Breaking changes and migration guide

Table of Contents

• Purpose
• Expected breaking changes in 6.0
  • Introduction
• Breaking changes in 5.0
  • Introduction
  • Many names are standardized
  • Column entries have a shape instead of repeat count
  • PtrRaster constructor change
  • Raster and Column refactoring
• Breaking changes in 4.0
  • Introduction
  • EL_FitsIO becomes EleFits and associated changes
  • 3rd handler level
  • RecordHdu becomes Hdu
  • FitsFile::Permission becomes FileMode
  • HduType becomes HduCategory
  • MefFile::accessPrimary() becomes MefFile::primary() and is not a template anymore
  • Raster::shape and Column::info become methods
• Breaking changes in 3.0
  • All indices are 0-based
• Breaking changes in 2.0
  • Method name change

Purpose

For each major version, this page lists the breaking changes, details the underlying rationale, the status in the previous version (e.g. what's there already and what's deprecated), and how to adapt the client code.

Expected breaking changes in 6.0

Introduction

With the increasing amount of supported features, EleFits is no more the right place to hold advanced data designs and processing services. Therefore, implementation of Raster and associated classes relies on Linx, a dedicated ND image processing library. Many interfaces were inherited from EleFits but this still comes with a lot of breaking chages, e.g. namespaces. Speaking of which, namespace Euclid is removed because it adds little value.

For integration purpose, Linx follows the standard library naming conventions for functions, which allows working with standard algorithms. So does EleFits.

Breaking changes in 5.0

Introduction

The brand new feature brought by version 5.0 is the support for multidimensional columns. This has a few impacts on the public API (e.g. the columns now have a dimension and shape), most of which are backward compatible (but not all of them).

In order to accomodate multidimensional columns, data classes (including Raster) were refactored. The refactoring brings a lot of improvements related to performance and flexibility. Yet, most changes in the API (including the additional template parameters, see below) won't even impact user codes.

Many names are standardized

In MefFile (breaking):

• accessFirst() -> find()
• select() -> filter()

In containers, type aliases are introduced generally without breaking the API, e.g. value_type is added, but Value is kept (though as std::decay_t<value_type> instead of value_type).

Rationale

Standard names are already understood by some users.

Impact on client code

Update names (previous names are kept for backward compatibility in this version).

Column entries have a shape instead of repeat count

Variable ColumnInfo::repeatCount becomes method ColumnInfo::repeatCount().

Rationale

The repeat count is not sufficient to describe multidimensional entries, while having both a repeat count and shape would be unsafe.

Impact on client code

No impact at construction.

To read the repeat count value, use ColumnInfo::repeatCount() instead of ColumnInfo::repeatCount.

To update the repeat count, use Column::reshape().

PtrRaster constructor change

PtrColumn(info, elementCount, data) becomes PtrColumn(info, rowCount, data).

Rationale

Implementation of the data classes was completely refactored for improved performance, more flexibility and easier maintenance (see below). This came with the merging of PtrRaster and VecRaster (which are now mere aliases) and therefore of their constructors.

Impact on client code

Calls to the constructor should be updated.

Raster and Column refactoring

Raster<T, N> has become Raster<T, N, TContainer>, where the added template parameter allows working with any contiguous container. PtrRaster and VecRaster are no more classes which inherit Raster but typedefs insead: PtrRaster<T, N> = Raster<T, N, T*> and VecRaster<T, N> = Raster<T, N, vector<T>>.

PtrRaster and VecRaster are backward compatible.

Column<T> has become Column<T, N, TContainer>, where the added template parameters allow supporting multidimensional entries and working with any contiguous container. PtrColumn and VecColumn are no more classes which inherit Column but typedefs insead: PtrColumn<T, N> = Column<T, N, T*> and VecColumn<T, N> = Column<T, N, vector<T>>.

The default value of N is 1 to limit impact on client code.

Let alone the change in PtrColumn's constructor described above, PtrColumn and VecColumn are backward compatible.

Impact on client code

None for basic usage.

For user-defined functions which used to return or take a Raster or a Column or a ColumnInfo as parameter, e.g. void f(Column<T>& column), there are several options:

• add the new template parameters, e.g. void f(Column<T, N, TContainer>& column);
• fix the new template parameters, e.g. void f(VecColumn<T>& column);
• use a template for the parameter itself, e.g. void f(TColumn& column) (which is the path taken by EleFits).

Breaking changes in 4.0

Introduction

Version 4.0 introduces many changes to the API. Most of them are already in place in version 3.2, but with backward compatibility ensured by aliases. This is done to make transition smoother on client code side. Therefore, in 3.2, the user can use both 3.x and 4.x versions of the API. Items removed from the API in 4.0 are marked deprecated in 3.2.

