Add "offset" argument to ElfNSlice::iter

So far iteration over an ElfNSlice was assumed to always start with the
slice's first element. With upcoming changes we are going to adjust
that, similarly to how things already work for ElfN_BoxedSyms. With this
change we introduce a start index argument to the ElfNSlice::iter()
method, which causes iteration to start at said index.

Signed-off-by: Daniel Müller <deso@posteo.net>

src/elf/parser.rs

@@ -985,7 +985,7 @@ impl ElfParser {
     // method instead.
     pub(crate) fn find_file_offset(&self, addr: Addr) -> Result<Option<u64>> {
         let phdrs = self.program_headers()?;
-        let offset = phdrs.iter().find_map(|phdr| {
+        let offset = phdrs.iter(0).find_map(|phdr| {
             let phdr = phdr.to_64bit();
 
             if phdr.p_type == PT_LOAD {
@@ -1019,7 +1019,7 @@ impl ElfParser {
     /// Translate a file offset into a virtual offset.
     pub(crate) fn file_offset_to_virt_offset(&self, offset: u64) -> Result<Option<Addr>> {
         let phdrs = self.program_headers()?;
-        let addr = phdrs.iter().find_map(|phdr| {
+        let addr = phdrs.iter(0).find_map(|phdr| {
             let phdr = phdr.to_64bit();
             if phdr.p_type == PT_LOAD {
                 if (phdr.p_offset..phdr.p_offset + phdr.p_filesz).contains(&offset) {

src/elf/types.rs

@@ -82,10 +82,10 @@ where
         }
     }
 
-    pub fn iter(&self) -> impl ExactSizeIterator<Item = ElfN<'elf, T>> {
+    pub fn iter(&self, start_idx: usize) -> impl ExactSizeIterator<Item = ElfN<'elf, T>> {
         match self {
-            Self::B32(slice) => Either::A(slice.iter().map(ElfN::B32)),
-            Self::B64(slice) => Either::B(slice.iter().map(ElfN::B64)),
+            Self::B32(slice) => Either::A(slice[start_idx..].iter().map(|x| ElfN::B32(x))),
+            Self::B64(slice) => Either::B(slice[start_idx..].iter().map(|x| ElfN::B64(x))),
         }
     }
 }

src/normalize/buildid.rs

@@ -22,7 +22,7 @@ pub type BuildId<'src> = Cow<'src, [u8]>;
 /// [`NT_GNU_BUILD_ID`][elf::types::NT_GNU_BUILD_ID].
 fn read_build_id_from_notes(parser: &ElfParser) -> Result<Option<BuildId<'_>>> {
     let shdrs = parser.section_headers()?;
-    for (idx, shdr) in shdrs.iter().enumerate() {
+    for (idx, shdr) in shdrs.iter(0).enumerate() {
         if shdr.type_() == elf::types::SHT_NOTE {
             // SANITY: We just found the index so the section data should always
             //         be found.