Struct ZlibHeader

#[repr(C)]
pub struct ZlibHeader {
    pub cmf: u8,
    pub flg: u8,
}

2 Byte header at the start of a zlib stream.

Fields

cmf: u8

Compression Method and Flags
0000_1111 => compression method (cm)
1111_0000 => compression info (cinfo)

flg: u8

Flags
0001_1111 => checksum adjustment (fcheck)
0010_0000 => preset dictionary used (fdict)
1100_0000 => compression level (flevel)

Implementations

impl ZlibHeader

pub fn new( cm: u8, cinfo: u8, fdict: bool, flevel: u8, ) -> Result<Self, OutOfRangeError>

Initializes with the given parameters and calls Self::set_fcheck.

pub fn from_hex(input: &str) -> Result<Self, FromHexError>

Parses input as 2 Byte hex string to initialize.

Errors

FromHexError::InvalidStringLength if input is not exactly 4 characters long.
Other FromHexError variants if hex::decode fails by other means.

pub fn get_cm(&self) -> u8

Gets the lower 4 bits of self.cmf, representing the compression method.

pub fn set_cm(&mut self, cm: u8) -> Result<(), OutOfRangeError>

Sets the lower 4 bits of self.cmf to cm, representing the compression method.

Errors

Returns OutOfRangeError::CompressionInfo if cm > 15

pub fn get_cm_str(&self) -> &str

Gets the string representation of cm.
DEFLATE if it is 8, UNDEFINED in all other cases.

pub fn get_cinfo(&self) -> u8

Gets the upper 4 bits of self.cmf, representing the compression info.
It is used to determine the sliding window size for de-/compression.
Read more on Self::get_window_size

pub fn set_cinfo(&mut self, cinfo: u8) -> Result<(), OutOfRangeError>

Sets the upper 4 bits of self.cmf to cinfo, representing the compression info.

Errors

Returns OutOfRangeError::CompressionInfo if cinfo > 15

pub fn get_window_size(&self) -> u32

Gets the size of the sliding window in Bytes.
Valid window sizes range from 256 to 32768 - means cinfo ranges from 0 to 7.
The formula is: 2.pow(cinfo + 8)

pub fn get_fcheck(&self) -> u8

Gets the lowest 5 bits of self.flg, representing the checksum adjustment.
The value is chosen to satisfy the checksum formula over the entire ZlibHeader.
Read more on Self::is_valid

pub fn set_fcheck<const CLEAN: bool>(&mut self)

Sets the lowest 5 bits of self.flg, representing the checksum adjustment.
The value is chosen to satisfy the checksum formula over the entire ZlibHeader.
The generic constant CLEAN dictates if the function has to zero the current fcheck bits.
Read more on Self::is_valid

pub fn is_valid(&self) -> bool

Returns true if the checksum formula over the ZlibHeader is satisfied.
The formula is: (self.cmf * 256 + self.flg) % 31 == 0

pub fn is_valid_strict(&self) -> bool

In addition to Self::is_valid it also checks cm == 8 and cinfo <= 7.

pub fn get_fdict(&self) -> bool

Gets the bit at index 5 of self.flg as bool, signaling the usage of a preset dictionary.

pub fn set_fdict(&mut self, fdict: bool)

Sets the bit at index 5 of self.flg, signaling the usage of a preset dictionary.

pub fn get_flevel(&self) -> u8

Returns the upper 2 bits of self.flg, which represents the compression level.

pub fn set_flevel(&mut self, flevel: u8) -> Result<(), OutOfRangeError>

Sets the upper 2 bits of self.flg to flevel, which represents the compression level.

Errors

Returns OutOfRangeError::CompressionLevel if flevel > 3

pub fn get_flevel_str(&self) -> &str

Gets the string representation of flevel.
The values are: fastest, fast, default, best

Trait Implementations

impl Debug for ZlibHeader

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

Formats the value using the given formatter.

impl Default for ZlibHeader

fn default() -> Self

789C - this is DEFLATE with default compression level and a 32 KiB window.

impl Display for ZlibHeader

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

Formats the value using the given formatter.

impl From<[u8; 2]> for ZlibHeader

fn from(bytes: [u8; 2]) -> Self

Converts to this type from the input type.

impl From<ZlibHeader> for [u8; 2]

fn from(header: ZlibHeader) -> Self

Converts to this type from the input type.

impl PartialEq<&[u8]> for ZlibHeader

fn eq(&self, slice: &&[u8]) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<[u8; 2]> for ZlibHeader

fn eq(&self, slice: &[u8; 2]) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<ZlibHeader> for &[u8]

fn eq(&self, header: &ZlibHeader) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<ZlibHeader> for [u8; 2]

fn eq(&self, header: &ZlibHeader) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.