EL_FitsIO becomes EleFits and associated changes

Namespace FitsIO becomes Fits. Prefix EL_Fits (resp. EL_FITSIO) becomes EleFits (resp. ELEFITS). EL_FitsFile becomes EleFits. Underscores in program names are removed.

Rationale

• Underscores are forbidden by some package managers;
• Easier to say, read and write;
• "EL" stands for Euclid library, while the project is instead a package with libraries and executables; "Ele" stands for Euclid libraries and executables.

Status in version 3.2

Change not applied: compatibility with 4.0 cannot be anticipated in code which depends on 3.2.

Impact on client code

• Find and replace word EL_FitsIO with EleFits in CMakeLists';
• Find and replace prefix EL_Fits with EleFits in CMakeLists' and in includes;
• Find and replace prefix EL_FITSIO with ELEFITS in macros;
• Find and replace FitsIO (e.g. namespace FitsIO or class FitsIOError) with Fits in sources;
• Remove underscores from program names in command lines.

3rd handler level

In addition to file- and HDU-level handlers, additional classes are defined at header or data level. For example, records are accessed through MefFile/RecordHdu/Header instead of MefFile/RecordHdu:

// Until 4.0
f.access<>(3).writeRecord("KEY", 1);
 
// Since 4.0
f.access<>(3).header().write("KEY", 1);

Rationale

• Better mapping to FITS structure (separate header unit and data unit);
• Cleaner SifFile (e.g. no more useless index() method);
• Better application of the Single Responsibility Principle (e.g. BintableHdu goes from 57 methods to 15 in BintableColumns);
• Better structured documentation, while many more services are provided;
• Enable row-wise binary table I/Os.

Status in version 3.2

Header- and data-level handlers are implemented. Methods in HDU-level handlers still exist for backward compatibility, although they are marked deprecated.

Impact on client code

• Manual fix: 1 to 2 more calls in user code for each HDU;
• Negligible impact on runtime.

RecordHdu becomes Hdu

Rationale

• Given the new handler level, (Record)Hdu is not responsible anymore for record I/Os;
• Inheritance is more explicit: ImageHdu and BintableHdu both extend Hdu.

Status in version 3.2

Name has changed. Deprecated alias RecordHdu is provided for backward-compatibility.

Impact on client code

• Find and replace word RecordHdu with Hdu, including in include directives.

FitsFile::Permission becomes FileMode

Rationale

• More classical;
• Analogous to RecordMode;
• Remove useless scoping, shorten usage.

Status in version 3.2

Name and scope have changed. A deprecated alias FitsFile::Permission is provided for backward compatibility.

Impact on client code

• Find and replace occurrences of FitsFile::Permission, SifFile::Permission and MefFile::Permission with FileMode.

HduType becomes HduCategory

And it is now a proper class instead of an enum.

Rationale

• Much richer concept now, e.g. with support for HDU state filtering;
• Enable implementation of HDU selectors, along with iterators;
• Analogous usage to KeywordCategory.

Status in version 3.2

Name has changed. A deprecated alias HduType is provided for backward compatibility.

Impact on client code

• Find and replace occurrences of word HduType with HduCategory.

MefFile::accessPrimary() becomes MefFile::primary() and is not a template anymore

An ImageHdu is always returned by MefFile::primary().

Rationale

• The Primary is always an image;
• With the 3rd handler layer, there is no more reason to return a RecordHdu (see impact below).

Status is version 3.2

Both MefFile::accessPrimary<T>() and MefFile::primary() are implemented.

Impact on client code

• Replace MefFile::accessPrimary<Hdu>() and MefFile::accessPrimary<ImageHdu>() with MefFile::access().

Raster::shape and Column::info become methods

Rationale

Data classes should ensure data integrity as much as possible. This is not possible with member variables.

Status in version 3.2

Not implemented.

Impact on client code

• For reading, replace raster.shape and column.info with raster.shape() and column.info().
• The values cannot be changed after construction (at least for now).

Breaking changes in 3.0

All indices are 0-based

Most indices in 2.0 were 0-based (e.g. in Raster and Column). A notable exception was the HDU index, which used to follow the CFITSIO convention. Yet, the FITS standard doesn't set any convention for HDU indices (well, HDU indices are not even mentioned in the standard). Therefore, it was decided to homogeneize indexing, and follow the C++ convention instead.

For more details, see On types.

Breaking changes in 2.0

Method name change

• Method name case is now pascalCase, according to Euclid quality rules;
• Method names are homogeneized.