pulldown-cmark 0.4.0

// Copyright 2015 Google Inc. All rights reserved.
//
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// furnished to do so, subject to the following conditions:
//
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// THE SOFTWARE.

//! Utility functions for HTML escaping

use std::io::{self, Write};
use std::str::from_utf8;

static HREF_SAFE: [u8; 128] = [
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,
        0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
    ];

static HEX_CHARS: &'static [u8] = b"0123456789ABCDEF";
static AMP_ESCAPE: &'static [u8] = b"&";
static SLASH_ESCAPE: &'static [u8] = b"'";

pub fn escape_href<W>(mut w: W, s: &str) -> io::Result<()>
where
    W: Write,
{
    let bytes = s.as_bytes();
    let mut mark = 0;
    for i in 0..bytes.len() {
        let c = bytes[i];
        if c >= 0x80 || HREF_SAFE[c as usize] == 0 {
            // character needing escape

            // write partial substring up to mark
            if mark < i {
                w.write_all(&bytes[mark..i])?;
            }
            match c {
                b'&' => {
                    w.write_all(AMP_ESCAPE)?;
                }
                b'\'' => {
                    w.write_all(SLASH_ESCAPE)?;
                }
                _ => {
                    let mut buf = [0u8; 3];
                    buf[0] = b'%';
                    buf[1] = HEX_CHARS[((c as usize) >> 4) & 0xF];
                    buf[2] = HEX_CHARS[(c as usize) & 0xF];
                    let escaped = from_utf8(&buf).unwrap().as_bytes();
                    w.write_all(escaped)?;
                }
            }
            mark = i + 1; // all escaped characters are ASCII
        }
    }
    w.write_all(&bytes[mark..])?;
    Ok(())
}

static HTML_ESCAPE_TABLE: [u8; 256] = [
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 3,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 5, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    ];

static HTML_ESCAPES: [&'static str; 6] = [
        "",
        "&quot;",
        "&amp;",
        "&#47;",
        "&lt;",
        "&gt;"
    ];

pub fn escape_html<W>(mut w: W, s: &str, secure: bool) -> io::Result<()>
where
    W: Write,
{
    let bytes = s.as_bytes();
    let mut mark = 0;
    let mut i = 0;
    while i < s.len() {
        match bytes[i..]
            .iter()
            .position(|&c| HTML_ESCAPE_TABLE[c as usize] != 0)
        {
            Some(pos) => {
                i += pos;
            }
            None => break,
        }
        let c = bytes[i];
        let escape = HTML_ESCAPE_TABLE[c as usize];
        if escape != 0 && (secure || c != b'/') {
            let escape_seq = HTML_ESCAPES[escape as usize];
            w.write_all(&bytes[mark..i])?;
            w.write_all(escape_seq.as_bytes())?;
            mark = i + 1; // all escaped characters are ASCII
        }
        i += 1;
    }
    w.write_all(&bytes[mark..])?;
    Ok(())
}