = 0;
         char[] qbuf = null;
@@ -152,11 +158,11 @@ public char[] quoteAsString(CharSequence input)
 
         TextBuffer textBuffer = null;
 
-        char[] outputBuffer = new char[INITIAL_CHAR_BUFFER_SIZE];
+        final int inputLen = input.length();
+        char[] outputBuffer = new char[_initialCharBufSize(inputLen)];
         final int[] escCodes = CharTypes.get7BitOutputEscapes();
         final int escCodeCount = escCodes.length;
         int inPtr = 0;
-        final int inputLen = input.length();
         int outPtr = 0;
         char[] qbuf = null;
 
@@ -274,7 +280,7 @@ public byte[] quoteAsUTF8(String text)
         int inputPtr = 0;
         int inputEnd = text.length();
         int outputPtr = 0;
-        byte[] outputBuffer = new byte[INITIAL_BYTE_BUFFER_SIZE];
+        byte[] outputBuffer = new byte[_initialByteBufSize(inputEnd)];
         ByteArrayBuilder bb = null;
 
         main:
@@ -380,7 +386,7 @@ public byte[] encodeAsUTF8(String text)
         int inputPtr = 0;
         int inputEnd = text.length();
         int outputPtr = 0;
-        byte[] outputBuffer = new byte[INITIAL_BYTE_BUFFER_SIZE];
+        byte[] outputBuffer = new byte[_initialByteBufSize(inputEnd)];
         int outputEnd = outputBuffer.length;
         ByteArrayBuilder bb = null;
 
@@ -481,7 +487,7 @@ public byte[] encodeAsUTF8(CharSequence text)
         int inputPtr = 0;
         int inputEnd = text.length();
         int outputPtr = 0;
-        byte[] outputBuffer = new byte[INITIAL_BYTE_BUFFER_SIZE];
+        byte[] outputBuffer = new byte[_initialByteBufSize(inputEnd)];
         int outputEnd = outputBuffer.length;
         ByteArrayBuilder bb = null;
 
@@ -628,4 +634,22 @@ private static int _convert(int p1, int p2) {
     private static void _illegal(int c) {
         throw new IllegalArgumentException(UTF8Writer.illegalSurrogateDesc(c));
     }
+
+    // non-private for unit test access
+    static int _initialCharBufSize(int strLen) {
+        // char->char won't expand but we need to give some room for escaping
+        // like 1/8 (12.5% expansion) but cap addition to something modest
+        final int estimated = Math.max(MIN_CHAR_BUFFER_SIZE,
+                strLen + Math.min(6 + (strLen >> 3), 1000));
+        return Math.min(estimated, MAX_CHAR_BUFFER_SIZE);
+    }
+
+    // non-private for unit test access
+    static int _initialByteBufSize(int strLen) {
+        // char->byte for UTF-8 can expand size by x3 itself, and escaping
+        // more... but let's use lower factor of 1.5
+        final int doubled = Math.max(MIN_BYTE_BUFFER_SIZE, strLen + 6 + (strLen>>1));
+        // but use upper bound for humongous cases (segmented)
+        return Math.min(doubled, MAX_BYTE_BUFFER_SIZE);
+    }
 }

src/test/java/com/fasterxml/jackson/core/io/TestJsonStringEncoder.java

@@ -130,13 +130,55 @@ public void testCharSequenceWithCtrlChars() throws Exception
         assertEquals("\\u0000\\u0001\\u0002\\u0003\\u0004", output.toString());
     }
 
+    // [core#712]: simple sanity checks for calculation logic
+    public void testByteBufferDefaultSize()
+    {
+        // byte size is simple, x2 except below buffer size 24
+        assertEquals(JsonStringEncoder.MIN_BYTE_BUFFER_SIZE,
+                JsonStringEncoder._initialByteBufSize(1));
+        assertEquals(JsonStringEncoder.MIN_BYTE_BUFFER_SIZE,
+                JsonStringEncoder._initialByteBufSize(11));
+
+        assertEquals(36, JsonStringEncoder._initialByteBufSize(20));
+        assertEquals(73, JsonStringEncoder._initialByteBufSize(45));
+        assertEquals(1506, JsonStringEncoder._initialByteBufSize(1000));
+        assertEquals(9006, JsonStringEncoder._initialByteBufSize(6000));
+
+        // and up to max initial size
+        assertEquals(JsonStringEncoder.MAX_BYTE_BUFFER_SIZE,
+                JsonStringEncoder._initialByteBufSize(JsonStringEncoder.MAX_BYTE_BUFFER_SIZE + 1));
+        assertEquals(JsonStringEncoder.MAX_BYTE_BUFFER_SIZE,
+                JsonStringEncoder._initialByteBufSize(999999));
+    }
+
+    // [core#712]: simple sanity checks for calculation logic
+    public void testCharBufferDefaultSize()
+    {
+        // char[] bit more complex, starts with minimum size of 16
+        assertEquals(JsonStringEncoder.MIN_CHAR_BUFFER_SIZE,
+                JsonStringEncoder._initialCharBufSize(1));
+        assertEquals(JsonStringEncoder.MIN_CHAR_BUFFER_SIZE,
+                JsonStringEncoder._initialCharBufSize(8));
+
+        // and then grows by ~5%
+        assertEquals(62, JsonStringEncoder._initialCharBufSize(50));
+        assertEquals(118, JsonStringEncoder._initialCharBufSize(100));
+        assertEquals(1131, JsonStringEncoder._initialCharBufSize(1000));
+        assertEquals(9000, JsonStringEncoder._initialCharBufSize(8000));
+
+        // up to max, simi
+        assertEquals(JsonStringEncoder.MAX_CHAR_BUFFER_SIZE,
+                JsonStringEncoder._initialCharBufSize(32000));
+        assertEquals(JsonStringEncoder.MAX_CHAR_BUFFER_SIZE,
+                JsonStringEncoder._initialCharBufSize(900000));
+    }
+
     /*
-    /**********************************************************
+    /**********************************************************************
     /* Helper methods
-    /**********************************************************
+    /**********************************************************************
      */
 
-    
     private String generateRandom(int length)
     {
         StringBuilder sb = new StringBuilder(length);