Error correction: Add libfec to read encoded data
Add libfec to read files or partitions with error-correcting codes
appended to them. Uses verity metadata to speed up I/O and improve
error correction effectiveness.
Bug: 21893453
Change-Id: I94b95058b084418019fc96595bb6055df36e2c2b
diff --git a/libfec/fec_process.cpp b/libfec/fec_process.cpp
new file mode 100644
index 0000000..3b2846c
--- /dev/null
+++ b/libfec/fec_process.cpp
@@ -0,0 +1,137 @@
+/*
+ * 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 "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 void * __process(void *cookie)
+{
+ process_info *p = static_cast<process_info *>(cookie);
+
+ 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(count, FEC_BLOCKSIZE);
+
+ 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("%d threads, %zu bytes per thread (total %zu)", threads,
+ count_per_thread, count);
+
+ std::vector<pthread_t> handles;
+ process_info info[threads];
+ ssize_t rc = 0;
+
+ /* start threads to process queue */
+ for (int i = 0; i < threads; ++i) {
+ check(left > 0);
+
+ 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;
+ }
+
+ pthread_t thread;
+
+ if (pthread_create(&thread, NULL, __process, &info[i]) != 0) {
+ error("failed to create thread: %s", strerror(errno));
+ rc = -1;
+ } else {
+ handles.push_back(thread);
+ }
+
+ pos = end;
+ end += count_per_thread;
+ left -= info[i].count;
+ }
+
+ check(left == 0);
+
+ ssize_t nread = 0;
+
+ /* wait for all threads to complete */
+ for (auto thread : handles) {
+ process_info *p = NULL;
+
+ if (pthread_join(thread, (void **)&p) != 0) {
+ error("failed to join thread: %s", strerror(errno));
+ rc = -1;
+ } else if (!p || p->rc == -1) {
+ rc = -1;
+ } else {
+ nread += p->rc;
+ f->errors += p->errors;
+ }
+ }
+
+ if (rc == -1) {
+ errno = EIO;
+ return -1;
+ }
+
+ return nread;
+}