Struct domain::bits::message::Message

pub struct Message { /* fields omitted */ }

A slice of a DNS message.

This types wraps a bytes slice with the binary content of a DNS message and allows parsing the content for further processing.

Typically, you create a message slice by passing a slice with its raw bytes to the from_bytes() function. This function only does a quick if there are enough bytes for the minimum message size. All further parsing happens lazily when you access more of the message.

Section 4 of RFC 1035 defines DNS messages as being divded into five sections named header, question, answer, authority, and additional.

The header section is of a fixed sized and can be accessed without further checks through the methods given under Header Section. Most likely, you will be interested in the first part of the header references to which are returned by the header() and header_mut() methods. The second part of the header section contains the number of entries in the following four sections and is of less interest as there are more sophisticated ways of accessing these sections. If you do care, you can get a reference through counts().

The question section contains what was asked of the DNS by a request. These questions consist of a domain name, a record type and class. With normal queries, a requests asks for all records of the given record type that are owned by the domain name within the class. There will normally be exactly one question for normal queries. With other query operations, the questions may refer to different things.

You can get access to the question section through the question() method. It returns a QuestionSection value that is an iterator over questions. Since a single question is a very common case, there is a convenience method first_question() that simple returns the first question if there is any.

The following three section all contain DNS resource records. In normal queries, they are empty in a request and may or may not contain records in a response. The answer section contains all the records that answer the given question. The authority section contains records declaring which name server provided authoritative information for the question, and the additional section can contain records that the name server thought might be useful for processing the question. For instance, if you trying to find out the mail server of a domain by asking for MX records, you likely also want the IP addresses for the server, so the name server may include these right away and free of charge.

There are functions to access all three sections directly: answer(), authority(), and additional(). However, since there are no pointers to where the later sections start, accessing them directly means iterating over the previous sections. This is why it is more efficitent to call next_section() on the returned value and process them in order. Alternatively, you can use the sections() function that gives you all four sections at once with the minimal amount of iterating necessary.

Each record in the record sections is of a specific type. Each type has its specific record data. Because there are so many types, we decided against having a giant enum. Instead, the type representing a record section, somewhat obviously named RecordSection, iterates over GenericRecords with limited options on what you can do with the data. If you are looking for a specific record type, you can get an iterator limited to records of that type through the limit_to() method. This method is generic over a record data type fit for parsing (typically meaning that it is taken from the domain::rdata::parsed module). So, if you want to iterate over the MX records in the answer section, you would do something like this:

use domain::rdata::parsed::Mx;

let msg = Message::from_bytes(bytes).unwrap();
for record in msg.answer().unwrap().limit_to::<Mx>() {
    // Do something with the record ...
}

Note that because of lazy parsing, the iterator actually returns a ParseResult<_>. One quick application of try!() fixes this:

use domain::bits::{Message, ParseResult};
use domain::rdata::parsed::Mx;

fn process_mx(msg: &Message) -> ParseResult<()> {
    for record in msg.answer().unwrap().limit_to::<Mx>() {
        let record = try!(record);
        // Do something with the record ...
    }
    Ok(())
}

Methods

impl Message

Creation and Conversion

pub fn from_bytes(bytes: &[u8]) -> ParseResult<&Self>

Creates a message from a bytes slice.

This fails if the slice is too short to even contain a complete header section. No further checks are done, though, so if this function returns Ok, the message may still be broken with methods returning Err(_).

pub unsafe fn from_bytes_unsafe(bytes: &[u8]) -> &Self

Creates a message from a bytes slice without further checks.

You need to make sure that the slice is at least the length of a full message header.

pub fn to_owned(&self) -> MessageBuf

Returns an owned copy of this message.

pub fn as_bytes(&self) -> &[u8]

Returns a reference to the underlying bytes slice.

impl Message

Header Section

pub fn header(&self) -> &Header

Returns a reference to the message header.

pub fn header_mut(&mut self) -> &mut Header

Returns a mutable reference to the message header.

The header is the only part of an already constructed message that can be safely manipulated without extra ado, so this is the only mutable method.

pub fn counts(&self) -> &HeaderCounts

Returns a reference to the header counts of the message.

pub fn no_error(&self) -> bool

Returns whether the rcode is NoError.

pub fn is_error(&self) -> bool

Returns whether the rcode is one of the error values.

impl Message

Sections

Important traits for QuestionSection<'a>

impl<'a> Iterator for QuestionSection<'a> type Item = ParseResult<Question<ParsedDName<'a>>>;

pub fn question(&self) -> QuestionSection

Returns the question section.

