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[sequence_generator] Fix parameters and span boundary checking

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This commit is contained in:
Ming-Hung Tsai 2020-07-28 00:32:30 +08:00
parent 661b4de5de
commit 0c3c5f6c1e
1 changed files with 60 additions and 30 deletions
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90
base/sequence_generator.cc
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@ -14,12 +14,12 @@ namespace {
uint64_t size,
uint64_t step)
: begin_(begin),
end_(begin + (size / step) * step),
step_(step),
current_(begin),
rounds_(0) {
if (size < step)
throw std::runtime_error("size must be greater than the step");
rounds_(0)
{
verify_parameters(size, step);
end_ = begin + (size / step) * step;
}
forward_sequence_generator()
@ -38,6 +38,8 @@ namespace {
}
void reset(uint64_t begin, uint64_t size, uint64_t step = 1) {
verify_parameters(size, step);
begin_ = begin;
end_ = begin + (size / step) * step;
step_ = step;
@ -45,6 +47,14 @@ namespace {
rounds_ = 0;
}
static void verify_parameters(uint64_t size, uint64_t step) {
if (!size || !step)
throw std::runtime_error("size or step must be non-zero");
if (size < step)
throw std::runtime_error("size must be greater than the step");
}
uint64_t get_rounds() {
return rounds_;
}
@ -68,11 +78,18 @@ namespace {
uint64_t step,
unsigned seq_nr = 1)
: begin_(begin),
nr_steps_(size / step),
step_(step),
max_forward_steps_(seq_nr),
nr_generated_(0)
{
if (!size || !step || !seq_nr)
throw std::runtime_error("size, step, or forward steps must be non-zero");
if (size < step)
throw std::runtime_error("size must be greater than the step");
nr_steps_ = size / step;
if (!max_forward_steps_ || max_forward_steps_ > nr_steps_)
throw std::runtime_error("invalid number of forward steps");
@ -84,7 +101,44 @@ namespace {
// FIXME: eliminate if-else
uint64_t step_idx = (max_forward_steps_ > 1) ?
next_forward_step() : next_random_step();
return begin_ + step_idx * step_;
}
private:
void reset_forward_generator() {
uint64_t begin = peek_random_step();
unsigned seq_nr = (std::rand() % max_forward_steps_) + 1;
base::run_set<uint64_t>::const_iterator it = rand_map_.upper_bound(begin);
if (it != rand_map_.end())
seq_nr = std::min<uint64_t>(seq_nr, *it->begin_ - begin);
else
seq_nr = std::min<uint64_t>(seq_nr, nr_steps_ - begin);
forward_gen_.reset(begin, seq_nr);
}
uint64_t next_forward_step() {
uint64_t step_idx = forward_gen_.next();
consume_random_map(step_idx);
if (forward_gen_.get_rounds())
reset_forward_generator();
return step_idx;
}
uint64_t next_random_step() {
uint64_t step_idx = peek_random_step();
consume_random_map(step_idx);
return step_idx;
}
void consume_random_map(uint64_t step_idx) {
rand_map_.add(step_idx);
++nr_generated_;
// wrap-around
@ -92,33 +146,9 @@ namespace {
rand_map_.clear();
nr_generated_ = 0;
}
return begin_ + step_idx * step_;
}
private:
void reset_forward_generator() {
uint64_t begin = next_random_step();
unsigned seq_nr = (std::rand() % max_forward_steps_) + 1;
forward_gen_.reset(begin, seq_nr);
}
uint64_t next_forward_step() {
uint64_t step_idx;
bool found = true;
while (found) {
step_idx = forward_gen_.next();
found = rand_map_.member(step_idx);
if (found || forward_gen_.get_rounds())
reset_forward_generator();
}
return step_idx;
}
uint64_t next_random_step() const {
uint64_t peek_random_step() const {
uint64_t step_idx;
bool found = true;