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Diffstat (limited to 'src/rust/tor_util/strings.rs')
-rw-r--r-- | src/rust/tor_util/strings.rs | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/src/rust/tor_util/strings.rs b/src/rust/tor_util/strings.rs new file mode 100644 index 0000000000..9321ce4f85 --- /dev/null +++ b/src/rust/tor_util/strings.rs @@ -0,0 +1,82 @@ +// Copyright (c) 2016-2017, The Tor Project, Inc. */ +// See LICENSE for licensing information */ + +//! Utilities for working with static strings. + +use std::ffi::CStr; + +/// A byte-array containing a single NUL byte (`b"\0"`). +pub const NUL_BYTE: &'static [u8] = b"\0"; + +/// Determine if a byte slice is a C-like string. +/// +/// These checks guarantee that: +/// +/// 1. there are no intermediate NUL bytes +/// 2. the last byte *is* a NUL byte +/// +/// # Warning +/// +/// This function does _not_ guarantee that the bytes represent any valid +/// encoding such as ASCII or UTF-8. +/// +/// # Examples +/// +/// ``` +/// # use tor_util::strings::byte_slice_is_c_like; +/// # +/// let bytes: &[u8] = b"foo bar baz"; +/// +/// assert!(byte_slice_is_c_like(&bytes) == false); +/// +/// let bytes: &[u8] = b"foo\0bar baz"; +/// +/// assert!(byte_slice_is_c_like(&bytes) == false); +/// +/// let bytes: &[u8] = b"foo bar baz\0"; +/// +/// assert!(byte_slice_is_c_like(&bytes) == true); +/// ``` +pub fn byte_slice_is_c_like(bytes: &[u8]) -> bool { + if !bytes[..bytes.len() - 1].contains(&0x00) && bytes[bytes.len() - 1] == 0x00 { + return true; + } + false +} + +/// Get a static `CStr` containing a single `NUL_BYTE`. +/// +/// # Examples +/// +/// When used as follows in a Rust FFI function, which could be called +/// from C: +/// +/// ``` +/// # extern crate libc; +/// # extern crate tor_util; +/// # +/// # use tor_util::strings::empty_static_cstr; +/// use libc::c_char; +/// use std::ffi::CStr; +/// +/// pub extern "C" fn give_c_code_an_empty_static_string() -> *const c_char { +/// let empty: &'static CStr = empty_static_cstr(); +/// +/// empty.as_ptr() +/// } +/// +/// # fn main() { +/// # give_c_code_an_empty_static_string(); +/// # } +/// ``` +/// +/// This equates to an "empty" `const char*` static string in C. +pub fn empty_static_cstr() -> &'static CStr { + let empty: &'static CStr; + + unsafe { + empty = CStr::from_bytes_with_nul_unchecked(NUL_BYTE); + } + + empty +} |