core: Inherit the ptr module

1 files changed, 736 insertions, 0 deletions

diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs
new file mode 100644
index 00000000000..9ac9e62b50d
--- /dev/null
+++ b/src/libcore/ptr.rs
@@ -0,0 +1,736 @@
+// 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.
+
+//! Conveniences for working with unsafe pointers, the `*T`, and `*mut T` types.
+//!
+//! Working with unsafe pointers in Rust is fairly uncommon,
+//! and often limited to some narrow use cases: holding
+//! an unsafe pointer when safe pointers are unsuitable;
+//! checking for null; and converting back to safe pointers.
+//! As a result, there is not yet an abundance of library code
+//! for working with unsafe pointers, and in particular,
+//! since pointer math is fairly uncommon in Rust, it is not
+//! all that convenient.
+//!
+//! Use the [`null` function](fn.null.html) to create null pointers,
+//! the [`is_null`](trait.RawPtr.html#tymethod.is_null)
+//! and [`is_not_null`](trait.RawPtr.html#method.is_not_null)
+//! methods of the [`RawPtr` trait](trait.RawPtr.html) to check for null.
+//! The `RawPtr` trait is imported by the prelude, so `is_null` etc.
+//! work everywhere.
+//!
+//! # Common ways to create unsafe pointers
+//!
+//! ## 1. Coerce a reference (`&T`) or mutable reference (`&mut T`).
+//!
+//! ```
+//! let my_num: int = 10;
+//! let my_num_ptr: *int = &my_num;
+//! let mut my_speed: int = 88;
+//! let my_speed_ptr: *mut int = &mut my_speed;
+//! ```
+//!
+//! This does not take ownership of the original allocation
+//! and requires no resource management later,
+//! but you must not use the pointer after its lifetime.
+//!
+//! ## 2. Transmute an owned box (`Box<T>`).
+//!
+//! The `transmute` function takes, by value, whatever it's given
+//! and returns it as whatever type is requested, as long as the
+//! types are the same size. Because `Box<T>` and `*T` have the same
+//! representation they can be trivially,
+//! though unsafely, transformed from one type to the other.
+//!
+//! ```
+//! use std::cast;
+//!
+//! unsafe {
+//!     let my_num: Box<int> = box 10;
+//!     let my_num: *int = cast::transmute(my_num);
+//!     let my_speed: Box<int> = box 88;
+//!     let my_speed: *mut int = cast::transmute(my_speed);
+//!
+//!     // By taking ownership of the original `Box<T>` though
+//!     // we are obligated to transmute it back later to be destroyed.
+//!     drop(cast::transmute::<_, Box<int>>(my_speed));
+//!     drop(cast::transmute::<_, Box<int>>(my_num));
+//! }
+//! ```
+//!
+//! Note that here the call to `drop` is for clarity - it indicates
+//! that we are done with the given value and it should be destroyed.
+//!
+//! ## 3. Get it from C.
+//!
+//! ```
+//! extern crate libc;
+//!
+//! use std::mem;
+//!
+//! fn main() {
+//!     unsafe {
+//!         let my_num: *mut int = libc::malloc(mem::size_of::<int>() as libc::size_t) as *mut int;
+//!         if my_num.is_null() {
+//!             fail!("failed to allocate memory");
+//!         }
+//!         libc::free(my_num as *mut libc::c_void);
+//!     }
+//! }
+//! ```
+//!
+//! Usually you wouldn't literally use `malloc` and `free` from Rust,
+//! but C APIs hand out a lot of pointers generally, so are a common source
+//! of unsafe pointers in Rust.
+
+use cast;
+use clone::Clone;
+use intrinsics;
+use iter::{range, Iterator};
+use mem;
+use option::{Some, None, Option};
+
+#[cfg(not(test))] use cmp::{Eq, TotalEq, Ord, Equiv};
+
+/// Return the offset of the first null pointer in `buf`.
