rust/src/libcore/ptr.rs

// Copyright 2012-2013 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.

//! Unsafe pointer utility functions

use cast;
use libc;
use libc::{c_void, size_t};
use unstable::intrinsics::{memmove32,memmove64};
use sys;

#[cfg(test)] use vec;
#[cfg(test)] use str;
#[cfg(notest)] use cmp::{Eq, Ord};
use uint;

pub mod libc_ {
    use libc::c_void;
    use libc;

    #[nolink]
    #[abi = "cdecl"]
    pub extern {
        #[rust_stack]
        unsafe fn memmove(dest: *mut c_void,
                          src: *const c_void,
                          n: libc::size_t)
                       -> *c_void;

        #[rust_stack]
        unsafe fn memset(dest: *mut c_void,
                         c: libc::c_int,
                         len: libc::size_t)
                      -> *c_void;
    }
}

pub mod rusti {
    #[abi = "rust-intrinsic"]
    pub extern {
        fn addr_of<T>(&&val: T) -> *T;
    }
}

/// Get an unsafe pointer to a value
#[inline(always)]
pub fn addr_of<T>(val: &T) -> *T { unsafe { rusti::addr_of(*val) } }

/// Calculate the offset from a pointer
#[inline(always)]
pub fn offset<T>(ptr: *T, count: uint) -> *T {
    unsafe {
        (ptr as uint + count * sys::size_of::<T>()) as *T
    }
}

/// Calculate the offset from a const pointer
#[inline(always)]
pub fn const_offset<T>(ptr: *const T, count: uint) -> *const T {
    unsafe {
        (ptr as uint + count * sys::size_of::<T>()) as *T
    }
}

/// Calculate the offset from a mut pointer
#[inline(always)]
pub fn mut_offset<T>(ptr: *mut T, count: uint) -> *mut T {
    (ptr as uint + count * sys::size_of::<T>()) as *mut T
}

/// Return the offset of the first null pointer in `buf`.
#[inline(always)]
pub unsafe fn buf_len<T>(buf: **T) -> uint {
    position(buf, |i| *i == null())
}

/// Return the first offset `i` such that `f(buf[i]) == true`.
#[inline(always)]
pub unsafe fn position<T>(buf: *T, f: &fn(&T) -> bool) -> uint {
    let mut i = 0;
    loop {
        if f(&(*offset(buf, i))) { return i; }
        else { i += 1; }
    }
}

/// Create an unsafe null pointer
#[inline(always)]
pub fn null<T>() -> *T { unsafe { cast::reinterpret_cast(&0u) } }

/// Create an unsafe mutable null pointer
#[inline(always)]
pub fn mut_null<T>() -> *mut T { unsafe { cast::reinterpret_cast(&0u) } }

/// Returns true if the pointer is equal to the null pointer.
#[inline(always)]
pub fn is_null<T>(ptr: *const T) -> bool { ptr == null() }

/// Returns true if the pointer is not equal to the null pointer.
#[inline(always)]
pub fn is_not_null<T>(ptr: *const T) -> bool { !is_null(ptr) }

/**
 * Copies data from one location to another
 *
 * Copies `count` elements (not bytes) from `src` to `dst`. The source
 * and destination may overlap.
 */
#[inline(always)]
#[cfg(target_word_size = "32")]
pub unsafe fn copy_memory<T>(dst: *mut T, src: *const T, count: uint) {
    let n = count * sys::size_of::<T>();
    memmove32(dst as *mut u8, src as *u8, n as u32);
}
#[inline(always)]
#[cfg(target_word_size = "64")]
pub unsafe fn copy_memory<T>(dst: *mut T, src: *const T, count: uint) {
    let n = count * sys::size_of::<T>();
    memmove64(dst as *mut u8, src as *u8, n as u64);
}

#[inline(always)]
pub unsafe fn set_memory<T>(dst: *mut T, c: int, count: uint) {
    let n = count * sys::size_of::<T>();
    libc_::memset(dst as *mut c_void, c as libc::c_int, n as size_t);
}

/**
  Transform a region pointer - &T - to an unsafe pointer - *T.
  This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.
*/
#[inline(always)]
pub fn to_unsafe_ptr<T>(thing: &T) -> *T {
    unsafe { cast::reinterpret_cast(&thing) }
}

/**
  Transform a const region pointer - &const T - to a const unsafe pointer -
  *const T. This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.
*/
#[inline(always)]
pub fn to_const_unsafe_ptr<T>(thing: &const T) -> *const T {
    unsafe { cast::reinterpret_cast(&thing) }
}

/**
  Transform a mutable region pointer - &mut T - to a mutable unsafe pointer -
  *mut T. This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.
*/
#[inline(always)]
pub fn to_mut_unsafe_ptr<T>(thing: &mut T) -> *mut T {
    unsafe { cast::reinterpret_cast(&thing) }
}

/**
  Cast a region pointer - &T - to a uint.
  This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.

