1use alloc::string::String;
2use core::convert::TryInto;
3use core::fmt;
4use core::marker::PhantomData;
5
6use crate::pod::{from_bytes, slice_from_bytes, Pod};
7use crate::read::ReadRef;
8
9/// A newtype for byte slices.
10///
11/// It has these important features:
12/// - no methods that can panic, such as `Index`
13/// - convenience methods for `Pod` types
14/// - a useful `Debug` implementation
15#[derive(Default, Clone, Copy, PartialEq, Eq)]
16pub struct Bytes<'data>(pub &'data [u8]);
17
18impl<'data> fmt::Debug for Bytes<'data> {
19 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
20 debug_list_bytes(self.0, fmt)
21 }
22}
23
24impl<'data> Bytes<'data> {
25 /// Return the length of the byte slice.
26 #[inline]
27 pub fn len(&self) -> usize {
28 self.0.len()
29 }
30
31 /// Return true if the byte slice is empty.
32 #[inline]
33 pub fn is_empty(&self) -> bool {
34 self.0.is_empty()
35 }
36
37 /// Skip over the given number of bytes at the start of the byte slice.
38 ///
39 /// Modifies the byte slice to start after the bytes.
40 ///
41 /// Returns an error if there are too few bytes.
42 #[inline]
43 pub fn skip(&mut self, offset: usize) -> Result<(), ()> {
44 match self.0.get(offset..) {
45 Some(tail) => {
46 self.0 = tail;
47 Ok(())
48 }
49 None => {
50 self.0 = &[];
51 Err(())
52 }
53 }
54 }
55
56 /// Return a reference to the given number of bytes at the start of the byte slice.
57 ///
58 /// Modifies the byte slice to start after the bytes.
59 ///
60 /// Returns an error if there are too few bytes.
61 #[inline]
62 pub fn read_bytes(&mut self, count: usize) -> Result<Bytes<'data>, ()> {
63 match (self.0.get(..count), self.0.get(count..)) {
64 (Some(head), Some(tail)) => {
65 self.0 = tail;
66 Ok(Bytes(head))
67 }
68 _ => {
69 self.0 = &[];
70 Err(())
71 }
72 }
73 }
74
75 /// Return a reference to the given number of bytes at the given offset of the byte slice.
76 ///
77 /// Returns an error if the offset is invalid or there are too few bytes.
78 #[inline]
79 pub fn read_bytes_at(mut self, offset: usize, count: usize) -> Result<Bytes<'data>, ()> {
80 self.skip(offset)?;
81 self.read_bytes(count)
82 }
83
84 /// Return a reference to a `Pod` struct at the start of the byte slice.
85 ///
86 /// Modifies the byte slice to start after the bytes.
87 ///
88 /// Returns an error if there are too few bytes or the slice is incorrectly aligned.
89 #[inline]
90 pub fn read<T: Pod>(&mut self) -> Result<&'data T, ()> {
91 match from_bytes(self.0) {
92 Ok((value, tail)) => {
93 self.0 = tail;
94 Ok(value)
95 }
96 Err(()) => {
97 self.0 = &[];
98 Err(())
99 }
100 }
101 }
102
103 /// Return a reference to a `Pod` struct at the given offset of the byte slice.
104 ///
105 /// Returns an error if there are too few bytes or the offset is incorrectly aligned.
106 #[inline]
107 pub fn read_at<T: Pod>(mut self, offset: usize) -> Result<&'data T, ()> {
108 self.skip(offset)?;
109 self.read()
110 }
111
112 /// Return a reference to a slice of `Pod` structs at the start of the byte slice.
113 ///
114 /// Modifies the byte slice to start after the bytes.
115 ///
116 /// Returns an error if there are too few bytes or the offset is incorrectly aligned.
117 #[inline]
118 pub fn read_slice<T: Pod>(&mut self, count: usize) -> Result<&'data [T], ()> {
119 match slice_from_bytes(self.0, count) {
120 Ok((value, tail)) => {
121 self.0 = tail;
122 Ok(value)
123 }
124 Err(()) => {
125 self.0 = &[];
126 Err(())
127 }
128 }
129 }
130
131 /// Return a reference to a slice of `Pod` structs at the given offset of the byte slice.
132 ///
133 /// Returns an error if there are too few bytes or the offset is incorrectly aligned.
134 #[inline]
135 pub fn read_slice_at<T: Pod>(mut self, offset: usize, count: usize) -> Result<&'data [T], ()> {
136 self.skip(offset)?;
137 self.read_slice(count)
138 }
139
140 /// Read a null terminated string.
141 ///
142 /// Does not assume any encoding.
143 /// Reads past the null byte, but doesn't return it.
144 #[inline]
145 pub fn read_string(&mut self) -> Result<&'data [u8], ()> {
146 match memchr::memchr(b'\0', self.0) {
147 Some(null) => {
148 // These will never fail.
