This allows us to recombine the reader and other file data in a Decoder
with any IFD, whether that of an image or an extension IFD as indicated
by an IFD pointer such as Exif and GPS.
This assumed that a `read` would succeed for the full length, thus
interpreting in a subsequent call some data bits as a header.
For instance, consider 77 bytes of literal were left and a buffer of
1024 bytes was provided. Then the `read` call might return 60 which was
ignored and assumed to be 77. Thus the next 17 bytes of literal data
were instead interpreted as a header due to setting `self.count` to 0.
- Switch to streaming decompression via `flate2`. Aside from performance improvements and lower RAM consumption, this fixes a bug where `max_uncompressed_length` was precalculated for a single tile but then used as a hard limit on the whole data, failing to decompress any tiled images.
- Deprecate `InflateError` - this was used for wrapping `miniz_oxide` raw status, but `flate2` already reports them as `io::Error` instead. This makes errors from both Lzw and Deflate modes more consistent - they're all now just `io::Error`.
- Add support for new `Deflate` tag in addition to `OldDeflate` - format-wise it's same Zlib, and on practice decodes successfully with the same underlying code.
- Slightly simplify partial reads from the `Reader` by using the `std::io::copy` helper instead of doing it manually.
Fixes#131.
When the required amount of data was just a tiny bit larger than full a
page size (one buffer increment), the decoder would stop since all
compressed data had been read. However, the lzw decoder contains a small
internal bit buffer for code decoding. That is, some remaining bytes had
been retained and were still left to be decoded.
Aurelia Molzer