forked from M-Labs/nac3
add SD card FAT filesystem interface
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e77cb5de7e
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1138db34a2
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@ -11,6 +11,7 @@ use log::info;
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use libboard_zynq::{timer::GlobalTimer, logger, devc};
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use libsupport_zynq::ram;
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mod sd_reader;
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mod proto_core_io;
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mod proto_async;
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mod comms;
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@ -0,0 +1,286 @@
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use core_io::{BufRead, Error, ErrorKind, Read, Result as IoResult, Seek, SeekFrom, Write};
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use fatfs;
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use libboard_zynq::sdio::{sd_card::SdCard, CmdTransferError};
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fn cmd_error_to_io_error(_: CmdTransferError) -> Error {
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Error::new(ErrorKind::Other, "Command transfer error")
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}
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const BLOCK_SIZE: usize = 512;
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/// SdReader struct implementing `Read + BufRead + Write + Seek` traits for `core_io`.
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/// Used as an adaptor for fatfs crate, but could be used directly for raw data access.
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///
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/// Implementation: all read/writes would be split into unaligned and block-aligned parts,
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/// unaligned read/writes would do a buffered read/write using a block-sized internal buffer,
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/// while aligned transactions would be sent to the SD card directly for performance reason.
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pub struct SdReader<'a> {
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/// Internal SdCard handle.
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sd: &'a mut SdCard,
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/// Read buffer with the size of 1 block.
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buffer: [u8; BLOCK_SIZE],
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/// Address for the next byte.
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byte_addr: u32,
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/// Internal index for the next byte.
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/// Normally in range `[0, BLOCK_SIZE - 1]`.
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///
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/// `index = BLOCK_SIZE` means that the `buffer` is invalid for the current `byte_addr`,
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/// the next `fill_buf` call would fill the buffer.
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index: usize,
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/// Dirty flag indicating the content has to be flushed.
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dirty: bool,
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/// Base offset for translation from logical address to physical address.
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offset: u32,
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}
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#[derive(Copy, Clone)]
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#[allow(unused)]
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// Partition entry enum, normally we would use entry1.
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pub enum PartitionEntry {
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Entry1 = 0x1BE,
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Entry2 = 0x1CE,
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Entry3 = 0x1DE,
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Entry4 = 0x1EE,
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}
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impl<'a> SdReader<'a> {
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/// Create SdReader from SdCard
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pub fn new(sd: &'a mut SdCard) -> SdReader<'a> {
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SdReader {
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sd,
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buffer: [0; BLOCK_SIZE],
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byte_addr: 0,
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index: BLOCK_SIZE,
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dirty: false,
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offset: 0,
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}
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}
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/// Internal read function for unaligned read.
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/// The read must not cross block boundary.
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fn read_unaligned(&mut self, buf: &mut [u8]) -> IoResult<usize> {
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if buf.len() == 0 {
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return Ok(0);
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}
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let filled_buffer = self.fill_buf()?;
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for (dest, src) in buf.iter_mut().zip(filled_buffer.iter()) {
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*dest = *src;
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}
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self.consume(buf.len());
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Ok(buf.len())
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}
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/// Internal write function for unaligned write.
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/// The write must not cross block boundary.
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fn write_unaligned(&mut self, buf: &[u8]) -> IoResult<usize> {
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if buf.len() == 0 {
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return Ok(0);
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}
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// update buffer if needed, as we will flush the entire block later.
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self.fill_buf()?;
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self.dirty = true;
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let dest_buffer = &mut self.buffer[self.index..];
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for (src, dest) in buf.iter().zip(dest_buffer.iter_mut()) {
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*dest = *src;
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}
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self.consume(buf.len());
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Ok(buf.len())
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}
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/// Split the slice into three segments, with the middle block-aligned.
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/// Alignment depends on the current `self.byte_addr` instead of the slice pointer address
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fn block_align<'b>(&self, buf: &'b [u8]) -> (&'b [u8], &'b [u8], &'b [u8]) {
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let head_len = BLOCK_SIZE - (self.byte_addr as usize % BLOCK_SIZE);
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if head_len > buf.len() {
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(buf, &[], &[])
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} else {
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let remaining_length = buf.len() - head_len;
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let mid_length = remaining_length - remaining_length % BLOCK_SIZE;
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let (head, remaining) = buf.split_at(head_len);
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let (mid, tail) = remaining.split_at(mid_length);
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(head, mid, tail)
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}
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}
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/// Split the mutable slice into three segments, with the middle block-aligned.
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/// Alignment depends on the current `self.byte_addr` instead of the slice pointer address
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fn block_align_mut<'b>(&self, buf: &'b mut [u8]) -> (&'b mut [u8], &'b mut [u8], &'b mut [u8]) {
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let head_len = BLOCK_SIZE - (self.byte_addr as usize % BLOCK_SIZE);
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if head_len > buf.len() {
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(buf, &mut [], &mut [])
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} else {
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let remaining_length = buf.len() - head_len;
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let mid_length = remaining_length - remaining_length % BLOCK_SIZE;
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let (head, remaining) = buf.split_at_mut(head_len);
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let (mid, tail) = remaining.split_at_mut(mid_length);
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(head, mid, tail)
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}
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}
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/// Invalidate the buffer, so later unaligned read/write would reload the buffer from SD card.
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fn invalidate_buffer(&mut self) {
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self.index = BLOCK_SIZE;
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}
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/// Set the base offset of the SD card, to transform from physical address to logical address.
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fn set_base_offset(&mut self, offset: u32) -> IoResult<u64> {
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self.offset = offset;
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self.seek(SeekFrom::Start(0))
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}
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/// Mount fatfs from partition entry, and return the fatfs object if success.
