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use alloc::string::String;
use core::convert::TryInto;
use core::fmt;
use core::marker::PhantomData;
use crate::pod::{from_bytes, slice_from_bytes, Pod};
use crate::ReadRef;
/// A newtype for byte slices.
///
/// It has these important features:
/// - no methods that can panic, such as `Index`
/// - convenience methods for `Pod` types
/// - a useful `Debug` implementation
#[derive(Default, Clone, Copy, PartialEq, Eq)]
pub struct Bytes<'data>(pub &'data [u8]);
impl<'data> fmt::Debug for Bytes<'data> {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
debug_list_bytes(self.0, fmt)
}
}
impl<'data> Bytes<'data> {
/// Return the length of the byte slice.
#[inline]
pub fn len(&self) -> usize {
self.0.len()
}
/// Return true if the byte slice is empty.
#[inline]
pub fn is_empty(&self) -> bool {
self.0.is_empty()
}
/// Skip over the given number of bytes at the start of the byte slice.
///
/// Modifies the byte slice to start after the bytes.
///
/// Returns an error if there are too few bytes.
#[inline]
pub fn skip(&mut self, offset: usize) -> Result<(), ()> {
match self.0.get(offset..) {
Some(tail) => {
self.0 = tail;
Ok(())
}
None => {
self.0 = &[];
Err(())
}
}
}
/// Return a reference to the given number of bytes at the start of the byte slice.
///
/// Modifies the byte slice to start after the bytes.
///
/// Returns an error if there are too few bytes.
#[inline]
pub fn read_bytes(&mut self, count: usize) -> Result<Bytes<'data>, ()> {
match (self.0.get(..count), self.0.get(count..)) {
(Some(head), Some(tail)) => {
self.0 = tail;
Ok(Bytes(head))
}
_ => {
self.0 = &[];
Err(())
}
}
}
/// Return a reference to the given number of bytes at the given offset of the byte slice.
///
/// Returns an error if the offset is invalid or there are too few bytes.
#[inline]
pub fn read_bytes_at(mut self, offset: usize, count: usize) -> Result<Bytes<'data>, ()> {
self.skip(offset)?;
self.read_bytes(count)
}
/// Return a reference to a `Pod` struct at the start of the byte slice.
///
/// Modifies the byte slice to start after the bytes.
///
/// Returns an error if there are too few bytes or the slice is incorrectly aligned.
#[inline]
pub fn read<T: Pod>(&mut self) -> Result<&'data T, ()> {
match from_bytes(self.0) {
Ok((value, tail)) => {
self.0 = tail;
Ok(value)
}
Err(()) => {
self.0 = &[];
Err(())
}
}
}
/// Return a reference to a `Pod` struct at the given offset of the byte slice.
///
/// Returns an error if there are too few bytes or the offset is incorrectly aligned.
#[inline]
pub fn read_at<T: Pod>(mut self, offset: usize) -> Result<&'data T, ()> {
self.skip(offset)?;
self.read()
}
/// Return a reference to a slice of `Pod` structs at the start of the byte slice.
///
/// Modifies the byte slice to start after the bytes.
///
/// Returns an error if there are too few bytes or the offset is incorrectly aligned.
#[inline]
pub fn read_slice<T: Pod>(&mut self, count: usize) -> Result<&'data [T], ()> {
match slice_from_bytes(self.0, count) {
Ok((value, tail)) => {
self.0 = tail;
Ok(value)
}
Err(()) => {
self.0 = &[];
Err(())
}
}
}
/// Return a reference to a slice of `Pod` structs at the given offset of the byte slice.
///
/// Returns an error if there are too few bytes or the offset is incorrectly aligned.
#[inline]
pub fn read_slice_at<T: Pod>(mut self, offset: usize, count: usize) -> Result<&'data [T], ()> {
self.skip(offset)?;
self.read_slice(count)
}
/// Read a null terminated string.
///
/// Does not assume any encoding.
/// Reads past the null byte, but doesn't return it.
