alex/beta-minecraft-rust

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use crate::error::{Error, Result};
use crate::tlsf::Tlsf;

/// TLSF allocator over an abstract range, e.g. descriptor slots inside a [`DescriptorHeap`](crate::DescriptorHeap)
/// or sub-ranges of a large buffer. No Vulkan memory is involved.
pub struct VirtualBlock(Tlsf);

/// A range handed out by a [`VirtualBlock`]. Must be returned to the block it came from.
#[derive(Debug, PartialEq, Eq, Hash)]
pub struct VirtualAllocation {
    node: u32,
    offset: u64,
}

impl VirtualAllocation {
    #[inline]
    pub fn offset(&self) -> u64 {
        self.offset
    }
}

impl VirtualBlock {
    pub fn new(size: u64) -> Result<Self> {
        if size == 0 {
            return Err(Error::ZeroSize);
        }
        Ok(Self(Tlsf::new(size, 1)))
    }

    #[inline]
    pub fn allocate(&mut self, size: u64, alignment: u64) -> Result<VirtualAllocation> {
        if size == 0 {
            return Err(Error::ZeroSize);
        }
        if !alignment.is_power_of_two() {
            return Err(Error::InvalidAlignment(alignment));
        }
        let (node, offset) = self
            .0
            .allocate(size, alignment, 0)
            .ok_or(Error::OutOfMemory)?;
        Ok(VirtualAllocation { node, offset })
    }

    #[inline]
    pub fn free(&mut self, allocation: VirtualAllocation) {
        self.0.free(allocation.node);
    }

    #[inline]
    pub fn allocation_size(&self, allocation: &VirtualAllocation) -> u64 {
        self.0.allocation_size(allocation.node)
    }

    #[inline]
    pub fn size(&self) -> u64 {
        self.0.size()
    }

    #[inline]
    pub fn free_bytes(&self) -> u64 {
        self.0.free_bytes()
    }

    #[inline]
    pub fn allocation_count(&self) -> u32 {
        self.0.allocation_count()
    }

    #[inline]
    pub fn is_empty(&self) -> bool {
        self.0.is_empty()
    }

    /// Checks all internal invariants, panicking on corruption. Intended for tests.
    #[doc(hidden)]
    pub fn validate(&self) {
        self.0.validate();
    }
}