reverting disastrous MOE commit, returning to r21

git-svn-id: https://leveldb.googlecode.com/svn/trunk@23 62dab493-f737-651d-591e-8d6aee1b9529

table/format.cc

@@ -0,0 +1,131 @@
+// 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 "table/format.h"
+
+#include "leveldb/env.h"
+#include "port/port.h"
+#include "table/block.h"
+#include "util/coding.h"
+#include "util/crc32c.h"
+
+namespace leveldb {
+
+void BlockHandle::EncodeTo(std::string* dst) const {
+  // Sanity check that all fields have been set
+  assert(offset_ != ~static_cast<uint64_t>(0));
+  assert(size_ != ~static_cast<uint64_t>(0));
+  PutVarint64(dst, offset_);
+  PutVarint64(dst, size_);
+}
+
+Status BlockHandle::DecodeFrom(Slice* input) {
+  if (GetVarint64(input, &offset_) &&
+      GetVarint64(input, &size_)) {
+    return Status::OK();
+  } else {
+    return Status::Corruption("bad block handle");
+  }
+}
+
+void Footer::EncodeTo(std::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
+  PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber));
+  PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber >> 32));
+  assert(dst->size() == original_size + kEncodedLength);
+}
+
+Status Footer::DecodeFrom(Slice* input) {
+  const char* magic_ptr = input->data() + kEncodedLength - 8;
+  const uint32_t magic_lo = DecodeFixed32(magic_ptr);
+  const uint32_t magic_hi = DecodeFixed32(magic_ptr + 4);
+  const uint64_t magic = ((static_cast<uint64_t>(magic_hi) << 32) |
+                          (static_cast<uint64_t>(magic_lo)));
+  if (magic != kTableMagicNumber) {
+    return Status::InvalidArgument("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 = Slice(end, input->data() + input->size() - end);
+  }
+  return result;
+}
+
+Status ReadBlock(RandomAccessFile* file,
+                 const ReadOptions& options,
+                 const BlockHandle& handle,
+                 Block** block) {
+  *block = NULL;
+
+  // 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 = handle.size();
+  char* buf = new char[n + kBlockTrailerSize];
+  Slice 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 Status::Corruption("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
+  if (options.verify_checksums) {
+    const uint32_t crc = crc32c::Unmask(DecodeFixed32(data + n + 1));
+    const uint32_t actual = crc32c::Value(data, n + 1);
+    if (actual != crc) {
+      delete[] buf;
+      s = Status::Corruption("block checksum mismatch");
+      return s;
+    }
+  }
+
+  switch (data[n]) {
+    case kNoCompression:
+      if (data != buf) {
+        // File implementation gave us pointer to some other data.
+        // Copy into buf[].
+        memcpy(buf, data, n + kBlockTrailerSize);
+      }
+
+      // Ok
+      break;
+    case kSnappyCompression: {
+      std::string decompressed;
+      if (!port::Snappy_Uncompress(data, n, &decompressed)) {
+        delete[] buf;
+        s = Status::Corruption("corrupted compressed block contents");
+        return s;
+      }
+      delete[] buf;     // Done with uncompressed data
+      buf = new char[decompressed.size()];
+      memcpy(buf, decompressed.data(), decompressed.size());
+      n = decompressed.size();
+      break;
+    }
+    default:
+      delete[] buf;
+      return Status::Corruption("bad block type");
+  }
+
+  *block = new Block(buf, n);  // Block takes ownership of buf[]
+  return Status::OK();
+}
+
+}