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// Copyright 2021 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/bigint/div-helpers.h"
#include "src/bigint/bigint-internal.h"
namespace v8 {
namespace bigint {
namespace {
void Copy(RWDigits Z, Digits X) {
if (Z == X) return;
int i = 0;
for (; i < X.len(); i++) Z[i] = X[i];
for (; i < Z.len(); i++) Z[i] = 0;
}
} // namespace
// Z := X << shift
// Z and X may alias for an in-place shift.
void LeftShift(RWDigits Z, Digits X, int shift) {
DCHECK(shift >= 0);
DCHECK(shift < kDigitBits);
DCHECK(Z.len() >= X.len());
if (shift == 0) return Copy(Z, X);
digit_t carry = 0;
int i = 0;
for (; i < X.len(); i++) {
digit_t d = X[i];
Z[i] = (d << shift) | carry;
carry = d >> (kDigitBits - shift);
}
if (i < Z.len()) {
Z[i++] = carry;
} else {
DCHECK(carry == 0);
}
for (; i < Z.len(); i++) Z[i] = 0;
}
// Z := X >> shift
// Z and X may alias for an in-place shift.
void RightShift(RWDigits Z, Digits X, int shift) {
DCHECK(shift >= 0);
DCHECK(shift < kDigitBits);
X.Normalize();
DCHECK(Z.len() >= X.len());
if (shift == 0) return Copy(Z, X);
int i = 0;
if (X.len() > 0) {
digit_t carry = X[0] >> shift;
int last = X.len() - 1;
for (; i < last; i++) {
digit_t d = X[i + 1];
Z[i] = (d << (kDigitBits - shift)) | carry;
carry = d >> shift;
}
Z[i++] = carry;
}
for (; i < Z.len(); i++) Z[i] = 0;
}
} // namespace bigint
} // namespace v8
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