Make the dependency filetime optional

Cargo.toml

@@ -19,14 +19,23 @@ contents are never required to be entirely resident in memory all at once.
 """
 
 [dependencies]
-filetime = "0.2.8"
+filetime = { version = "0.2.8", optional = true }
 
 [dev-dependencies]
 tempfile = "3"
 
 [target."cfg(unix)".dependencies]
 xattr = { version = "0.2", optional = true }
-libc = "0.2"
+libc = { version = "0.2", optional = true }
 
 [features]
-default = ["xattr"]
+default = ["builder", "filetime", "xattr"]
+builder = ["libc"]
+
+[[test]]
+name = "entry"
+required-features = ["builder"]
+
+[[example]]
+name = "write"
+required-features = ["builder"]

README.md

@@ -58,6 +58,14 @@ fn main() {
 }
 ```
 
+# Cargo features
+
+- **builder** (enabled by default): provides tools for creating tarballs:
+  `Builder` and `Header::{set_metadata, set_metadata_in_mode}`. Depends on
+  libc on unix, and methods touching `std::fs` are unimplemented on wasm.
+- **filetime** (enabled by default): write file times when unpacking a tarball.
+- **xattr** (enabled by defeult): write xattrs when unpacking a tarball on unix.
+
 # License
 
 This project is licensed under either of

src/entry.rs

@@ -7,6 +7,7 @@ use std::io::{self, Error, ErrorKind, SeekFrom};
 use std::marker;
 use std::path::{Component, Path, PathBuf};
 
+#[cfg(feature = "filetime")]
 use filetime::{self, FileTime};
 
 use crate::archive::ArchiveInner;
@@ -617,6 +618,7 @@ impl<'a> EntryFields<'a> {
             )
         })?;
 
+        #[cfg(feature = "filetime")]
         if self.preserve_mtime {
             if let Ok(mtime) = self.header.mtime() {
                 // For some more information on this see the comments in

src/header.rs

@@ -5,6 +5,7 @@ use std::os::windows::prelude::*;
 
 use std::borrow::Cow;
 use std::fmt;
+#[cfg(feature = "builder")]
 use std::fs;
 use std::io;
 use std::iter;
@@ -279,12 +280,14 @@ impl Header {
     /// This is useful for initializing a `Header` from the OS's metadata from a
     /// file. By default, this will use `HeaderMode::Complete` to include all
     /// metadata.
+    #[cfg(feature = "builder")]
     pub fn set_metadata(&mut self, meta: &fs::Metadata) {
         self.fill_from(meta, HeaderMode::Complete);
     }
 
     /// Sets only the metadata relevant to the given HeaderMode in this header
     /// from the metadata argument provided.
+    #[cfg(feature = "builder")]
     pub fn set_metadata_in_mode(&mut self, meta: &fs::Metadata, mode: HeaderMode) {
         self.fill_from(meta, mode);
     }
@@ -714,6 +717,7 @@ impl Header {
             .fold(0, |a, b| a + (*b as u32))
     }
 
+    #[cfg(feature = "builder")]
     fn fill_from(&mut self, meta: &fs::Metadata, mode: HeaderMode) {
         self.fill_platform_from(meta, mode);
         // Set size of directories to zero
@@ -732,13 +736,7 @@ impl Header {
         }
     }
 
-    #[cfg(target_arch = "wasm32")]
-    #[allow(unused_variables)]
-    fn fill_platform_from(&mut self, meta: &fs::Metadata, mode: HeaderMode) {
-        unimplemented!();
-    }
-
-    #[cfg(unix)]
+    #[cfg(all(unix, feature = "builder"))]
     fn fill_platform_from(&mut self, meta: &fs::Metadata, mode: HeaderMode) {
         match mode {
             HeaderMode::Complete => {
@@ -797,39 +795,53 @@ impl Header {
         }
     }
 
-    #[cfg(windows)]
+    #[cfg(all(not(unix), feature = "builder"))]
+    #[allow(unused_variables)]
     fn fill_platform_from(&mut self, meta: &fs::Metadata, mode: HeaderMode) {
-        // There's no concept of a file mode on Windows, so do a best approximation here.
-        match mode {
+        // Fallback implementation: approximate modes, and get as good an mtime as we can.
+        let mtime = match mode {
+            #[cfg(windows)]
             HeaderMode::Complete => {
-                self.set_uid(0);
-                self.set_gid(0);
                 // The dates listed in tarballs are always seconds relative to
                 // January 1, 1970. On Windows, however, the timestamps are returned as
                 // dates relative to January 1, 1601 (in 100ns intervals), so we need to
                 // add in some offset for those dates.
-                let mtime = (meta.last_write_time() / (1_000_000_000 / 100)) - 11644473600;
-                self.set_mtime(mtime);
-                let fs_mode = {
-                    const FILE_ATTRIBUTE_READONLY: u32 = 0x00000001;
-                    let readonly = meta.file_attributes() & FILE_ATTRIBUTE_READONLY;
-                    match (meta.is_dir(), readonly != 0) {
-                        (true, false) => 0o755,
-                        (true, true) => 0o555,
-                        (false, false) => 0o644,
-                        (false, true) => 0o444,
-                    }
-                };
-                self.set_mode(fs_mode);
+                (meta.last_write_time() / (1_000_000_000 / 100)) - 11644473600
             }
-            HeaderMode::Deterministic => {
-                self.set_uid(0);
-                self.set_gid(0);
-                self.set_mtime(123456789); // see above in unix
-                let fs_mode = if meta.is_dir() { 0o755 } else { 0o644 };
-                self.set_mode(fs_mode);
+            #[cfg(not(windows))]
+            HeaderMode::Complete => {
+                meta.modified()
+                    .ok()
+                    .and_then(|time| time.duration_since(std::time::SystemTime::UNIX_EPOCH).ok())
+                    .map(|duration| duration.as_secs())
+                    .unwrap_or(1) // avoiding zero mtimes, see above in unix
             }
-        }
+            HeaderMode::Deterministic => 123456789, // see above in unix
+        };
+        let fs_mode = match mode {
+            #[cfg(windows)]
+            HeaderMode::Complete => {
+                const FILE_ATTRIBUTE_READONLY: u32 = 0x00000001;
+                let readonly = meta.file_attributes() & FILE_ATTRIBUTE_READONLY;
+                match (meta.is_dir(), readonly != 0) {
+                    (true, false) => 0o755,
+                    (true, true) => 0o555,
+                    (false, false) => 0o644,
+                    (false, true) => 0o444,
+                }
+            }
+            _ => {
+                if meta.is_dir() {
+                    0o755
+                } else {
+                    0o644
+                }
+            }
+        };
+        self.set_uid(0);
+        self.set_gid(0);
+        self.set_mtime(mtime);
+        self.set_mode(fs_mode);
 
         let ft = meta.file_type();
         self.set_entry_type(if ft.is_dir() {

src/lib.rs

@@ -24,6 +24,7 @@
 use std::io::{Error, ErrorKind};
 
 pub use crate::archive::{Archive, Entries};
+#[cfg(feature = "builder")]
 pub use crate::builder::Builder;
 pub use crate::entry::{Entry, Unpacked};
 pub use crate::entry_type::EntryType;
@@ -32,6 +33,7 @@ pub use crate::header::{GnuHeader, GnuSparseHeader, Header, HeaderMode, OldHeade
 pub use crate::pax::{PaxExtension, PaxExtensions};
 
 mod archive;
+#[cfg(feature = "builder")]
 mod builder;
 mod entry;
 mod entry_type;