1 files changed, 81 insertions, 0 deletions
diff --git a/src/csum_file.rs b/src/csum_file.rs
new file mode 100644
index 0000000000..7f2c6c4fcb
--- /dev/null
+++ b/src/csum_file.rs
@@ -0,0 +1,81 @@
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation: version 2 of the License, dated June 1991.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, see <https://www.gnu.org/licenses/>.
+
+use crate::hash::{HashAlgorithm, GIT_MAX_RAWSZ};
+use std::ffi::CStr;
+use std::io::{self, Write};
+use std::os::raw::c_void;
+
+/// A writer that can write files identified by their hash or containing a trailing hash.
+pub struct HashFile {
+    ptr: *mut c_void,
+    algo: HashAlgorithm,
+}
+
+impl HashFile {
+    /// Create a new HashFile.
+    ///
+    /// The hash used will be `algo`, its name should be in `name`, and an open file descriptor
+    /// pointing to that file should be in `fd`.
+    pub fn new(algo: HashAlgorithm, fd: i32, name: &CStr) -> HashFile {
+        HashFile {
+            ptr: unsafe { c::hashfd(algo.hash_algo_ptr(), fd, name.as_ptr()) },
+            algo,
+        }
+    }
+
+    /// Finalize this HashFile instance.
+    ///
+    /// Returns the hash computed over the data.
+    pub fn finalize(self, component: u32, flags: u32) -> Vec<u8> {
+        let mut result = vec![0u8; GIT_MAX_RAWSZ];
+        unsafe { c::finalize_hashfile(self.ptr, result.as_mut_ptr(), component, flags) };
+        result.truncate(self.algo.raw_len());
+        result
+    }
+}
+
+impl Write for HashFile {
+    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
+        for chunk in data.chunks(u32::MAX as usize) {
+            unsafe {
+                c::hashwrite(
+                    self.ptr,
+                    chunk.as_ptr() as *const c_void,
+                    chunk.len() as u32,
+                )
+            };
+        }
+        Ok(data.len())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        unsafe { c::hashflush(self.ptr) };
+        Ok(())
+    }
+}
+
+pub mod c {
+    use std::os::raw::{c_char, c_int, c_void};
+
+    extern "C" {
+        pub fn hashfd(algop: *const c_void, fd: i32, name: *const c_char) -> *mut c_void;
+        pub fn hashwrite(f: *mut c_void, data: *const c_void, len: u32);
+        pub fn hashflush(f: *mut c_void);
+        pub fn finalize_hashfile(
+            f: *mut c_void,
+            data: *mut u8,
+            component: u32,
+            flags: u32,
+        ) -> c_int;
+    }
+}