//! Conversion between URI/IRI types.
use core::fmt;
#[cfg(feature = "alloc")]
use alloc::collections::TryReserveError;
#[cfg(all(feature = "alloc", not(feature = "std")))]
use alloc::string::String;
#[cfg(feature = "alloc")]
use crate::format::{ToDedicatedString, ToStringFallible};
use crate::spec::Spec;
use crate::types::{
RiAbsoluteStr, RiFragmentStr, RiQueryStr, RiReferenceStr, RiRelativeStr, RiStr,
};
#[cfg(feature = "alloc")]
use crate::types::{
RiAbsoluteString, RiFragmentString, RiQueryString, RiReferenceString, RiRelativeString,
RiString,
};
#[cfg(feature = "alloc")]
use crate::types::{
UriAbsoluteString, UriFragmentString, UriQueryString, UriReferenceString, UriRelativeString,
UriString,
};
/// Hexadecimal digits for a nibble.
const HEXDIGITS: [u8; 16] = [
b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7', b'8', b'9', b'A', b'B', b'C', b'D', b'E', b'F',
];
/// A resource identifier mapped to a URI of some kind.
///
/// Supported `Src` type are:
///
/// * IRIs:
/// + [`IriAbsoluteStr`] (alias of `RiAbsoluteStr<IriSpec>`)
/// + [`IriReferenceStr`] (alias of `RiReferenceStr<IriSpec>`)
/// + [`IriRelativeStr`] (alias of `RiRelativeStr<IriSpec>`)
/// + [`IriStr`] (alias of `RiStr<IriSpec>`)
/// * URIs:
/// + [`UriAbsoluteStr`] (alias of `RiAbsoluteStr<UriSpec>`)
/// + [`UriReferenceStr`] (alias of `RiReferenceStr<UriSpec>`)
/// + [`UriRelativeStr`] (alias of `RiRelativeStr<UriSpec>`)
/// + [`UriStr`] (alias of `RiStr<UriSpec>`)
///
/// # Examples
///
/// ```
/// use iri_string::convert::MappedToUri;
/// use iri_string::types::{IriStr, UriStr};
///
/// let src = IriStr::new("http://example.com/?alpha=\u{03B1}")?;
/// // The type is `MappedToUri<IriStr>`, but you usually don't need to specify.
/// let mapped = MappedToUri::from(src).to_string();
/// assert_eq!(mapped, "http://example.com/?alpha=%CE%B1");
/// # Ok::<_, iri_string::validate::Error>(())
/// ```
///
/// [`IriAbsoluteStr`]: crate::types::IriAbsoluteStr
/// [`IriReferenceStr`]: crate::types::IriReferenceStr
/// [`IriRelativeStr`]: crate::types::IriRelativeStr
/// [`IriStr`]: crate::types::IriStr
/// [`UriAbsoluteStr`]: crate::types::UriAbsoluteStr
/// [`UriReferenceStr`]: crate::types::UriReferenceStr
/// [`UriRelativeStr`]: crate::types::UriRelativeStr
/// [`UriStr`]: crate::types::UriStr
#[derive(Debug, Clone, Copy)]
pub struct MappedToUri<'a, Src: ?Sized>(&'a Src);
/// Implement conversions for an IRI string type.
macro_rules! impl_for_iri {
($borrowed:ident, $owned:ident, $owned_uri:ident) => {
impl<S: Spec> fmt::Display for MappedToUri<'_, $borrowed<S>> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write_percent_encoded(f, self.0.as_str())
}
}
#[cfg(feature = "alloc")]
impl<S: Spec> ToDedicatedString for MappedToUri<'_, $borrowed<S>> {
type Target = $owned_uri;
fn try_to_dedicated_string(&self) -> Result<Self::Target, TryReserveError> {
let s = self.try_to_string()?;
Ok(TryFrom::try_from(s)
.expect("[validity] the IRI must be encoded into a valid URI"))
}
}
impl<'a, S: Spec> From<&'a $borrowed<S>> for MappedToUri<'a, $borrowed<S>> {
#[inline]
fn from(iri: &'a $borrowed<S>) -> Self {
Self(iri)
}
}
#[cfg(feature = "alloc")]
impl<'a, S: Spec> From<&'a $owned<S>> for MappedToUri<'a, $borrowed<S>> {
#[inline]
fn from(iri: &'a $owned<S>) -> Self {
Self(iri.as_slice())
}
}
};
}
impl_for_iri!(RiReferenceStr, RiReferenceString, UriReferenceString);
impl_for_iri!(RiStr, RiString, UriString);
impl_for_iri!(RiAbsoluteStr, RiAbsoluteString, UriAbsoluteString);
impl_for_iri!(RiRelativeStr, RiRelativeString, UriRelativeString);
impl_for_iri!(RiQueryStr, RiQueryString, UriQueryString);
impl_for_iri!(RiFragmentStr, RiFragmentString, UriFragmentString);
/// Percent-encodes and writes the IRI string using the given buffer.
fn write_percent_encoded(f: &mut fmt::Formatter<'_>, mut s: &str) -> fmt::Result {
while !s.is_empty() {
// Skip ASCII characters.
let non_ascii_pos = s.bytes().position(|b| !b.is_ascii()).unwrap_or(s.len());
let (ascii, rest) = s.split_at(non_ascii_pos);
if !ascii.is_empty() {
f.write_str(ascii)?;
s = rest;
}
if s.is_empty() {
return Ok(());
}
// Search for the next ASCII character.
let nonascii_end = s.bytes().position(|b| b.is_ascii()).unwrap_or(s.len());
let (nonasciis, rest) = s.split_at(nonascii_end);
debug_assert!(
!nonasciis.is_empty(),
"string without non-ASCII characters should have caused early return"
);
s = rest;
// Escape non-ASCII characters as percent-encoded bytes.
