zynq-rs/libconfig/src/sd_reader.rs

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use core_io::{BufRead, Error, ErrorKind, Read, Result as IoResult, Seek, SeekFrom, Write};
use fatfs;
use libboard_zynq::sdio::{sd_card::SdCard, CmdTransferError};
use log::debug;
use alloc::vec::Vec;
const MBR_SIGNATURE: [u8; 2] = [0x55, 0xAA];
const PARTID_FAT12: u8 = 0x01;
const PARTID_FAT16_LESS32M: u8 = 0x04;
const PARTID_FAT16: u8 = 0x06;
const PARTID_FAT32: u8 = 0x0B;
const PARTID_FAT32_LBA: u8 = 0x0C;
const PARTID_FAT16_LBA: u8 = 0x0E;
fn cmd_error_to_io_error(_: CmdTransferError) -> Error {
Error::new(ErrorKind::Other, "Command transfer error")
}
const BLOCK_SIZE: usize = 512;
/// SdReader struct implementing `Read + BufRead + Write + Seek` traits for `core_io`.
/// Used as an adaptor for fatfs crate, but could be used directly for raw data access.
///
/// Implementation: all read/writes would be split into unaligned and block-aligned parts,
/// unaligned read/writes would do a buffered read/write using a block-sized internal buffer,
/// while aligned transactions would be sent to the SD card directly for performance reason.
pub struct SdReader {
/// Internal SdCard handle.
sd: SdCard,
/// Read buffer with the size of 1 block.
buffer: Vec<u8>,
/// Address for the next byte.
byte_addr: u32,
/// Internal index for the next byte.
/// Normally in range `[0, BLOCK_SIZE - 1]`.
///
/// `index = BLOCK_SIZE` means that the `buffer` is invalid for the current `byte_addr`,
/// the next `fill_buf` call would fill the buffer.
index: usize,
/// Dirty flag indicating the content has to be flushed.
dirty: bool,
/// Base offset for translation from logical address to physical address.
offset: u32,
}
#[derive(Copy, Clone)]
#[allow(unused)]
// Partition entry enum, normally we would use entry1.
pub enum PartitionEntry {
Entry1 = 0x1BE,
Entry2 = 0x1CE,
Entry3 = 0x1DE,
Entry4 = 0x1EE,
}
impl SdReader {
/// Create SdReader from SdCard
pub fn new(sd: SdCard) -> SdReader {
let mut vec: Vec<u8> = Vec::with_capacity(BLOCK_SIZE);
unsafe {
vec.set_len(vec.capacity());
}
SdReader {
sd,
buffer: vec,
byte_addr: 0,
index: BLOCK_SIZE,
dirty: false,
offset: 0,
}
}
/// Internal read function for unaligned read.
/// The read must not cross block boundary.
fn read_unaligned(&mut self, buf: &mut [u8]) -> IoResult<usize> {
if buf.len() == 0 {
return Ok(0);
}
let filled_buffer = self.fill_buf()?;
for (dest, src) in buf.iter_mut().zip(filled_buffer.iter()) {
*dest = *src;
}
self.consume(buf.len());
Ok(buf.len())
}
/// Internal write function for unaligned write.
/// The write must not cross block boundary.
fn write_unaligned(&mut self, buf: &[u8]) -> IoResult<usize> {
if buf.len() == 0 {
return Ok(0);
}
// update buffer if needed, as we will flush the entire block later.
self.fill_buf()?;
self.dirty = true;
let dest_buffer = &mut self.buffer[self.index..];
for (src, dest) in buf.iter().zip(dest_buffer.iter_mut()) {
*dest = *src;
}
self.consume(buf.len());
Ok(buf.len())
}
/// Split the slice into three segments, with the middle block-aligned.
/// Alignment depends on the current `self.byte_addr` instead of the slice pointer address
fn block_align<'b>(&self, buf: &'b [u8]) -> (&'b [u8], &'b [u8], &'b [u8]) {
let head_len = BLOCK_SIZE - (self.byte_addr as usize % BLOCK_SIZE);
if head_len > buf.len() {
(buf, &[], &[])
} else {
let remaining_length = buf.len() - head_len;
let mid_length = remaining_length - remaining_length % BLOCK_SIZE;
let (head, remaining) = buf.split_at(head_len);
let (mid, tail) = remaining.split_at(mid_length);
(head, mid, tail)
}
}
/// Split the mutable slice into three segments, with the middle block-aligned.
/// Alignment depends on the current `self.byte_addr` instead of the slice pointer address
fn block_align_mut<'b>(&self, buf: &'b mut [u8]) -> (&'b mut [u8], &'b mut [u8], &'b mut [u8]) {
let head_len = BLOCK_SIZE - (self.byte_addr as usize % BLOCK_SIZE);
if head_len > buf.len() {
(buf, &mut [], &mut [])
} else {
let remaining_length = buf.len() - head_len;
let mid_length = remaining_length - remaining_length % BLOCK_SIZE;
let (head, remaining) = buf.split_at_mut(head_len);
let (mid, tail) = remaining.split_at_mut(mid_length);
(head, mid, tail)
}
}
/// Invalidate the buffer, so later unaligned read/write would reload the buffer from SD card.
fn invalidate_buffer(&mut self) {
self.index = BLOCK_SIZE;
}
/// Set the base offset of the SD card, to transform from physical address to logical address.
fn set_base_offset(&mut self, offset: u32) -> IoResult<u64> {
self.offset = offset;
self.seek(SeekFrom::Start(0))
}
/// Mount fatfs from partition entry, and return the fatfs object if success.