+#[inline]
+pub unsafe fn buf_len<T>(buf: **T) -> uint {
+    position(buf, |i| *i == null())
+}
+
+impl<T> Clone for *T {
+    #[inline]
+    fn clone(&self) -> *T {
+        *self
+    }
+}
+
+impl<T> Clone for *mut T {
+    #[inline]
+    fn clone(&self) -> *mut T {
+        *self
+    }
+}
+
+/// Return the first offset `i` such that `f(buf[i]) == true`.
+#[inline]
+pub unsafe fn position<T>(buf: *T, f: |&T| -> bool) -> uint {
+    let mut i = 0;
+    loop {
+        if f(&(*buf.offset(i as int))) { return i; }
+        else { i += 1; }
+    }
+}
+
+/// Create a null pointer.
+///
+/// # Example
+///
+/// ```
+/// use std::ptr;
+///
+/// let p: *int = ptr::null();
+/// assert!(p.is_null());
+/// ```
+#[inline]
+pub fn null<T>() -> *T { 0 as *T }
+
+/// Create an unsafe mutable null pointer.
+///
+/// # Example
+///
+/// ```
+/// use std::ptr;
+///
+/// let p: *mut int = ptr::mut_null();
+/// assert!(p.is_null());
+/// ```
+#[inline]
+pub fn mut_null<T>() -> *mut T { 0 as *mut T }
+
+/// Copies data from one location to another.
+///
+/// Copies `count` elements (not bytes) from `src` to `dst`. The source
+/// and destination may overlap.
+///
+/// `copy_memory` is semantically equivalent to C's `memmove`.
+///
+/// # Example
+///
+/// Efficiently create a Rust vector from an unsafe buffer:
+///
+/// ```
+/// use std::ptr;
+///
+/// unsafe fn from_buf_raw<T>(ptr: *T, elts: uint) -> Vec<T> {
+///     let mut dst = Vec::with_capacity(elts);
+///     dst.set_len(elts);
+///     ptr::copy_memory(dst.as_mut_ptr(), ptr, elts);
+///     dst
+/// }
+/// ```
+///
+#[inline]
+pub unsafe fn copy_memory<T>(dst: *mut T, src: *T, count: uint) {
+    intrinsics::copy_memory(dst, src, count)
+}
+
+/// Copies data from one location to another.
+///
+/// Copies `count` elements (not bytes) from `src` to `dst`. The source
+/// and destination may *not* overlap.
+///
+/// `copy_nonoverlapping_memory` is semantically equivalent to C's `memcpy`.
+///
+/// # Example
+///
+/// A safe swap function:
+///
+/// ```
+/// use std::cast;
+/// use std::mem;
+/// use std::ptr;
+///
+/// fn swap<T>(x: &mut T, y: &mut T) {
+///     unsafe {
+///         // Give ourselves some scratch space to work with
+///         let mut t: T = mem::uninit();
+///
+///         // Perform the swap, `&mut` pointers never alias
+///         ptr::copy_nonoverlapping_memory(&mut t, &*x, 1);
+///         ptr::copy_nonoverlapping_memory(x, &*y, 1);
+///         ptr::copy_nonoverlapping_memory(y, &t, 1);
+///
+///         // y and t now point to the same thing, but we need to completely forget `tmp`
+///         // because it's no longer relevant.
+///         cast::forget(t);
+///     }
+/// }
+/// ```
+///
+/// # Safety Note
+///
+/// If the source and destination overlap then the behavior of this
+/// function is undefined.
+#[inline]
+pub unsafe fn copy_nonoverlapping_memory<T>(dst: *mut T,
+                                            src: *T,
+                                            count: uint) {
+    intrinsics::copy_nonoverlapping_memory(dst, src, count)
+}
+
+/// Invokes memset on the specified pointer, setting `count * size_of::<T>()`
+/// bytes of memory starting at `dst` to `c`.
