Struct Fields 

pub struct Fields { /* private fields */ }

A common representation for headers and trailers.

Examples

Initialise response headers from a list:

let response_headers = Fields::from_list(&[
    ("content-type".to_owned(), "text/plain".into())
]).unwrap();

let response = OutgoingResponse::new(response_headers);

Build response headers up dynamically:

let accepts_json = req.headers()
    .get(&"accept".to_owned())
    .iter()
    .flat_map(|v| String::from_utf8(v.clone()).ok())
    .any(|s| s == "application/json");

let response_headers = Fields::new();
if accepts_json {
    response_headers.set(&"content-type".to_owned(), &["application/json".into()]).unwrap();
};

WASI resource documentation

This following block defines the fields resource which corresponds to HTTP standard Fields. Fields are a common representation used for both Headers and Trailers.

A fields may be mutable or immutable. A fields created using the constructor, from-list, or clone will be mutable, but a fields resource given by other means (including, but not limited to, incoming-request.headers, outgoing-request.headers) might be be immutable. In an immutable fields, the set, append, and delete operations will fail with header-error.immutable.

Implementations

impl Fields

pub fn new() -> Self

Construct an empty HTTP Fields.

The resulting fields is mutable.

impl Fields

pub fn from_list( entries: &[(FieldKey, FieldValue)], ) -> Result<Fields, HeaderError>

Construct an HTTP Fields.

The resulting fields is mutable.

The list represents each key-value pair in the Fields. Keys which have multiple values are represented by multiple entries in this list with the same key.

The tuple is a pair of the field key, represented as a string, and Value, represented as a list of bytes. In a valid Fields, all keys and values are valid UTF-8 strings. However, values are not always well-formed, so they are represented as a raw list of bytes.

An error result will be returned if any header or value was syntactically invalid, or if a header was forbidden.

impl Fields

pub fn get(&self, name: &str) -> Vec<FieldValue>

Get all of the values corresponding to a key. If the key is not present in this fields, an empty list is returned. However, if the key is present but empty, this is represented by a list with one or more empty field-values present.

impl Fields

pub fn has(&self, name: &str) -> bool

Returns true when the key is present in this fields. If the key is syntactically invalid, false is returned.

impl Fields

pub fn set(&self, name: &str, value: &[FieldValue]) -> Result<(), HeaderError>

Set all of the values for a key. Clears any existing values for that key, if they have been set.

Fails with header-error.immutable if the fields are immutable.

impl Fields

pub fn delete(&self, name: &str) -> Result<(), HeaderError>

Delete all values for a key. Does nothing if no values for the key exist.

Fails with header-error.immutable if the fields are immutable.

impl Fields

pub fn append(&self, name: &str, value: &[u8]) -> Result<(), HeaderError>

Append a value for a key. Does not change or delete any existing values for that key.

Fails with header-error.immutable if the fields are immutable.

impl Fields

pub fn entries(&self) -> Vec<(FieldKey, FieldValue)>

Retrieve the full set of keys and values in the Fields. Like the constructor, the list represents each key-value pair.

The outer list represents each key-value pair in the Fields. Keys which have multiple values are represented by multiple entries in this list with the same key.

impl Fields

pub fn clone(&self) -> Fields

Make a deep copy of the Fields. Equivelant in behavior to calling the fields constructor on the return value of entries. The resulting fields is mutable.

Trait Implementations

impl Debug for Fields

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

Formats the value using the given formatter.