rust/src/libstd/c_str.rs
2014-02-14 21:23:37 -08:00

781 lines
22 KiB
Rust

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
/*!
C-string manipulation and management
This modules provides the basic methods for creating and manipulating
null-terminated strings for use with FFI calls (back to C). Most C APIs require
that the string being passed to them is null-terminated, and by default rust's
string types are *not* null terminated.
The other problem with translating Rust strings to C strings is that Rust
strings can validly contain a null-byte in the middle of the string (0 is a
valid unicode codepoint). This means that not all Rust strings can actually be
translated to C strings.
# Creation of a C string
A C string is managed through the `CString` type defined in this module. It
"owns" the internal buffer of characters and will automatically deallocate the
buffer when the string is dropped. The `ToCStr` trait is implemented for `&str`
and `&[u8]`, but the conversions can fail due to some of the limitations
explained above.
This also means that currently whenever a C string is created, an allocation
must be performed to place the data elsewhere (the lifetime of the C string is
not tied to the lifetime of the original string/data buffer). If C strings are
heavily used in applications, then caching may be advisable to prevent
unnecessary amounts of allocations.
An example of creating and using a C string would be:
```rust
use std::libc;
extern {
fn puts(s: *libc::c_char);
}
let my_string = "Hello, world!";
// Allocate the C string with an explicit local that owns the string. The
// `c_buffer` pointer will be deallocated when `my_c_string` goes out of scope.
let my_c_string = my_string.to_c_str();
my_c_string.with_ref(|c_buffer| {
unsafe { puts(c_buffer); }
});
// Don't save off the allocation of the C string, the `c_buffer` will be
// deallocated when this block returns!
my_string.with_c_str(|c_buffer| {
unsafe { puts(c_buffer); }
});
```
*/
use cast;
use container::Container;
use iter::{Iterator, range};
use libc;
use kinds::marker;
use ops::Drop;
use cmp::Eq;
use clone::Clone;
use mem;
use option::{Option, Some, None};
use ptr::RawPtr;
use ptr;
use str::StrSlice;
use str;
use vec::{ImmutableVector, MutableVector};
use vec;
use rt::global_heap::malloc_raw;
use unstable::raw::Slice;
/// The representation of a C String.
///
/// This structure wraps a `*libc::c_char`, and will automatically free the
/// memory it is pointing to when it goes out of scope.
pub struct CString {
priv buf: *libc::c_char,
priv owns_buffer_: bool,
}
impl Clone for CString {
/// Clone this CString into a new, uniquely owned CString. For safety
/// reasons, this is always a deep clone, rather than the usual shallow
/// clone.
fn clone(&self) -> CString {
if self.buf.is_null() {
CString { buf: self.buf, owns_buffer_: self.owns_buffer_ }
} else {
let len = self.len() + 1;
let buf = unsafe { malloc_raw(len) } as *mut libc::c_char;
unsafe { ptr::copy_nonoverlapping_memory(buf, self.buf, len); }
CString { buf: buf as *libc::c_char, owns_buffer_: true }
}
}
}
impl Eq for CString {
fn eq(&self, other: &CString) -> bool {
if self.buf as uint == other.buf as uint {
true
} else if self.buf.is_null() || other.buf.is_null() {
false
} else {
unsafe {
libc::strcmp(self.buf, other.buf) == 0
}
}
}
}
impl CString {
/// Create a C String from a pointer.
pub unsafe fn new(buf: *libc::c_char, owns_buffer: bool) -> CString {
CString { buf: buf, owns_buffer_: owns_buffer }
}
/// Unwraps the wrapped `*libc::c_char` from the `CString` wrapper.
/// Any ownership of the buffer by the `CString` wrapper is forgotten.
pub unsafe fn unwrap(self) -> *libc::c_char {
let mut c_str = self;
c_str.owns_buffer_ = false;
c_str.buf
}
/// Calls a closure with a reference to the underlying `*libc::c_char`.
///
/// # Failure
///
/// Fails if the CString is null.
pub fn with_ref<T>(&self, f: |*libc::c_char| -> T) -> T {
if self.buf.is_null() { fail!("CString is null!"); }
f(self.buf)
}
/// Calls a closure with a mutable reference to the underlying `*libc::c_char`.
///
/// # Failure
///
/// Fails if the CString is null.
pub fn with_mut_ref<T>(&mut self, f: |*mut libc::c_char| -> T) -> T {
if self.buf.is_null() { fail!("CString is null!"); }
f(unsafe { cast::transmute_mut_unsafe(self.buf) })
}
/// Returns true if the CString is a null.
pub fn is_null(&self) -> bool {
self.buf.is_null()
}
/// Returns true if the CString is not null.
pub fn is_not_null(&self) -> bool {
self.buf.is_not_null()
}
/// Returns whether or not the `CString` owns the buffer.
pub fn owns_buffer(&self) -> bool {
self.owns_buffer_
}
/// Converts the CString into a `&[u8]` without copying.
