Trait Rules 

pub trait Rules {
    // Required methods
    fn follows(&self, w: &Walk<'_>, parent: &Ifd, kind: Kind, e: &Entry) -> bool;
    fn follows_next(&self, w: &Walk<'_>, ifd: &Ifd, kind: Kind) -> bool;
    fn ifd(&self, w: &Walk<'_>, ifd: &Ifd) -> Fate;
    fn entry(&self, w: &Walk<'_>, ifd: &Ifd, index: usize) -> Fate;
    fn image_data(&self, w: &Walk<'_>, ifd: &Ifd) -> Fate;
    fn jpeg_stream(&self, w: &Walk<'_>, ifd: &Ifd) -> Fate;

    // Provided methods
    fn magic(&self, _magic: u16) -> bool { ... }
    fn header_extension(&self, _w: &Walk<'_>) -> Option<(u64, Fate)> { ... }
    fn value_tail(
        &self,
        _w: &Walk<'_>,
        _ifd: &Ifd,
        _index: usize,
    ) -> Option<(u64, Fate)> { ... }
    fn chunk_use(
        &self,
        w: &Walk<'_>,
        ifd: &Ifd,
        tiles: bool,
        offs: &[u64],
        cnts: &[u64],
    ) -> Vec<ChunkUse> { ... }
    fn pointer(&self, kind: Kind, e: &Entry) -> Option<(Kind, &'static str)> { ... }
    fn pointer_offsets(&self, w: &Walk<'_>, e: &Entry, max: usize) -> Vec<u64> { ... }
    fn value(&self, w: &Walk<'_>, ifd: &Ifd, index: usize) -> Fate { ... }
    fn jpeg_table(&self, _w: &Walk<'_>, _ifd: &Ifd, _tag: u16) -> Fate { ... }
    fn cancelled(&self) -> bool { ... }
    fn rejects(
        &self,
        _w: &Walk<'_>,
        _at: u64,
        _kind: Kind,
    ) -> Option<&'static str> { ... }
    fn extents(&self, w: &Walk<'_>, ifd: &Ifd) -> Vec<ExtentRule> { ... }
}

What one decode path does with a TIFF’s directories, entries and extents.

Required Methods

fn follows(&self, w: &Walk<'_>, parent: &Ifd, kind: Kind, e: &Entry) -> bool

Whether the decode path reads the directory the pointer entry e of parent, reached as a kind directory, leads to.

fn follows_next(&self, w: &Walk<'_>, ifd: &Ifd, kind: Kind) -> bool

Whether the decode path reads the directory the next pointer of ifd, reached as a kind directory, leads to.

fn ifd(&self, w: &Walk<'_>, ifd: &Ifd) -> Fate

fn entry(&self, w: &Walk<'_>, ifd: &Ifd, index: usize) -> Fate

The entry (and, unless value says otherwise, its out-of-line value).

fn image_data(&self, w: &Walk<'_>, ifd: &Ifd) -> Fate

Strips and tiles.

fn jpeg_stream(&self, w: &Walk<'_>, ifd: &Ifd) -> Fate

A JPEG stream located by JPEGInterchangeFormat (513/514).

Provided Methods

fn magic(&self, _magic: u16) -> bool

Accept a TIFF version number other than 42 and 43 (ORF, RW2).

fn header_extension(&self, _w: &Walk<'_>) -> Option<(u64, Fate)>

Bytes after the classic 8-byte header that the file format defines (CR2), and what the decode path does with them.

fn value_tail( &self, _w: &Walk<'_>, _ifd: &Ifd, _index: usize, ) -> Option<(u64, Fate)>

For a value the decode path consumes only in part: how many leading bytes it uses, and the fate of the rest (an ASCII value’s bytes after its NUL, for example).

fn chunk_use( &self, w: &Walk<'_>, ifd: &Ifd, tiles: bool, offs: &[u64], cnts: &[u64], ) -> Vec<ChunkUse>

How much of each strip or tile, located at offs with declared lengths cnts, the decoder reads. The default follows image-tiff: default_chunk_use.

fn pointer(&self, kind: Kind, e: &Entry) -> Option<(Kind, &'static str)>

The directory pointer entry e in a kind IFD leads to.

fn pointer_offsets(&self, w: &Walk<'_>, e: &Entry, max: usize) -> Vec<u64>

The TIFF-relative offsets a pointer entry holds, at most max of them (the walk reads only as many as it can still queue).

fn value(&self, w: &Walk<'_>, ifd: &Ifd, index: usize) -> Fate

The entry’s out-of-line value.

fn jpeg_table(&self, _w: &Walk<'_>, _ifd: &Ifd, _tag: u16) -> Fate

External old-style JPEG tables (519, 520 or 521). Locating a table does not establish that the decoder uses it: an embedded JPEG header can supply tables instead. The default deliberately leaves consumption unknown, independently of strips and JPEGInterchangeFormat streams.

Override only when the codec’s rules establish the same disposition for every table reached by this tag. This is not privacy evidence.

fn cancelled(&self) -> bool

Whether the caller’s stop token asks the walk to end early.

fn rejects(&self, _w: &Walk<'_>, _at: u64, _kind: Kind) -> Option<&'static str>

Why the decoder rejects the directory at absolute offset at, reached as kind, before reading its entries (an entry-count cap), if it does. Such a directory is walked as not followed.

fn extents(&self, w: &Walk<'_>, ifd: &Ifd) -> Vec<ExtentRule>

Extents ifd locates. The default covers strips, tiles, free space and JPEGInterchangeFormat streams and external JPEG tables of image IFDs.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors