Skip to content

Commit

Permalink
feat: more efficient indexing
Browse files Browse the repository at this point in the history
  • Loading branch information
@dufkan
dufkan committed Apr 29, 2023
1 parent ac3d5bf commit 408062d
Showing 1 changed file with 62 additions and 59 deletions.
121 changes: 62 additions & 59 deletions applet/src/main/java/opencrypto/jcmathlib/BigNatInternal.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -154,13 +154,13 @@ public void prependZeros(short targetLength, byte[] outBuffer, short outOffset)
*/
public void shrink() {
short i;
for (i = 0; i < size; i++) { // Find first non-zero byte
if (value[(short) (i + this.offset)] != 0) {
for (i = offset; i < value.length; i++) { // Find first non-zero byte
if (value[i] != 0) {
break;
}
}

short newSize = (short) (size - i);
short newSize = (short) (value.length - i);
if (newSize < 0) {
ISOException.throwIt(ReturnCodes.SW_BIGNAT_INVALIDRESIZE);
}
Expand Down Expand Up @@ -203,26 +203,27 @@ public void setValue(short newValue) {
*/
public void copy(BigNatInternal other) {
short thisStart, otherStart, len;
if (size >= other.size) {
thisStart = (short) (size - other.size);
otherStart = 0;
short diff = (short) (size - other.size);
if (diff >= 0) {
thisStart = (short) (diff + offset);
otherStart = other.offset;
len = other.size;

if (thisStart > 0) {
Util.arrayFillNonAtomic(value, offset, thisStart, (byte) 0);
if (diff > 0) {
Util.arrayFillNonAtomic(value, offset, diff, (byte) 0);
}
} else {
thisStart = 0;
otherStart = (short) (other.size - size);
thisStart = offset;
otherStart = (short) (other.offset - diff);
len = size;
// Verify here that other have leading zeroes up to otherStart
for (short i = 0; i < otherStart; i++) {
if (other.value[(short) (i + other.offset)] != 0) {
for (short i = other.offset; i < otherStart; i++) {
if (other.value[i] != 0) {
ISOException.throwIt(ReturnCodes.SW_BIGNAT_INVALIDCOPYOTHER);
}
}
}
Util.arrayCopyNonAtomic(other.value, (short) (other.offset + otherStart), value, (short) (this.offset + thisStart), len);
Util.arrayCopyNonAtomic(other.value, otherStart, value, thisStart, len);
}

/**
Expand Down Expand Up @@ -286,17 +287,17 @@ public boolean isLesser(BigNatInternal other) {
* Returns true if this is lesser than other shifted by a given number of digits.
*/
private boolean isLesser(BigNatInternal other, short shift, short start) {
short j = (short) (other.size + shift - size + start);
short j = (short) (other.size + shift - size + start + other.offset);

for (short i = start; i < j; ++i) {
if (other.value[(short) (i + other.offset)] != 0) {
for (short i = (short) (start + other.offset); i < j; ++i) {
if (other.value[i] != 0) {
return true;
}
}

for (short i = start; i < size; i++, j++) {
short thisValue = (short) (value[(short) (i + offset)] & DIGIT_MASK);
short otherValue = (j >= 0 && j < other.size) ? (short) (other.value[(short) (j + other.offset)] & DIGIT_MASK) : (short) 0;
for (short i = (short) (start + offset); i < (short) value.length; i++, j++) {
short thisValue = (short) (value[i] & DIGIT_MASK);
short otherValue = (j >= other.offset && j < (short) other.value.length) ? (short) (other.value[j] & DIGIT_MASK) : (short) 0;
if (thisValue < otherValue) {
return true; // CTO
}
Expand Down Expand Up @@ -344,9 +345,9 @@ public boolean equals(BigNatInternal other) {
* Increment this BigNat.
*/
public void increment() {
for (short i = (short) (size - 1); i >= 0; i--) {
short tmp = (short) (value[(short) (i + offset)] & 0xff);
value[(short) (i + offset)] = (byte) (tmp + 1);
for (short i = (short) (value.length - 1); i >= offset; i--) {
short tmp = (short) (value[i] & 0xff);
value[i] = (byte) (tmp + 1);
if (tmp < 255) {
break; // CTO
}
Expand All @@ -358,9 +359,9 @@ public void increment() {
*/
public void decrement() {
short tmp;
for (short i = (short) (size - 1); i >= 0; i--) {
tmp = (short) (value[(short) (i + offset)] & 0xff);
value[(short) (i + offset)] = (byte) (tmp - 1);
for (short i = (short) (value.length - 1); i >= offset; i--) {
tmp = (short) (value[i] & 0xff);
value[i] = (byte) (tmp - 1);
if (tmp != 0) {
break; // CTO
}
Expand Down Expand Up @@ -397,18 +398,18 @@ public byte add(BigNatInternal other) {
*/
private byte add(BigNatInternal other, short shift, short multiplier) {
short acc = 0;
short i = (short) (other.size - 1);
short j = (short) (size - 1 - shift);
for (; i >= 0 && j >= 0; i--, j--) {
acc += (short) ((short) (value[(short) (j + this.offset)] & DIGIT_MASK) + (short) (multiplier * (other.value[(short) (i + other.offset)] & DIGIT_MASK)));
short i = (short) (other.size - 1 + other.offset);
short j = (short) (size - 1 - shift + offset);
for (; i >= other.offset && j >= offset; i--, j--) {
acc += (short) ((short) (value[j] & DIGIT_MASK) + (short) (multiplier * (other.value[i] & DIGIT_MASK)));