149 let bytes = self.read_bytes(null)?;
150 self.skip(1)?;
151 Ok(bytes.0)
152 }
153 None => {
154 self.0 = &[];
155 Err(())
156 }
157 }
158 }
159
160 /// Read a null terminated string at an offset.
161 ///
162 /// Does not assume any encoding. Does not return the null byte.
163 #[inline]
164 pub fn read_string_at(mut self, offset: usize) -> Result<&'data [u8], ()> {
165 self.skip(offset)?;
166 self.read_string()
167 }
168
169 /// Read an unsigned LEB128 number.
170 pub fn read_uleb128(&mut self) -> Result<u64, ()> {
171 let mut result = 0;
172 let mut shift = 0;
173
174 loop {
175 let byte = *self.read::<u8>()?;
176 if shift == 63 && byte != 0x00 && byte != 0x01 {
177 return Err(());
178 }
179 result |= u64::from(byte & 0x7f) << shift;
180 shift += 7;
181
182 if byte & 0x80 == 0 {
183 return Ok(result);
184 }
185 }
186 }
187
188 /// Read a signed LEB128 number.
189 pub fn read_sleb128(&mut self) -> Result<i64, ()> {
190 let mut result = 0;
191 let mut shift = 0;
192
193 loop {
194 let byte = *self.read::<u8>()?;
195 if shift == 63 && byte != 0x00 && byte != 0x7f {
196 return Err(());
197 }
198 result |= i64::from(byte & 0x7f) << shift;
199 shift += 7;
200
201 if byte & 0x80 == 0 {
202 if shift < 64 && (byte & 0x40) != 0 {
203 // Sign extend the result.
204 result |= !0 << shift;
205 }
206 return Ok(result);
207 }
208 }
209 }
210}
211
212// Only for Debug impl of `Bytes`.
213fn debug_list_bytes(bytes: &[u8], fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
214 let mut list: DebugList<'_, '_> = fmt.debug_list();
215 list.entries(bytes.iter().take(8).copied().map(DebugByte));
216 if bytes.len() > 8 {
217 list.entry(&DebugLen(bytes.len()));
218 }
219 list.finish()
220}
221
222struct DebugByte(u8);
223
224impl fmt::Debug for DebugByte {
225 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
226 write!(fmt, "0x{:02x}", self.0)
227 }
228}
229
230struct DebugLen(usize);
231
232impl fmt::Debug for DebugLen {
233 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
234 write!(fmt, "...; {}", self.0)
235 }
236}
237
238/// A newtype for byte strings.
239///
240/// For byte slices that are strings of an unknown encoding.
241///
242/// Provides a `Debug` implementation that interprets the bytes as UTF-8.
243#[derive(Default, Clone, Copy, PartialEq, Eq)]
244pub(crate) struct ByteString<'data>(pub &'data [u8]);
245
246impl<'data> fmt::Debug for ByteString<'data> {
247 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
248 write!(fmt, "\"{}\"", String::from_utf8_lossy(self.0))
249 }
250}
251
252#[allow(dead_code)]
253#[inline]
254pub(crate) fn align(offset: usize, size: usize) -> usize {
255 (offset + (size - 1)) & !(size - 1)
256}
257
258#[allow(dead_code)]
259pub(crate) fn data_range(
260 data: &[u8],
261 data_address: u64,
262 range_address: u64,
263 size: u64,
264) -> Option<&[u8]> {
265 let offset: u64 = range_address.checked_sub(data_address)?;
266 data.get(offset.try_into().ok()?..)?
267 .get(..size.try_into().ok()?)
268}
269
270/// A table of zero-terminated strings.
271///
272/// This is used by most file formats for strings such as section names and symbol names.
273#[derive(Debug, Clone, Copy)]
274pub struct StringTable<'data, R = &'data [u8]>
275where
276 R: ReadRef<'data>,
277{
278 data: Option<R>,
279 start: u64,
280 end: u64,
281 marker: PhantomData<&'data ()>,
282}
283
284impl<'data, R: ReadRef<'data>> StringTable<'data, R> {
285 /// Interpret the given data as a string table.
286 pub fn new(data: R, start: u64, end: u64) -> Self {
287 StringTable {
288 data: Some(data),
289 start,
290 end,
291 marker: PhantomData,
292 }
293 }
294
295 /// Return the string at the given offset.
