// Copyright 2025 Google

// SPDX-License-Identifier: MIT

use std::ffi::CString;

use crate::sys::platform::page_size;

use crate::sys::platform::SharedMemory as PlatformSharedMemory;

use crate::AsRawDescriptor;

use crate::FromRawDescriptor;

use crate::IntoRawDescriptor;

use crate::MesaError;

use crate::MesaResult;

use crate::OwnedDescriptor;

use crate::RawDescriptor;

pub struct SharedMemory(pub(crate) PlatformSharedMemory);

impl SharedMemory {

    /// Creates a new shared memory object of the given size.

    ///

    /// |name| is purely for debugging purposes. It does not need to be unique, and it does

    /// not affect any non-debugging related properties of the constructed shared memory.

    pub fn new<T: Into<Vec<u8>>>(debug_name: T, size: u64) -> MesaResult<SharedMemory> {

        let debug_name = CString::new(debug_name)?;

        PlatformSharedMemory::new(&debug_name, size).map(SharedMemory)

    }

Unexecuted instantiation: <mesa3d_util::shm::SharedMemory>::new::<&str>

Unexecuted instantiation: <mesa3d_util::shm::SharedMemory>::new::<_>

    pub fn size(&self) -> u64 {

        self.0.size()

    }

}

impl AsRawDescriptor for SharedMemory {

    fn as_raw_descriptor(&self) -> RawDescriptor {

        self.0.as_raw_descriptor()

    }

}

impl IntoRawDescriptor for SharedMemory {

    fn into_raw_descriptor(self) -> RawDescriptor {

        self.0.into_raw_descriptor()

    }

}

impl From<SharedMemory> for OwnedDescriptor {

    fn from(sm: SharedMemory) -> OwnedDescriptor {

        // SAFETY:

        // Safe because we own the SharedMemory at this point.

        unsafe { OwnedDescriptor::from_raw_descriptor(sm.into_raw_descriptor()) }

    }

}

/// Uses the system's page size in bytes to round the given value up to the nearest page boundary.

pub fn round_up_to_page_size(v: u64) -> MesaResult<u64> {

    v.checked_next_multiple_of(page_size()? as _)

        .ok_or(MesaError::WithContext("rounding up caused overflow"))

}