//
// RFC 3987 (section 3.1 step 2) says "for each character in
// 'ucschar' or 'iprivate'", but this simply means "for each
// non-ASCII characters" since any non-ASCII characters that can
// appear in an IRI match `ucschar` or `iprivate`.
/// Number of source bytes to encode at once.
const NUM_BYTES_AT_ONCE: usize = 21;
percent_encode_bytes(f, nonasciis, &mut [0_u8; NUM_BYTES_AT_ONCE * 3])?;
}
Ok(())
}
/// Percent-encode the string and pass the encoded chunks to the given function.
///
/// `buf` is used as a temporary working buffer. It is initialized by this
/// function, so users can pass any mutable byte slice with enough size.
///
/// # Precondition
///
/// The length of `buf` must be 3 bytes or more.
fn percent_encode_bytes(f: &mut fmt::Formatter<'_>, s: &str, buf: &mut [u8]) -> fmt::Result {
/// Fill the buffer by percent-encoded bytes.
///
/// Note that this function applies percent-encoding to every characters,
/// even if it is ASCII alphabet.
///
/// # Precondition
///
/// * The length of `buf` must be 3 bytes or more.
/// * All of the `buf[i * 3]` elements should already be set to `b'%'`.
// This function have many preconditions and I don't want checks for them
// to be mandatory, so make this nested inner function.
fn fill_by_percent_encoded<'a>(buf: &'a mut [u8], bytes: &mut core::str::Bytes<'_>) -> &'a str {
let src_len = bytes.len();
// `<[u8; N]>::array_chunks_mut` is unstable as of Rust 1.58.1.
for (dest, byte) in buf.chunks_exact_mut(3).zip(bytes.by_ref()) {
debug_assert_eq!(
dest.len(),
3,
"[validity] `chunks_exact()` must return a slice with the exact length"
);
debug_assert_eq!(
dest[0], b'%',
"[precondition] the buffer must be properly initialized"
);
let upper = byte >> 4;
let lower = byte & 0b1111;
dest[1] = HEXDIGITS[usize::from(upper)];
dest[2] = HEXDIGITS[usize::from(lower)];
}
let num_dest_written = (src_len - bytes.len()) * 3;
let buf_filled = &buf[..num_dest_written];
// SAFETY: `b'%'` and `HEXDIGITS[_]` are all ASCII characters, so
// `buf_filled` is filled with ASCII characters and is valid UTF-8 bytes.
unsafe {
debug_assert!(core::str::from_utf8(buf_filled).is_ok());
core::str::from_utf8_unchecked(buf_filled)
}
}
assert!(
buf.len() >= 3,
"[precondition] length of `buf` must be 3 bytes or more"
);
// Drop the elements that will never be used.
// The length to be used is always a multiple of three.
let buf_len = buf.len() / 3 * 3;
let buf = &mut buf[..buf_len];
// Fill some bytes with `%`.
// This will be vectorized by optimization (especially for long buffers),
// so no need to selectively set `buf[i * 3]`.
buf.fill(b'%');
let mut bytes = s.bytes();
// `<core::str::Bytes as ExactSizeIterator>::is_empty` is unstable as of Rust 1.58.1.
while bytes.len() != 0 {
let encoded = fill_by_percent_encoded(buf, &mut bytes);
f.write_str(encoded)?;
}
Ok(())
}
/// Percent-encodes the given IRI using the given buffer.
#[cfg(feature = "alloc")]
pub(crate) fn try_percent_encode_iri_inline(
iri: &mut String,
) -> Result<(), alloc::collections::TryReserveError> {
// Calculate the result length and extend the buffer.
let num_nonascii = count_nonascii(iri);
if num_nonascii == 0 {
// No need to escape.
return Ok(());
}
let additional = num_nonascii * 2;
iri.try_reserve(additional)?;
let src_len = iri.len();
// Temporarily take the ownership of the internal buffer.
let mut buf = core::mem::take(iri).into_bytes();
// `b'\0'` cannot appear in a valid IRI, so this default value would be
// useful in case of debugging.
buf.extend(core::iter::repeat(b'\0').take(additional));
// Fill the buffer from the tail to the head.
let mut dest_end = buf.len();
let mut src_end = src_len;
let mut rest_nonascii = num_nonascii;
while rest_nonascii > 0 {
debug_assert!(
src_end > 0,
"[validity] the source position should not overrun"
);
debug_assert!(
dest_end > 0,
"[validity] the destination position should not overrun"
);
src_end -= 1;
dest_end -= 1;
let byte = buf[src_end];
if byte.is_ascii() {
buf[dest_end] = byte;
// Use the ASCII character directly.
} else {
// Percent-encode the byte.
dest_end -= 2;
buf[dest_end] = b'%';
let upper = byte >> 4;
let lower = byte & 0b1111;
buf[dest_end + 1] = HEXDIGITS[usize::from(upper)];
buf[dest_end + 2] = HEXDIGITS[usize::from(lower)];
rest_nonascii -= 1;
}
}
// Move the result from the temporary buffer to the destination.
let s = String::from_utf8(buf).expect("[consistency] the encoding result is an ASCII string");
*iri = s;
Ok(())
}
/// Returns the number of non-ASCII characters.
#[cfg(feature = "alloc")]
#[inline]
#[must_use]
fn count_nonascii(s: &str) -> usize {
s.bytes().filter(|b| !b.is_ascii()).count()
}
