pod: add slice_from_all_bytes{_mut} (#672)

Also convert some code to use it.

src/pod.rs

@@ -21,9 +21,11 @@ type Result<T> = result::Result<T, ()>;
 /// - have no padding
 pub unsafe trait Pod: Copy + 'static {}
 
-/// Cast a byte slice to a `Pod` type.
+/// Cast the head of a byte slice to a `Pod` type.
 ///
-/// Returns the type and the tail of the slice.
+/// Returns the type and the tail of the byte slice.
+///
+/// Returns an error if the byte slice is too short or the alignment is invalid.
 #[inline]
 pub fn from_bytes<T: Pod>(data: &[u8]) -> Result<(&T, &[u8])> {
     let size = mem::size_of::<T>();
@@ -39,9 +41,11 @@ pub fn from_bytes<T: Pod>(data: &[u8]) -> Result<(&T, &[u8])> {
     Ok((val, tail))
 }
 
-/// Cast a mutable byte slice to a `Pod` type.
+/// Cast the head of a mutable byte slice to a `Pod` type.
+///
+/// Returns the type and the tail of the byte slice.
 ///
-/// Returns the type and the tail of the slice.
+/// Returns an error if the byte slice is too short or the alignment is invalid.
 #[inline]
 pub fn from_bytes_mut<T: Pod>(data: &mut [u8]) -> Result<(&mut T, &mut [u8])> {
     let size = mem::size_of::<T>();
@@ -60,9 +64,11 @@ pub fn from_bytes_mut<T: Pod>(data: &mut [u8]) -> Result<(&mut T, &mut [u8])> {
     Ok((val, tail))
 }
 
-/// Cast a byte slice to a slice of a `Pod` type.
+/// Cast the head of a byte slice to a slice of a `Pod` type.
 ///
 /// Returns the type slice and the tail of the byte slice.
+///
+/// Returns an error if the byte slice is too short or the alignment is invalid.
 #[inline]
 pub fn slice_from_bytes<T: Pod>(data: &[u8], count: usize) -> Result<(&[T], &[u8])> {
     let size = count.checked_mul(mem::size_of::<T>()).ok_or(())?;
@@ -78,9 +84,11 @@ pub fn slice_from_bytes<T: Pod>(data: &[u8], count: usize) -> Result<(&[T], &[u8
     Ok((slice, tail))
 }
 
-/// Cast a mutable byte slice to a slice of a `Pod` type.
+/// Cast the head of a mutable byte slice to a slice of a `Pod` type.
 ///
 /// Returns the type slice and the tail of the byte slice.
+///
+/// Returns an error if the byte slice is too short or the alignment is invalid.
 #[inline]
 pub fn slice_from_bytes_mut<T: Pod>(
     data: &mut [u8],
@@ -102,6 +110,38 @@ pub fn slice_from_bytes_mut<T: Pod>(
     Ok((slice, tail))
 }
 
+/// Cast all of a byte slice to a slice of a `Pod` type.
+///
+/// Returns the type slice.
+///
+/// Returns an error if the size of the byte slice is not an exact multiple
+/// of the type size, or the alignment is invalid.
+#[inline]
+pub fn slice_from_all_bytes<T: Pod>(data: &[u8]) -> Result<&[T]> {
+    let count = data.len() / mem::size_of::<T>();
+    let (slice, tail) = slice_from_bytes(data, count)?;
+    if !tail.is_empty() {
+        return Err(());
+    }
+    Ok(slice)
+}
+
+/// Cast all of a byte slice to a slice of a `Pod` type.
+///
+/// Returns the type slice.
+///
+/// Returns an error if the size of the byte slice is not an exact multiple
+/// of the type size, or the alignment is invalid.
+#[inline]
+pub fn slice_from_all_bytes_mut<T: Pod>(data: &mut [u8]) -> Result<&mut [T]> {
+    let count = data.len() / mem::size_of::<T>();
+    let (slice, tail) = slice_from_bytes_mut(data, count)?;
+    if !tail.is_empty() {
+        return Err(());
+    }
+    Ok(slice)
+}
+
 /// Cast a `Pod` type to a byte slice.
 #[inline]
 pub fn bytes_of<T: Pod>(val: &T) -> &[u8] {

src/read/elf/section.rs

@@ -1,12 +1,12 @@
 use core::fmt::Debug;
-use core::{iter, mem, slice, str};
+use core::{iter, slice, str};
 
 use crate::elf;
 use crate::endian::{self, Endianness, U32Bytes};
-use crate::pod::Pod;
+use crate::pod::{self, Pod};
 use crate::read::{
-    self, Bytes, CompressedData, CompressedFileRange, CompressionFormat, Error, ObjectSection,
-    ReadError, ReadRef, RelocationMap, SectionFlags, SectionIndex, SectionKind, StringTable,
+    self, CompressedData, CompressedFileRange, CompressionFormat, Error, ObjectSection, ReadError,
+    ReadRef, RelocationMap, SectionFlags, SectionIndex, SectionKind, StringTable,
 };
 
 use super::{
@@ -671,8 +671,7 @@ pub trait SectionHeader: Debug + Pod {
         endian: Self::Endian,
         data: R,
     ) -> read::Result<&'data [T]> {
-        let mut data = self.data(endian, data).map(Bytes)?;
-        data.read_slice(data.len() / mem::size_of::<T>())
+        pod::slice_from_all_bytes(self.data(endian, data)?)
             .read_error("Invalid ELF section size or offset")
     }
 
@@ -816,19 +815,11 @@ pub trait SectionHeader: Debug + Pod {
         if self.sh_type(endian) != elf::SHT_GROUP {
             return Ok(None);
         }
-        let mut data = self
-            .data(endian, data)
-            .read_error("Invalid ELF group section offset or size")
-            .map(Bytes)?;
-        let flag = data
-            .read::<U32Bytes<_>>()
-            .read_error("Invalid ELF group section offset or size")?
-            .get(endian);
-        let count = data.len() / mem::size_of::<U32Bytes<Self::Endian>>();
-        let sections = data
-            .read_slice(count)
-            .read_error("Invalid ELF group section offset or size")?;
-        Ok(Some((flag, sections)))
+        let msg = "Invalid ELF group section offset or size";
+        let data = self.data(endian, data).read_error(msg)?;
+        let (flag, data) = pod::from_bytes::<U32Bytes<_>>(data).read_error(msg)?;
+        let sections = pod::slice_from_all_bytes(data).read_error(msg)?;
+        Ok(Some((flag.get(endian), sections)))
     }
 
     /// Return the header of a SysV hash section.

src/read/elf/segment.rs

@@ -1,10 +1,10 @@
 use core::fmt::Debug;
-use core::{mem, slice, str};
+use core::{slice, str};
 
 use crate::elf;
 use crate::endian::{self, Endianness};
-use crate::pod::Pod;
-use crate::read::{self, Bytes, ObjectSegment, ReadError, ReadRef, SegmentFlags};
+use crate::pod::{self, Pod};
+use crate::read::{self, ObjectSegment, ReadError, ReadRef, SegmentFlags};
 
 use super::{ElfFile, FileHeader, NoteIterator};
 
@@ -180,8 +180,7 @@ pub trait ProgramHeader: Debug + Pod {
         endian: Self::Endian,
         data: R,
     ) -> Result<&'data [T], ()> {
-        let mut data = self.data(endian, data).map(Bytes)?;
-        data.read_slice(data.len() / mem::size_of::<T>())
+        pod::slice_from_all_bytes(self.data(endian, data)?)
     }
 
     /// Return the segment data in the given virtual address range

src/read/pe/file.rs

@@ -6,7 +6,7 @@ use core::convert::TryInto;
 
 use crate::endian::{LittleEndian as LE, U32};
 use crate::pe;
-use crate::pod::Pod;
+use crate::pod::{self, Pod};
 use crate::read::coff::{CoffCommon, CoffSymbol, CoffSymbolIterator, CoffSymbolTable, SymbolTable};
 use crate::read::{
     self, Architecture, ByteString, Bytes, CodeView, ComdatKind, Error, Export, FileFlags, Import,
@@ -317,17 +317,8 @@ where
             Some(data_dir) => data_dir,
             None => return Ok(None),
         };
-        let debug_data = data_dir.data(self.data, &self.common.sections).map(Bytes)?;
-        let debug_data_size = data_dir.size.get(LE) as usize;
-
-        let count = debug_data_size / mem::size_of::<pe::ImageDebugDirectory>();
-        let rem = debug_data_size % mem::size_of::<pe::ImageDebugDirectory>();
-        if rem != 0 || count < 1 {
-            return Err(Error("Invalid PE debug dir size"));
-        }
-
-        let debug_dirs = debug_data
-            .read_slice_at::<pe::ImageDebugDirectory>(0, count)
+        let debug_data = data_dir.data(self.data, &self.common.sections)?;
+        let debug_dirs = pod::slice_from_all_bytes::<pe::ImageDebugDirectory>(debug_data)
             .read_error("Invalid PE debug dir size")?;
 
         for debug_dir in debug_dirs {