296 pub fn get(&self, offset: u32) -> Result<&'data [u8], ()> {
297 match self.data {
298 Some(data: R) => {
299 let r_start: u64 = self.start.checked_add(offset.into()).ok_or(())?;
300 data.read_bytes_at_until(range:r_start..self.end, delimiter:0)
301 }
302 None => Err(()),
303 }
304 }
305}
306
307impl<'data, R: ReadRef<'data>> Default for StringTable<'data, R> {
308 fn default() -> Self {
309 StringTable {
310 data: None,
311 start: 0,
312 end: 0,
313 marker: PhantomData,
314 }
315 }
316}
317
318#[cfg(test)]
319mod tests {
320 use super::*;
321 use crate::pod::bytes_of;
322
323 #[test]
324 fn bytes() {
325 let x = u32::to_be(0x0123_4567);
326 let data = Bytes(bytes_of(&x));
327
328 let mut bytes = data;
329 assert_eq!(bytes.skip(0), Ok(()));
330 assert_eq!(bytes, data);
331
332 let mut bytes = data;
333 assert_eq!(bytes.skip(4), Ok(()));
334 assert_eq!(bytes, Bytes(&[]));
335
336 let mut bytes = data;
337 assert_eq!(bytes.skip(5), Err(()));
338 assert_eq!(bytes, Bytes(&[]));
339
340 let mut bytes = data;
341 assert_eq!(bytes.read_bytes(0), Ok(Bytes(&[])));
342 assert_eq!(bytes, data);
343
344 let mut bytes = data;
345 assert_eq!(bytes.read_bytes(4), Ok(data));
346 assert_eq!(bytes, Bytes(&[]));
347
348 let mut bytes = data;
349 assert_eq!(bytes.read_bytes(5), Err(()));
350 assert_eq!(bytes, Bytes(&[]));
351
352 assert_eq!(data.read_bytes_at(0, 0), Ok(Bytes(&[])));
353 assert_eq!(data.read_bytes_at(4, 0), Ok(Bytes(&[])));
354 assert_eq!(data.read_bytes_at(0, 4), Ok(data));
355 assert_eq!(data.read_bytes_at(1, 4), Err(()));
356
357 let mut bytes = data;
358 assert_eq!(bytes.read::<u16>(), Ok(&u16::to_be(0x0123)));
359 assert_eq!(bytes, Bytes(&[0x45, 0x67]));
360 assert_eq!(data.read_at::<u16>(2), Ok(&u16::to_be(0x4567)));
361 assert_eq!(data.read_at::<u16>(3), Err(()));
362 assert_eq!(data.read_at::<u16>(4), Err(()));
363
364 let mut bytes = data;
365 assert_eq!(bytes.read::<u32>(), Ok(&x));
366 assert_eq!(bytes, Bytes(&[]));
367
368 let mut bytes = data;
369 assert_eq!(bytes.read::<u64>(), Err(()));
370 assert_eq!(bytes, Bytes(&[]));
371
372 let mut bytes = data;
373 assert_eq!(bytes.read_slice::<u8>(0), Ok(&[][..]));
374 assert_eq!(bytes, data);
375
376 let mut bytes = data;
377 assert_eq!(bytes.read_slice::<u8>(4), Ok(data.0));
378 assert_eq!(bytes, Bytes(&[]));
379
380 let mut bytes = data;
381 assert_eq!(bytes.read_slice::<u8>(5), Err(()));
382 assert_eq!(bytes, Bytes(&[]));
383
384 assert_eq!(data.read_slice_at::<u8>(0, 0), Ok(&[][..]));
385 assert_eq!(data.read_slice_at::<u8>(4, 0), Ok(&[][..]));
386 assert_eq!(data.read_slice_at::<u8>(0, 4), Ok(data.0));
387 assert_eq!(data.read_slice_at::<u8>(1, 4), Err(()));
388
389 let data = Bytes(&[0x01, 0x02, 0x00, 0x04]);
390
391 let mut bytes = data;
392 assert_eq!(bytes.read_string(), Ok(&data.0[..2]));
393 assert_eq!(bytes.0, &data.0[3..]);
394
395 let mut bytes = data;
396 bytes.skip(3).unwrap();
397 assert_eq!(bytes.read_string(), Err(()));
398 assert_eq!(bytes.0, &[]);
399
400 assert_eq!(data.read_string_at(0), Ok(&data.0[..2]));
401 assert_eq!(data.read_string_at(1), Ok(&data.0[1..2]));
402 assert_eq!(data.read_string_at(2), Ok(&[][..]));
403 assert_eq!(data.read_string_at(3), Err(()));
404 }
405
406 #[test]
407 fn bytes_debug() {
408 assert_eq!(format!("{:?}", Bytes(&[])), "[]");
409 assert_eq!(format!("{:?}", Bytes(&[0x01])), "[0x01]");
410 assert_eq!(
411 format!(
412 "{:?}",
413 Bytes(&[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08])
414 ),
415 "[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08]"
416 );
417 assert_eq!(
418 format!(
419 "{:?}",
420 Bytes(&[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09])
421 ),
422 "[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, ...; 9]"
423 );
424 }
425}
426