+#[inline]
+pub unsafe fn set_memory<T>(dst: *mut T, c: u8, count: uint) {
+    intrinsics::set_memory(dst, c, count)
+}
+
+/// Zeroes out `count * size_of::<T>` bytes of memory at `dst`
+#[inline]
+pub unsafe fn zero_memory<T>(dst: *mut T, count: uint) {
+    set_memory(dst, 0, count);
+}
+
+/// Swap the values at two mutable locations of the same type, without
+/// deinitialising either. They may overlap.
+#[inline]
+pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
+    // Give ourselves some scratch space to work with
+    let mut tmp: T = mem::uninit();
+    let t: *mut T = &mut tmp;
+
+    // Perform the swap
+    copy_nonoverlapping_memory(t, &*x, 1);
+    copy_memory(x, &*y, 1); // `x` and `y` may overlap
+    copy_nonoverlapping_memory(y, &*t, 1);
+
+    // y and t now point to the same thing, but we need to completely forget `tmp`
+    // because it's no longer relevant.
+    cast::forget(tmp);
+}
+
+/// Replace the value at a mutable location with a new one, returning the old
+/// value, without deinitialising either.
+#[inline]
+pub unsafe fn replace<T>(dest: *mut T, mut src: T) -> T {
+    mem::swap(cast::transmute(dest), &mut src); // cannot overlap
+    src
+}
+
+/// Reads the value from `*src` and returns it.
+#[inline(always)]
+pub unsafe fn read<T>(src: *T) -> T {
+    let mut tmp: T = mem::uninit();
+    copy_nonoverlapping_memory(&mut tmp, src, 1);
+    tmp
+}
+
+/// Reads the value from `*src` and nulls it out.
+/// This currently prevents destructors from executing.
+#[inline(always)]
+pub unsafe fn read_and_zero<T>(dest: *mut T) -> T {
+    // Copy the data out from `dest`:
+    let tmp = read(&*dest);
+
+    // Now zero out `dest`:
+    zero_memory(dest, 1);
+
+    tmp
+}
+
+/// Given a **T (pointer to an array of pointers),
+/// iterate through each *T, up to the provided `len`,
+/// passing to the provided callback function
+pub unsafe fn array_each_with_len<T>(arr: **T, len: uint, cb: |*T|) {
+    if arr.is_null() {
+        fail!("ptr::array_each_with_len failure: arr input is null pointer");
+    }
+    //let start_ptr = *arr;
+    for e in range(0, len) {
+        let n = arr.offset(e as int);
+        cb(*n);
+    }
+}
+
+/// 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.
+pub unsafe fn array_each<T>(arr: **T, cb: |*T|) {
+    if arr.is_null()  {
+        fail!("ptr::array_each_with_len failure: arr input is null pointer");
+    }
+    let len = buf_len(arr);
+    array_each_with_len(arr, len, cb);
+}
+
+/// Extension methods for raw pointers.
+pub trait RawPtr<T> {
+    /// Returns the null pointer.
+    fn null() -> Self;
+    /// Returns true if the pointer is equal to the null pointer.
+    fn is_null(&self) -> bool;
+    /// Returns true if the pointer is not equal to the null pointer.
+    fn is_not_null(&self) -> bool { !self.is_null() }
+    /// Returns the value of this pointer (ie, the address it points to)
+    fn to_uint(&self) -> uint;
+    /// Returns `None` if the pointer is null, or else returns the value wrapped
+    /// in `Some`.
+    ///
+    /// # Safety Notes
+    ///
+    /// While this method is useful for null-safety, it is important to note
+    /// that this is still an unsafe operation because the returned value could
+    /// be pointing to invalid memory.
+    unsafe fn to_option(&self) -> Option<&T>;
+    /// Calculates the offset from a pointer. The offset *must* be in-bounds of
+    /// the object, or one-byte-past-the-end.  `count` is in units of T; e.g. a
+    /// `count` of 3 represents a pointer offset of `3 * sizeof::<T>()` bytes.
