uint64_t and size_t changes to compile for iOS

Summary:
In attempting to build a static lib for use in iOS, I ran in to lots of type errors between uint64_t and size_t.  This PR contains the changes I made to get `TARGET_OS=IOS make static_lib` to succeed while also getting Xcode to build successfully with the resulting `librocksdb.a` library imported.

This also compiles for me on macOS and tests fine, but I'm really not sure if I made the correct decisions about where to `static_cast` and where to change types.

Also up for discussion: is iOS worth supporting?  Getting the static lib is just part one, we aren't providing any bridging headers or wrappers like the ObjectiveRocks project, it won't be a great experience.
Closes https://github.com/facebook/rocksdb/pull/3503

Differential Revision: D7106457

Pulled By: gfosco

fbshipit-source-id: 82ac2073de7e1f09b91f6b4faea91d18bd311f8e

build_tools/build_detect_platform

@@ -485,6 +485,8 @@ if test -z "$PORTABLE"; then
   elif test -n "`echo $TARGET_ARCHITECTURE | grep ^arm`"; then
     # TODO: Handle this with approprite options.
     COMMON_FLAGS="$COMMON_FLAGS"
+  elif [ "$TARGET_OS" == IOS ]; then
+    COMMON_FLAGS="$COMMON_FLAGS"
   elif [ "$TARGET_OS" != AIX ] && [ "$TARGET_OS" != SunOS ]; then
     COMMON_FLAGS="$COMMON_FLAGS -march=native "
   elif test "$USE_SSE"; then

db/compaction_job.cc

@@ -723,13 +723,15 @@ void CompactionJob::ProcessKeyValueCompaction(SubcompactionState* sub_compact) {
   std::set<size_t> sample_begin_offsets;
   if (bottommost_level_ && kSampleBytes > 0) {
     const size_t kMaxSamples = kSampleBytes >> kSampleLenShift;
-    const size_t kOutFileLen = mutable_cf_options->MaxFileSizeForLevel(
-        compact_->compaction->output_level());
+    const size_t kOutFileLen = static_cast<size_t>(
+      mutable_cf_options->MaxFileSizeForLevel(
+        compact_->compaction->output_level()));
     if (kOutFileLen != port::kMaxSizet) {
       const size_t kOutFileNumSamples = kOutFileLen >> kSampleLenShift;
       Random64 generator{versions_->NewFileNumber()};
       for (size_t i = 0; i < kMaxSamples; ++i) {
-        sample_begin_offsets.insert(generator.Uniform(kOutFileNumSamples)
+        sample_begin_offsets.insert(
+          static_cast<size_t>(generator.Uniform(kOutFileNumSamples))
             << kSampleLenShift);
       }
     }

db/compaction_picker.cc

@@ -41,7 +41,7 @@ bool FindIntraL0Compaction(const std::vector<FileMetaData*>& level_files,
                            size_t min_files_to_compact,
                            uint64_t max_compact_bytes_per_del_file,
                            CompactionInputFiles* comp_inputs) {
-  size_t compact_bytes = level_files[0]->fd.file_size;
+  size_t compact_bytes = static_cast<size_t>(level_files[0]->fd.file_size);
   size_t compact_bytes_per_del_file = port::kMaxSizet;
   // compaction range will be [0, span_len).
   size_t span_len;

db/db_impl_write.cc

@@ -214,7 +214,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
                     write_group.size > 1;
     size_t total_count = 0;
     size_t valid_batches = 0;
-    uint64_t total_byte_size = 0;
+    size_t total_byte_size = 0;
     for (auto* writer : write_group) {
       if (writer->CheckCallback(this)) {
         valid_batches += writer->batch_cnt;
@@ -550,7 +550,7 @@ Status DBImpl::WriteImplWALOnly(const WriteOptions& write_options,
   // Note: no need to update last_batch_group_size_ here since the batch writes
   // to WAL only
 
-  uint64_t total_byte_size = 0;
+  size_t total_byte_size = 0;
   for (auto* writer : write_group) {
     if (writer->CheckCallback(this)) {
       total_byte_size = WriteBatchInternal::AppendedByteSize(
@@ -1369,11 +1369,13 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
 
 size_t DBImpl::GetWalPreallocateBlockSize(uint64_t write_buffer_size) const {
   mutex_.AssertHeld();
-  size_t bsize = write_buffer_size / 10 + write_buffer_size;
+  size_t bsize = static_cast<size_t>(
+    write_buffer_size / 10 + write_buffer_size);
   // Some users might set very high write_buffer_size and rely on
   // max_total_wal_size or other parameters to control the WAL size.
   if (mutable_db_options_.max_total_wal_size > 0) {
-    bsize = std::min<size_t>(bsize, mutable_db_options_.max_total_wal_size);
+    bsize = std::min<size_t>(bsize, static_cast<size_t>(
+      mutable_db_options_.max_total_wal_size));
   }
   if (immutable_db_options_.db_write_buffer_size > 0) {
     bsize = std::min<size_t>(bsize, immutable_db_options_.db_write_buffer_size);

db/log_writer.cc

@@ -58,7 +58,8 @@ Status Writer::AddRecord(const Slice& slice) {
         // kRecyclableHeaderSize being <= 11)
         assert(header_size <= 11);
         dest_->Append(
-            Slice("\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", leftover));
+            Slice("\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
+                  static_cast<size_t>(leftover)));
       }
       block_offset_ = 0;
     }

env/mock_env.cc

@@ -94,35 +94,37 @@ class MemFile {
     uint64_t end = std::min(start + 512, size_.load());
     MutexLock lock(&mutex_);
     for (uint64_t pos = start; pos < end; ++pos) {
-      data_[pos] = static_cast<char>(rnd_.Uniform(256));
+      data_[static_cast<size_t>(pos)] = static_cast<char>(rnd_.Uniform(256));
     }
   }
 
   Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const {
     MutexLock lock(&mutex_);
     const uint64_t available = Size() - std::min(Size(), offset);
+    size_t offset_ = static_cast<size_t>(offset);
     if (n > available) {
-      n = available;
+      n = static_cast<size_t>(available);
     }
     if (n == 0) {
       *result = Slice();
       return Status::OK();
     }
     if (scratch) {
-      memcpy(scratch, &(data_[offset]), n);
+      memcpy(scratch, &(data_[offset_]), n);
       *result = Slice(scratch, n);
     } else {
-      *result = Slice(&(data_[offset]), n);
+      *result = Slice(&(data_[offset_]), n);
     }
     return Status::OK();
   }
 
   Status Write(uint64_t offset, const Slice& data) {
     MutexLock lock(&mutex_);
+    size_t offset_ = static_cast<size_t>(offset);
     if (offset + data.size() > data_.size()) {
-      data_.resize(offset + data.size());
+      data_.resize(offset_ + data.size());
     }
-    data_.replace(offset, data.size(), data.data(), data.size());
+    data_.replace(offset_, data.size(), data.data(), data.size());
     size_ = data_.size();
     modified_time_ = Now();
     return Status::OK();
@@ -203,7 +205,7 @@ class MockSequentialFile : public SequentialFile {
     if (pos_ > file_->Size()) {
       return Status::IOError("pos_ > file_->Size()");
     }
-    const size_t available = file_->Size() - pos_;
+    const uint64_t available = file_->Size() - pos_;
     if (n > available) {
       n = available;
     }
@@ -273,7 +275,7 @@ class MockWritableFile : public WritableFile {
   }
 
   virtual Status Append(const Slice& data) override {
-    uint64_t bytes_written = 0;
+    size_t bytes_written = 0;
     while (bytes_written < data.size()) {
       auto bytes = RequestToken(data.size() - bytes_written);
       Status s = file_->Append(Slice(data.data() + bytes_written, bytes));
@@ -285,7 +287,7 @@ class MockWritableFile : public WritableFile {
     return Status::OK();
   }
   virtual Status Truncate(uint64_t size) override {
-    file_->Truncate(size);
+    file_->Truncate(static_cast<size_t>(size));
     return Status::OK();
   }
   virtual Status Close() override { return file_->Fsync(); }

monitoring/histogram_windowing.cc

@@ -60,7 +60,7 @@ void HistogramWindowingImpl::Add(uint64_t value){
   stats_.Add(value);
 
   // Current window update
-  window_stats_[current_window()].Add(value);
+  window_stats_[static_cast<size_t>(current_window())].Add(value);
 }
 
 void HistogramWindowingImpl::Merge(const Histogram& other) {
@@ -89,8 +89,11 @@ void HistogramWindowingImpl::Merge(const HistogramWindowingImpl& other) {
         (cur_window + num_windows_ - i) % num_windows_;
     uint64_t other_window_index =
         (other_cur_window + other.num_windows_ - i) % other.num_windows_;
+    size_t windex = static_cast<size_t>(window_index);
+    size_t other_windex = static_cast<size_t>(other_window_index);
 
-    window_stats_[window_index].Merge(other.window_stats_[other_window_index]);
+    window_stats_[windex].Merge(
+      other.window_stats_[other_windex]);
   }
 }
 
@@ -129,8 +132,9 @@ void HistogramWindowingImpl::Data(HistogramData * const data) const {
 
 void HistogramWindowingImpl::TimerTick() {
   uint64_t curr_time = env_->NowMicros();
+  size_t curr_window_ = static_cast<size_t>(current_window());
   if (curr_time - last_swap_time() > micros_per_window_ &&
-      window_stats_[current_window()].num() >= min_num_per_window_) {
+      window_stats_[curr_window_].num() >= min_num_per_window_) {
     SwapHistoryBucket();
   }
 }
@@ -149,7 +153,8 @@ void HistogramWindowingImpl::SwapHistoryBucket() {
                                                     0 : curr_window + 1;
 
