1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139

use embassy_sync::blocking_mutex::raw::RawMutex;
use embassy_sync::mutex::Mutex;
use embedded_storage::nor_flash::ErrorType;
use embedded_storage_async::nor_flash::{NorFlash, ReadNorFlash};

use super::Error;

/// A logical partition of an underlying shared flash
///
/// A partition holds an offset and a size of the flash,
/// and is restricted to operate with that range.
/// There is no guarantee that muliple partitions on the same flash
/// operate on mutually exclusive ranges - such a separation is up to
/// the user to guarantee.
pub struct Partition<'a, M: RawMutex, T: NorFlash> {
    flash: &'a Mutex<M, T>,
    offset: u32,
    size: u32,
}

impl<'a, M: RawMutex, T: NorFlash> Partition<'a, M, T> {
    /// Create a new partition
    pub const fn new(flash: &'a Mutex<M, T>, offset: u32, size: u32) -> Self {
        if offset % T::READ_SIZE as u32 != 0 || offset % T::WRITE_SIZE as u32 != 0 || offset % T::ERASE_SIZE as u32 != 0
        {
            panic!("Partition offset must be a multiple of read, write and erase size");
        }
        if size % T::READ_SIZE as u32 != 0 || size % T::WRITE_SIZE as u32 != 0 || size % T::ERASE_SIZE as u32 != 0 {
            panic!("Partition size must be a multiple of read, write and erase size");
        }
        Self { flash, offset, size }
    }

    /// Get the partition offset within the flash
    pub const fn offset(&self) -> u32 {
        self.offset
    }

    /// Get the partition size
    pub const fn size(&self) -> u32 {
        self.size
    }
}

impl<M: RawMutex, T: NorFlash> ErrorType for Partition<'_, M, T> {
    type Error = Error<T::Error>;
}

impl<M: RawMutex, T: NorFlash> ReadNorFlash for Partition<'_, M, T> {
    const READ_SIZE: usize = T::READ_SIZE;

    async fn read(&mut self, offset: u32, bytes: &mut [u8]) -> Result<(), Self::Error> {
        if offset + bytes.len() as u32 > self.size {
            return Err(Error::OutOfBounds);
        }

        let mut flash = self.flash.lock().await;
        flash.read(self.offset + offset, bytes).await.map_err(Error::Flash)
    }

    fn capacity(&self) -> usize {
        self.size as usize
    }
}

impl<M: RawMutex, T: NorFlash> NorFlash for Partition<'_, M, T> {
    const WRITE_SIZE: usize = T::WRITE_SIZE;
    const ERASE_SIZE: usize = T::ERASE_SIZE;

    async fn write(&mut self, offset: u32, bytes: &[u8]) -> Result<(), Self::Error> {
        if offset + bytes.len() as u32 > self.size {
            return Err(Error::OutOfBounds);
        }

        let mut flash = self.flash.lock().await;
        flash.write(self.offset + offset, bytes).await.map_err(Error::Flash)
    }

    async fn erase(&mut self, from: u32, to: u32) -> Result<(), Self::Error> {
        if to > self.size {
            return Err(Error::OutOfBounds);
        }

        let mut flash = self.flash.lock().await;
        flash
            .erase(self.offset + from, self.offset + to)
            .await
            .map_err(Error::Flash)
    }
}

#[cfg(test)]
mod tests {
    use embassy_sync::blocking_mutex::raw::NoopRawMutex;

    use super::*;
    use crate::flash::mem_flash::MemFlash;

    #[futures_test::test]
    async fn can_read() {
        let mut flash = MemFlash::<1024, 128, 4>::default();
        flash.mem[132..132 + 8].fill(0xAA);

        let flash = Mutex::<NoopRawMutex, _>::new(flash);
        let mut partition = Partition::new(&flash, 128, 256);

        let mut read_buf = [0; 8];
        partition.read(4, &mut read_buf).await.unwrap();

        assert!(read_buf.iter().position(|&x| x != 0xAA).is_none());
    }

    #[futures_test::test]
    async fn can_write() {
        let flash = MemFlash::<1024, 128, 4>::default();

        let flash = Mutex::<NoopRawMutex, _>::new(flash);
        let mut partition = Partition::new(&flash, 128, 256);

        let write_buf = [0xAA; 8];
        partition.write(4, &write_buf).await.unwrap();

        let flash = flash.try_lock().unwrap();
        assert!(flash.mem[132..132 + 8].iter().position(|&x| x != 0xAA).is_none());
    }

    #[futures_test::test]
    async fn can_erase() {
        let flash = MemFlash::<1024, 128, 4>::new(0x00);

        let flash = Mutex::<NoopRawMutex, _>::new(flash);
        let mut partition = Partition::new(&flash, 128, 256);

        partition.erase(0, 128).await.unwrap();

        let flash = flash.try_lock().unwrap();
        assert!(flash.mem[128..256].iter().position(|&x| x != 0xFF).is_none());
    }
}