Struct cloudflare_soos::Scans

pub struct Scans {
    pub metadata_end: Option<usize>,
    pub first_scan_end: Option<usize>,
    pub good_scan_end: Option<usize>,
    pub file_size: usize,
}

Key positions in a progressive image file

cloudflare_soos::Scans::from_file(&input_file)?.cf_priority_change_headers()?;

Fields

metadata_end: Option<usize>

Byte position where metadata ends. This many bytes are preceeding start of pixel data. It's usually <200 bytes, unless the image has color profiles or other bloat.

first_scan_end: Option<usize>

Byte position where the first (lowest-quality) progressive scan ends. This many bytes are needed to display anything on screen. It's usually 12-15% of the file size.

good_scan_end: Option<usize>

Byte position where most of ok-quality pixel data ends. This many bytes are needed to display a good-enough image. It's usually about 50% of the file size.

file_size: usize

Size of the whole image file, in bytes

Implementations

impl Scans

pub fn from_file(input_file: &[u8]) -> Result<Self>

Analyze an image file to find byte ranges of its metadata and progressive scans

impl Scans

pub fn cf_priority_change_headers(&self) -> Result<(String, String)>

Assumes the priorities are:

• 50 = critical js/css, fonts + image metadata
• 30 = regular js/css, followed by other images + JPEG DC
• 20 = low-priority image bodies
• 10 = idle

Returns cf-priority and cf-priority-change header values, respectively.

Trait Implementations

impl Clone for Scans

fn clone(&self) -> Scans

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Scans

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Scans

fn default() -> Scans

Returns the "default value" for a type.

impl PartialEq<Scans> for Scans

fn eq(&self, other: &Scans) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Scans) -> bool

This method tests for !=.

impl StructuralPartialEq for Scans