feat(archive): Add LZ4 support

Author: sorairolake

README.md

@@ -176,6 +176,7 @@ assert_eq!(kind.extension(), "foo");
 - **rpm** - `application/x-rpm`
 - **dcm** - `application/dicom`
 - **zst** - `application/zstd`
+- **lz4** - `application/x-lz4`
 - **msi** - `application/x-ole-storage`
 - **cpio** - `application/x-cpio`
 

src/map.rs

@@ -576,6 +576,12 @@ matcher_map!(
         "zst",
         matchers::archive::is_zst
     ),
+    (
+        MatcherType::Archive,
+        "application/x-lz4",
+        "lz4",
+        matchers::archive::is_lz4
+    ),
     (
         MatcherType::Archive,
         "application/x-ole-storage",

src/matchers/archive.rs

@@ -249,6 +249,41 @@ pub fn is_zst(buf: &[u8]) -> bool {
     is_zst(next_frame)
 }
 
+/// Returns whether a buffer is a LZ4 archive.
+// LZ4 compressed data is made of one or more frames.
+// There are two frame formats defined by LZ4: LZ4 Frame format and Skippable frames.
+// See more details from https://github.com/lz4/lz4/blob/v1.9.4/doc/lz4_Frame_format.md
+pub fn is_lz4(buf: &[u8]) -> bool {
+    if buf.len() > 3 && buf[0] == 0x04 && buf[1] == 0x22 && buf[2] == 0x4D && buf[3] == 0x18 {
+        return true;
+    }
+
+    if buf.len() < 8 {
+        return false;
+    }
+
+    let magic = u32::from_le_bytes(buf[0..4].try_into().unwrap());
+    let Ok(magic) = usize::try_from(magic) else {
+        return false;
+    };
+
+    if magic & ZSTD_SKIP_MASK != ZSTD_SKIP_START {
+        return false;
+    }
+
+    let data_len = u32::from_le_bytes(buf[4..8].try_into().unwrap());
+    let Ok(data_len) = usize::try_from(data_len) else {
+        return false;
+    };
+
+    if buf.len() < 8 + data_len {
+        return false;
+    }
+
+    let next_frame = &buf[8 + data_len..];
+    is_lz4(next_frame)
+}
+
 /// Returns whether a buffer is a MSI Windows Installer archive.
 pub fn is_msi(buf: &[u8]) -> bool {
     buf.len() > 7

testdata/sample.tar.lz4

@@ -16,6 +16,7 @@ test_format!(
 );
 
 test_format!(Archive, "application/zstd", "zst", zst, "sample.tar.zst");
+test_format!(Archive, "application/x-lz4", "lz4", lz4, "sample.tar.lz4");
 test_format!(Archive, "application/x-cpio", "cpio", cpio, "sample.cpio");
 test_format!(
     Archive,