Struct HeaderValue

pub struct HeaderValue { /* private fields */ }

Expand description

Represents an HTTP header field value.

In practice, HTTP header field values are usually valid ASCII. However, the HTTP spec allows for a header value to contain opaque bytes as well. In this case, the header field value is not able to be represented as a string.

To handle this, the HeaderValue is useable as a type and can be compared with strings and implements Debug. A to_str fn is provided that returns an Err if the header value contains non visible ascii characters.

Implementations§

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impl HeaderValue

pub const fn from_static(src: &'static str) -> HeaderValue

Convert a static string to a HeaderValue.

This function will not perform any copying, however the string is checked to ensure that no invalid characters are present. Only visible ASCII characters (32-127) are permitted.

§Panics

This function panics if the argument contains invalid header value characters.

Until Allow panicking in constants makes its way into stable, the panic message at compile-time is going to look cryptic, but should at least point at your header value:

error: any use of this value will cause an error
  --> http/src/header/value.rs:67:17
   |
67 |                 ([] as [u8; 0])[0]; // Invalid header value
   |                 ^^^^^^^^^^^^^^^^^^
   |                 |
   |                 index out of bounds: the length is 0 but the index is 0
   |                 inside `HeaderValue::from_static` at http/src/header/value.rs:67:17
   |                 inside `INVALID_HEADER` at src/main.rs:73:33
   |
  ::: src/main.rs:73:1
   |
73 | const INVALID_HEADER: HeaderValue = HeaderValue::from_static("жsome value");
   | ----------------------------------------------------------------------------

§Examples

let val = HeaderValue::from_static("hello");
assert_eq!(val, "hello");

pub fn from_str(src: &str) -> Result<HeaderValue, InvalidHeaderValue>

Attempt to convert a string to a HeaderValue.

If the argument contains invalid header value characters, an error is returned. Only visible ASCII characters (32-127) are permitted. Use from_bytes to create a HeaderValue that includes opaque octets (128-255).

This function is intended to be replaced in the future by a TryFrom implementation once the trait is stabilized in std.

§Examples

let val = HeaderValue::from_str("hello").unwrap();
assert_eq!(val, "hello");

An invalid value

let val = HeaderValue::from_str("\n");
assert!(val.is_err());

pub fn from_name(name: HeaderName) -> HeaderValue

Converts a HeaderName into a HeaderValue

Since every valid HeaderName is a valid HeaderValue this is done infallibly.

§Examples

let val = HeaderValue::from_name(ACCEPT);
assert_eq!(val, HeaderValue::from_bytes(b"accept").unwrap());

pub fn from_bytes(src: &[u8]) -> Result<HeaderValue, InvalidHeaderValue>

Attempt to convert a byte slice to a HeaderValue.

If the argument contains invalid header value bytes, an error is returned. Only byte values between 32 and 255 (inclusive) are permitted, excluding byte 127 (DEL).

This function is intended to be replaced in the future by a TryFrom implementation once the trait is stabilized in std.

§Examples

let val = HeaderValue::from_bytes(b"hello\xfa").unwrap();
assert_eq!(val, &b"hello\xfa"[..]);

An invalid value

let val = HeaderValue::from_bytes(b"\n");
assert!(val.is_err());

pub fn from_maybe_shared<T>(src: T) -> Result<HeaderValue, InvalidHeaderValue>
where T: AsRef<[u8]> + 'static,

Attempt to convert a Bytes buffer to a HeaderValue.

This will try to prevent a copy if the type passed is the type used internally, and will copy the data if it is not.

pub unsafe fn from_maybe_shared_unchecked<T>(src: T) -> HeaderValue
where T: AsRef<[u8]> + 'static,

Convert a Bytes directly into a HeaderValue without validating.

This function does NOT validate that illegal bytes are not contained within the buffer.

§Panics

In a debug build this will panic if src is not valid UTF-8.

§Safety

src must contain valid UTF-8. In a release build it is undefined behaviour to call this with src that is not valid UTF-8.

pub fn to_str(&self) -> Result<&str, ToStrError>

Yields a &str slice if the HeaderValue only contains visible ASCII chars.

This function will perform a scan of the header value, checking all the characters.

§Examples

let val = HeaderValue::from_static("hello");
assert_eq!(val.to_str().unwrap(), "hello");

pub fn len(&self) -> usize

Returns the length of self.

This length is in bytes.

§Examples

let val = HeaderValue::from_static("hello");
assert_eq!(val.len(), 5);

pub fn is_empty(&self) -> bool

Returns true if the HeaderValue has a length of zero bytes.

§Examples

let val = HeaderValue::from_static("");
assert!(val.is_empty());

let val = HeaderValue::from_static("hello");
assert!(!val.is_empty());

pub fn as_bytes(&self) -> &[u8] ⓘ

Converts a HeaderValue to a byte slice.

§Examples

let val = HeaderValue::from_static("hello");
assert_eq!(val.as_bytes(), b"hello");

pub fn set_sensitive(&mut self, val: bool)

Mark that the header value represents sensitive information.

§Examples

let mut val = HeaderValue::from_static("my secret");

val.set_sensitive(true);
assert!(val.is_sensitive());

val.set_sensitive(false);
assert!(!val.is_sensitive());

pub fn is_sensitive(&self) -> bool

Returns true if the value represents sensitive data.

Sensitive data could represent passwords or other data that should not be stored on disk or in memory. By marking header values as sensitive, components using this crate can be instructed to treat them with special care for security reasons. For example, caches can avoid storing sensitive values, and HPACK encoders used by HTTP/2.0 implementations can choose not to compress them.

Additionally, sensitive values will be masked by the Debug implementation of HeaderValue.

Note that sensitivity is not factored into equality or ordering.

§Examples

let mut val = HeaderValue::from_static("my secret");

val.set_sensitive(true);
assert!(val.is_sensitive());

val.set_sensitive(false);
assert!(!val.is_sensitive());

Trait Implementations§

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impl AsRef<[u8]> for HeaderValue

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fn as_ref(&self) -> &[u8] ⓘ

Converts this type into a shared reference of the (usually inferred) input type.

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impl Clone for HeaderValue

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fn clone(&self) -> HeaderValue

Returns a copy of the value. Read more

1.0.0 · source§

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

Performs copy-assignment from source. Read more

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impl Debug for HeaderValue

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

Formats the value using the given formatter. Read more

source §