value[(short) (j + this.offset)] = (byte) (acc & DIGIT_MASK);
value[j] = (byte) (acc & DIGIT_MASK);
acc = (short) ((acc >> DIGIT_LEN) & DIGIT_MASK);
}

for (; acc > 0 && j >= 0; --j) {
acc += (short) (value[(short) (j + this.offset)] & DIGIT_MASK);
value[(short) (j + this.offset)] = (byte) (acc & DIGIT_MASK);
for (; acc > 0 && j >= offset; --j) {
acc += (short) (value[j] & DIGIT_MASK);
value[j] = (byte) (acc & DIGIT_MASK);
acc = (short) ((acc >> DIGIT_LEN) & DIGIT_MASK);
}

Expand All @@ -431,23 +432,23 @@ public void subtract(BigNatInternal other) {
*/
private void subtract(BigNatInternal other, short shift, short multiplier) {
short acc = 0;
short i = (short) (size - 1 - shift);
short j = (short) (other.size - 1);
for (; i >= 0 && j >= 0; i--, j--) {
acc += (short) (multiplier * (other.value[(short) (j + other.offset)] & DIGIT_MASK));
short tmp = (short) ((value[(short) (i + this.offset)] & DIGIT_MASK) - (acc & DIGIT_MASK));
short i = (short) (size - 1 - shift + offset);
short j = (short) (other.size - 1 + other.offset);
for (; i >= offset && j >= other.offset; i--, j--) {
acc += (short) (multiplier * (other.value[j] & DIGIT_MASK));
short tmp = (short) ((value[i] & DIGIT_MASK) - (acc & DIGIT_MASK));

value[(short) (i + this.offset)] = (byte) (tmp & DIGIT_MASK);
value[i] = (byte) (tmp & DIGIT_MASK);
acc = (short) ((acc >> DIGIT_LEN) & DIGIT_MASK);
if (tmp < 0) {
acc++;
}
}

// deal with carry as long as there are digits left in this
for (; i >= 0 && acc != 0; --i) {
short tmp = (short) ((value[(short) (i + this.offset)] & DIGIT_MASK) - (acc & DIGIT_MASK));
value[(short) (i + this.offset)] = (byte) (tmp & DIGIT_MASK);
for (; i >= offset && acc != 0; --i) {
short tmp = (short) ((value[i] & DIGIT_MASK) - (acc & DIGIT_MASK));
value[i] = (byte) (tmp & DIGIT_MASK);
acc = (short) ((acc >> DIGIT_LEN) & DIGIT_MASK);
if (tmp < 0) {
acc++;
Expand All @@ -462,8 +463,8 @@ private void subtract(BigNatInternal other, short shift, short multiplier) {
* @param y right operand
*/
public void mult(BigNatInternal x, BigNatInternal y) {
for (short i = (short) (y.size - 1); i >= 0; i--) {
add(x, (short) (y.size - 1 - i), (short) (y.value[(short) (i + y.offset)] & DIGIT_MASK));
for (short i = (short) (y.value.length - 1); i >= y.offset; i--) {
add(x, (short) (y.value.length - 1 - i), (short) (y.value[i] & DIGIT_MASK));
}
}

