116 lines
3.2 KiB
Rust
116 lines
3.2 KiB
Rust
// Copyright (c) 2016-2017, The Tor Project, Inc. */
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// See LICENSE for licensing information */
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use std::slice;
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use libc::{c_char, c_int};
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use std::ffi::CStr;
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/// Smartlists are a type used in C code in tor to define a collection of a
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/// generic type, which has a capacity and a number used. Each Smartlist
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/// defines how to extract the list of values from the underlying C structure
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///
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/// Implementations are required to have a C representation, as this module
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/// serves purely to translate smartlists as defined in tor to vectors in Rust.
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pub trait Smartlist<T> {
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fn get_list(&self) -> Vec<T>;
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}
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#[repr(C)]
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pub struct Stringlist {
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pub list: *const *const c_char,
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pub num_used: c_int,
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pub capacity: c_int,
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}
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impl Smartlist<String> for Stringlist {
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fn get_list(&self) -> Vec<String> {
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let empty: Vec<String> = Vec::new();
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let mut rust_list: Vec<String> = Vec::new();
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if self.list.is_null() || self.num_used == 0 {
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return empty;
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}
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// unsafe, as we need to extract the smartlist list into a vector of
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// pointers, and then transform each element into a Rust string.
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let elems: &[*const c_char] =
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unsafe { slice::from_raw_parts(self.list, self.num_used as usize) };
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for elem in elems.iter() {
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if elem.is_null() {
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continue;
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}
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// unsafe, as we need to create a cstring from the referenced
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// element
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let c_string = unsafe { CStr::from_ptr(*elem) };
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let r_string = match c_string.to_str() {
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Ok(n) => n,
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Err(_) => return empty,
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};
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rust_list.push(String::from(r_string));
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}
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rust_list
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}
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}
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// TODO: CHK: this module maybe should be tested from a test in C with a
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// smartlist as defined in tor.
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#[cfg(test)]
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mod test {
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#[test]
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fn test_get_list_of_strings() {
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extern crate libc;
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use std::ffi::CString;
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use libc::c_char;
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use super::Smartlist;
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use super::Stringlist;
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{
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// test to verify that null pointers are gracefully handled
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use std::ptr;
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let sl = Stringlist {
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list: ptr::null(),
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num_used: 0,
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capacity: 0,
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};
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let data = sl.get_list();
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assert_eq!(0, data.len());
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}
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{
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let args = vec![String::from("a"), String::from("b")];
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// for each string, transform it into a CString
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let c_strings: Vec<_> = args.iter()
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.map(|arg| CString::new(arg.as_str()).unwrap())
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.collect();
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// then, collect a pointer for each CString
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let p_args: Vec<_> =
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c_strings.iter().map(|arg| arg.as_ptr()).collect();
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let p: *const *const c_char = p_args.as_ptr();
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// This is the representation that we expect when receiving a
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// smartlist at the Rust/C FFI layer.
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let sl = Stringlist {
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list: p,
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num_used: 2,
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capacity: 2,
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};
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let data = sl.get_list();
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assert_eq!("a", &data[0]);
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assert_eq!("b", &data[1]);
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}
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}
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}
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