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ferenc-csakyFerenc Csaky
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Ferenc Csaky
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added O(n^1.5) BigDecimal parser implementation (#677)
Co-authored-by: Ferenc Csaky <[email protected]>
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+166
-15
lines changed

3 files changed

+166
-15
lines changed

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

+155
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,155 @@
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package com.fasterxml.jackson.core.io;
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import java.math.BigDecimal;
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// Based on a great idea of Eric Obermühlner to use a tree of smaller BigDecimals for parsing really big numbers
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// with O(n^1.5) complexity instead of O(n^2) when using the constructor for a decimal representation from JDK 8/11:
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// https://github.com/eobermuhlner/big-math/commit/7a5419aac8b2adba2aa700ccf00197f97b2ad89f
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public final class BigDecimalParser {
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private final char[] chars;
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private final int off;
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private final int len;
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BigDecimalParser(char[] chars, int off, int len) {
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this.chars = chars;
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this.off = off;
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this.len = len;
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}
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BigDecimal parse() throws NumberFormatException {
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try {
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if (len < 500) {
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return new BigDecimal(chars, off, len);
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}
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int splitLen = len / 10;
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return parseBigDecimal(splitLen);
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} catch (NumberFormatException e) {
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String val = new String(chars, off, len);
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throw new NumberFormatException("Value \"" + val + "\" can not be represented as BigDecimal."
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+ " Reason: " + e.getMessage());
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}
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}
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private BigDecimal parseBigDecimal(int splitLen) {
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boolean numHasSign = false;
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boolean expHasSign = false;
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boolean neg = false;
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int numIdx = 0;
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int expIdx = -1;
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int dotIdx = -1;
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int scale = 0;
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for (int i = off; i < len; i++) {
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char c = chars[i];
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switch (c) {
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case '+':
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if (expIdx >= 0) {
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if (expHasSign) {
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throw new NumberFormatException("Multiple signs in exponent");
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}
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expHasSign = true;
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} else {
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if (numHasSign) {
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throw new NumberFormatException("Multiple signs in number");
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}
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numHasSign = true;
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numIdx = i + 1;
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}
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break;
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case '-':
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if (expIdx >= 0) {
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if (expHasSign) {
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throw new NumberFormatException("Multiple signs in exponent");
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}
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expHasSign = true;
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} else {
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if (numHasSign) {
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throw new NumberFormatException("Multiple signs in number");
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}
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numHasSign = true;
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neg = true;
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numIdx = i + 1;
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}
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break;
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case 'e':
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case 'E':
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if (expIdx >= 0) {
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throw new NumberFormatException("Multiple exponent markers");
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}
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expIdx = i;
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break;
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case '.':
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if (dotIdx >= 0) {
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throw new NumberFormatException("Multiple decimal points");
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}
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dotIdx = i;
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break;
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default:
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if (dotIdx >= 0 && expIdx == -1) {
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scale++;
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}
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}
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}
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int numEndIdx;
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int exp = 0;
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if (expIdx >= 0) {
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numEndIdx = expIdx;
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String expStr = new String(chars, expIdx + 1, len - expIdx - 1);
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exp = Integer.parseInt(expStr);
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scale = adjustScale(scale, exp);
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} else {
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numEndIdx = len;
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}
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BigDecimal res;
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if (dotIdx >= 0) {
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int leftLen = dotIdx - numIdx;
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BigDecimal left = toBigDecimalRec(numIdx, leftLen, exp, splitLen);
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int rightLen = numEndIdx - dotIdx - 1;
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BigDecimal right = toBigDecimalRec(dotIdx + 1, rightLen, exp - rightLen, splitLen);
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res = left.add(right);
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} else {
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res = toBigDecimalRec(numIdx, numEndIdx - numIdx, exp, splitLen);
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}
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if (scale != 0) {
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res = res.setScale(scale);
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}
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if (neg) {
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res = res.negate();
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}
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return res;
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}
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private int adjustScale(int scale, long exp) {
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long adjScale = scale - exp;
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if (adjScale > Integer.MAX_VALUE || adjScale < Integer.MIN_VALUE) {
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throw new NumberFormatException(
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"Scale out of range: " + adjScale + " while adjusting scale " + scale + " to exponent " + exp);
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}
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return (int) adjScale;
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}
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private BigDecimal toBigDecimalRec(int off, int len, int scale, int splitLen) {
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if (len > splitLen) {
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int mid = len / 2;
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BigDecimal left = toBigDecimalRec(off, mid, scale + len - mid, splitLen);
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BigDecimal right = toBigDecimalRec(off + mid, len - mid, scale, splitLen);
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return left.add(right);
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}
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return len == 0 ? BigDecimal.ZERO : new BigDecimal(chars, off, len).movePointRight(scale);
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}
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}

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

+9-13
Original file line numberDiff line numberDiff line change
@@ -311,22 +311,18 @@ public static double parseDouble(String s) throws NumberFormatException {
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}
312312

313313
public static BigDecimal parseBigDecimal(String s) throws NumberFormatException {
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try { return new BigDecimal(s); } catch (NumberFormatException e) {
315-
throw _badBD(s);
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}
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}
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char[] ch = s.toCharArray();
318315

319-
public static BigDecimal parseBigDecimal(char[] b) throws NumberFormatException {
320-
return parseBigDecimal(b, 0, b.length);
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return parseBigDecimal(ch);
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}
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public static BigDecimal parseBigDecimal(char[] b, int off, int len) throws NumberFormatException {
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try { return new BigDecimal(b, off, len); } catch (NumberFormatException e) {
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throw _badBD(new String(b, off, len));
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}
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public static BigDecimal parseBigDecimal(char[] ch) throws NumberFormatException {
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return parseBigDecimal(ch, 0, ch.length);
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}
328322

329-
private static NumberFormatException _badBD(String s) {
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return new NumberFormatException("Value \""+s+"\" can not be represented as BigDecimal");
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public static BigDecimal parseBigDecimal(char[] ch, int off, int len) throws NumberFormatException {
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BigDecimalParser parser = new BigDecimalParser(ch, off, len);
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return parser.parse();
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}
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}

‎src/test/java/com/fasterxml/jackson/core/util/TestTextBuffer.java

+2-2
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
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package com.fasterxml.jackson.core.util;
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3-
import com.fasterxml.jackson.core.io.NumberInput;
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import com.fasterxml.jackson.core.io.BigDecimalParser;
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public class TestTextBuffer
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extends com.fasterxml.jackson.core.BaseTest
@@ -139,7 +139,7 @@ public void testContentsAsDecimalThrowsNumberFormatException() {
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textBuffer.contentsAsDecimal();
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fail("Expecting exception: NumberFormatException");
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} catch(NumberFormatException e) {
142-
assertEquals(NumberInput.class.getName(), e.getStackTrace()[0].getClassName());
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assertEquals(BigDecimalParser.class.getName(), e.getStackTrace()[0].getClassName());
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}
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}
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