Important traits for QuestionSection<'a>

impl<'a> Iterator for QuestionSection<'a> type Item = ParseResult<Question<ParsedDName<'a>>>;

pub fn zone(&self) -> QuestionSection

Returns the zone section of an UPDATE message.

This is identical to self.question().

pub fn answer(&self) -> ParseResult<RecordSection>

Returns the answer section.

pub fn prerequisite(&self) -> ParseResult<RecordSection>

Returns the prerequisite section of an UPDATE message.

This is identical to self.answer().

pub fn authority(&self) -> ParseResult<RecordSection>

Returns the authority section.

pub fn update(&self) -> ParseResult<RecordSection>

Returns the update section of an UPDATE message.

This is identical to self.authority().

pub fn additional(&self) -> ParseResult<RecordSection>

Returns the additional section.

pub fn sections(     &self ) -> ParseResult<(QuestionSection, RecordSection, RecordSection, RecordSection)>

Returns all four sections in one fell swoop.

impl Message

Helpers for Common Tasks

pub fn is_answer<M: AsRef<Message>>(&self, query: M) -> bool

Returns whether this is the answer to some other message.

The method checks whether the ID fields of the headers are the same, whether the QR flag is set in this message, and whether the questions are the same.

pub fn first_question(&self) -> Option<Question<ParsedDName>>

Returns the first question, if there is any.

The method will return None both if there are no questions or if parsing fails.

pub fn qtype(&self) -> Option<Rtype>

Returns the query type of the first question, if any.

pub fn contains_answer<'a, D: ParsedRecordData<'a>>(&'a self) -> bool

Returns whether the message contains answers of a given type.

pub fn canonical_name(&self) -> Option<ParsedDName>

Resolves the canonical name of the answer.

Returns None if either the message doesn’t have a question or there was a parse error. Otherwise starts with the question’s name, follows any CNAME trail and returns the name answers should be for.

Methods from Deref<Target = [u8]>

pub const fn len(&self) -> usize

Returns the number of elements in the slice.

Examples

let a = [1, 2, 3];
assert_eq!(a.len(), 3);

pub const fn is_empty(&self) -> bool

Returns true if the slice has a length of 0.

Examples

let a = [1, 2, 3];
assert!(!a.is_empty());

pub fn first(&self) -> Option<&T>

Returns the first element of the slice, or None if it is empty.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&10), v.first());

let w: &[i32] = &[];
assert_eq!(None, w.first());

pub fn split_first(&self) -> Option<(&T, &[T])>

Returns the first and all the rest of the elements of the slice, or None if it is empty.

Examples

let x = &[0, 1, 2];

if let Some((first, elements)) = x.split_first() {
    assert_eq!(first, &0);
    assert_eq!(elements, &[1, 2]);
}

pub fn split_last(&self) -> Option<(&T, &[T])>

Returns the last and all the rest of the elements of the slice, or None if it is empty.

Examples

let x = &[0, 1, 2];

if let Some((last, elements)) = x.split_last() {
    assert_eq!(last, &2);
    assert_eq!(elements, &[0, 1]);
}

pub fn last(&self) -> Option<&T>

Returns the last element of the slice, or None if it is empty.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&30), v.last());

let w: &[i32] = &[];
assert_eq!(None, w.last());

pub fn get<I>(&self, index: I) -> Option<&<I as SliceIndex<[T]>>::Output> where     I: SliceIndex<[T]>,

Returns a reference to an element or subslice depending on the type of index.

• If given a position, returns a reference to the element at that position or None if out of bounds.
• If given a range, returns the subslice corresponding to that range, or None if out of bounds.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&40), v.get(1));
assert_eq!(Some(&[10, 40][..]), v.get(0..2));
assert_eq!(None, v.get(3));
assert_eq!(None, v.get(0..4));

pub unsafe fn get_unchecked<I>(     &self,     index: I ) -> &<I as SliceIndex<[T]>>::Output where     I: SliceIndex<[T]>,

Returns a reference to an element or subslice, without doing bounds checking.

This is generally not recommended, use with caution! For a safe alternative see get.

Examples

let x = &[1, 2, 4];

unsafe {
    assert_eq!(x.get_unchecked(1), &2);
}

pub const fn as_ptr(&self) -> *const T

Returns a raw pointer to the slice's buffer.

The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.

Modifying the container referenced by this slice may cause its buffer to be reallocated, which would also make any pointers to it invalid.

Examples

let x = &[1, 2, 4];
let x_ptr = x.as_ptr();

unsafe {
    for i in 0..x.len() {
        assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize));
    }
}

pub fn iter(&self) -> Iter<T>

Returns an iterator over the slice.

