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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "tensorflow/core/lib/io/format.h"
#include "tensorflow/core/public/env.h"
#include "tensorflow/core/lib/io/block.h"
#include "tensorflow/core/lib/core/coding.h"
#include "tensorflow/core/lib/hash/crc32c.h"
#include "tensorflow/core/platform/port.h"
#include "tensorflow/core/lib/core/errors.h"
namespace tensorflow {
namespace table {
void BlockHandle::EncodeTo(string* dst) const {
// Sanity check that all fields have been set
assert(offset_ != ~static_cast<uint64>(0));
assert(size_ != ~static_cast<uint64>(0));
core::PutVarint64(dst, offset_);
core::PutVarint64(dst, size_);
}
Status BlockHandle::DecodeFrom(StringPiece* input) {
if (core::GetVarint64(input, &offset_) && core::GetVarint64(input, &size_)) {
return Status::OK();
} else {
return errors::DataLoss("bad block handle");
}
}
void Footer::EncodeTo(string* dst) const {
#ifndef NDEBUG
const size_t original_size = dst->size();
#endif
metaindex_handle_.EncodeTo(dst);
index_handle_.EncodeTo(dst);
dst->resize(2 * BlockHandle::kMaxEncodedLength); // Padding
core::PutFixed32(dst, static_cast<uint32>(kTableMagicNumber & 0xffffffffu));
core::PutFixed32(dst, static_cast<uint32>(kTableMagicNumber >> 32));
assert(dst->size() == original_size + kEncodedLength);
}
Status Footer::DecodeFrom(StringPiece* input) {
const char* magic_ptr = input->data() + kEncodedLength - 8;
const uint32 magic_lo = core::DecodeFixed32(magic_ptr);
const uint32 magic_hi = core::DecodeFixed32(magic_ptr + 4);
const uint64 magic =
((static_cast<uint64>(magic_hi) << 32) | (static_cast<uint64>(magic_lo)));
if (magic != kTableMagicNumber) {
return errors::DataLoss("not an sstable (bad magic number)");
}
Status result = metaindex_handle_.DecodeFrom(input);
if (result.ok()) {
result = index_handle_.DecodeFrom(input);
}
if (result.ok()) {
// We skip over any leftover data (just padding for now) in "input"
const char* end = magic_ptr + 8;
*input = StringPiece(end, input->data() + input->size() - end);
}
return result;
}
Status ReadBlock(RandomAccessFile* file, const BlockHandle& handle,
BlockContents* result) {
result->data = StringPiece();
result->cachable = false;
result->heap_allocated = false;
// Read the block contents as well as the type/crc footer.
// See table_builder.cc for the code that built this structure.
size_t n = static_cast<size_t>(handle.size());
char* buf = new char[n + kBlockTrailerSize];
StringPiece contents;
Status s =
file->Read(handle.offset(), n + kBlockTrailerSize, &contents, buf);
if (!s.ok()) {
delete[] buf;
return s;
}
if (contents.size() != n + kBlockTrailerSize) {
delete[] buf;
return errors::DataLoss("truncated block read");
}
// Check the crc of the type and the block contents
const char* data = contents.data(); // Pointer to where Read put the data
// This checksum verification is optional. We leave it on for now
const bool verify_checksum = true;
if (verify_checksum) {
const uint32 crc = crc32c::Unmask(core::DecodeFixed32(data + n + 1));
const uint32 actual = crc32c::Value(data, n + 1);
if (actual != crc) {
delete[] buf;
s = errors::DataLoss("block checksum mismatch");
return s;
}
}
switch (data[n]) {
case kNoCompression:
if (data != buf) {
// File implementation gave us pointer to some other data.
// Use it directly under the assumption that it will be live
// while the file is open.
delete[] buf;
result->data = StringPiece(data, n);
result->heap_allocated = false;
result->cachable = false; // Do not double-cache
} else {
result->data = StringPiece(buf, n);
result->heap_allocated = true;
result->cachable = true;
}
// Ok
break;
case kSnappyCompression: {
size_t ulength = 0;
if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
delete[] buf;
return errors::DataLoss("corrupted compressed block contents");
}
char* ubuf = new char[ulength];
if (!port::Snappy_Uncompress(data, n, ubuf)) {
delete[] buf;
delete[] ubuf;
return errors::DataLoss("corrupted compressed block contents");
}
delete[] buf;
result->data = StringPiece(ubuf, ulength);
result->heap_allocated = true;
result->cachable = true;
break;
}
default:
delete[] buf;
return errors::DataLoss("bad block type");
}
return Status::OK();
}
} // namespace table
} // namespace tensorflow
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