+    unsafe fn offset(self, count: int) -> Self;
+}
+
+impl<T> RawPtr<T> for *T {
+    #[inline]
+    fn null() -> *T { null() }
+
+    #[inline]
+    fn is_null(&self) -> bool { *self == RawPtr::null() }
+
+    #[inline]
+    fn to_uint(&self) -> uint { *self as uint }
+
+    #[inline]
+    unsafe fn offset(self, count: int) -> *T { intrinsics::offset(self, count) }
+
+    #[inline]
+    unsafe fn to_option(&self) -> Option<&T> {
+        if self.is_null() {
+            None
+        } else {
+            Some(cast::transmute(*self))
+        }
+    }
+}
+
+impl<T> RawPtr<T> for *mut T {
+    #[inline]
+    fn null() -> *mut T { mut_null() }
+
+    #[inline]
+    fn is_null(&self) -> bool { *self == RawPtr::null() }
+
+    #[inline]
+    fn to_uint(&self) -> uint { *self as uint }
+
+    #[inline]
+    unsafe fn offset(self, count: int) -> *mut T {
+        intrinsics::offset(self as *T, count) as *mut T
+    }
+
+    #[inline]
+    unsafe fn to_option(&self) -> Option<&T> {
+        if self.is_null() {
+            None
+        } else {
+            Some(cast::transmute(*self))
+        }
+    }
+}
+
+// Equality for pointers
+#[cfg(not(test))]
+impl<T> Eq for *T {
+    #[inline]
+    fn eq(&self, other: &*T) -> bool {
+        *self == *other
+    }
+    #[inline]
+    fn ne(&self, other: &*T) -> bool { !self.eq(other) }
+}
+
+#[cfg(not(test))]
+impl<T> TotalEq for *T {}
+
+#[cfg(not(test))]
+impl<T> Eq for *mut T {
+    #[inline]
+    fn eq(&self, other: &*mut T) -> bool {
+        *self == *other
+    }
+    #[inline]
+    fn ne(&self, other: &*mut T) -> bool { !self.eq(other) }
+}
+
+#[cfg(not(test))]
+impl<T> TotalEq for *mut T {}
+
+// Equivalence for pointers
+#[cfg(not(test))]
+impl<T> Equiv<*mut T> for *T {
+    fn equiv(&self, other: &*mut T) -> bool {
+        self.to_uint() == other.to_uint()
+    }
+}
+
+#[cfg(not(test))]
+impl<T> Equiv<*T> for *mut T {
+    fn equiv(&self, other: &*T) -> bool {
+        self.to_uint() == other.to_uint()
+    }
+}
+
+// Equality for extern "C" fn pointers
+#[cfg(not(test))]
+mod externfnpointers {
+    use cast;
+    use cmp::Eq;
+
+    impl<_R> Eq for extern "C" fn() -> _R {
+        #[inline]
+        fn eq(&self, other: &extern "C" fn() -> _R) -> bool {
+            let self_: *() = unsafe { cast::transmute(*self) };
+            let other_: *() = unsafe { cast::transmute(*other) };
+            self_ == other_
+        }
+    }
+    macro_rules! fnptreq(
+        ($($p:ident),*) => {
+            impl<_R,$($p),*> Eq for extern "C" fn($($p),*) -> _R {
+                #[inline]
+                fn eq(&self, other: &extern "C" fn($($p),*) -> _R) -> bool {
+                    let self_: *() = unsafe { cast::transmute(*self) };
+                    let other_: *() = unsafe { cast::transmute(*other) };
+                    self_ == other_
+                }
+            }
+        }
+    )
+    fnptreq!(A)
+    fnptreq!(A,B)
+    fnptreq!(A,B,C)
+    fnptreq!(A,B,C,D)
+    fnptreq!(A,B,C,D,E)
+}
+
+// Comparison for pointers
+#[cfg(not(test))]
+impl<T> Ord for *T {
+    #[inline]
+    fn lt(&self, other: &*T) -> bool { *self < *other }
+}
+
+#[cfg(not(test))]
+impl<T> Ord for *mut T {
+    #[inline]
+    fn lt(&self, other: &*mut T) -> bool { *self < *other }
+}
+
+#[cfg(test)]
+pub mod ptr_tests {
+    use super::*;
+    use prelude::*;
+
+    use c_str::ToCStr;
+    use cast;
+    use libc;
+    use str;
+    use slice::{ImmutableVector, MutableVector};
+
+    #[test]
+    fn test() {
+        unsafe {
+            struct Pair {
+                fst: int,
+                snd: int
+            };