#[inline]
pub fn read_string(&mut self) -> Result<&'data [u8], ()> {
match memchr::memchr(b'\0', self.0) {
Some(null) => {
// These will never fail.
let bytes = self.read_bytes(null)?;
self.skip(1)?;
Ok(bytes.0)
}
None => {
self.0 = &[];
Err(())
}
}
}
/// Read a null terminated string at an offset.
///
/// Does not assume any encoding. Does not return the null byte.
#[inline]
pub fn read_string_at(mut self, offset: usize) -> Result<&'data [u8], ()> {
self.skip(offset)?;
self.read_string()
}
/// Read an unsigned LEB128 number.
pub fn read_uleb128(&mut self) -> Result<u64, ()> {
let mut result = 0;
let mut shift = 0;
loop {
let byte = *self.read::<u8>()?;
if shift == 63 && byte != 0x00 && byte != 0x01 {
return Err(());
}
result |= u64::from(byte & 0x7f) << shift;
shift += 7;
if byte & 0x80 == 0 {
return Ok(result);
}
}
}
/// Read a signed LEB128 number.
pub fn read_sleb128(&mut self) -> Result<i64, ()> {
let mut result = 0;
let mut shift = 0;
loop {
let byte = *self.read::<u8>()?;
if shift == 63 && byte != 0x00 && byte != 0x7f {
return Err(());
}
result |= i64::from(byte & 0x7f) << shift;
shift += 7;
if byte & 0x80 == 0 {
if shift < 64 && (byte & 0x40) != 0 {
// Sign extend the result.
result |= !0 << shift;
}
return Ok(result);
}
}
}
}
// Only for Debug impl of `Bytes`.
fn debug_list_bytes(bytes: &[u8], fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut list = fmt.debug_list();
list.entries(bytes.iter().take(8).copied().map(DebugByte));
if bytes.len() > 8 {
list.entry(&DebugLen(bytes.len()));
}
list.finish()
}
struct DebugByte(u8);
impl fmt::Debug for DebugByte {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(fmt, "0x{:02x}", self.0)
}
}
struct DebugLen(usize);
impl fmt::Debug for DebugLen {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(fmt, "...; {}", self.0)
}
}
/// A newtype for byte strings.
///
/// For byte slices that are strings of an unknown encoding.
///
/// Provides a `Debug` implementation that interprets the bytes as UTF-8.
#[derive(Default, Clone, Copy, PartialEq, Eq)]
pub(crate) struct ByteString<'data>(pub &'data [u8]);
impl<'data> fmt::Debug for ByteString<'data> {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(fmt, "\"{}\"", String::from_utf8_lossy(self.0))
}
}
#[allow(dead_code)]
#[inline]
pub(crate) fn align(offset: usize, size: usize) -> usize {
(offset + (size - 1)) & !(size - 1)
}
#[allow(dead_code)]
pub(crate) fn data_range(
data: &[u8],
data_address: u64,
range_address: u64,
size: u64,
) -> Option<&[u8]> {
let offset = range_address.checked_sub(data_address)?;
data.get(offset.try_into().ok()?..)?
.get(..size.try_into().ok()?)
}
/// A table of zero-terminated strings.
///
/// This is used for most file formats.
#[derive(Debug, Clone, Copy)]
pub struct StringTable<'data, R = &'data [u8]>
where
R: ReadRef<'data>,
{
data: Option<R>,
start: u64,
end: u64,
marker: PhantomData<&'data ()>,
}
impl<'data, R: ReadRef<'data>> StringTable<'data, R> {
/// Interpret the given data as a string table.
pub fn new(data: R, start: u64, end: u64) -> Self {
StringTable {
data: Some(data),
start,
end,
marker: PhantomData,
}
}
/// Return the string at the given offset.