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/// This takes the ownership of self, so currently there is no way to recover from an error,
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/// except creating a new SD card instance.
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pub fn mount_fatfs(mut self, entry: PartitionEntry) -> IoResult<fatfs::FileSystem<Self>> {
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let mut buffer: [u8; 4] = [0; 4];
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self.seek(SeekFrom::Start(0x1FE))?;
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self.read_exact(&mut buffer[..2])?;
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// check MBR signature
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if buffer[0] != 0x55 || buffer[1] != 0xAA {
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return Err(Error::new(
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ErrorKind::InvalidData,
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"Incorrect signature for MBR sector.",
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));
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}
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// Read partition ID.
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self.seek(SeekFrom::Start(entry as u64 + 0x4))?;
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self.read_exact(&mut buffer[..1])?;
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match buffer[0] {
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0x01 | 0x04 | 0x06 | 0x0B => (),
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_ => {
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return Err(Error::new(
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ErrorKind::InvalidData,
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"No FAT partition found for the specified entry.",
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))
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}
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};
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// Read LBA
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self.seek(SeekFrom::Current(0x3))?;
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self.read_exact(&mut buffer)?;
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let mut lba: u32 = 0;
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// Little endian
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for i in 0..4 {
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lba |= (buffer[i] as u32) << (i * 8);
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}
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// Set to logical address
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self.set_base_offset(lba * BLOCK_SIZE as u32)?;
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// setup fatfs
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fatfs::FileSystem::new(self, fatfs::FsOptions::new())
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}
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}
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impl<'a> Read for SdReader<'a> {
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fn read(&mut self, buf: &mut [u8]) -> IoResult<usize> {
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let total_length = buf.len();
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let (a, b, c) = self.block_align_mut(buf);
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self.read_unaligned(a)?;
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if b.len() > 0 {
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// invalidate internal buffer
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self.invalidate_buffer();
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if let Err(_) = self.sd.read_block(
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self.byte_addr / BLOCK_SIZE as u32,
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(b.len() / BLOCK_SIZE) as u16,
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b,
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) {
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// we have to allow partial read, as per the trait required
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return Ok(a.len());
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}
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}
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if let Err(_) = self.read_unaligned(c) {
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// we have to allow partial read, as per the trait required
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return Ok(a.len() + b.len());
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}
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Ok(total_length)
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}
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}
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impl<'a> BufRead for SdReader<'a> {
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fn fill_buf(&mut self) -> IoResult<&[u8]> {
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if self.index == BLOCK_SIZE {
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// flush the buffer if it is dirty before overwriting it with new data
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if self.dirty {
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self.flush()?;
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}
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// reload buffer
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self.sd
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.read_block(self.byte_addr / (BLOCK_SIZE as u32), 1, &mut self.buffer)
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.map_err(cmd_error_to_io_error)?;
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self.index = (self.byte_addr as usize) % BLOCK_SIZE;
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}
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Ok(&self.buffer[self.index..])
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}
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fn consume(&mut self, amt: usize) {
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self.index += amt;
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self.byte_addr += amt as u32;
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}
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}
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impl<'a> Write for SdReader<'a> {
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fn write(&mut self, buf: &[u8]) -> IoResult<usize> {
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let (a, b, c) = self.block_align(buf);
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self.write_unaligned(a)?;
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if b.len() > 0 {
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self.invalidate_buffer();
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if let Err(_) = self.sd.write_block(
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self.byte_addr / BLOCK_SIZE as u32,
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(b.len() / BLOCK_SIZE) as u16,
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b,
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) {
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return Ok(a.len());
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}
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}
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if let Err(_) = self.write_unaligned(c) {
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return Ok(a.len() + b.len());
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}
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Ok(buf.len())
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}
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fn flush(&mut self) -> IoResult<()> {
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if self.dirty {
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let block_addr = (self.byte_addr - self.index as u32) / (BLOCK_SIZE as u32);
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self.sd
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.write_block(block_addr, 1, &self.buffer)
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.map_err(cmd_error_to_io_error)?;
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self.dirty = false;
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}
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Ok(())
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}
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}
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impl<'a> Seek for SdReader<'a> {
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fn seek(&mut self, pos: SeekFrom) -> IoResult<u64> {
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let raw_target = match pos {
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SeekFrom::Start(x) => self.offset as i64 + x as i64,
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SeekFrom::Current(x) => self.byte_addr as i64 + x,
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SeekFrom::End(_) => panic!("SD card does not support seek from end"),
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};
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if raw_target < self.offset as i64 || raw_target > core::u32::MAX as i64 {
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return Err(Error::new(ErrorKind::InvalidInput, "Invalid address"));
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}
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let target_byte_addr = raw_target as u32;
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let address_same_block =
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self.byte_addr / (BLOCK_SIZE as u32) == target_byte_addr / (BLOCK_SIZE as u32);
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// if the buffer was invalidated, we consider seek as different block
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let same_block = address_same_block && self.index != BLOCK_SIZE;
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if !same_block {
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self.flush()?;
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}
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self.byte_addr = target_byte_addr;
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self.index = if same_block {
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target_byte_addr as usize % BLOCK_SIZE
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} else {
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// invalidate the buffer as we moved to a different block
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BLOCK_SIZE
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};
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Ok((self.byte_addr - self.offset) as u64)
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}
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}
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impl<'a> Drop for SdReader<'a> {
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fn drop(&mut self) {
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// just try to flush it, ignore error if any
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self.flush().unwrap_or(());
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}
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}
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