/// This takes the ownership of self, so currently there is no way to recover from an error,
/// except creating a new SD card instance.
pub fn mount_fatfs(mut self, entry: PartitionEntry) -> IoResult<fatfs::FileSystem<Self>> {
let mut buffer: [u8; 4] = [0; 4];
self.seek(SeekFrom::Start(0x1FE))?;
self.read_exact(&mut buffer[..2])?;
// check MBR signature
if buffer[..2] != MBR_SIGNATURE {
return Err(Error::new(
ErrorKind::InvalidData,
"Incorrect signature for MBR sector.",
));
}
// Read partition ID.
self.seek(SeekFrom::Start(entry as u64 + 0x4))?;
self.read_exact(&mut buffer[..1])?;
debug!("Partition ID: {:0X}", buffer[0]);
match buffer[0] {
PARTID_FAT12 | PARTID_FAT16_LESS32M | PARTID_FAT16 |
PARTID_FAT16_LBA | PARTID_FAT32 | PARTID_FAT32_LBA => {}
_ => {
return Err(Error::new(
ErrorKind::InvalidData,
"No FAT partition found for the specified entry.",
));
}
}
// Read LBA
self.seek(SeekFrom::Current(0x3))?;
self.read_exact(&mut buffer)?;
let mut lba: u32 = 0;
// Little endian
for i in 0..4 {
lba |= (buffer[i] as u32) << (i * 8);
}
// Set to logical address
self.set_base_offset(lba * BLOCK_SIZE as u32)?;
// setup fatfs
fatfs::FileSystem::new(self, fatfs::FsOptions::new())
}
}
impl Read for SdReader {
fn read(&mut self, buf: &mut [u8]) -> IoResult<usize> {
let total_length = buf.len();
let (a, b, c) = self.block_align_mut(buf);
self.read_unaligned(a)?;
if b.len() > 0 {
// invalidate internal buffer
self.invalidate_buffer();
if let Err(_) = self.sd.read_block(
self.byte_addr / BLOCK_SIZE as u32,
(b.len() / BLOCK_SIZE) as u16,
b,
) {
// we have to allow partial read, as per the trait required
return Ok(a.len());
}
self.byte_addr += b.len() as u32;
}
if let Err(_) = self.read_unaligned(c) {
// we have to allow partial read, as per the trait required
return Ok(a.len() + b.len());
}
Ok(total_length)
}
}
impl BufRead for SdReader {
fn fill_buf(&mut self) -> IoResult<&[u8]> {
if self.index == BLOCK_SIZE {
// flush the buffer if it is dirty before overwriting it with new data
if self.dirty {
self.flush()?;
}
// reload buffer
self.sd
.read_block(self.byte_addr / (BLOCK_SIZE as u32), 1, &mut self.buffer)
.map_err(cmd_error_to_io_error)?;
self.index = (self.byte_addr as usize) % BLOCK_SIZE;
}
Ok(&self.buffer[self.index..])
}
fn consume(&mut self, amt: usize) {
self.index += amt;
self.byte_addr += amt as u32;
}
}
impl Write for SdReader {
fn write(&mut self, buf: &[u8]) -> IoResult<usize> {
let (a, b, c) = self.block_align(buf);
self.write_unaligned(a)?;
if b.len() > 0 {
self.flush()?;
self.invalidate_buffer();
if let Err(_) = self.sd.write_block(
self.byte_addr / BLOCK_SIZE as u32,
(b.len() / BLOCK_SIZE) as u16,
b,
) {
return Ok(a.len());
}
self.byte_addr += b.len() as u32;
}
if let Err(_) = self.write_unaligned(c) {
return Ok(a.len() + b.len());
}
Ok(buf.len())
}
fn flush(&mut self) -> IoResult<()> {
if self.dirty {
let block_addr = (self.byte_addr - self.index as u32) / (BLOCK_SIZE as u32);
self.sd
.write_block(block_addr, 1, &self.buffer)
.map_err(cmd_error_to_io_error)?;
self.dirty = false;
}
Ok(())
}
}
impl Seek for SdReader {
fn seek(&mut self, pos: SeekFrom) -> IoResult<u64> {
let raw_target = match pos {
SeekFrom::Start(x) => self.offset as i64 + x as i64,
SeekFrom::Current(x) => self.byte_addr as i64 + x,
SeekFrom::End(_) => panic!("SD card does not support seek from end"),
};
if raw_target < self.offset as i64 || raw_target > core::u32::MAX as i64 {
return Err(Error::new(ErrorKind::InvalidInput, "Invalid address"));
}
let target_byte_addr = raw_target as u32;
let address_same_block =
self.byte_addr / (BLOCK_SIZE as u32) == target_byte_addr / (BLOCK_SIZE as u32);
// if the buffer was invalidated, we consider seek as different block
let same_block = address_same_block && self.index != BLOCK_SIZE;
if !same_block {
self.flush()?;
}
self.byte_addr = target_byte_addr;
self.index = if same_block {
target_byte_addr as usize % BLOCK_SIZE
} else {
// invalidate the buffer as we moved to a different block
BLOCK_SIZE
};
Ok((self.byte_addr - self.offset) as u64)
}
}
impl Drop for SdReader {
fn drop(&mut self) {
// just try to flush it, ignore error if any
self.flush().unwrap_or(());
}
}