Replaced inline file reading logic with `FileReader` to standardize handling across chunkers. Improved buffer updates and allocation handling for sparse files and optimized read operations.
Includes cases for simple reads, multiple reads, and mock chunk scenarios to verify behavior with mixed allocation types.
Also: change Chunk type for empty read result for better consistency.
Simplified and improved handling of mixed types of chunks during reading. The allocation type of resulting chunks is now determined based on contributing chunks.
The `header_size` parameter and related logic have been removed from file readers, simplifying their implementation. This change eliminates unnecessary complexity while maintaining all functional capabilities via `read_size` and `fmap`.
`FileFMAPReader` deals with sparse files (data vs holes) or fmap and yields blocks of some specific read_size using a generator.
`FileReader` uses the `FileFMAPReader` to fill an internal buffer and lets users use its `read` method to read arbitrary sized chunks from the buffer.
For both classes, instances now only deal with a single file.
Replaced `ChunkerFixed`'s block-reading functionality with a new `FileReader` class to streamline code and improve separation of concerns. Adjusted `ChunkerFixed` to delegate file reading to `FileReader` while focusing on chunk assembly.
`FileReader` is intended to be useful for other chunkers also, so they can easily implement sparse file reading / fmap support.
The `-Wno-unreachable-code-fallthrough` compiler flag suppresses warnings about fallthrough annotations in unreachable code.
In C switch statements, "fallthrough" occurs when execution continues from one case to the next without a break statement. This is often a source of bugs, so modern compilers warn about it. To indicate intentional fallthrough, developers use annotations like `__attribute__((fallthrough))`.
In Cython-generated C code, the `CYTHON_FALLTHROUGH` macro is defined to expand to the appropriate fallthrough annotation for the compiler being used. For example, in `compress.c`:
```c
#define CYTHON_FALLTHROUGH __attribute__((fallthrough))
```
The issue occurs because Cython generates code with conditional branches that may be unreachable on certain platforms or configurations. When these branches contain switch statements with fallthrough annotations, compilers like Clang issue warnings like:
```
warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
```
These warnings appear in the generated C code, not in the original Cython source. They're harmless but noisy, cluttering the build output with warnings about code we don't control.
By adding `-Wno-unreachable-code-fallthrough` to the compiler flags in `setup.py`, we specifically tell the compiler to ignore these particular warnings, resulting in a cleaner build output without affecting the actual functionality of the code.
This is a common practice when working with generated code - suppress specific warnings that are unavoidable due to the code generation process while keeping other useful warnings enabled.
