Vendor things

third-party/vendor/data-url/src/lib.rs

@@ -0,0 +1,347 @@
+//! Processing of `data:` URLs according to the Fetch Standard:
+//! <https://fetch.spec.whatwg.org/#data-urls>
+//! but starting from a string rather than a parsed URL to avoid extra copies.
+//!
+//! ```rust
+//! use data_url::{DataUrl, mime};
+//!
+//! let url = DataUrl::process("data:,Hello%20World!").unwrap();
+//! let (body, fragment) = url.decode_to_vec().unwrap();
+//!
+//! assert_eq!(url.mime_type().type_, "text");
+//! assert_eq!(url.mime_type().subtype, "plain");
+//! assert_eq!(url.mime_type().get_parameter("charset"), Some("US-ASCII"));
+//! assert_eq!(body, b"Hello World!");
+//! assert!(fragment.is_none());
+//! ```
+#![no_std]
+
+// For forwards compatibility
+#[cfg(feature = "std")]
+extern crate std;
+
+#[macro_use]
+extern crate alloc;
+
+#[cfg(not(feature = "alloc"))]
+compile_error!("the `alloc` feature must be enabled");
+
+use alloc::{string::String, vec::Vec};
+use core::fmt;
+
+macro_rules! require {
+    ($condition: expr) => {
+        if !$condition {
+            return None;
+        }
+    };
+}
+
+pub mod forgiving_base64;
+pub mod mime;
+
+pub struct DataUrl<'a> {
+    mime_type: mime::Mime,
+    base64: bool,
+    encoded_body_plus_fragment: &'a str,
+}
+
+#[derive(Debug)]
+pub enum DataUrlError {
+    NotADataUrl,
+    NoComma,
+}
+
+impl fmt::Display for DataUrlError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::NotADataUrl => write!(f, "not a valid data url"),
+            Self::NoComma => write!(
+                f,
+                "data url is missing comma delimiting attributes and body"
+            ),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for DataUrlError {}
+
+impl<'a> DataUrl<'a> {
+    /// <https://fetch.spec.whatwg.org/#data-url-processor>
+    /// but starting from a string rather than a parsed `Url`, to avoid extra string copies.
+    pub fn process(input: &'a str) -> Result<Self, DataUrlError> {
+        use crate::DataUrlError::*;
+
+        let after_colon = pretend_parse_data_url(input).ok_or(NotADataUrl)?;
+
+        let (from_colon_to_comma, encoded_body_plus_fragment) =
+            find_comma_before_fragment(after_colon).ok_or(NoComma)?;
+
+        let (mime_type, base64) = parse_header(from_colon_to_comma);
+
+        Ok(DataUrl {
+            mime_type,
+            base64,
+            encoded_body_plus_fragment,
+        })
+    }
+
+    pub fn mime_type(&self) -> &mime::Mime {
+        &self.mime_type
+    }
+
+    /// Streaming-decode the data URL’s body to `write_body_bytes`,
+    /// and return the URL’s fragment identifier if it has one.
+    pub fn decode<F, E>(
+        &self,
+        write_body_bytes: F,
+    ) -> Result<Option<FragmentIdentifier<'a>>, forgiving_base64::DecodeError<E>>
+    where
+        F: FnMut(&[u8]) -> Result<(), E>,
+    {
+        if self.base64 {
+            decode_with_base64(self.encoded_body_plus_fragment, write_body_bytes)
+        } else {
+            decode_without_base64(self.encoded_body_plus_fragment, write_body_bytes)
+                .map_err(forgiving_base64::DecodeError::WriteError)
+        }
+    }
+
+    /// Return the decoded body, and the URL’s fragment identifier if it has one.
+    pub fn decode_to_vec(
+        &self,
+    ) -> Result<(Vec<u8>, Option<FragmentIdentifier<'a>>), forgiving_base64::InvalidBase64> {
+        let mut body = Vec::new();
+        let fragment = self.decode(|bytes| {
+            body.extend_from_slice(bytes);
+            Ok(())
+        })?;
+        Ok((body, fragment))
+    }
+}
+
+/// The URL’s fragment identifier (after `#`)
+pub struct FragmentIdentifier<'a>(&'a str);
+
+impl<'a> FragmentIdentifier<'a> {
+    /// Like in a parsed URL
+    pub fn to_percent_encoded(&self) -> String {
+        let mut string = String::new();
+        for byte in self.0.bytes() {
+            match byte {
+                // Ignore ASCII tabs or newlines like the URL parser would
+                b'\t' | b'\n' | b'\r' => continue,
+                // https://url.spec.whatwg.org/#fragment-percent-encode-set
+                b'\0'..=b' ' | b'"' | b'<' | b'>' | b'`' | b'\x7F'..=b'\xFF' => {
+                    percent_encode(byte, &mut string)
+                }
+                // Printable ASCII
+                _ => string.push(byte as char),
+            }
+        }
+        string
+    }
+}
+
+/// Similar to <https://url.spec.whatwg.org/#concept-basic-url-parser>
+/// followed by <https://url.spec.whatwg.org/#concept-url-serializer>
+///
+/// * `None`: not a data URL.
