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use std::convert::TryFrom;
use std::io::{self, Write};
use crate::error::IntoIOError;
macro_rules! guard {
($cond:expr) => {
if !$cond {
return None;
}
}
}
pub fn from_latin_1(bytes: &[u8]) -> Option<String> {
guard!(bytes.len() >= 1);
Some(bytes.iter().map(|&b| char::from(b)).collect())
}
pub fn from_ucs_2_bom(bytes: &[u8]) -> Option<String> {
let len = bytes.len();
guard!(len % 2 == 0);
guard!(len >= 2);
let bom = read_big_endian(&bytes[0..2], 8);
guard!(bom == 0xfeff || bom == 0xfffe);
let mut res = String::with_capacity(len/2 - 1);
for i in 1 .. len/2 {
let val = if bom == 0xfeff {
256 * bytes[2*i] as u16 + bytes[2*i+1] as u16
} else {
256 * bytes[2*i+1] as u16 + bytes[2*i] as u16
};
match char::try_from(val as u32) {
Ok(c) => res.push(c),
Err(_) => return None,
};
}
Some(res)
}
pub fn from_utf8_mistaken_as_latin1(latin1: &str) -> io::Result<String> {
latin1
.chars()
.map(|c| u8::try_from(u32::from(c)))
.collect::<Result<Vec<u8>, _>>()
.map_err(|e| e.ioerr())
.and_then(|v| std::str::from_utf8(&v)
.map(|s| s.to_string())
.map_err(|e| e.ioerr()))
}
pub fn read_big_endian(bytes: &[u8], bits: usize) -> usize {
if bits > 8 {
panic!("Invalid number of bits in encoding::read_big_endian()");
}
bytes
.iter()
.enumerate()
.map(|(i, &b)| (b as usize) << (bits * (bytes.len() - 1 - i)))
.sum()
}
pub fn write_big_endian<W: Write>(mut stream: W, mut value: usize, num_bytes: usize, bits: usize) -> io::Result<()> {
if num_bytes > 8 {
panic!("Invalid number of bytes in encoding::write_big_endian()");
}
if bits > 8 || bits == 0 {
panic!("Invalid number of bits in encoding::write_big_endian()");
}
let mask = (1 << bits) - 1;
let mut bytes = [0u8; 8];
for i in (0..num_bytes).rev() {
bytes[i] = (value & mask) as u8;
value >>= bits;
}
if value != 0 {
panic!("Value doesn't fit in encoding::write_big_endian()");
}
stream.write_all(&bytes[0..num_bytes])
}
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