/// Includes the terminating NUL byte.
///
/// # Failure
///
/// Fails if the CString is null.
#[inline]
pub fn as_bytes<'a>(&'a self) -> &'a [u8] {
if self.buf.is_null() { fail!("CString is null!"); }
unsafe {
cast::transmute(Slice { data: self.buf, len: self.len() + 1 })
}
}
/// Converts the CString into a `&[u8]` without copying.
/// Does not include the terminating NUL byte.
///
/// # Failure
///
/// Fails if the CString is null.
#[inline]
pub fn as_bytes_no_nul<'a>(&'a self) -> &'a [u8] {
if self.buf.is_null() { fail!("CString is null!"); }
unsafe {
cast::transmute(Slice { data: self.buf, len: self.len() })
}
}
/// Converts the CString into a `&str` without copying.
/// Returns None if the CString is not UTF-8.
///
/// # Failure
///
/// Fails if the CString is null.
#[inline]
pub fn as_str<'a>(&'a self) -> Option<&'a str> {
let buf = self.as_bytes_no_nul();
str::from_utf8(buf)
}
/// Return a CString iterator.
///
/// # Failure
///
/// Fails if the CString is null.
pub fn iter<'a>(&'a self) -> CChars<'a> {
if self.buf.is_null() { fail!("CString is null!"); }
CChars {
ptr: self.buf,
marker: marker::ContravariantLifetime,
}
}
}
impl Drop for CString {
fn drop(&mut self) {
if self.owns_buffer_ {
unsafe {
libc::free(self.buf as *mut libc::c_void)
}
}
}
}
impl Container for CString {
/// Return the number of bytes in the CString (not including the NUL terminator).
///
/// # Failure
///
/// Fails if the CString is null.
#[inline]
fn len(&self) -> uint {
if self.buf.is_null() { fail!("CString is null!"); }
unsafe {
ptr::position(self.buf, |c| *c == 0)
}
}
}
/// A generic trait for converting a value to a CString.
pub trait ToCStr {
/// Copy the receiver into a CString.
///
/// # Failure
///
/// Fails the task if the receiver has an interior null.
fn to_c_str(&self) -> CString;
/// Unsafe variant of `to_c_str()` that doesn't check for nulls.
unsafe fn to_c_str_unchecked(&self) -> CString;
/// Work with a temporary CString constructed from the receiver.
/// The provided `*libc::c_char` will be freed immediately upon return.
///
/// # Example
///
/// ```rust
/// use std::libc;
///
/// let s = "PATH".with_c_str(|path| unsafe {
/// libc::getenv(path)
/// });
/// ```
///
/// # Failure
///
/// Fails the task if the receiver has an interior null.
#[inline]
fn with_c_str<T>(&self, f: |*libc::c_char| -> T) -> T {
self.to_c_str().with_ref(f)
}
/// Unsafe variant of `with_c_str()` that doesn't check for nulls.
#[inline]
unsafe fn with_c_str_unchecked<T>(&self, f: |*libc::c_char| -> T) -> T {
self.to_c_str_unchecked().with_ref(f)
}
}
impl<'a> ToCStr for &'a str {
#[inline]
fn to_c_str(&self) -> CString {
self.as_bytes().to_c_str()
}
#[inline]
unsafe fn to_c_str_unchecked(&self) -> CString {
self.as_bytes().to_c_str_unchecked()
}
#[inline]
fn with_c_str<T>(&self, f: |*libc::c_char| -> T) -> T {
self.as_bytes().with_c_str(f)
}
#[inline]
unsafe fn with_c_str_unchecked<T>(&self, f: |*libc::c_char| -> T) -> T {
self.as_bytes().with_c_str_unchecked(f)
}
}
// The length of the stack allocated buffer for `vec.with_c_str()`
static BUF_LEN: uint = 128;
impl<'a> ToCStr for &'a [u8] {
fn to_c_str(&self) -> CString {
let mut cs = unsafe { self.to_c_str_unchecked() };
cs.with_mut_ref(|buf| check_for_null(*self, buf));
cs
}
unsafe fn to_c_str_unchecked(&self) -> CString {
let self_len = self.len();
let buf = malloc_raw(self_len + 1);
ptr::copy_memory(buf, self.as_ptr(), self_len);
*buf.offset(self_len as int) = 0;
CString::new(buf as *libc::c_char, true)
}
fn with_c_str<T>(&self, f: |*libc::c_char| -> T) -> T {
unsafe { with_c_str(*self, true, f) }
}
unsafe fn with_c_str_unchecked<T>(&self, f: |*libc::c_char| -> T) -> T {
with_c_str(*self, false, f)
}
}
// Unsafe function that handles possibly copying the &[u8] into a stack array.