Expand All @@ -476,11 +477,11 @@ public void mult(BigNatInternal x, BigNatInternal y) {
protected void shiftRight(short bits, short carry) {
// assumes 0 <= bits < 8
short mask = (short) ((short) (1 << bits) - 1); // lowest `bits` bits set to 1
for (short i = 0; i < size; i++) {
short current = (short) (value[(short) (i + this.offset)] & 0xff);
for (short i = offset; i < (short) value.length; i++) {
short current = (short) (value[i] & 0xff);
short previous = current;
current >>= bits;
value[(short) (i + this.offset)] = (byte) (current | carry);
value[i] = (byte) (current | carry);
carry = (short) (previous & mask);
carry <<= (short) (8 - bits);
}
Expand Down Expand Up @@ -508,22 +509,23 @@ public void remainderDivide(BigNatInternal divisor, BigNatInternal quotient) {
quotient.zero();
}

short divisorIndex = 0;
while (divisor.value[(short) (divisorIndex + divisor.offset)] == 0) {
short divisorIndex = divisor.offset;
while (divisor.value[divisorIndex] == 0) {
divisorIndex++;
}

short divisorShift = (short) (size - divisor.size + divisorIndex);
short divisorShift = (short) (size - divisor.size + divisorIndex - divisor.offset);
short divisionRound = 0;
short firstDivisorDigit = (short) (divisor.value[(short) (divisorIndex + divisor.offset)] & DIGIT_MASK);
short firstDivisorDigit = (short) (divisor.value[divisorIndex] & DIGIT_MASK);
short divisorBitShift = (short) (highestOneBit((short) (firstDivisorDigit + 1)) - 1);
byte secondDivisorDigit = divisorIndex < (short) (divisor.size - 1) ? divisor.value[(short) (divisorIndex + 1 + divisor.offset)] : 0;
byte thirdDivisorDigit = divisorIndex < (short) (divisor.size - 2) ? divisor.value[(short) (divisorIndex + 2 + divisor.offset)] : 0;
byte secondDivisorDigit = divisorIndex < (short) (divisor.value.length - 1) ? divisor.value[(short) (divisorIndex + 1)] : 0;
byte thirdDivisorDigit = divisorIndex < (short) (divisor.value.length - 2) ? divisor.value[(short) (divisorIndex + 2)] : 0;

while (divisorShift >= 0) {
while (!isLesser(divisor, divisorShift, (short) (divisionRound > 0 ? divisionRound - 1 : 0))) {
short dividentDigits = divisionRound == 0 ? 0 : (short) ((short) (value[(short) (divisionRound - 1 + this.offset)]) << DIGIT_LEN);
dividentDigits |= (short) (value[(short) (divisionRound + this.offset)] & DIGIT_MASK);
short divisionRoundOffset = (short) (divisionRound + offset);
short dividentDigits = divisionRound == 0 ? 0 : (short) ((short) (value[(short) (divisionRoundOffset - 1)]) << DIGIT_LEN);
dividentDigits |= (short) (value[(short) (divisionRound + offset)] & DIGIT_MASK);

short divisorDigit;
if (dividentDigits < 0) {
Expand All @@ -534,8 +536,8 @@ public void remainderDivide(BigNatInternal divisor, BigNatInternal quotient) {
short bitShift = dividentBitShift <= divisorBitShift ? dividentBitShift : divisorBitShift;

dividentDigits = shiftBits(
dividentDigits, divisionRound < (short) (size - 1) ? value[(short) (divisionRound + 1 + this.offset)] : 0,
divisionRound < (short) (size - 2) ? value[(short) (divisionRound + 2 + this.offset)] : 0,
dividentDigits, divisionRound < (short) (size - 1) ? value[(short) (divisionRoundOffset + 1)] : 0,
divisionRound < (short) (size - 2) ? value[(short) (divisionRoundOffset + 2)] : 0,
bitShift
);
divisorDigit = shiftBits(firstDivisorDigit, secondDivisorDigit, thirdDivisorDigit, bitShift);
Expand All @@ -549,8 +551,9 @@ public void remainderDivide(BigNatInternal divisor, BigNatInternal quotient) {
subtract(divisor, divisorShift, multiple);

if (quotient != null) {
short quotientDigit = (short) ((quotient.value[(short) (quotient.size - 1 - divisorShift + quotient.offset)] & DIGIT_MASK) + multiple);
quotient.value[(short) (quotient.size - 1 - divisorShift + quotient.offset)] = (byte) quotientDigit;
short divisorShiftOffset = (short) (divisorShift - quotient.offset);
short quotientDigit = (short) ((quotient.value[(short) (quotient.size - 1 - divisorShiftOffset)] & DIGIT_MASK) + multiple);
quotient.value[(short) (quotient.size - 1 - divisorShiftOffset)] = (byte) quotientDigit;
}
}
divisionRound++;
Expand Down

0 comments on commit 408062d

Please sign in to comment.