// Copyright 2018 The Chromium OS Authors. All rights reserved.
// Copyright © 2019 Intel Corporation
//
// Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE-BSD-3-Clause file.
//
// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause

use vm_memory::{GuestAddress, GuestUsize};

use crate::address::AddressAllocator;

use libc::{sysconf, _SC_PAGESIZE};

/// Safe wrapper for `sysconf(_SC_PAGESIZE)`.
#[inline(always)]
fn pagesize() -> usize {
    // Trivially safe
    unsafe { sysconf(_SC_PAGESIZE) as usize }
}

/// Manages allocating system resources such as address space and interrupt numbers.
///
/// # Example - Use the `SystemAddress` builder.
///
/// ```
/// # use vm_allocator::SystemAllocator;
/// # use vm_memory::{Address, GuestAddress, GuestUsize};
///   let mut allocator = SystemAllocator::new(
///           Some(GuestAddress(0x1000)), Some(0x10000),
///           GuestAddress(0x10000000), 0x10000000,
///           5).unwrap();
///    assert_eq!(allocator.allocate_irq(), Some(5));
///    assert_eq!(allocator.allocate_irq(), Some(6));
///    assert_eq!(allocator.allocate_mmio_addresses(None, 0x1000), Some(GuestAddress(0x1fffe000)));
///
/// ```
pub struct SystemAllocator {
    io_address_space: Option<AddressAllocator>,
    mmio_address_space: AddressAllocator,
    next_irq: u32,
}

impl SystemAllocator {
    /// Creates a new `SystemAllocator` for managing addresses and irq numvers.
    /// Can return `None` if `base` + `size` overflows a u64 or if alignment isn't a power
    /// of two.
    ///
    /// * `io_base` - The starting address of IO memory.
    /// * `io_size` - The size of IO memory.
    /// * `mmio_base` - The starting address of MMIO memory.
    /// * `mmio_size` - The size of MMIO memory.
    /// * `first_irq` - The first irq number to give out.
    pub fn new(
        io_base: Option<GuestAddress>,
        io_size: Option<GuestUsize>,
        mmio_base: GuestAddress,
        mmio_size: GuestUsize,
        first_irq: u32,
    ) -> Option<Self> {
        let page_size = pagesize() as u64;
        Some(SystemAllocator {
            io_address_space: if let (Some(b), Some(s)) = (io_base, io_size) {
                Some(AddressAllocator::new(b, s, Some(0x1))?)
            } else {
                None
            },
            mmio_address_space: AddressAllocator::new(mmio_base, mmio_size, Some(page_size))?,
            next_irq: first_irq,
        })
    }

    /// Reserves the next available system irq number.
    pub fn allocate_irq(&mut self) -> Option<u32> {
        if let Some(irq_num) = self.next_irq.checked_add(1) {
            self.next_irq = irq_num;
            Some(irq_num - 1)
        } else {
            None
        }
    }

    /// Reserves a section of `size` bytes of IO address space.
    pub fn allocate_io_addresses(
        &mut self,
        address: GuestAddress,
        size: GuestUsize,
    ) -> Option<GuestAddress> {
        self.io_address_space
            .as_mut()?
            .allocate(Some(address), size)
    }

    /// Reserves a section of `size` bytes of MMIO address space.
    pub fn allocate_mmio_addresses(
        &mut self,
        address: Option<GuestAddress>,
        size: GuestUsize,
    ) -> Option<GuestAddress> {
        self.mmio_address_space.allocate(address, size)
    }

    /// Free an IO address range.
    /// We can only free a range if it matches exactly an already allocated range.
    pub fn free_io_addresses(&mut self, address: GuestAddress, size: GuestUsize) {
        if let Some(io_address) = self.io_address_space.as_mut() {
            io_address.free(address, size)
        }
    }

    /// Free an MMIO address range.
    /// We can only free a range if it matches exactly an already allocated range.
    pub fn free_mmio_addresses(&mut self, address: GuestAddress, size: GuestUsize) {
        self.mmio_address_space.free(address, size)
    }
}