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#![doc(html_root_url = "https://docs.rs/codepage-strings/1.0.2")]
/*!
This Rust crate builds on the excellent work of the
[`encoding_rs`], [`codepage`], and [`oem-cp`] crates in an attempt
to provide idiomatic encoding and decoding of strings coded
according to
[Windows code pages](https://en.wikipedia.org/wiki/Windows_code_page).
Because Windows code pages are a legacy rathole, it is
difficult to transcode strings using them. Sadly, there are
still a lot of files out there that use these encodings.
This crate was specifically created for use with
[RIFF](https://www.aelius.com/njh/wavemetatools/doc/riffmci.pdf),
a file format that has code pages baked in for text
internationalization.
No effort has been made to deal with Windows code pages
beyond those supported by [`codepage`] and [`oem-cp`]. If the
single-byte codepage you need is missing, I suggest taking a
look at adding it to [`oem-cp`], which seems to be the main
Rust repository for unusual Windows code page tables. I
believe that most of the single-byte code pages supported by
`iconv` are dealt with here, but I haven't checked
carefully.
Other than UTF-16LE and UTF-16BE, multibyte Windows code
pages are not (for now) currently supported — in particular
various Asian languages. Code page 65001 (UTF-8) is
supported as an identity transformation. UTF-32LE and
UTF32-Be are not supported. EBCDIC code pages and UTF-7 are
not supported and are low priority, because seriously?
No particular effort has been put into performance. The
interface allows [`std::borrow::Cow`] to some extent, but this
is limited by the minor impedance mismatches between
[`encoding_rs`] and [`oem-cp`].
# Examples
Do some string conversions on Windows code page 869
(alternate Greek).
```rust
# use codepage_strings::*;
# fn main() -> Result<(), Box<dyn std::error::Error>> {
let coding = Coding::new(869)?;
assert_eq!(
coding.encode("αβ")?,
vec![214, 215],
);
assert_eq!(
coding.decode(&[214, 215])?,
"αβ",
);
assert_eq!(
coding.decode_lossy(&[214, 147]),
"α\u{fffd}",
);
assert_eq!(
coding.decode(&[214, 147]),
Err(ConvertError::StringDecoding),
);
# Ok(())
# }
```
[`encoding_rs`]: http://crates.io/crates/encoding_rs
[`codepage`]: http://crates.io/crates/codepage
[`oem-cp`]: http://crates.io/crates/oem-cp
[`std::borrow::Cow`]: https://doc.rust-lang.org/nightly/alloc/borrow/enum.Cow.html
*/
use std::borrow::Cow;
/// Errors that can result from various conversions.
#[non_exhaustive]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ConvertError {
/// Could not encode string as requested.
StringEncoding,
/// Could not decode string as requested.
StringDecoding,
/// Requested a Windows code page the library doesn't understand.
UnknownCodepage,
/// Requested a Windows code page the library can't do.
UnsupportedCodepage,
}
impl std::fmt::Display for ConvertError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let msg = match self {
ConvertError::StringEncoding => "string codepage encoding error",
ConvertError::StringDecoding => "string decoding error",
ConvertError::UnknownCodepage => "invalid / unknown Windows code page",
ConvertError::UnsupportedCodepage => "cannot transcode this Windows code page",
};
write!(f, "{}", msg)
}
}
impl std::error::Error for ConvertError {}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum Endian {
Le,
Be,
}
#[derive(Debug, Clone)]
enum Codings {
Ers(&'static encoding_rs::Encoding),
OemCp {
encode: &'static oem_cp::OEMCPHashMap<char, u8>,
decode: &'static oem_cp::code_table_type::TableType,
},
Identity,
UTF16(Endian),
}
/// Coding information derived from a Windows code page.
#[derive(Debug, Clone)]
pub struct Coding(Codings);
impl Coding {
/// Get an encoding for the given code page.
///
/// # Errors
///
/// Will fail with [`ConvertError::UnknownCodepage`] or
/// [`ConvertError::UnsupportedCodepage`] if an encoding
/// for the given page is unavailable.
pub fn new(cp: u16) -> Result<Self, ConvertError> {
if cp == 65001 {
// UTF-8
return Ok(Coding(Codings::Identity));
}
if cp == 1200 {
// UTF-16LE
return Ok(Coding(Codings::UTF16(Endian::Le)));
}
if cp == 1201 {
// UTF-16BE
return Ok(Coding(Codings::UTF16(Endian::Be)));
}
if [12000, 12001, 65000].contains(&cp) {
// Weird UTF format (UTF-32LE, UTF-32BE, UTF-7).
return Err(ConvertError::UnsupportedCodepage);
}
if let Some(c) = codepage::to_encoding(cp) {
return Ok(Coding(Codings::Ers(c)));
}
let encode = match (*oem_cp::code_table::ENCODING_TABLE_CP_MAP).get(&cp) {
Some(e) => e,
None => return Err(ConvertError::UnknownCodepage),
};
let decode = match (*oem_cp::code_table::DECODING_TABLE_CP_MAP).get(&cp) {
Some(e) => e,
None => return Err(ConvertError::UnknownCodepage),
};
Ok(Coding(Codings::OemCp { encode, decode }))
}
/// Encode a UTF-8 string into a byte vector according
/// to this encoding.