+///
+/// * `Some(s)`: sort of the result of serialization, except:
+///
+///   - `data:` prefix removed
+///   - The fragment is included
+///   - Other components are **not** UTF-8 percent-encoded
+///   - ASCII tabs and newlines in the middle are **not** removed
+fn pretend_parse_data_url(input: &str) -> Option<&str> {
+    // Trim C0 control or space
+    let left_trimmed = input.trim_start_matches(|ch| ch <= ' ');
+
+    let mut bytes = left_trimmed.bytes();
+    {
+        // Ignore ASCII tabs or newlines like the URL parser would
+        let mut iter = bytes
+            .by_ref()
+            .filter(|&byte| !matches!(byte, b'\t' | b'\n' | b'\r'));
+        require!(iter.next()?.to_ascii_lowercase() == b'd');
+        require!(iter.next()?.to_ascii_lowercase() == b'a');
+        require!(iter.next()?.to_ascii_lowercase() == b't');
+        require!(iter.next()?.to_ascii_lowercase() == b'a');
+        require!(iter.next()? == b':');
+    }
+    let bytes_consumed = left_trimmed.len() - bytes.len();
+    let after_colon = &left_trimmed[bytes_consumed..];
+
+    // Trim C0 control or space
+    Some(after_colon.trim_end_matches(|ch| ch <= ' '))
+}
+
+fn find_comma_before_fragment(after_colon: &str) -> Option<(&str, &str)> {
+    for (i, byte) in after_colon.bytes().enumerate() {
+        if byte == b',' {
+            return Some((&after_colon[..i], &after_colon[i + 1..]));
+        }
+        if byte == b'#' {
+            break;
+        }
+    }
+    None
+}
+
+fn parse_header(from_colon_to_comma: &str) -> (mime::Mime, bool) {
+    // "Strip leading and trailing ASCII whitespace"
+    //     \t, \n, and \r would have been filtered by the URL parser
+    //     \f percent-encoded by the URL parser
+    //     space is the only remaining ASCII whitespace
+    let trimmed = from_colon_to_comma.trim_matches(|c| matches!(c, ' ' | '\t' | '\n' | '\r'));
+
+    let without_base64_suffix = remove_base64_suffix(trimmed);
+    let base64 = without_base64_suffix.is_some();
+    let mime_type = without_base64_suffix.unwrap_or(trimmed);
+
+    let mut string = String::new();
+    if mime_type.starts_with(';') {
+        string.push_str("text/plain")
+    }
+    let mut in_query = false;
+    for byte in mime_type.bytes() {
+        match byte {
+            // Ignore ASCII tabs or newlines like the URL parser would
+            b'\t' | b'\n' | b'\r' => continue,
+
+            // https://url.spec.whatwg.org/#c0-control-percent-encode-set
+            b'\0'..=b'\x1F' | b'\x7F'..=b'\xFF' => percent_encode(byte, &mut string),
+
+            // Bytes other than the C0 percent-encode set that are percent-encoded
+            // by the URL parser in the query state.
+            // '#' is also in that list but cannot occur here
+            // since it indicates the start of the URL’s fragment.
+            b' ' | b'"' | b'<' | b'>' if in_query => percent_encode(byte, &mut string),
+
+            b'?' => {
+                in_query = true;
+                string.push('?')
+            }
+
+            // Printable ASCII
+            _ => string.push(byte as char),
+        }
+    }
+
+    // FIXME: does Mime::from_str match the MIME Sniffing Standard’s parsing algorithm?
