json-codec-wasm 0.1.0

// Translation of Bjoern Hoehrmann's "Flexible and Economical UTF-8 Decoder".
// See http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
//
// License
//
// Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files
// (the "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject
// to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

use std::char::from_u32_unchecked;
use std::error::Error;
use std::fmt;
use std::io::{self, Read};

const UTF8D: [u8; 364] = [
    // The first part of the table maps bytes to character classes that
    // to reduce the size of the transition table and create bitmasks.
    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,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
    8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    10, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 11, 6, 6, 6, 5, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    8,
    // The second part is a transition table that maps a combination
    // of a state of the automaton and a character class to a state.
    0, 12, 24, 36, 60, 96, 84, 12, 12, 12, 48, 72, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
    12, 0, 12, 12, 12, 12, 12, 0, 12, 0, 12, 12, 12, 24, 12, 12, 12, 12, 12, 24, 12, 24, 12, 12,
    12, 12, 12, 12, 12, 12, 12, 24, 12, 12, 12, 12, 12, 24, 12, 12, 12, 12, 12, 12, 12, 24, 12, 12,
    12, 12, 12, 12, 12, 12, 12, 36, 12, 36, 12, 12, 12, 36, 12, 12, 12, 12, 12, 36, 12, 36, 12, 12,
    12, 36, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
];

pub const UTF8_ACCEPT: u32 = 0;
pub const UTF8_REJECT: u32 = 12;

#[inline]
pub fn decode(state: u32, byte: u32, codep: &mut u32) -> u32 {
    let typ = UTF8D[byte as usize] as u32;

    *codep = if state != UTF8_ACCEPT {
        (byte & 0x3f) | (*codep << 6)
    } else {
        (0xff >> typ) & byte
    };

    let ix = 256 + state + typ;
    UTF8D[ix as usize] as u32
}

pub struct Chars<R> {
    reader: R,
    state: u32,
    codep: u32,
}

impl<R: Read> Chars<R> {
    pub fn new(r: R) -> Chars<R> {
        Chars {
            reader: r,
            state: UTF8_ACCEPT,
            codep: 0,
        }
    }
}

impl<R: Read> Iterator for Chars<R> {
    type Item = Result<char, ReadError>;

    fn next(&mut self) -> Option<Result<char, ReadError>> {
        loop {
            match read_byte(&mut self.reader) {
                Some(Ok(b)) => {
                    self.state = decode(self.state, b as u32, &mut self.codep);
                    match self.state {
                        UTF8_ACCEPT => unsafe { return Some(Ok(from_u32_unchecked(self.codep))) },
                        UTF8_REJECT => return Some(Err(ReadError::InvalidUtf8)),
                        _ => {}
                    }
                }
                Some(Err(e)) => return Some(Err(e.into())),
                None => return None,
            }
        }
    }
}

fn read_byte<R: Read>(r: &mut R) -> Option<io::Result<u8>> {
    let mut b = [0];
    loop {
        match r.read(&mut b) {
            Ok(0) => return None,
            Ok(_) => return Some(Ok(b[0])),
            Err(e) => {
                if e.kind() == io::ErrorKind::Interrupted {
                    continue;
                } else {
                    return Some(Err(e));
                }
            }
        }
    }
}

#[derive(Debug)]
pub enum ReadError {
    InvalidUtf8,
    Io(io::Error),
}

impl fmt::Display for ReadError {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        match *self {
            ReadError::InvalidUtf8 => write!(f, "invalid utf-8 encoding"),
            ReadError::Io(ref e) => write!(f, "i/o: {}", e),
        }
    }
}

impl Error for ReadError {
    fn description(&self) -> &str {
        match *self {
            ReadError::InvalidUtf8 => "invalid utf-8 encoding",
            ReadError::Io(_) => "i/o error",
        }
    }

    fn cause(&self) -> Option<&dyn Error> {
        match *self {
            ReadError::Io(ref e) => Some(e),
            _ => None,
        }
    }
}

impl From<io::Error> for ReadError {
    fn from(e: io::Error) -> ReadError {
        ReadError::Io(e)
    }
}