///
/// # Errors
///
/// Returns [`ConvertError::StringEncoding`] if any
/// character cannot be encoded.
pub fn encode<'a, S>(&self, src: S) -> Result<Vec<u8>, ConvertError>
where
S: Into<Cow<'a, str>>,
{
match self.0 {
Codings::Ers(c) => {
let src = src.into();
let oe = c.output_encoding();
let (out, _, fail) = oe.encode(src.as_ref());
if fail {
Err(ConvertError::StringEncoding)
} else {
Ok(out.to_owned().to_vec())
}
}
Codings::OemCp { encode: et, .. } => match oem_cp::encode_string_checked(src, et) {
Some(out) => Ok(out),
None => Err(ConvertError::StringEncoding),
},
Codings::Identity => Ok(src.into().as_ref().as_bytes().to_vec()),
Codings::UTF16(e) => {
let encoded = src
.into()
.as_ref()
.encode_utf16()
.flat_map(|w| {
let lo = (w & 0xff) as u8;
let hi = (w >> 8) as u8;
let bs: Vec<u8> = match e {
Endian::Le => vec![lo, hi],
Endian::Be => vec![hi, lo],
};
bs.into_iter()
})
.collect();
Ok(encoded)
}
}
}
/// Decode a byte vector into UTF-8 [`Cow`]`<`[`str`]`>` according
/// to this encoding.
///
/// # Errors
///
/// Returns [`ConvertError::StringDecoding`] if any
/// character cannot be decoded.
pub fn decode<'a>(&self, src: &'a [u8]) -> Result<Cow<'a, str>, ConvertError> {
match self.0 {
Codings::Ers(c) => {
let (out, _, fail) = c.decode(src.as_ref());
if fail {
Err(ConvertError::StringDecoding)
} else {
Ok(out)
}
}
Codings::OemCp { decode: dt, .. } => match dt.decode_string_checked(src) {
Some(s) => Ok(Cow::from(s)),
None => Err(ConvertError::StringDecoding),
},
Codings::Identity => match std::str::from_utf8(src) {
Ok(s) => Ok(Cow::from(s)),
Err(_) => Err(ConvertError::StringDecoding),
},
Codings::UTF16(e) => {
let ws = src
.chunks(2)
.map(|bs| {
if bs.len() < 2 {
return Err(ConvertError::StringDecoding);
}
let (hi, lo) = (bs[0] as u16, bs[1] as u16);
match e {
Endian::Le => Ok((lo << 8) | hi),
Endian::Be => Ok((hi << 8) | lo),
}
})
.collect::<Result<Vec<u16>, ConvertError>>()?;
match String::from_utf16(&ws) {
Ok(s) => Ok(Cow::from(s)),
Err(_) => Err(ConvertError::StringDecoding),
}
}
}
}
/// Decode a byte vector into UTF-8 [`Cow`]`<`[`str`]`>` according
/// to this encoding. Replace any bytes that cannot be
/// encoded with the Unicode
/// "[replacement character](https://en.wikipedia.org/wiki/Specials_%28Unicode_block%29#Replacement_character)"
/// (`\u{fffd}`).
pub fn decode_lossy<'a>(&self, src: &'a [u8]) -> Cow<'a, str> {
match self.0 {
Codings::Ers(c) => {
let (out, _, _) = c.decode(src.as_ref());
out
}
Codings::OemCp { decode: dt, .. } => Cow::from(dt.decode_string_lossy(src)),
Codings::Identity => match std::str::from_utf8(src) {
Ok(s) => Cow::from(s),
Err(_) => String::from_utf8_lossy(src),
},
Codings::UTF16(e) => {
let ws: Vec<u16> = src
.chunks(2)
.map(|bs| {
let (hi, lo) = if bs.len() == 1 {
// Unicode replacement character.
(0xff, 0xfd)
} else {
// Big-endian by default.
(bs[0] as u16, bs[1] as u16)
};
match e {
Endian::Le => (lo << 8) | hi,
Endian::Be => (hi << 8) | lo,
}
})
.collect();
Cow::from(String::from_utf16_lossy(&ws))
}
}
}
}