From 2c0fcc47a0ff32f611bb603ddb1af02035e21bc4 Mon Sep 17 00:00:00 2001
From: Nathan Fisher <jeang3nie@hitchhiker-linux.org>
Date: Tue, 23 Jan 2024 00:07:03 -0500
Subject: [PATCH] Add detection for zstd compression. Reader must implement
 Read + Seek

---
 .gitignore      |   1 +
 README.md       |   2 +-
 src/lib.rs      |  25 ++++++++++++++++++++++++-
 test/li.txt.zst | Bin 0 -> 537 bytes
 4 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 test/li.txt.zst

diff --git a/.gitignore b/.gitignore
index bd670cc..5cfe772 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 /target
 test/
 !test/li.txt
+!test/li.txt.zst
diff --git a/README.md b/README.md
index deb3885..38777dc 100644
--- a/README.md
+++ b/README.md
@@ -38,4 +38,4 @@ to see Haggis implemented in other languages.
 - [x] List archive nodes
 - [x] Override user/group when creating archives
 - [x] Override user/group when extracting archives
-- [ ] Automatically detect zstd compressed archives
+- [x] Automatically detect zstd compressed archives
diff --git a/src/lib.rs b/src/lib.rs
index cc91538..1e00ae8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,7 @@
 use std::{
     collections::HashMap,
     fs,
-    io::{BufWriter, Write},
+    io::{BufWriter, Read, Seek, Write},
     sync::Mutex,
 };
 #[cfg(feature = "parallel")]
@@ -41,6 +41,18 @@ pub use stream::Message as StreamMessage;
 
 pub static MAGIC: [u8; 7] = [0x89, b'h', b'a', b'g', b'g', b'i', b's'];
 
+static ZSTD_MAGIC: [u8; 4] = [0x28, 0xb5, 0x2f, 0xfd];
+
+/// Tries to detect if the bytes in *reader* are zstd compressed
+/// # Errors
+/// Returns `Error` if io fails
+pub fn detect_zstd<R: Read + Seek>(reader: &mut R) -> Result<bool, Error> {
+    let mut buf = [0; 4];
+    reader.read_exact(&mut buf)?;
+    reader.rewind()?;
+    Ok(buf == ZSTD_MAGIC)
+}
+
 /// Creates a haggis archive from a list of files
 /// # Errors
 /// Returns `crate::Error` if io fails or several other error conditions
@@ -176,3 +188,14 @@ pub fn par_stream_archive<W: Write + Send>(
     sender.send(Message::Eof).map_err(|_| Error::SenderError)?;
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn check_zstd() {
+        let mut fd = fs::File::open("test/li.txt.zst").unwrap();
+        assert!(detect_zstd(&mut fd).unwrap());
+    }
+}
diff --git a/test/li.txt.zst b/test/li.txt.zst
new file mode 100644
index 0000000000000000000000000000000000000000..bd71f7d3c6780ec9878a7490cde98cf3bfb3f283
GIT binary patch
literal 537
zcmV+!0_OcFwJ-f-?E+m802ZZM9B@gJ2Y4Z6w6X~8Z=cvMl{k=^f`Os+P3i9rAyEKR
z08s$%I(Mm7Skt;Pdu+}^t;36x5<hBhDv!X8!`lf@d!9U#mZ3|It=#%kSE>~%Z|F-J
zaD(mYNSawo?4WCNv8l~tUT`6uZLjCfaqLa(Sb7Qqg>a)3XuFn(9p@@Nq=$`JPx4~h
z(9vBVoZ}!K^CjN3t3ydzY-8vq```v=A7;|{Yubco`Vs=67(-OTkPE37S(ea#`>y!g
zXbXf#G9I`=*N9!kX-8@WJAfNlrj#h?l-lR+dx4gfR9OJUpk2bW7uLtO4Q84SH`)1Z
z?c^wN99%2b5^XM|!|9;jI>J{Lu5YucEaNrhn?Vnrlh_P|cyZQU#h|;+V_zGLw-PVv
zNl*-?g!@k73~nF{mPgBA_qA4dQHqmZaB1n0g*YFr7uam<xVCn{4Z1TVO%H`E&Cq>2
z!D8;OF&jci)A3toO!>NC9~wR&5EKDYmL9PO2oSls3xKlJCjqSY?$#p99$*xjo&~yw
ziFfP3cFv7~Q_mM0xU2(5QPvu5sRPMqrVyY~FsiC>paJ6Vb7v6}6zOc7$d30Fp{};3
zj<DN?opYb<3u(6V_=2-AUkLt+UnFXpFVbrsT8O#>^59_W2Db0XsC0i@F*(F+zJR<n
b$QC#C5UZC9D!KN;+q#)m46KzX^Z+aK<%<M~

literal 0
HcmV?d00001