*****************
From v4.2 to v4.3
*****************

.. highlight:: c++


Storage Management
------------------

The layout of flash memory has been revised and is now managed via partition table.
Hardware configuration is stored in a JSON file (with .hw extension).

If your project has minimal customisation then you may only need to change
the :envvar:`HWCONFIG` setting.

You can find full details in the :component:`Storage` library.
See also background on :doc:`/information/flash`.

Removed build targets
    spiffs-image-update
        Use the new ``buildpart`` target instead
    spiffs-image-clean
        Use the new ``part-clean`` target instead

New and updated build targets
    hwconfig
        Displays the current configuration in JSON format
    hwconfig-list
        Show available hardware configs
    hwconfig-options
        Show available hardware configuration options
    map
        Display the current flash memory map
    readmap
        Read partition table from device and display the map
    readpart
        Read contents of partition into a file, e.g. ``make readpart PART=spiffs0``
        will create ``out/Esp8266/debug/spiffs0.read.bin``
    flash
        Flash partition table and all partitions. Previously it was necessary to run
        ``make flashinit`` to write system parameter information. Failure to do this
        was a common problem and should now be a thing of the past.
    flashinit
        This now just erases the flash memory.
        The ESP8266 initialisation data gets written when running ``make flash``.
    flashmap
        Flash just the partition map
    flashpart
        Flash a single partition, e.g. ``make flashpart PART=spiffs0``
    erasepart
        Erase a partition, e.g. ``make erasepart PART=spiffs0``
    buildpart
        Re-builds images associated with partitions, such as SPIFFS or other filesystem images.
    part-clean
        Removes any partition images with build information. This is done as part of a normal project `clean`.

Configuration variables
    A number of configuration variables have been removed or made read-only, as these are now
    generated from the :ref:`hardware_config`.

    :envvar:`SPI_MODE`, :envvar:`SPI_SIZE`, :envvar:`SPI_SPEED`
        The variables are still used internally but are read-only; they cannot be set at the command line.
        Values are read from the hardware configuration under ``/devices/spiFlash``.

    :envvar:`RBOOT_ROM0_ADDR`, :envvar:`RBOOT_ROM1_ADDR`, :envvar:`RBOOT_ROM2_ADDR`
        Used by :component:`rboot`, and are now read-only.
        Values are read from the ``address`` property of ``rom0-2`` in the hardware configuration.

    :envvar:`RBOOT_SPIFFS_0`, :envvar:`RBOOT_SPIFFS_1`
        Removed.

    :envvar:`SPIFF_SIZE`
        Removed. Attempting to set this automatically within a hardware configuration is
        liable to cause more problems than it solves, so updating the hardware config is
        the now only way to change this setting.

    :envvar:`SPIFF_FILES`
        [deprecated]

        You can still use this to specify the source location for the primary
        SPIFFS partition (spiffs0). The preferred method is to set the ``files``
        property in a partition ``build`` key.

        The default SPIFFS partition settings can be overridden in a custom profile.
        For example:

        .. code-block:: json

            {
                ...
                "base_config": "spiffs",
                "partitions": {
                    "spiffs0": {
                        "size": "128K",
                        "build": {
                            "files": "some/other/folder"
                        }
                    }
                }
            }


Installable File System (IFS)
-----------------------------

Sming now supports multiple filesystems via :component:`IFS`.

See :sample:`Basic_IFS` for a demonstration.

:source:`Core/FileSystem.h` has been modified to use IFS but the API remains largely unchanged, although somewhat expanded.
Functions are now mainly just wrappers around filing system calls.

A single global IFileSystem instance is used.

SPIFFS
    All access is now managed via the ``IFS::SPIFFS::FileSystem`` implementation.

    Applications should not use SPIFFS functions directly.

    .. important::

        SPIFFS is now built with ``SPIFFS_OBJ_META_LEN=16`` to store extended attribute information.
        Existing volumes built with other values will not be directly compatible; the file listing may be
        correct but file contents will not.

        To accommodate use of existing pre-built SPIFFS images, :envvar:`SPIFFS_OBJ_META_LEN` has been added::

            make SPIFFS_OBJ_META_LEN=0

        You will, however, lose the additional file information (such as modification time).

File open flags
    e.g. eFO_ReadOnly. These will still work but are now deprecated and should be replaced with their
    C++ equivalent such as ``File::ReadOnly``.