@@ -27,7 +27,7 @@ options:
         title: Controls compression for the TRAP files written by the extractor.
         description: >
           This option is only intended for use in debugging the extractor. Accepted
-          values are 'gzip' (the default, to write gzip-compressed TRAP) and 'none'
-          (to write uncompressed TRAP).
+          values are 'gzip' (the default, to write gzip-compressed TRAP) 'zstd' (to
+          write Zstandard-compressed TRAP) and 'none' (to write uncompressed TRAP).
         type: string
-        pattern: "^(none|gzip)$"
+        pattern: "^(none|gzip|zstd)$"
@@ -23,10 +23,10 @@ options:
         title: Controls compression for the TRAP files written by the extractor.
         description: >
           This option is only intended for use in debugging the extractor. Accepted
-          values are 'gzip' (to write gzip-compressed TRAP) and 'none'
-          (currently the default, to write uncompressed TRAP).
+          values are 'gzip' (the default, to write gzip-compressed TRAP) 'zstd' (to
+          write Zstandard-compressed TRAP) and 'none' (to write uncompressed TRAP).
         type: string
-        pattern: "^(none|gzip)$"
+        pattern: "^(none|gzip|zstd)$"
   cargo_target_dir:
     title: Directory to use for cargo output files.
     description: >
 
@@ -29,13 +29,15 @@ pub enum Compression {
     #[default] // TODO make gzip default
     None,
     Gzip,
+    Zstd,
 }
 
 impl From<Compression> for trap::Compression {
     fn from(val: Compression) -> Self {
         match val {
             Compression::None => Self::None,
             Compression::Gzip => Self::Gzip,
+            Compression::Zstd => Self::Zstd,
         }
     }
 }
 
@@ -20,6 +20,7 @@ def test_do_not_print_env(codeql, rust, rust_edition, cargo, check_env_not_dumpe
 @pytest.mark.ql_test("steps.ql", expected=".cargo.expected")
 @pytest.mark.parametrize(("rust_edition", "compression", "suffix"), [
     pytest.param(2024, "gzip", ".gz", id="gzip"),
+    pytest.param(2024, "zstd", ".zst", id="zstd"),
 ])
 def test_compression(codeql, rust, rust_edition, compression, suffix, cargo, rust_check_diagnostics, cwd):
     codeql.database.create(cleanup=False, _env={
 
@@ -96,18 +96,25 @@ impl Writer {
                 self.write_trap_entries(&mut trap_file)
             }
             Compression::Gzip => {
-                let trap_file = GzEncoder::new(trap_file, flate2::Compression::fast());
+                let trap_file = GzEncoder::new(trap_file, Compression::GZIP_LEVEL);
                 let mut trap_file = BufWriter::new(trap_file);
                 self.write_trap_entries(&mut trap_file)
             }
+            Compression::Zstd => {
+                let trap_file = zstd::stream::Encoder::new(trap_file, Compression::ZSTD_LEVEL)?;
+                let mut trap_file = BufWriter::new(trap_file);
+                self.write_trap_entries(&mut trap_file)?;
+                trap_file.into_inner()?.finish()?;
+                Ok(())
+            }
         }
     }
 
     fn write_trap_entries<W: Write>(&self, file: &mut W) -> std::io::Result<()> {
         for trap_entry in &self.trap_output {
             writeln!(file, "{}", trap_entry)?;
         }
-        std::io::Result::Ok(())
+        Ok(())
     }
 }
 
@@ -280,9 +287,13 @@ fn limit_string(string: &str, max_size: usize) -> &str {
 pub enum Compression {
     None,
     Gzip,
+    Zstd,
 }
 
