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improved BigDecimal parsing performance #3992

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37 changes: 14 additions & 23 deletions core/src/main/java/com/alibaba/fastjson2/JSONReaderUTF16.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4379,18 +4379,12 @@ public final BigDecimal readBigDecimal() {
}

valueType = JSON_TYPE_INT;
boolean overflow = false;
int digitCount = 0; // Total digit count for overflow detection
long longValue = 0;
while (ch >= '0' && ch <= '9') {
valid = true;
if (!overflow) {
long r = longValue * 10;
if ((longValue | 10) >>> 31 == 0L || (r / 10 == longValue)) {
longValue = r + (ch - '0');
} else {
overflow = true;
}
}
longValue = (longValue << 3) + (longValue << 1) + (ch & 0xf);
digitCount++;

if (offset == end) {
ch = EOI;
Expand All @@ -4400,25 +4394,15 @@ public final BigDecimal readBigDecimal() {
ch = chars[offset++];
}

if (longValue < 0) {
overflow = true;
}

this.scale = 0;
if (ch == '.') {
valueType = JSON_TYPE_DEC;
ch = chars[offset++];
while (ch >= '0' && ch <= '9') {
valid = true;
this.scale++;
if (!overflow) {
long r = longValue * 10;
if ((longValue | 10) >>> 31 == 0L || (r / 10 == longValue)) {
longValue = r + (ch - '0');
} else {
overflow = true;
}
}
longValue = (longValue << 3) + (longValue << 1) + (ch & 0xf);
digitCount++;

if (offset == end) {
ch = EOI;
Expand All @@ -4429,6 +4413,9 @@ public final BigDecimal readBigDecimal() {
}
}

// Check overflow: more than 18 digits, or 19 digits with negative value (sign bit set)
boolean overflow = digitCount > 18 && (digitCount > 19 || longValue < 0);

int expValue = 0;
if (ch == 'e' || ch == 'E') {
boolean negativeExp;
Expand Down Expand Up @@ -4520,8 +4507,12 @@ public final BigDecimal readBigDecimal() {
}
}
if (!value) {
if (expValue == 0 && !overflow && longValue != 0) {
decimal = BigDecimal.valueOf(negative ? -longValue : longValue, scale);
if (!overflow && longValue != 0) {
// Combine scale and exponent: scale - expValue
// For 1.5E3: scale=1, exp=3 => combined=-2 => 1500
// For 1.5E-3: scale=1, exp=-3 => combined=4 => 0.0015
int combinedScale = scale - expValue;
decimal = BigDecimal.valueOf(negative ? -longValue : longValue, combinedScale);
value = true;
}

Expand Down
37 changes: 14 additions & 23 deletions core/src/main/java/com/alibaba/fastjson2/JSONReaderUTF8.java
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Original file line number Diff line number Diff line change
Expand Up @@ -6822,18 +6822,12 @@ public final BigDecimal readBigDecimal() {
}

valueType = JSON_TYPE_INT;
boolean overflow = false;
int digitCount = 0; // Total digit count for overflow detection
long longValue = 0;
while (ch >= '0' && ch <= '9') {
valid = true;
if (!overflow) {
long r = longValue * 10;
if ((longValue | 10) >>> 31 == 0L || (r / 10 == longValue)) {
longValue = r + (ch - '0');
} else {
overflow = true;
}
}
longValue = (longValue << 3) + (longValue << 1) + (ch & 0xf);
digitCount++;

if (offset == end) {
ch = EOI;
Expand All @@ -6843,25 +6837,15 @@ public final BigDecimal readBigDecimal() {
ch = bytes[offset++];
}

if (longValue < 0) {
overflow = true;
}

this.scale = 0;
if (ch == '.') {
valueType = JSON_TYPE_DEC;
ch = bytes[offset++];
while (ch >= '0' && ch <= '9') {
valid = true;
this.scale++;
if (!overflow) {
long r = longValue * 10;
if ((longValue | 10) >>> 31 == 0L || (r / 10 == longValue)) {
longValue = r + (ch - '0');
} else {
overflow = true;
}
}
longValue = (longValue << 3) + (longValue << 1) + (ch & 0xf);
digitCount++;

if (offset == end) {
ch = EOI;
Expand All @@ -6872,6 +6856,9 @@ public final BigDecimal readBigDecimal() {
}
}

// Check overflow: more than 18 digits, or 19 digits with negative value (sign bit set)
boolean overflow = digitCount > 18 && (digitCount > 19 || longValue < 0);

int expValue = 0;
if (ch == 'e' || ch == 'E') {
boolean negativeExp;
Expand Down Expand Up @@ -6959,8 +6946,12 @@ public final BigDecimal readBigDecimal() {
}
}
if (!value) {
if (expValue == 0 && !overflow && longValue != 0) {
decimal = BigDecimal.valueOf(negative ? -longValue : longValue, scale);
if (!overflow && longValue != 0) {
// Combine scale and exponent: scale - expValue
// For 1.5E3: scale=1, exp=3 => combined=-2 => 1500
// For 1.5E-3: scale=1, exp=-3 => combined=4 => 0.0015
int combinedScale = scale - expValue;
decimal = BigDecimal.valueOf(negative ? -longValue : longValue, combinedScale);
value = true;
}

Expand Down
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