fix: Support sparse entries of enormous size (#373)

Just like the `GnuHeader::size` field, fields `GnuHeader::realsize` and
`GnuSparseHeader::{offset, numbytes}` could be encoded in a binary
format for values greater than 8Gi.

src/header.rs

@@ -1250,7 +1250,7 @@ impl GnuHeader {
     /// This is applicable for sparse files where the returned size here is the
     /// size of the entire file after the sparse regions have been filled in.
     pub fn real_size(&self) -> io::Result<u64> {
-        octal_from(&self.realsize).map_err(|err| {
+        num_field_wrapper_from(&self.realsize).map_err(|err| {
             io::Error::new(
                 err.kind(),
                 format!(
@@ -1322,7 +1322,7 @@ impl GnuSparseHeader {
     ///
     /// Returns `Err` for a malformed `offset` field.
     pub fn offset(&self) -> io::Result<u64> {
-        octal_from(&self.offset).map_err(|err| {
+        num_field_wrapper_from(&self.offset).map_err(|err| {
             io::Error::new(
                 err.kind(),
                 format!("{} when getting offset from sparse header", err),
@@ -1334,7 +1334,7 @@ impl GnuSparseHeader {
     ///
     /// Returns `Err` for a malformed `numbytes` field.
     pub fn length(&self) -> io::Result<u64> {
-        octal_from(&self.numbytes).map_err(|err| {
+        num_field_wrapper_from(&self.numbytes).map_err(|err| {
             io::Error::new(
                 err.kind(),
                 format!("{} when getting length from sparse header", err),

tests/all.rs

@@ -1157,6 +1157,18 @@ fn extract_sparse() {
     assert!(s[0x2fa0 + 6..0x4000].chars().all(|x| x == '\u{0}'));
 }
 
+#[test]
+fn large_sparse() {
+    let rdr = Cursor::new(tar!("sparse-large.tar"));
+    let mut ar = Archive::new(rdr);
+    let mut entries = t!(ar.entries());
+    // Only check the header info without extracting, as the file is very large,
+    // and not all filesystems support sparse files.
+    let a = t!(entries.next().unwrap());
+    let h = a.header().as_gnu().unwrap();
+    assert_eq!(h.real_size().unwrap(), 12626929280);
+}
+
 #[test]
 fn sparse_with_trailing() {
     let rdr = Cursor::new(tar!("sparse-1.tar"));

tests/header/mod.rs

@@ -236,6 +236,13 @@ fn extended_numeric_format() {
         0x80, 0, 0, 0, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
     ];
     assert_eq!(h.as_header().mtime().unwrap(), 0x0123456789abcdef);
+
+    h.realsize = [0x80, 0, 0, 0, 0, 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde];
+    assert_eq!(h.real_size().unwrap(), 0x00123456789abcde);
+    h.sparse[0].offset = [0x80, 0, 0, 0, 0, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd];
+    assert_eq!(h.sparse[0].offset().unwrap(), 0x000123456789abcd);
+    h.sparse[0].numbytes = [0x80, 0, 0, 0, 0, 0, 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc];
+    assert_eq!(h.sparse[0].length().unwrap(), 0x0000123456789abc);
 }
 
 #[test]