unsafe fn with_c_str<T>(v: &[u8], checked: bool, f: |*libc::c_char| -> T) -> T {
if v.len() < BUF_LEN {
let mut buf: [u8, .. BUF_LEN] = mem::uninit();
vec::bytes::copy_memory(buf, v);
buf[v.len()] = 0;
let buf = buf.as_mut_ptr();
if checked {
check_for_null(v, buf as *mut libc::c_char);
}
f(buf as *libc::c_char)
} else if checked {
v.to_c_str().with_ref(f)
} else {
v.to_c_str_unchecked().with_ref(f)
}
}
#[inline]
fn check_for_null(v: &[u8], buf: *mut libc::c_char) {
for i in range(0, v.len()) {
unsafe {
let p = buf.offset(i as int);
assert!(*p != 0);
}
}
}
/// External iterator for a CString's bytes.
///
/// Use with the `std::iter` module.
pub struct CChars<'a> {
priv ptr: *libc::c_char,
priv marker: marker::ContravariantLifetime<'a>,
}
impl<'a> Iterator<libc::c_char> for CChars<'a> {
fn next(&mut self) -> Option<libc::c_char> {
let ch = unsafe { *self.ptr };
if ch == 0 {
None
} else {
self.ptr = unsafe { self.ptr.offset(1) };
Some(ch)
}
}
}
/// Parses a C "multistring", eg windows env values or
/// the req->ptr result in a uv_fs_readdir() call.
///
/// Optionally, a `count` can be passed in, limiting the
/// parsing to only being done `count`-times.
///
/// The specified closure is invoked with each string that
/// is found, and the number of strings found is returned.
pub unsafe fn from_c_multistring(buf: *libc::c_char,
count: Option<uint>,
f: |&CString|) -> uint {
let mut curr_ptr: uint = buf as uint;
let mut ctr = 0;
let (limited_count, limit) = match count {
Some(limit) => (true, limit),
None => (false, 0)
};
while ((limited_count && ctr < limit) || !limited_count)
&& *(curr_ptr as *libc::c_char) != 0 as libc::c_char {
let cstr = CString::new(curr_ptr as *libc::c_char, false);
f(&cstr);
curr_ptr += cstr.len() + 1;
ctr += 1;
}
return ctr;
}
#[cfg(test)]
mod tests {
use prelude::*;
use super::*;
use libc;
use ptr;
#[test]
fn test_str_multistring_parsing() {
unsafe {
let input = bytes!("zero", "\x00", "one", "\x00", "\x00");
let ptr = input.as_ptr();
let expected = ["zero", "one"];
let mut it = expected.iter();
let result = from_c_multistring(ptr as *libc::c_char, None, |c| {
let cbytes = c.as_bytes_no_nul();
assert_eq!(cbytes, it.next().unwrap().as_bytes());
});
assert_eq!(result, 2);
assert!(it.next().is_none());
}
}
#[test]
fn test_str_to_c_str() {
"".to_c_str().with_ref(|buf| {
unsafe {
assert_eq!(*buf.offset(0), 0);
}
});
"hello".to_c_str().with_ref(|buf| {
unsafe {
assert_eq!(*buf.offset(0), 'h' as libc::c_char);
assert_eq!(*buf.offset(1), 'e' as libc::c_char);
assert_eq!(*buf.offset(2), 'l' as libc::c_char);
assert_eq!(*buf.offset(3), 'l' as libc::c_char);
assert_eq!(*buf.offset(4), 'o' as libc::c_char);
assert_eq!(*buf.offset(5), 0);
}
})
}
#[test]
fn test_vec_to_c_str() {
let b: &[u8] = [];
b.to_c_str().with_ref(|buf| {
unsafe {
assert_eq!(*buf.offset(0), 0);
}
});
let _ = bytes!("hello").to_c_str().with_ref(|buf| {
unsafe {
assert_eq!(*buf.offset(0), 'h' as libc::c_char);
assert_eq!(*buf.offset(1), 'e' as libc::c_char);
assert_eq!(*buf.offset(2), 'l' as libc::c_char);
assert_eq!(*buf.offset(3), 'l' as libc::c_char);
assert_eq!(*buf.offset(4), 'o' as libc::c_char);
assert_eq!(*buf.offset(5), 0);
}
});
let _ = bytes!("foo", 0xff).to_c_str().with_ref(|buf| {
unsafe {