Examples

let x = &[1, 2, 4];
let mut iterator = x.iter();

assert_eq!(iterator.next(), Some(&1));
assert_eq!(iterator.next(), Some(&2));
assert_eq!(iterator.next(), Some(&4));
assert_eq!(iterator.next(), None);

pub fn windows(&self, size: usize) -> Windows<T>

Returns an iterator over all contiguous windows of length size. The windows overlap. If the slice is shorter than size, the iterator returns no values.

Panics

Panics if size is 0.

Examples

let slice = ['r', 'u', 's', 't'];
let mut iter = slice.windows(2);
assert_eq!(iter.next().unwrap(), &['r', 'u']);
assert_eq!(iter.next().unwrap(), &['u', 's']);
assert_eq!(iter.next().unwrap(), &['s', 't']);
assert!(iter.next().is_none());

If the slice is shorter than size:

let slice = ['f', 'o', 'o'];
let mut iter = slice.windows(4);
assert!(iter.next().is_none());

pub fn chunks(&self, chunk_size: usize) -> Chunks<T>

Returns an iterator over chunk_size elements of the slice at a time. The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last chunk will not have length chunk_size.

See exact_chunks for a variant of this iterator that returns chunks of always exactly chunk_size elements.

Panics

Panics if chunk_size is 0.

Examples

let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.chunks(2);
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert_eq!(iter.next().unwrap(), &['m']);
assert!(iter.next().is_none());

pub fn exact_chunks(&self, chunk_size: usize) -> ExactChunks<T>

🔬 This is a nightly-only experimental API. (exact_chunks)

Returns an iterator over chunk_size elements of the slice at a time. The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last up to chunk_size-1 elements will be omitted.

Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of chunks.

Panics

Panics if chunk_size is 0.

Examples

#![feature(exact_chunks)]

let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.exact_chunks(2);
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert!(iter.next().is_none());

pub fn split_at(&self, mid: usize) -> (&[T], &[T])

Divides one slice into two at an index.

The first will contain all indices from [0, mid) (excluding the index mid itself) and the second will contain all indices from [mid, len) (excluding the index len itself).

Panics

Panics if mid > len.

Examples

let v = [1, 2, 3, 4, 5, 6];

{
   let (left, right) = v.split_at(0);
   assert!(left == []);
   assert!(right == [1, 2, 3, 4, 5, 6]);
}

{
    let (left, right) = v.split_at(2);
    assert!(left == [1, 2]);
    assert!(right == [3, 4, 5, 6]);
}

{
    let (left, right) = v.split_at(6);
    assert!(left == [1, 2, 3, 4, 5, 6]);
    assert!(right == []);
}

pub fn split<F>(&self, pred: F) -> Split<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred. The matched element is not contained in the subslices.

Examples

let slice = [10, 40, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

If the first element is matched, an empty slice will be the first item returned by the iterator. Similarly, if the last element in the slice is matched, an empty slice will be the last item returned by the iterator:

let slice = [10, 40, 33];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[]);
assert!(iter.next().is_none());

If two matched elements are directly adjacent, an empty slice will be present between them:

let slice = [10, 6, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10]);
assert_eq!(iter.next().unwrap(), &[]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred, starting at the end of the slice and working backwards. The matched element is not contained in the subslices.

Examples

let slice = [11, 22, 33, 0, 44, 55];
let mut iter = slice.rsplit(|num| *num == 0);

assert_eq!(iter.next().unwrap(), &[44, 55]);
assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
assert_eq!(iter.next(), None);

As with split(), if the first or last element is matched, an empty slice will be the first (or last) item returned by the iterator.

let v = &[0, 1, 1, 2, 3, 5, 8];
let mut it = v.rsplit(|n| *n % 2 == 0);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next().unwrap(), &[3, 5]);
assert_eq!(it.next().unwrap(), &[1, 1]);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next(), None);

pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once by numbers divisible by 3 (i.e. [10, 40], [20, 60, 50]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.splitn(2, |num| *num % 3 == 0) {
    println!("{:?}", group);
}

pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once, starting from the end, by numbers divisible by 3 (i.e. [50], [10, 40, 30, 20]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.rsplitn(2, |num| *num % 3 == 0) {
    println!("{:?}", group);
}

pub fn contains(&self, x: &T) -> bool where     T: PartialEq<T>,

Returns true if the slice contains an element with the given value.

Examples

let v = [10, 40, 30];
assert!(v.contains(&30));
assert!(!v.contains(&50));

pub fn starts_with(&self, needle: &[T]) -> bool where     T: PartialEq<T>,

Returns true if needle is a prefix of the slice.

