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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/bigint-internal.h"
#include "src/bigint/vector-arithmetic.h"
namespace v8 {
namespace bigint {
// The classic algorithm: for every part, multiply the accumulator with
// the appropriate multiplier, and add the part. O(n²) overall.
void ProcessorImpl::FromStringClassic(RWDigits Z,
FromStringAccumulator* accumulator) {
// We always have at least one part to process.
DCHECK(accumulator->stack_parts_used_ > 0); // NOLINT(readability/check)
Z[0] = accumulator->stack_parts_[0];
RWDigits already_set(Z, 0, 1);
for (int i = 1; i < Z.len(); i++) Z[i] = 0;
// The {FromStringAccumulator} uses stack-allocated storage for the first
// few parts; if heap storage is used at all then all parts are copied there.
int num_stack_parts = accumulator->stack_parts_used_;
if (num_stack_parts == 1) return;
const std::vector<digit_t>& heap_parts = accumulator->heap_parts_;
int num_heap_parts = static_cast<int>(heap_parts.size());
// All multipliers are the same, except possibly for the last.
const digit_t max_multiplier = accumulator->max_multiplier_;
if (num_heap_parts == 0) {
for (int i = 1; i < num_stack_parts - 1; i++) {
MultiplySingle(Z, already_set, max_multiplier);
Add(Z, accumulator->stack_parts_[i]);
already_set.set_len(already_set.len() + 1);
}
MultiplySingle(Z, already_set, accumulator->last_multiplier_);
Add(Z, accumulator->stack_parts_[num_stack_parts - 1]);
return;
}
// Parts are stored on the heap.
for (int i = 1; i < num_heap_parts - 1; i++) {
MultiplySingle(Z, already_set, max_multiplier);
if (should_terminate()) return;
Add(Z, accumulator->heap_parts_[i]);
already_set.set_len(already_set.len() + 1);
}
MultiplySingle(Z, already_set, accumulator->last_multiplier_);
Add(Z, accumulator->heap_parts_.back());
}
void ProcessorImpl::FromString(RWDigits Z, FromStringAccumulator* accumulator) {
if (accumulator->inline_everything_) {
int i = 0;
for (; i < accumulator->stack_parts_used_; i++) {
Z[i] = accumulator->stack_parts_[i];
}
for (; i < Z.len(); i++) Z[i] = 0;
} else if (accumulator->stack_parts_used_ == 0) {
for (int i = 0; i < Z.len(); i++) Z[i] = 0;
} else {
FromStringClassic(Z, accumulator);
}
}
Status Processor::FromString(RWDigits Z, FromStringAccumulator* accumulator) {
ProcessorImpl* impl = static_cast<ProcessorImpl*>(this);
impl->FromString(Z, accumulator);
return impl->get_and_clear_status();
}
} // namespace bigint
} // namespace v8
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