pub fn get(&self, offset: u32) -> Result<&'data [u8], ()> {
match self.data {
Some(data) => {
let r_start = self.start.checked_add(offset.into()).ok_or(())?;
data.read_bytes_at_until(r_start..self.end, 0)
}
None => Err(()),
}
}
}
impl<'data, R: ReadRef<'data>> Default for StringTable<'data, R> {
fn default() -> Self {
StringTable {
data: None,
start: 0,
end: 0,
marker: PhantomData,
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::pod::bytes_of;
#[test]
fn bytes() {
let x = u32::to_be(0x0123_4567);
let data = Bytes(bytes_of(&x));
let mut bytes = data;
assert_eq!(bytes.skip(0), Ok(()));
assert_eq!(bytes, data);
let mut bytes = data;
assert_eq!(bytes.skip(4), Ok(()));
assert_eq!(bytes, Bytes(&[]));
let mut bytes = data;
assert_eq!(bytes.skip(5), Err(()));
assert_eq!(bytes, Bytes(&[]));
let mut bytes = data;
assert_eq!(bytes.read_bytes(0), Ok(Bytes(&[])));
assert_eq!(bytes, data);
let mut bytes = data;
assert_eq!(bytes.read_bytes(4), Ok(data));
assert_eq!(bytes, Bytes(&[]));
let mut bytes = data;
assert_eq!(bytes.read_bytes(5), Err(()));
assert_eq!(bytes, Bytes(&[]));
assert_eq!(data.read_bytes_at(0, 0), Ok(Bytes(&[])));
assert_eq!(data.read_bytes_at(4, 0), Ok(Bytes(&[])));
assert_eq!(data.read_bytes_at(0, 4), Ok(data));
assert_eq!(data.read_bytes_at(1, 4), Err(()));
let mut bytes = data;
assert_eq!(bytes.read::<u16>(), Ok(&u16::to_be(0x0123)));
assert_eq!(bytes, Bytes(&[0x45, 0x67]));
assert_eq!(data.read_at::<u16>(2), Ok(&u16::to_be(0x4567)));
assert_eq!(data.read_at::<u16>(3), Err(()));
assert_eq!(data.read_at::<u16>(4), Err(()));
let mut bytes = data;
assert_eq!(bytes.read::<u32>(), Ok(&x));
assert_eq!(bytes, Bytes(&[]));
let mut bytes = data;
assert_eq!(bytes.read::<u64>(), Err(()));
assert_eq!(bytes, Bytes(&[]));
let mut bytes = data;
assert_eq!(bytes.read_slice::<u8>(0), Ok(&[][..]));
assert_eq!(bytes, data);
let mut bytes = data;
assert_eq!(bytes.read_slice::<u8>(4), Ok(data.0));
assert_eq!(bytes, Bytes(&[]));
let mut bytes = data;
assert_eq!(bytes.read_slice::<u8>(5), Err(()));
assert_eq!(bytes, Bytes(&[]));
assert_eq!(data.read_slice_at::<u8>(0, 0), Ok(&[][..]));
assert_eq!(data.read_slice_at::<u8>(4, 0), Ok(&[][..]));
assert_eq!(data.read_slice_at::<u8>(0, 4), Ok(data.0));
assert_eq!(data.read_slice_at::<u8>(1, 4), Err(()));
let data = Bytes(&[0x01, 0x02, 0x00, 0x04]);
let mut bytes = data;
assert_eq!(bytes.read_string(), Ok(&data.0[..2]));
assert_eq!(bytes.0, &data.0[3..]);
let mut bytes = data;
bytes.skip(3).unwrap();
assert_eq!(bytes.read_string(), Err(()));
assert_eq!(bytes.0, &[]);
assert_eq!(data.read_string_at(0), Ok(&data.0[..2]));
assert_eq!(data.read_string_at(1), Ok(&data.0[1..2]));
assert_eq!(data.read_string_at(2), Ok(&[][..]));
assert_eq!(data.read_string_at(3), Err(()));
}
#[test]
fn bytes_debug() {
assert_eq!(format!("{:?}", Bytes(&[])), "[]");
assert_eq!(format!("{:?}", Bytes(&[0x01])), "[0x01]");
assert_eq!(
format!(
"{:?}",
Bytes(&[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08])
),
"[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08]"
);
assert_eq!(
format!(
"{:?}",
Bytes(&[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09])
),
"[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, ...; 9]"
);
}
}