  (I couldn't think of a cutesy name for this one.)
*/
#[inline(always)]
pub fn to_uint<T>(thing: &T) -> uint {
    unsafe {
        cast::reinterpret_cast(&thing)
    }
}

/// Determine if two borrowed pointers point to the same thing.
#[inline(always)]
pub fn ref_eq<'a,'b,T>(thing: &'a T, other: &'b T) -> bool {
    to_uint(thing) == to_uint(other)
}

/**
  Given a **T (pointer to an array of pointers),
  iterate through each *T, up to the provided `len`,
  passing to the provided callback function

  SAFETY NOTE: Pointer-arithmetic. Dragons be here.
*/
pub unsafe fn array_each_with_len<T>(arr: **T, len: uint, cb: &fn(*T)) {
    debug!("array_each_with_len: before iterate");
    if (arr as uint == 0) {
        fail!(~"ptr::array_each_with_len failure: arr input is null pointer");
    }
    //let start_ptr = *arr;
    uint::iterate(0, len, |e| {
        let n = offset(arr, e);
        cb(*n);
        true
    });
    debug!("array_each_with_len: after iterate");
}

/**
  Given a null-pointer-terminated **T (pointer to
  an array of pointers), iterate through each *T,
  passing to the provided callback function

  SAFETY NOTE: This will only work with a null-terminated
  pointer array. Barely less-dodgey Pointer Arithmetic.
  Dragons be here.
*/
pub unsafe fn array_each<T>(arr: **T, cb: &fn(*T)) {
    if (arr as uint == 0) {
        fail!(~"ptr::array_each_with_len failure: arr input is null pointer");
    }
    let len = buf_len(arr);
    debug!("array_each inferred len: %u",
                    len);
    array_each_with_len(arr, len, cb);
}

pub trait Ptr<T> {
    fn is_null(&const self) -> bool;
    fn is_not_null(&const self) -> bool;
    fn offset(&self, count: uint) -> Self;
}

/// Extension methods for immutable pointers
impl<T> Ptr<T> for *T {
    /// Returns true if the pointer is equal to the null pointer.
    #[inline(always)]
    fn is_null(&const self) -> bool { is_null(*self) }

    /// Returns true if the pointer is not equal to the null pointer.
    #[inline(always)]
    fn is_not_null(&const self) -> bool { is_not_null(*self) }

    /// Calculates the offset from a pointer.
    #[inline(always)]
    fn offset(&self, count: uint) -> *T { offset(*self, count) }
}

/// Extension methods for mutable pointers
impl<T> Ptr<T> for *mut T {
    /// Returns true if the pointer is equal to the null pointer.
    #[inline(always)]
    fn is_null(&const self) -> bool { is_null(*self) }

    /// Returns true if the pointer is not equal to the null pointer.
    #[inline(always)]
    fn is_not_null(&const self) -> bool { is_not_null(*self) }

    /// Calculates the offset from a mutable pointer.
    #[inline(always)]
    fn offset(&self, count: uint) -> *mut T { mut_offset(*self, count) }
}

// Equality for pointers
#[cfg(notest)]
impl<T> Eq for *const T {
    #[inline(always)]
    fn eq(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a == b;
        }
    }
    #[inline(always)]
    fn ne(&self, other: &*const T) -> bool { !(*self).eq(other) }
}

// Comparison for pointers
#[cfg(notest)]
impl<T> Ord for *const T {
    #[inline(always)]
    fn lt(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a < b;
        }
    }
    #[inline(always)]
    fn le(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a <= b;
        }
    }
    #[inline(always)]
    fn ge(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a >= b;
        }
    }
    #[inline(always)]
    fn gt(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a > b;
        }
    }
}

// Equality for region pointers
#[cfg(notest)]
impl<'self,T:Eq> Eq for &'self const T {
    #[inline(always)]
    fn eq(&self, other: & &'self const T) -> bool {
        return *(*self) == *(*other);
    }
    #[inline(always)]
    fn ne(&self, other: & &'self const T) -> bool {
        return *(*self) != *(*other);
    }
}

// Comparison for region pointers
#[cfg(notest)]
impl<'self,T:Ord> Ord for &'self const T {
    #[inline(always)]
    fn lt(&self, other: & &'self const T) -> bool {
        *(*self) < *(*other)
    }
    #[inline(always)]
    fn le(&self, other: & &'self const T) -> bool {
        *(*self) <= *(*other)
    }
    #[inline(always)]
    fn ge(&self, other: & &'self const T) -> bool {
        *(*self) >= *(*other)
    }
    #[inline(always)]
    fn gt(&self, other: & &'self const T) -> bool {
        *(*self) > *(*other)
    }
}

#[test]
pub fn test() {
    unsafe {
        struct Pair {mut fst: int, mut snd: int};
        let mut p = Pair {fst: 10, snd: 20};
        let pptr: *mut Pair = &mut p;
        let iptr: *mut int = cast::reinterpret_cast(&pptr);
        fail_unless!((*iptr == 10));;
        *iptr = 30;
        fail_unless!((*iptr == 30));
        fail_unless!((p.fst == 30));;