+    // <https://mimesniff.spec.whatwg.org/#parse-a-mime-type>
+    let mime_type = string.parse().unwrap_or_else(|_| mime::Mime {
+        type_: String::from("text"),
+        subtype: String::from("plain"),
+        parameters: vec![(String::from("charset"), String::from("US-ASCII"))],
+    });
+
+    (mime_type, base64)
+}
+
+/// None: no base64 suffix
+#[allow(clippy::skip_while_next)]
+fn remove_base64_suffix(s: &str) -> Option<&str> {
+    let mut bytes = s.bytes();
+    {
+        // Ignore ASCII tabs or newlines like the URL parser would
+        let iter = bytes
+            .by_ref()
+            .filter(|&byte| !matches!(byte, b'\t' | b'\n' | b'\r'));
+
+        // Search from the end
+        let mut iter = iter.rev();
+
+        require!(iter.next()? == b'4');
+        require!(iter.next()? == b'6');
+        require!(iter.next()?.to_ascii_lowercase() == b'e');
+        require!(iter.next()?.to_ascii_lowercase() == b's');
+        require!(iter.next()?.to_ascii_lowercase() == b'a');
+        require!(iter.next()?.to_ascii_lowercase() == b'b');
+        require!(iter.skip_while(|&byte| byte == b' ').next()? == b';');
+    }
+    Some(&s[..bytes.len()])
+}
+
+fn percent_encode(byte: u8, string: &mut String) {
+    const HEX_UPPER: [u8; 16] = *b"0123456789ABCDEF";
+    string.push('%');
+    string.push(HEX_UPPER[(byte >> 4) as usize] as char);
+    string.push(HEX_UPPER[(byte & 0x0f) as usize] as char);
+}
+
+/// This is <https://url.spec.whatwg.org/#string-percent-decode> while also:
+///
+/// * Ignoring ASCII tab or newlines
+/// * Stopping at the first '#' (which indicates the start of the fragment)
+///
+/// Anything that would have been UTF-8 percent-encoded by the URL parser
+/// would be percent-decoded here.
+/// We skip that round-trip and pass it through unchanged.
+fn decode_without_base64<F, E>(
+    encoded_body_plus_fragment: &str,
+    mut write_bytes: F,
+) -> Result<Option<FragmentIdentifier<'_>>, E>
+where
+    F: FnMut(&[u8]) -> Result<(), E>,
+{
+    let bytes = encoded_body_plus_fragment.as_bytes();
+    let mut slice_start = 0;
+    for (i, &byte) in bytes.iter().enumerate() {
+        // We only need to look for 5 different "special" byte values.
+        // For everything else we make slices as large as possible, borrowing the input,
+        // in order to make fewer write_all() calls.
+        if matches!(byte, b'%' | b'#' | b'\t' | b'\n' | b'\r') {
+            // Write everything (if anything) "non-special" we’ve accumulated
+            // before this special byte
+            if i > slice_start {
+                write_bytes(&bytes[slice_start..i])?;
+            }
+            // Then deal with the special byte.
+            match byte {
+                b'%' => {
+                    let l = bytes.get(i + 2).and_then(|&b| (b as char).to_digit(16));
+                    let h = bytes.get(i + 1).and_then(|&b| (b as char).to_digit(16));
+                    if let (Some(h), Some(l)) = (h, l) {
+                        // '%' followed by two ASCII hex digits
+                        let one_byte = h as u8 * 0x10 + l as u8;
+                        write_bytes(&[one_byte])?;
+                        slice_start = i + 3;
+                    } else {
+                        // Do nothing. Leave slice_start unchanged.
+                        // The % sign will be part of the next slice.
+                    }
+                }
+
+                b'#' => {
+                    let fragment_start = i + 1;
+                    let fragment = &encoded_body_plus_fragment[fragment_start..];
+                    return Ok(Some(FragmentIdentifier(fragment)));
+                }
+
+                // Ignore over '\t' | '\n' | '\r'
+                _ => slice_start = i + 1,
+            }
+        }
+    }
+    write_bytes(&bytes[slice_start..])?;
+    Ok(None)
+}
+
+/// `decode_without_base64()` composed with
+/// <https://infra.spec.whatwg.org/#isomorphic-decode> composed with
+/// <https://infra.spec.whatwg.org/#forgiving-base64-decode>.
+fn decode_with_base64<F, E>(
+    encoded_body_plus_fragment: &str,
+    write_bytes: F,
+) -> Result<Option<FragmentIdentifier<'_>>, forgiving_base64::DecodeError<E>>
+where
+    F: FnMut(&[u8]) -> Result<(), E>,
+{
+    let mut decoder = forgiving_base64::Decoder::new(write_bytes);
+    let fragment = decode_without_base64(encoded_body_plus_fragment, |bytes| decoder.feed(bytes))?;
+    decoder.finish()?;
+    Ok(fragment)
+}