Examples

let v = [10, 40, 30];
assert!(v.starts_with(&[10]));
assert!(v.starts_with(&[10, 40]));
assert!(!v.starts_with(&[50]));
assert!(!v.starts_with(&[10, 50]));

Always returns true if needle is an empty slice:

let v = &[10, 40, 30];
assert!(v.starts_with(&[]));
let v: &[u8] = &[];
assert!(v.starts_with(&[]));

pub fn ends_with(&self, needle: &[T]) -> bool where     T: PartialEq<T>,

Returns true if needle is a suffix of the slice.

Examples

let v = [10, 40, 30];
assert!(v.ends_with(&[30]));
assert!(v.ends_with(&[40, 30]));
assert!(!v.ends_with(&[50]));
assert!(!v.ends_with(&[50, 30]));

Always returns true if needle is an empty slice:

let v = &[10, 40, 30];
assert!(v.ends_with(&[]));
let v: &[u8] = &[];
assert!(v.ends_with(&[]));

pub fn binary_search(&self, x: &T) -> Result<usize, usize> where     T: Ord,

Binary searches this sorted slice for a given element.

If the value is found then Ok is returned, containing the index of the matching element; if the value is not found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Examples

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

assert_eq!(s.binary_search(&13),  Ok(9));
assert_eq!(s.binary_search(&4),   Err(7));
assert_eq!(s.binary_search(&100), Err(13));
let r = s.binary_search(&1);
assert!(match r { Ok(1...4) => true, _ => false, });

pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize> where     F: FnMut(&'a T) -> Ordering,

Binary searches this sorted slice with a comparator function.

The comparator function should implement an order consistent with the sort order of the underlying slice, returning an order code that indicates whether its argument is Less, Equal or Greater the desired target.

If a matching value is found then returns Ok, containing the index for the matched element; if no match is found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Examples

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

let seek = 13;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
let seek = 4;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
let seek = 100;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
let seek = 1;
let r = s.binary_search_by(|probe| probe.cmp(&seek));
assert!(match r { Ok(1...4) => true, _ => false, });

pub fn binary_search_by_key<'a, B, F>(     &'a self,     b: &B,     f: F ) -> Result<usize, usize> where     B: Ord,     F: FnMut(&'a T) -> B,

Binary searches this sorted slice with a key extraction function.

Assumes that the slice is sorted by the key, for instance with sort_by_key using the same key extraction function.

If a matching value is found then returns Ok, containing the index for the matched element; if no match is found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Examples

Looks up a series of four elements in a slice of pairs sorted by their second elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
         (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
         (1, 21), (2, 34), (4, 55)];

assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b),  Ok(9));
assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b),   Err(7));
assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
let r = s.binary_search_by_key(&1, |&(a,b)| b);
assert!(match r { Ok(1...4) => true, _ => false, });

pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T])

🔬 This is a nightly-only experimental API. (slice_align_to)

Transmute the slice to a slice of another type, ensuring aligment of the types is maintained.

This method splits the slice into three distinct slices: prefix, correctly aligned middle slice of a new type, and the suffix slice. The middle slice will have the greatest length possible for a given type and input slice.

This method has no purpose when either input element T or output element U are zero-sized and will return the original slice without splitting anything.

Unsafety

This method is essentially a transmute with respect to the elements in the returned middle slice, so all the usual caveats pertaining to transmute::<T, U> also apply here.

Examples

Basic usage:

unsafe {
    let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
    let (prefix, shorts, suffix) = bytes.align_to::<u16>();
    // less_efficient_algorithm_for_bytes(prefix);
    // more_efficient_algorithm_for_aligned_shorts(shorts);
    // less_efficient_algorithm_for_bytes(suffix);
}

Trait Implementations

impl Deref for Message

type Target = [u8]

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl Borrow<[u8]> for Message

fn borrow(&self) -> &[u8]

Immutably borrows from an owned value.

impl AsRef<Message> for Message

fn as_ref(&self) -> &Message

Performs the conversion.

impl AsRef<[u8]> for Message

fn as_ref(&self) -> &[u8]

Performs the conversion.

impl ToOwned for Message

type Owned = MessageBuf

fn to_owned(&self) -> Self::Owned

Creates owned data from borrowed data, usually by cloning.

fn clone_into(&self, target: &mut Self::Owned)

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning.

impl Borrow<Message> for MessageBuf

fn borrow(&self) -> &Message

Immutably borrows from an owned value.

impl AsRef<Message> for MessageBuf

fn as_ref(&self) -> &Message

Performs the conversion.

impl AsMut<Message> for MessageBuf

fn as_mut(&mut self) -> &mut Message

Performs the conversion.

impl AsRef<Message> for AdditionalBuilder

fn as_ref(&self) -> &Message

Performs the conversion.