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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <future>
#include "fec_private.h"
struct process_info {
int id;
fec_handle* f;
uint8_t* buf;
size_t count;
uint64_t offset;
read_func func;
ssize_t rc;
size_t errors;
};
/* thread function */
static process_info* __process(process_info* p) {
debug("thread %d: [%" PRIu64 ", %" PRIu64 ")", p->id, p->offset, p->offset + p->count);
p->rc = p->func(p->f, p->buf, p->count, p->offset, &p->errors);
return p;
}
/* launches a maximum number of threads to process a read */
ssize_t process(fec_handle* f, uint8_t* buf, size_t count, uint64_t offset, read_func func) {
check(f);
check(buf);
check(func);
if (count == 0) {
return 0;
}
int threads = sysconf(_SC_NPROCESSORS_ONLN);
if (threads < WORK_MIN_THREADS) {
threads = WORK_MIN_THREADS;
} else if (threads > WORK_MAX_THREADS) {
threads = WORK_MAX_THREADS;
}
uint64_t start = (offset / FEC_BLOCKSIZE) * FEC_BLOCKSIZE;
size_t blocks = fec_div_round_up(offset + count - start, FEC_BLOCKSIZE);
/* start at most one thread per block we're accessing */
if ((size_t)threads > blocks) {
threads = (int)blocks;
}
size_t count_per_thread = fec_div_round_up(blocks, threads) * FEC_BLOCKSIZE;
size_t left = count;
uint64_t pos = offset;
uint64_t end = start + count_per_thread;
debug("max %d threads, %zu bytes per thread (total %zu spanning %zu blocks)", threads,
count_per_thread, count, blocks);
std::vector<std::future<process_info*>> handles;
process_info info[threads];
ssize_t rc = 0;
/* start threads to process queue */
for (int i = 0; i < threads && left > 0; ++i) {
info[i].id = i;
info[i].f = f;
info[i].buf = &buf[pos - offset];
info[i].count = (size_t)(end - pos);
info[i].offset = pos;
info[i].func = func;
info[i].rc = -1;
info[i].errors = 0;
if (info[i].count > left) {
info[i].count = left;
}
handles.push_back(std::async(std::launch::async, __process, &info[i]));
pos = end;
end += count_per_thread;
left -= info[i].count;
}
ssize_t nread = 0;
/* wait for all threads to complete */
for (auto&& future : handles) {
process_info* p = future.get();
if (!p || p->rc == -1) {
rc = -1;
} else {
nread += p->rc;
f->errors += p->errors;
}
}
if (left > 0 || rc == -1) {
errno = EIO;
return -1;
}
return nread;
}
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