assert_eq!(*buf.offset(0), 'f' as libc::c_char);
assert_eq!(*buf.offset(1), 'o' as libc::c_char);
assert_eq!(*buf.offset(2), 'o' as libc::c_char);
assert_eq!(*buf.offset(3), 0xff as i8);
assert_eq!(*buf.offset(4), 0);
}
});
}
#[test]
fn test_is_null() {
let c_str = unsafe { CString::new(ptr::null(), false) };
assert!(c_str.is_null());
assert!(!c_str.is_not_null());
}
#[test]
fn test_unwrap() {
let c_str = "hello".to_c_str();
unsafe { libc::free(c_str.unwrap() as *mut libc::c_void) }
}
#[test]
fn test_with_ref() {
let c_str = "hello".to_c_str();
let len = unsafe { c_str.with_ref(|buf| libc::strlen(buf)) };
assert!(!c_str.is_null());
assert!(c_str.is_not_null());
assert_eq!(len, 5);
}
#[test]
#[should_fail]
fn test_with_ref_empty_fail() {
let c_str = unsafe { CString::new(ptr::null(), false) };
c_str.with_ref(|_| ());
}
#[test]
fn test_iterator() {
let c_str = "".to_c_str();
let mut iter = c_str.iter();
assert_eq!(iter.next(), None);
let c_str = "hello".to_c_str();
let mut iter = c_str.iter();
assert_eq!(iter.next(), Some('h' as libc::c_char));
assert_eq!(iter.next(), Some('e' as libc::c_char));
assert_eq!(iter.next(), Some('l' as libc::c_char));
assert_eq!(iter.next(), Some('l' as libc::c_char));
assert_eq!(iter.next(), Some('o' as libc::c_char));
assert_eq!(iter.next(), None);
}
#[test]
fn test_to_c_str_fail() {
use task;
assert!(task::try(proc() { "he\x00llo".to_c_str() }).is_err());
}
#[test]
fn test_to_c_str_unchecked() {
unsafe {
"he\x00llo".to_c_str_unchecked().with_ref(|buf| {
assert_eq!(*buf.offset(0), 'h' as libc::c_char);
assert_eq!(*buf.offset(1), 'e' as libc::c_char);
assert_eq!(*buf.offset(2), 0);
assert_eq!(*buf.offset(3), 'l' as libc::c_char);
assert_eq!(*buf.offset(4), 'l' as libc::c_char);
assert_eq!(*buf.offset(5), 'o' as libc::c_char);
assert_eq!(*buf.offset(6), 0);
})
}
}
#[test]
fn test_as_bytes() {
let c_str = "hello".to_c_str();
assert_eq!(c_str.as_bytes(), bytes!("hello", 0));
let c_str = "".to_c_str();
assert_eq!(c_str.as_bytes(), bytes!(0));
let c_str = bytes!("foo", 0xff).to_c_str();
assert_eq!(c_str.as_bytes(), bytes!("foo", 0xff, 0));
}
#[test]
fn test_as_bytes_no_nul() {
let c_str = "hello".to_c_str();
assert_eq!(c_str.as_bytes_no_nul(), bytes!("hello"));
let c_str = "".to_c_str();
let exp: &[u8] = [];
assert_eq!(c_str.as_bytes_no_nul(), exp);
let c_str = bytes!("foo", 0xff).to_c_str();
assert_eq!(c_str.as_bytes_no_nul(), bytes!("foo", 0xff));
}
#[test]
#[should_fail]
fn test_as_bytes_fail() {
let c_str = unsafe { CString::new(ptr::null(), false) };
c_str.as_bytes();
}
#[test]
#[should_fail]
fn test_as_bytes_no_nul_fail() {
let c_str = unsafe { CString::new(ptr::null(), false) };
c_str.as_bytes_no_nul();
}
#[test]
fn test_as_str() {
let c_str = "hello".to_c_str();
assert_eq!(c_str.as_str(), Some("hello"));
let c_str = "".to_c_str();
assert_eq!(c_str.as_str(), Some(""));
let c_str = bytes!("foo", 0xff).to_c_str();
assert_eq!(c_str.as_str(), None);
}
#[test]
#[should_fail]
fn test_as_str_fail() {
let c_str = unsafe { CString::new(ptr::null(), false) };
c_str.as_str();
}
#[test]
#[should_fail]
fn test_len_fail() {
let c_str = unsafe { CString::new(ptr::null(), false) };
c_str.len();
}
#[test]
#[should_fail]
fn test_iter_fail() {