 impl Compression {
+    pub const ZSTD_LEVEL: i32 = 2;
+    pub const GZIP_LEVEL: flate2::Compression = flate2::Compression::fast();
+
     pub fn from_env(var_name: &str) -> Result<Compression, String> {
         match std::env::var(var_name) {
             Ok(method) => match Compression::from_string(&method) {
@@ -298,6 +309,7 @@ impl Compression {
         match s.to_lowercase().as_ref() {
             "none" => Some(Compression::None),
             "gzip" => Some(Compression::Gzip),
+            "zstd" => Some(Compression::Zstd),
             _ => None,
         }
     }
@@ -306,6 +318,7 @@ impl Compression {
         match self {
             Compression::None => "trap",
             Compression::Gzip => "trap.gz",
+            Compression::Zstd => "trap.zst",
         }
     }
 }
Original file line number	Diff line number	Diff line change
`@@ -29,13 +29,15 @@ pub enum Compression {`
`29`	`29`	`#[default] // TODO make gzip default`
`30`	`30`	`None,`
`31`	`31`	`Gzip,`
	`32`	`+ Zstd,`
`32`	`33`	`}`
`33`	`34`
`34`	`35`	`impl From<Compression> for trap::Compression {`
`35`	`36`	`fn from(val: Compression) -> Self {`
`36`	`37`	`match val {`
`37`	`38`	`Compression::None => Self::None,`
`38`	`39`	`Compression::Gzip => Self::Gzip,`
	`40`	`+ Compression::Zstd => Self::Zstd,`
`39`	`41`	`}`
`40`	`42`	`}`
`41`	`43`	`}`
Original file line number	Diff line number	Diff line change
`@@ -96,18 +96,25 @@ impl Writer {`
`96`	`96`	`self.write_trap_entries(&mut trap_file)`
`97`	`97`	`}`
`98`	`98`	`Compression::Gzip => {`
`99`		`- let trap_file = GzEncoder::new(trap_file, flate2::Compression::fast());`
	`99`	`+ let trap_file = GzEncoder::new(trap_file, Compression::GZIP_LEVEL);`
`100`	`100`	`let mut trap_file = BufWriter::new(trap_file);`
`101`	`101`	`self.write_trap_entries(&mut trap_file)`
`102`	`102`	`}`
	`103`	`+ Compression::Zstd => {`
	`104`	`+ let trap_file = zstd::stream::Encoder::new(trap_file, Compression::ZSTD_LEVEL)?;`
	`105`	`+ let mut trap_file = BufWriter::new(trap_file);`
	`106`	`+ self.write_trap_entries(&mut trap_file)?;`
	`107`	`+ trap_file.into_inner()?.finish()?;`
	`108`	`+ Ok(())`
	`109`	`+ }`
`103`	`110`	`}`
`104`	`111`	`}`
`105`	`112`
`106`	`113`	`fn write_trap_entries<W: Write>(&self, file: &mut W) -> std::io::Result<()> {`
`107`	`114`	`for trap_entry in &self.trap_output {`
`108`	`115`	`writeln!(file, "{}", trap_entry)?;`
`109`	`116`	`}`
`110`		`- std::io::Result::Ok(())`
	`117`	`+ Ok(())`
`111`	`118`	`}`
`112`	`119`	`}`
`113`	`120`
`@@ -280,9 +287,13 @@ fn limit_string(string: &str, max_size: usize) -> &str {`
`280`	`287`	`pub enum Compression {`
`281`	`288`	`None,`
`282`	`289`	`Gzip,`
	`290`	`+ Zstd,`
`283`	`291`	`}`
`284`	`292`
`285`	`293`	`impl Compression {`
	`294`	`+ pub const ZSTD_LEVEL: i32 = 2;`
	`295`	`+ pub const GZIP_LEVEL: flate2::Compression = flate2::Compression::fast();`
	`296`	`+`
`286`	`297`	`pub fn from_env(var_name: &str) -> Result<Compression, String> {`
`287`	`298`	`match std::env::var(var_name) {`
`288`	`299`	`Ok(method) => match Compression::from_string(&method) {`
`@@ -298,6 +309,7 @@ impl Compression {`
`298`	`309`	`match s.to_lowercase().as_ref() {`
`299`	`310`	`"none" => Some(Compression::None),`
`300`	`311`	`"gzip" => Some(Compression::Gzip),`
	`312`	`+ "zstd" => Some(Compression::Zstd),`
`301`	`313`	`_ => None,`
`302`	`314`	`}`
`303`	`315`	`}`
`@@ -306,6 +318,7 @@ impl Compression {`
`306`	`318`	`match self {`
`307`	`319`	`Compression::None => "trap",`
`308`	`320`	`Compression::Gzip => "trap.gz",`
	`321`	`+ Compression::Zstd => "trap.zst",`
`309`	`322`	`}`
`310`	`323`	`}`
`311`	`324`	`}`