commit a4a714ebf90f7dfad2d7390aa83a028378590849
author Tess Strickland <sstrickl@google.com> Wed Sep 23 21:05:59 2020 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> Wed Sep 23 21:05:59 2020 +0000
tree 19a028f77768936109620a7206894c4945dfb666
parent 6cb9c66f28e04bcdffa500dc411b6b6e1b41d415

[vm] Consolidate the *WriteStream hierarchy.

All *WriteStream classes are now part of the same hierarchy:

class BaseWriteStream : ValueObject;

  Base class for all *WriteStreams. Provides all the methods from
  the old WriteStream except for buffer() and SetPosition()
  (relegated to NonStreamingWriteStreams). Has one pure virtual
  method Realloc that must be overridden by concrete subclasses.

class NonStreamingWriteStream : BaseWriteStream;

  Base class for all *WriteStreams where the entire stream is available
  at all times (i.e., no flushing to an external sink). Extends the
  public BaseWriteStream API with buffer() (for accessing the stream
  contents) and SetPosition() (for changing the current stream pointer
  to the given absolute position in the stream).

class MallocWriteStream : NonStreamingWriteStream;

  Uses realloc to reallocate the internal buffer.  Almost the same as
  the old WriteStream, except that it only takes an initial size.  Adds
  one public method Steal() for taking ownership of the current buffer
  contents (after which the buffer is reset to an empty state). Instead
  of passing a pointer to a buffer, the internal buffer must be accessed
  via either Steal() or buffer(), which allows access to the current
  stream contents without changing ownership or resetting the stream.
  The internal buffer is freed on stream destruction.

class ZoneWriteStream: NonStreamingWriteStream;

  Takes a zone and reallocates the internal buffer in that zone. No
  additional public methods beyond those available from
  NonStreamingWriteStream.

class StreamingWriteStream : BaseWriteStream;

  Uses realloc to reallocate the internal buffer.  Generally same as
  before, where the contents of the stream are periodically flushed
  using Dart_StreamingWriteCallback. Since it extends BaseWriteStream,
  there are now more methods available for writing data to the stream
  than just Print/VPrint/WriteBytes. Since portions of the stream may be
  flushed and thus no longer in the internal buffer, does not provide
  access to the contents of the stream or a way to reposition the
  current stream pointer. Flushes any unflushed data and frees the
  internal buffer on stream destruction.

Also refactor things so that write streams are passed to appropriate
recipients, instead of the recipients taking arguments they only used to
create a WriteStream internally. Thus, recipients now can just specify
the appropriate base class for the public API used:

* BaseWriteStream for just writing to the stream, or
* NonStreamingWriteStream if re-positioning or the stream contents are
  needed.

Change-Id: I419096ecd9331483d168b079fca55b69ef397f15
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/164080
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>