        *pptr = Pair {fst: 50, snd: 60};
        fail_unless!((*iptr == 50));
        fail_unless!((p.fst == 50));
        fail_unless!((p.snd == 60));

        let mut v0 = ~[32000u16, 32001u16, 32002u16];
        let mut v1 = ~[0u16, 0u16, 0u16];

        copy_memory(mut_offset(vec::raw::to_mut_ptr(v1), 1u),
                    offset(vec::raw::to_ptr(v0), 1u), 1u);
        fail_unless!((v1[0] == 0u16 && v1[1] == 32001u16 && v1[2] == 0u16));
        copy_memory(vec::raw::to_mut_ptr(v1),
                    offset(vec::raw::to_ptr(v0), 2u), 1u);
        fail_unless!((v1[0] == 32002u16 && v1[1] == 32001u16 &&
                      v1[2] == 0u16));
        copy_memory(mut_offset(vec::raw::to_mut_ptr(v1), 2u),
                    vec::raw::to_ptr(v0), 1u);
        fail_unless!((v1[0] == 32002u16 && v1[1] == 32001u16 &&
                      v1[2] == 32000u16));
    }
}

#[test]
pub fn test_position() {
    use str::as_c_str;
    use libc::c_char;

    let s = ~"hello";
    unsafe {
        fail_unless!(2u == as_c_str(s, |p| position(p,
            |c| *c == 'l' as c_char)));
        fail_unless!(4u == as_c_str(s, |p| position(p,
            |c| *c == 'o' as c_char)));
        fail_unless!(5u == as_c_str(s, |p| position(p,
            |c| *c == 0 as c_char)));
    }
}

#[test]
pub fn test_buf_len() {
    let s0 = ~"hello";
    let s1 = ~"there";
    let s2 = ~"thing";
    do str::as_c_str(s0) |p0| {
        do str::as_c_str(s1) |p1| {
            do str::as_c_str(s2) |p2| {
                let v = ~[p0, p1, p2, null()];
                do vec::as_imm_buf(v) |vp, len| {
                    fail_unless!(unsafe { buf_len(vp) } == 3u);
                    fail_unless!(len == 4u);
                }
            }
        }
    }
}

#[test]
pub fn test_is_null() {
   let p: *int = null();
   fail_unless!(p.is_null());
   fail_unless!(!p.is_not_null());

   let q = offset(p, 1u);
   fail_unless!(!q.is_null());
   fail_unless!(q.is_not_null());

   let mp: *mut int = mut_null();
   fail_unless!(mp.is_null());
   fail_unless!(!mp.is_not_null());

   let mq = mp.offset(1u);
   fail_unless!(!mq.is_null());
   fail_unless!(mq.is_not_null());
}

#[cfg(test)]
pub mod ptr_tests {
    use ptr;
    use str;
    use libc;
    use vec;
    #[test]
    pub fn test_ptr_array_each_with_len() {
        unsafe {
            let one = ~"oneOne";
            let two = ~"twoTwo";
            let three = ~"threeThree";
            let arr: ~[*i8] = ~[
                ::cast::transmute(&one[0]),
                ::cast::transmute(&two[0]),
                ::cast::transmute(&three[0]),
            ];
            let expected_arr = [
                one, two, three
            ];
            let arr_ptr = &arr[0];
            let mut ctr = 0;
            let mut iteration_count = 0;
            ptr::array_each_with_len(arr_ptr, vec::len(arr),
                |e| {
                let actual = str::raw::from_c_str(e);
                let expected = copy expected_arr[ctr];
                debug!(
                    "test_ptr_array_each e: %s, a: %s",
                         expected, actual);
                fail_unless!(actual == expected);
                ctr += 1;
                iteration_count += 1;
            });
            fail_unless!(iteration_count == 3u);
        }
    }
    #[test]
    pub fn test_ptr_array_each() {
        unsafe {
            let one = ~"oneOne";
            let two = ~"twoTwo";
            let three = ~"threeThree";
            let arr: ~[*i8] = ~[
                ::cast::transmute(&one[0]),
                ::cast::transmute(&two[0]),
                ::cast::transmute(&three[0]),
                // fake a null terminator
                0 as *i8
            ];
            let expected_arr = [
                one, two, three
            ];
            let arr_ptr = &arr[0];
            let mut ctr = 0;
            let mut iteration_count = 0;
            ptr::array_each(arr_ptr, |e| {
                let actual = str::raw::from_c_str(e);
                let expected = copy expected_arr[ctr];
                debug!(
                    "test_ptr_array_each e: %s, a: %s",
                         expected, actual);
                fail_unless!(actual == expected);
                ctr += 1;
                iteration_count += 1;
            });
            fail_unless!(iteration_count == 3);
        }
    }
    #[test]
    #[should_fail]
    #[ignore(cfg(windows))]
    pub fn test_ptr_array_each_with_len_null_ptr() {
        unsafe {
            ptr::array_each_with_len(0 as **libc::c_char, 1, |e| {
                str::raw::from_c_str(e);
            });
        }
    }
    #[test]
    #[should_fail]
    #[ignore(cfg(windows))]
    pub fn test_ptr_array_each_null_ptr() {
        unsafe {
            ptr::array_each(0 as **libc::c_char, |e| {
                str::raw::from_c_str(e);
            });
        }
    }
}