+            let mut p = Pair {fst: 10, snd: 20};
+            let pptr: *mut Pair = &mut p;
+            let iptr: *mut int = cast::transmute(pptr);
+            assert_eq!(*iptr, 10);
+            *iptr = 30;
+            assert_eq!(*iptr, 30);
+            assert_eq!(p.fst, 30);
+
+            *pptr = Pair {fst: 50, snd: 60};
+            assert_eq!(*iptr, 50);
+            assert_eq!(p.fst, 50);
+            assert_eq!(p.snd, 60);
+
+            let v0 = box [32000u16, 32001u16, 32002u16];
+            let mut v1 = box [0u16, 0u16, 0u16];
+
+            copy_memory(v1.as_mut_ptr().offset(1),
+                        v0.as_ptr().offset(1), 1);
+            assert!((v1[0] == 0u16 && v1[1] == 32001u16 && v1[2] == 0u16));
+            copy_memory(v1.as_mut_ptr(),
+                        v0.as_ptr().offset(2), 1);
+            assert!((v1[0] == 32002u16 && v1[1] == 32001u16 &&
+                     v1[2] == 0u16));
+            copy_memory(v1.as_mut_ptr().offset(2),
+                        v0.as_ptr(), 1u);
+            assert!((v1[0] == 32002u16 && v1[1] == 32001u16 &&
+                     v1[2] == 32000u16));
+        }
+    }
+
+    #[test]
+    fn test_position() {
+        use libc::c_char;
+
+        "hello".with_c_str(|p| {
+            unsafe {
+                assert!(2u == position(p, |c| *c == 'l' as c_char));
+                assert!(4u == position(p, |c| *c == 'o' as c_char));
+                assert!(5u == position(p, |c| *c == 0 as c_char));
+            }
+        })
+    }
+
+    #[test]
+    fn test_buf_len() {
+        "hello".with_c_str(|p0| {
+            "there".with_c_str(|p1| {
+                "thing".with_c_str(|p2| {
+                    let v = box [p0, p1, p2, null()];
+                    unsafe {
+                        assert_eq!(buf_len(v.as_ptr()), 3u);
+                    }
+                })
+            })
+        })
+    }
+
+    #[test]
+    fn test_is_null() {
+        let p: *int = null();
+        assert!(p.is_null());
+        assert!(!p.is_not_null());
+
+        let q = unsafe { p.offset(1) };
+        assert!(!q.is_null());
+        assert!(q.is_not_null());
+
+        let mp: *mut int = mut_null();
+        assert!(mp.is_null());
+        assert!(!mp.is_not_null());
+
+        let mq = unsafe { mp.offset(1) };
+        assert!(!mq.is_null());
+        assert!(mq.is_not_null());
+    }
+
+    #[test]
+    fn test_to_option() {
+        unsafe {
+            let p: *int = null();
+            assert_eq!(p.to_option(), None);
+
+            let q: *int = &2;
+            assert_eq!(q.to_option().unwrap(), &2);
+
+            let p: *mut int = mut_null();
+            assert_eq!(p.to_option(), None);
+
+            let q: *mut int = &mut 2;
+            assert_eq!(q.to_option().unwrap(), &2);
+        }
+    }
+
+    #[test]
+    fn test_ptr_addition() {
+        unsafe {
+            let xs = box [5, ..16];
+            let mut ptr = xs.as_ptr();
+            let end = ptr.offset(16);
+
+            while ptr < end {
+                assert_eq!(*ptr, 5);
+                ptr = ptr.offset(1);
+            }
+
+            let mut xs_mut = xs.clone();
+            let mut m_ptr = xs_mut.as_mut_ptr();
+            let m_end = m_ptr.offset(16);
+
+            while m_ptr < m_end {
+                *m_ptr += 5;
+                m_ptr = m_ptr.offset(1);
+            }
+
+            assert_eq!(xs_mut, box [10, ..16]);
+        }
+    }
+
+    #[test]
+    fn test_ptr_subtraction() {
+        unsafe {
+            let xs = box [0,1,2,3,4,5,6,7,8,9];
+            let mut idx = 9i8;