     // subtract next buckets from totals and swap to next buckets
-    HistogramStat& stats_to_drop = window_stats_[next_window];
+    HistogramStat& stats_to_drop = 
+      window_stats_[static_cast<size_t>(next_window)];
 
     if (!stats_to_drop.Empty()) {
       for (size_t b = 0; b < stats_.num_buckets_; b++){

table/block_based_table_reader.cc

@@ -260,7 +260,8 @@ class PartitionIndexReader : public IndexReader, public Cleanable {
     std::unique_ptr<FilePrefetchBuffer> prefetch_buffer;
     auto& file = table_->rep_->file;
     prefetch_buffer.reset(new FilePrefetchBuffer());
-    s = prefetch_buffer->Prefetch(file.get(), prefetch_off, prefetch_len);
+    s = prefetch_buffer->Prefetch(file.get(), prefetch_off,
+      static_cast<size_t>(prefetch_len));
 
     // After prefetch, read the partitions one by one
     biter.SeekToFirst();
@@ -654,9 +655,9 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
   size_t prefetch_len;
   if (file_size < kTailPrefetchSize) {
     prefetch_off = 0;
-    prefetch_len = file_size;
+    prefetch_len = static_cast<size_t>(file_size);
   } else {
-    prefetch_off = file_size - kTailPrefetchSize;
+    prefetch_off = static_cast<size_t>(file_size - kTailPrefetchSize);
     prefetch_len = kTailPrefetchSize;
   }
   Status s;
@@ -1896,7 +1897,8 @@ void BlockBasedTableIterator::InitDataBlock() {
         readahead_size_ = std::min(kMaxReadaheadSize, readahead_size_);
         table_->get_rep()->file->Prefetch(data_block_handle.offset(),
                                           readahead_size_);
-        readahead_limit_ = data_block_handle.offset() + readahead_size_;
+        readahead_limit_ = static_cast<size_t>(data_block_handle.offset()
+          + readahead_size_);
         // Keep exponentially increasing readahead size until kMaxReadaheadSize.
         readahead_size_ *= 2;
       }

table/partitioned_filter_block.cc

@@ -279,7 +279,8 @@ void PartitionedFilterBlockReader::CacheDependencies(bool pin) {
   std::unique_ptr<FilePrefetchBuffer> prefetch_buffer;
   auto& file = table_->rep_->file;
   prefetch_buffer.reset(new FilePrefetchBuffer());
-  s = prefetch_buffer->Prefetch(file.get(), prefetch_off, prefetch_len);
+  s = prefetch_buffer->Prefetch(file.get(), prefetch_off,
+    static_cast<size_t>(prefetch_len));
 
   // After prefetch, read the partitions one by one
   biter.SeekToFirst();

util/file_reader_writer.cc

@@ -516,7 +516,7 @@ class ReadaheadRandomAccessFile : public RandomAccessFile {
       *result = Slice(scratch, cached_len);
       return Status::OK();
     }
-    size_t advanced_offset = offset + cached_len;
+    size_t advanced_offset = static_cast<size_t>(offset + cached_len);
     // In the case of cache hit advanced_offset is already aligned, means that
     // chunk_offset equals to advanced_offset
     size_t chunk_offset = TruncateToPageBoundary(alignment_, advanced_offset);
@@ -549,12 +549,13 @@ class ReadaheadRandomAccessFile : public RandomAccessFile {
       // `Read()` assumes a smaller prefetch buffer indicates EOF was reached.
       return Status::OK();
     }
-    size_t prefetch_offset = TruncateToPageBoundary(alignment_, offset);
+    size_t offset_ = static_cast<size_t>(offset);
+    size_t prefetch_offset = TruncateToPageBoundary(alignment_, offset_);
     if (prefetch_offset == buffer_offset_) {
       return Status::OK();
     }
     return ReadIntoBuffer(prefetch_offset,
-                          Roundup(offset + n, alignment_) - prefetch_offset);
+                          Roundup(offset_ + n, alignment_) - prefetch_offset);
   }
 
   virtual size_t GetUniqueId(char* id, size_t max_size) const override {
@@ -614,17 +615,18 @@ class ReadaheadRandomAccessFile : public RandomAccessFile {
 Status FilePrefetchBuffer::Prefetch(RandomAccessFileReader* reader,
                                     uint64_t offset, size_t n) {
   size_t alignment = reader->file()->GetRequiredBufferAlignment();
-  uint64_t rounddown_offset = Rounddown(offset, alignment);
-  uint64_t roundup_end = Roundup(offset + n, alignment);
+  size_t offset_ = static_cast<size_t>(offset);
+  uint64_t rounddown_offset = Rounddown(offset_, alignment);
+  uint64_t roundup_end = Roundup(offset_ + n, alignment);
   uint64_t roundup_len = roundup_end - rounddown_offset;
   assert(roundup_len >= alignment);
   assert(roundup_len % alignment == 0);
   buffer_.Alignment(alignment);
-  buffer_.AllocateNewBuffer(roundup_len);
+  buffer_.AllocateNewBuffer(static_cast<size_t>(roundup_len));
 
   Slice result;
-  Status s = reader->Read(rounddown_offset, roundup_len, &result,
-                          buffer_.BufferStart());
+  Status s = reader->Read(rounddown_offset, static_cast<size_t>(roundup_len),
+                          &result, buffer_.BufferStart());
   if (s.ok()) {
     buffer_offset_ = rounddown_offset;
     buffer_len_ = result.size();