Fix #1284: avoid buffering-as-String for JsonParser.getFloat()/getDouble()/getDecimal()

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -33,6 +33,8 @@ a pure JSON library.
 #1274: `NUL`-corrupted keys, values on JSON serialization
  (reported, fix contributed by Jared S)
 #1277: Add back Java 22 optimisation in FastDoubleParser
+#1284: Optimize `JsonParser.getDoubleValue()/getFloatValue()/getDecimalValue()`
+  to avoid String allocation
 #1305: Make helper methods of `WriterBasedJsonGenerator` non-final to allow overriding
   (contributed by @zhangOranges)
 #1310: Add new `StreamReadConstraints` (`maxTokenCount`) to limit maximum number

src/main/java/com/fasterxml/jackson/core/base/ParserBase.java

@@ -847,6 +847,7 @@ public double getDoubleValue() throws IOException
             if (_numTypesValid == NR_UNKNOWN) {
                 _parseNumericValue(NR_DOUBLE);
             }
+            // if underlying type not FP, need conversion:
             if ((_numTypesValid & NR_DOUBLE) == 0) {
                 convertNumberToDouble();
             }
@@ -987,17 +988,19 @@ private void _parseSlowFloat(int expType) throws IOException
         if (expType == NR_BIGDECIMAL) {
             // 04-Dec-2022, tatu: Let's defer actual decoding until it is certain
             //    value is actually needed.
-            _numberBigDecimal = null;
-            _numberString = _textBuffer.contentsAsString();
+            // 24-Jun-2024, tatu: No; we shouldn't have to defer unless specifically
+            //    request w/ `getNumberValueDeferred()` or so
+            _numberBigDecimal = _textBuffer.contentsAsDecimal(isEnabled(StreamReadFeature.USE_FAST_DOUBLE_PARSER));
             _numTypesValid = NR_BIGDECIMAL;
+        } else if (expType == NR_DOUBLE) {
+            _numberDouble = _textBuffer.contentsAsDouble(isEnabled(StreamReadFeature.USE_FAST_DOUBLE_PARSER));
+            _numTypesValid = NR_DOUBLE;
         } else if (expType == NR_FLOAT) {
-            _numberFloat = 0.0f;
-            _numberString = _textBuffer.contentsAsString();
+            _numberFloat = _textBuffer.contentsAsFloat(isEnabled(StreamReadFeature.USE_FAST_DOUBLE_PARSER));
             _numTypesValid = NR_FLOAT;
-        } else {
-            // Otherwise double has to do
-            // 04-Dec-2022, tatu: We can get all kinds of values here, NR_DOUBLE
-            //    but also NR_INT or even NR_UNKNOWN. Shouldn't we try further
+        } else { // NR_UNKOWN, or one of int types
+            // 04-Dec-2022, tatu: We can get all kinds of values here
+            //    (NR_INT, NR_LONG or even NR_UNKNOWN). Should we try further
             //    deferring some typing?
             _numberDouble = 0.0;
             _numberString = _textBuffer.contentsAsString();
@@ -1248,7 +1251,8 @@ protected BigInteger _convertBigDecimalToBigInteger(BigDecimal bigDec) throws IO
     protected BigInteger _getBigInteger() throws JsonParseException {
         if (_numberBigInt != null) {
             return _numberBigInt;
-        } else if (_numberString == null) {
+        }
+        if (_numberString == null) {
             throw new IllegalStateException("cannot get BigInteger from current parser state");
         }
         try {
@@ -1276,7 +1280,8 @@ protected BigInteger _getBigInteger() throws JsonParseException {
     protected BigDecimal _getBigDecimal() throws JsonParseException {
         if (_numberBigDecimal != null) {
             return _numberBigDecimal;
-        } else if (_numberString == null) {
+        }
+        if (_numberString == null) {
             throw new IllegalStateException("cannot get BigDecimal from current parser state");
         }
         try {

src/main/java/com/fasterxml/jackson/core/util/TextBuffer.java

@@ -643,18 +643,38 @@ public float contentsAsFloat(final boolean useFastParser) throws NumberFormatExc
     }
 
     /**
-     * @return Buffered text value parsed as a {@link BigDecimal}, if possible
-     * @throws NumberFormatException if contents are not a valid Java number
-     *
-     * @deprecated Since 2.15 just access String contents if necessary, call
-     *   {@link NumberInput#parseBigDecimal(String, boolean)} (or other overloads)
-     *   directly instead
+     * @deprecated Since 2.15 use {@link #contentsAsDecimal(boolean)} instead.
      */
     @Deprecated
     public BigDecimal contentsAsDecimal() throws NumberFormatException {
-        // Was more optimized earlier, removing special handling due to deprecation
+        return contentsAsDecimal(false);
+    }
+
+    /**
+     * @since 2.18
+     */
+    public BigDecimal contentsAsDecimal(final boolean useFastParser) throws NumberFormatException
+    {
+        // Order in which check is somewhat arbitrary... try likeliest ones
+        // that do not require allocation first
+
+        // except _resultString first since it works best with JDK (non-fast parser)
+        if (_resultString != null) {
+            return NumberInput.parseBigDecimal(_resultString, useFastParser);
+        }
+        if (_inputStart >= 0) { // shared?
+            return NumberInput.parseBigDecimal(_inputBuffer, _inputStart, _inputLen, useFastParser);
+        }
+        if (_currentSize == 0) { // all content in current segment!
+            return NumberInput.parseBigDecimal(_currentSegment, 0, _currentSize, useFastParser);
+        }
+        if (_resultArray != null) {
+            return NumberInput.parseBigDecimal(_resultArray, useFastParser);
+        }
+
+        // Otherwise, segmented so need to use slow path
         try {
-            return NumberInput.parseBigDecimal(contentsAsArray());
+            return NumberInput.parseBigDecimal(contentsAsArray(), useFastParser);
         } catch (IOException e) {
             // JsonParseException is used to denote a string that is too long
             throw new NumberFormatException(e.getMessage());

src/test/java/com/fasterxml/jackson/core/base/NumberReadDeferralTest.java

@@ -0,0 +1,45 @@
+package com.fasterxml.jackson.core.base;
+
+import com.fasterxml.jackson.core.*;
+import com.fasterxml.jackson.core.JsonParser.NumberType;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+// Tests to verify [core#1284]: no buffering for specific
+// access
+public class NumberReadDeferralTest extends JUnit5TestBase
+{
+    private final JsonFactory JSON_F = newStreamFactory();
+
+    private final String NUM_DOC = "[ 0.1 ]";
+
+    @Test
+    public void testDoubleWrtBuffering() throws Exception
+    {
+        try (ParserBase p = (ParserBase) JSON_F.createParser(NUM_DOC)) {
+            assertNull(p._numberString);
+            assertToken(JsonToken.START_ARRAY, p.nextToken());
+
+            assertToken(JsonToken.VALUE_NUMBER_FLOAT, p.nextToken());
+            assertEquals(NumberType.DOUBLE, p.getNumberType());
+//            assertNull(p._numberString);
+            assertEquals(0.1, p.getDoubleValue());
+            assertNull(p._numberString);
+        }
+    }
+
+    @Test
+    public void testFloatWrtBuffering() throws Exception
+    {
+        
+    }
+
+    @Test
+    public void testBigDecimalWrtBuffering() throws Exception
+    {
+        
+    }
+}