+            let ptr = xs.as_ptr();
+
+            while idx >= 0i8 {
+                assert_eq!(*(ptr.offset(idx as int)), idx as int);
+                idx = idx - 1i8;
+            }
+
+            let mut xs_mut = xs.clone();
+            let m_start = xs_mut.as_mut_ptr();
+            let mut m_ptr = m_start.offset(9);
+
+            while m_ptr >= m_start {
+                *m_ptr += *m_ptr;
+                m_ptr = m_ptr.offset(-1);
+            }
+
+            assert_eq!(xs_mut, box [0,2,4,6,8,10,12,14,16,18]);
+        }
+    }
+
+    #[test]
+    fn test_ptr_array_each_with_len() {
+        unsafe {
+            let one = "oneOne".to_c_str();
+            let two = "twoTwo".to_c_str();
+            let three = "threeThree".to_c_str();
+            let arr = box [
+                one.with_ref(|buf| buf),
+                two.with_ref(|buf| buf),
+                three.with_ref(|buf| buf),
+            ];
+            let expected_arr = [
+                one, two, three
+            ];
+
+            let mut ctr = 0;
+            let mut iteration_count = 0;
+            array_each_with_len(arr.as_ptr(), arr.len(), |e| {
+                    let actual = str::raw::from_c_str(e);
+                    let expected = expected_arr[ctr].with_ref(|buf| {
+                            str::raw::from_c_str(buf)
+                        });
+                    debug!(
+                        "test_ptr_array_each_with_len e: {}, a: {}",
+                        expected, actual);
+                    assert_eq!(actual, expected);
+                    ctr += 1;
+                    iteration_count += 1;
+                });
+            assert_eq!(iteration_count, 3u);
+        }
+    }
+
+    #[test]
+    fn test_ptr_array_each() {
+        unsafe {
+            let one = "oneOne".to_c_str();
+            let two = "twoTwo".to_c_str();
+            let three = "threeThree".to_c_str();
+            let arr = box [
+                one.with_ref(|buf| buf),
+                two.with_ref(|buf| buf),
+                three.with_ref(|buf| buf),
+                // fake a null terminator
+                null(),
+            ];
+            let expected_arr = [
+                one, two, three
+            ];
+
+            let arr_ptr = arr.as_ptr();
+            let mut ctr = 0;
+            let mut iteration_count = 0;
+            array_each(arr_ptr, |e| {
+                    let actual = str::raw::from_c_str(e);
+                    let expected = expected_arr[ctr].with_ref(|buf| {
+                        str::raw::from_c_str(buf)
+                    });
+                    debug!(
+                        "test_ptr_array_each e: {}, a: {}",
+                        expected, actual);
+                    assert_eq!(actual, expected);
+                    ctr += 1;
+                    iteration_count += 1;
+                });
+            assert_eq!(iteration_count, 3);
+        }
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_ptr_array_each_with_len_null_ptr() {
+        unsafe {
+            array_each_with_len(0 as **libc::c_char, 1, |e| {
+                str::raw::from_c_str(e);
+            });
+        }
+    }
+    #[test]
+    #[should_fail]
+    fn test_ptr_array_each_null_ptr() {
+        unsafe {
+            array_each(0 as **libc::c_char, |e| {
+                str::raw::from_c_str(e);
+            });
+        }
+    }
+
+    #[test]
+    fn test_set_memory() {
+        let mut xs = [0u8, ..20];
+        let ptr = xs.as_mut_ptr();
+        unsafe { set_memory(ptr, 5u8, xs.len()); }
+        assert!(xs == [5u8, ..20]);
+    }
+}