//! Thread specific operations.
use std::io;
use std::os::raw::c_char;

use {get, get_mib, name_to_mib};

#[deprecated(note = "renamed to AllocatedP", since = "0.1.3")]
pub use thread::AllocatedP as Allocated;
#[deprecated(note = "renamed to DeallocatedP", since = "0.1.3")]
pub use thread::DeallocatedP as Deallocated;

const ALLOCATEDP: *const c_char = b"thread.allocatedp\0" as *const _ as *const _;

/// Returns a thread-local pointer to the total number of bytes allocated by the current thread.
///
/// Unlike [`stats::allocated`], the value returned by this type is not the number of bytes
/// *currently* allocated, but rather the number of bytes that have *ever* been allocated by this
/// thread.
///
/// This function doesn't return the value directly, but actually a pointer to the value. This
/// allows for very fast repeated lookup, since there is no function call overhead. The pointer type
/// cannot be sent to other threads, but `allocated` can be called on different threads and will
/// return the appropriate pointer for each of them.
///
/// This corresponds to `thread.allocatedp` in jemalloc's API.
///
/// # Examples
///
/// ```
/// let allocated = jemalloc_ctl::thread::allocatedp().unwrap();
///
/// let a = allocated.get();
/// let buf = vec![0; 1024 * 1024];
/// let b = allocated.get();
/// drop(buf);
/// let c = allocated.get();
///
/// assert!(a < b);
/// assert_eq!(b, c);
/// ```
pub fn allocatedp() -> io::Result<ThreadLocal<u64>> {
    unsafe { get(ALLOCATEDP).map(ThreadLocal) }
}

/// A type providing access to the total number of bytes allocated by the current thread.
///
/// Unlike [`stats::Allocated`], the value returned by this type is not the number of bytes
/// *currently* allocated, but rather the number of bytes that have *ever* been allocated by this
/// thread.
///
/// The `get` method doesn't return the value directly, but actually a pointer to the value. This
/// allows for very fast repeated lookup, since there is no function call overhead. The pointer type
/// cannot be sent to other threads, but `Allocated::get` can be called on different threads and
/// will return the appropriate pointer for each of them.
///
/// # Example
///
/// ```
/// use jemalloc_ctl::thread::AllocatedP;
///
/// let allocated = AllocatedP::new().unwrap();
/// let allocated = allocated.get().unwrap();
///
/// let a = allocated.get();
/// let buf = vec![0; 1024 * 1024];
/// let b = allocated.get();
/// drop(buf);
/// let c = allocated.get();
///
/// assert!(a < b);
/// assert_eq!(b, c);
/// ```
///
/// [`stats::Allocated`]: ../stats/struct.Allocated.html
#[derive(Copy, Clone)]
pub struct AllocatedP([usize; 2]);

impl AllocatedP {
    /// Returns a new `Allocated`.
    pub fn new() -> io::Result<AllocatedP> {
        let mut mib = [0; 2];
        unsafe {
            name_to_mib(ALLOCATEDP, &mut mib)?;
        }
        Ok(AllocatedP(mib))
    }

    /// Returns a thread-local pointer to the total number of bytes allocated by this thread.
    pub fn get(&self) -> io::Result<ThreadLocal<u64>> {
        unsafe { get_mib(&self.0).map(ThreadLocal) }
    }
}

const DEALLOCATEDP: *const c_char = b"thread.deallocatedp\0" as *const _ as *const _;

/// Returns a pointer to the total number of bytes deallocated by the current thread.
///
/// This function doesn't return the value directly, but actually a pointer to the value. This
/// allows for very fast repeated lookup, since there is no function call overhead. The pointer type
/// cannot be sent to other threads, but `deallocatedp` can be called on different threads and will
/// return the appropriate pointer for each of them.
///
/// This corresponds to `thread.deallocatedp` in jemalloc's API.
///
/// # Examples
///
/// ```
/// let deallocated = jemalloc_ctl::thread::deallocatedp().unwrap();
///
/// let a = deallocated.get();
/// let buf = vec![0; 1024 * 1024];
/// let b = deallocated.get();
/// drop(buf);
/// let c = deallocated.get();
///
/// assert_eq!(a, b);
/// assert!(b < c);
/// ```
pub fn deallocatedp() -> io::Result<ThreadLocal<u64>> {
    unsafe { get(DEALLOCATEDP).map(ThreadLocal) }
}

/// A type providing access to the total number of bytes deallocated by the current thread.
///
/// The `get` method doesn't return the value directly, but actually a pointer to the value. This
/// allows for very fast repeated lookup, since there is no function call overhead. The pointer type
/// cannot be sent to other threads, but `DeallocatedP::get` can be called on different threads and
/// will return the appropriate pointer for each of them.
///
/// # Example
///
/// ```
/// use jemalloc_ctl::thread::DeallocatedP;
///
/// let deallocated = DeallocatedP::new().unwrap();
/// let deallocated = deallocated.get().unwrap();
///
/// let a = deallocated.get();
/// let buf = vec![0; 1024 * 1024];
/// let b = deallocated.get();
/// drop(buf);
/// let c = deallocated.get();
///
/// assert_eq!(a, b);
/// assert!(b < c);
/// ```
#[derive(Copy, Clone)]
pub struct DeallocatedP([usize; 2]);

impl DeallocatedP {
    /// Returns a new `Deallocated`.
    pub fn new() -> io::Result<DeallocatedP> {
        let mut mib = [0; 2];
        unsafe {
            name_to_mib(DEALLOCATEDP, &mut mib)?;
        }
        Ok(DeallocatedP(mib))
    }

    /// Returns a thread-local pointer to the total number of bytes deallocated by this thread.
    pub fn get(&self) -> io::Result<ThreadLocal<u64>> {
        unsafe {
            let ptr = get_mib::<*mut u64>(&self.0)?;
            Ok(ThreadLocal(ptr))
        }
    }
}

/// A thread-local pointer.
///
/// It is neither `Sync` nor `Send`.
// NB we need *const here specifically since it's !Sync + !Send
#[derive(Copy, Clone)]
pub struct ThreadLocal<T>(*const T);

impl<T> ThreadLocal<T>
where
    T: Copy,
{
    /// Returns the current value at the pointer.
    #[inline]
    pub fn get(&self) -> T {
        unsafe { *self.0 }
    }
}