let c_str = unsafe { CString::new(ptr::null(), false) };
c_str.iter();
}
#[test]
fn test_clone() {
let a = "hello".to_c_str();
let b = a.clone();
assert!(a == b);
}
#[test]
fn test_clone_noleak() {
fn foo(f: |c: &CString|) {
let s = ~"test";
let c = s.to_c_str();
// give the closure a non-owned CString
let mut c_ = c.with_ref(|c| unsafe { CString::new(c, false) } );
f(&c_);
// muck with the buffer for later printing
c_.with_mut_ref(|c| unsafe { *c = 'X' as libc::c_char } );
}
let mut c_: Option<CString> = None;
foo(|c| {
c_ = Some(c.clone());
c.clone();
// force a copy, reading the memory
c.as_bytes().to_owned();
});
let c_ = c_.unwrap();
// force a copy, reading the memory
c_.as_bytes().to_owned();
}
#[test]
fn test_clone_eq_null() {
let x = unsafe { CString::new(ptr::null(), false) };
let y = x.clone();
assert!(x == y);
}
}
#[cfg(test)]
mod bench {
use extra::test::BenchHarness;
use libc;
use prelude::*;
#[inline]
fn check(s: &str, c_str: *libc::c_char) {
let s_buf = s.as_ptr();
for i in range(0, s.len()) {
unsafe {
assert_eq!(
*s_buf.offset(i as int) as libc::c_char,
*c_str.offset(i as int));
}
}
}
static s_short: &'static str = "Mary";
static s_medium: &'static str = "Mary had a little lamb";
static s_long: &'static str = "\
Mary had a little lamb, Little lamb
Mary had a little lamb, Little lamb
Mary had a little lamb, Little lamb
Mary had a little lamb, Little lamb
Mary had a little lamb, Little lamb
Mary had a little lamb, Little lamb";
fn bench_to_str(bh: &mut BenchHarness, s: &str) {
bh.iter(|| {
let c_str = s.to_c_str();
c_str.with_ref(|c_str_buf| check(s, c_str_buf))
})
}
#[bench]
fn bench_to_c_str_short(bh: &mut BenchHarness) {
bench_to_str(bh, s_short)
}
#[bench]
fn bench_to_c_str_medium(bh: &mut BenchHarness) {
bench_to_str(bh, s_medium)
}
#[bench]
fn bench_to_c_str_long(bh: &mut BenchHarness) {
bench_to_str(bh, s_long)
}
fn bench_to_c_str_unchecked(bh: &mut BenchHarness, s: &str) {
bh.iter(|| {
let c_str = unsafe { s.to_c_str_unchecked() };
c_str.with_ref(|c_str_buf| check(s, c_str_buf))
})
}
#[bench]
fn bench_to_c_str_unchecked_short(bh: &mut BenchHarness) {
bench_to_c_str_unchecked(bh, s_short)
}
#[bench]
fn bench_to_c_str_unchecked_medium(bh: &mut BenchHarness) {
bench_to_c_str_unchecked(bh, s_medium)
}
#[bench]
fn bench_to_c_str_unchecked_long(bh: &mut BenchHarness) {
bench_to_c_str_unchecked(bh, s_long)
}
fn bench_with_c_str(bh: &mut BenchHarness, s: &str) {
bh.iter(|| {
s.with_c_str(|c_str_buf| check(s, c_str_buf))
})
}
#[bench]
fn bench_with_c_str_short(bh: &mut BenchHarness) {
bench_with_c_str(bh, s_short)
}
#[bench]
fn bench_with_c_str_medium(bh: &mut BenchHarness) {
bench_with_c_str(bh, s_medium)
}
#[bench]
fn bench_with_c_str_long(bh: &mut BenchHarness) {
bench_with_c_str(bh, s_long)
}
fn bench_with_c_str_unchecked(bh: &mut BenchHarness, s: &str) {
bh.iter(|| {
unsafe {
s.with_c_str_unchecked(|c_str_buf| check(s, c_str_buf))
}
})
}
#[bench]
fn bench_with_c_str_unchecked_short(bh: &mut BenchHarness) {
bench_with_c_str_unchecked(bh, s_short)
}
#[bench]
fn bench_with_c_str_unchecked_medium(bh: &mut BenchHarness) {
bench_with_c_str_unchecked(bh, s_medium)
}
#[bench]
fn bench_with_c_str_unchecked_long(bh: &mut BenchHarness) {
bench_with_c_str_unchecked(bh, s_long)
}
}