80 lines
2.6 KiB
Rust
80 lines
2.6 KiB
Rust
use std::io::{self, Read};
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use std::mem;
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use std::slice;
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#[repr(C, packed)]
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#[derive(Debug, Copy, Clone)]
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struct Configuration {
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item1: u8,
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item2: u16,
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item3: i32,
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item4: [char; 8],
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}
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const CONFIG_DATA: &[u8] = &[
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0xfd, // u8
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0xb4, 0x50, // u16
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0x45, 0xcd, 0x3c, 0x15, // i32
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0x71, 0x3c, 0x87, 0xff, // char
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0xe8, 0x5d, 0x20, 0xe7, // char
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0x5f, 0x38, 0x05, 0x4a, // char
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0xc4, 0x58, 0x8f, 0xdc, // char
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0x67, 0x1d, 0xb4, 0x64, // char
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0xf2, 0xc5, 0x2c, 0x15, // char
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0xd8, 0x9a, 0xae, 0x23, // char
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0x7d, 0xce, 0x4b, 0xeb, // char
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];
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fn read_struct<T, R: Read>(mut read: R) -> io::Result<T> {
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let num_bytes = ::std::mem::size_of::<T>();
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unsafe {
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let mut s = mem::zeroed();//mem::uninitialized();
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let buffer = slice::from_raw_parts_mut(&mut s as *mut T as *mut u8, num_bytes);
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match read.read_exact(buffer) {
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Ok(()) => Ok(s),
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Err(e) => {
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::std::mem::forget(s);
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Err(e)
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}
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}
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}
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}
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//// Here is a function that can read a struct (of a POD type) from a file:
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// fn read_structs<T, P: AsRef<std::path::Path>>(path: P) -> io::Result<Vec<T>> {
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// let path = path.as_ref();
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// let struct_size = ::std::mem::size_of::<T>();
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// let num_bytes = std::fs::metadata(path)?.len() as usize;
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// let num_structs = num_bytes / struct_size;
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// let mut reader = std::io::BufReader::new(std::fs::File::open(path)?);
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// let mut r = Vec::<T>::with_capacity(num_structs);
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// unsafe {
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// let buffer = slice::from_raw_parts_mut(r.as_mut_ptr() as *mut u8, num_bytes);
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// reader.read_exact(buffer)?;
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// r.set_len(num_structs);
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// }
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// Ok(r)
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// }
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//// If you want to read a sequence of structs from a file, you can execute read_struct multiple times or read all the file at once:
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// fn read_structs<T, P: AsRef<std::path::Path>>(path: P) -> io::Result<Vec<T>> {
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// let path = path.as_ref();
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// let struct_size = ::std::mem::size_of::<T>();
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// let num_bytes = std::fs::metadata(path)?.len() as usize;
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// let num_structs = num_bytes / struct_size;
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// let mut reader = std::io::BufReader::new(std::fs::File::open(path)?);
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// let mut r = Vec::<T>::with_capacity(num_structs);
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// unsafe {
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// let buffer = slice::from_raw_parts_mut(r.as_mut_ptr() as *mut u8, num_bytes);
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// reader.read_exact(buffer)?;
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// r.set_len(num_structs);
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// }
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// Ok(r)
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// }
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pub fn run_main() {
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let c: io::Result<Configuration> = read_struct(CONFIG_DATA);
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println!("{:#?}", c.unwrap());
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} |