From d9d4f0a905cdb6624d6c17bc97d36ff7c3807ec7 Mon Sep 17 00:00:00 2001
From: "Sergey \"Shnatsel\" Davidoff" <shnatsel@gmail.com>
Date: Thu, 5 Mar 2026 13:10:07 +0000
Subject: [PATCH] Add safe Rust Zstd decoding option

---
 Cargo.toml             | 4 ++++
 src/decoder/image.rs   | 2 ++
 tests/decode_images.rs | 2 +-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Cargo.toml b/Cargo.toml
index d1531f7..f4f5223 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,6 +25,7 @@ fax34 = { package = "fax", version = "0.2.6", optional = true }
 flate2 = { version = "1.0.20", optional = true }
 weezl = { version = "0.1.10", optional = true }
 zstd = { version = "0.13", optional = true }
+ruzstd = { version = "0.8.2", optional = true }
 zune-jpeg = { version = "0.5.1", optional = true }
 image-webp = {version = "0.2.4", optional = true }
 
@@ -45,6 +46,9 @@ jpeg = ["dep:zune-jpeg"]
 lzw = ["dep:weezl"]
 webp = ["dep:image-webp"]
 zstd = ["dep:zstd"]
+# Fully safe Rust but much slower Zstd decoding.
+# When both zstd and safe-rust-zstd are enabled, zstd takes precedence.
+safe-rust-zstd = ["dep:ruzstd"]
 
 [[bench]]
 name = "lzw"
diff --git a/src/decoder/image.rs b/src/decoder/image.rs
index 2a4366f..fb8fcb4 100644
--- a/src/decoder/image.rs
+++ b/src/decoder/image.rs
@@ -659,6 +659,8 @@ impl Image {
             )),
             #[cfg(feature = "zstd")]
             CompressionMethod::ZSTD => Box::new(zstd::Decoder::new(reader)?),
+            #[cfg(all(not(feature = "zstd"), feature = "safe-rust-zstd"))]
+            CompressionMethod::ZSTD => Box::new(ruzstd::decoding::StreamingDecoder::new(reader).unwrap()), // TODO: Error handling
             CompressionMethod::PackBits => Box::new(PackBitsReader::new(reader, compressed_length)),
             #[cfg(feature = "deflate")]
             CompressionMethod::Deflate | CompressionMethod::OldDeflate => {
diff --git a/tests/decode_images.rs b/tests/decode_images.rs
index 74f9f9f..08314af 100644
--- a/tests/decode_images.rs
+++ b/tests/decode_images.rs
@@ -569,7 +569,7 @@ fn test_predictor_3_gray_f32() {
 }
 
 #[test]
-#[cfg(feature = "zstd")]
+#[cfg(any(feature = "zstd", feature = "safe-rust-zstd"))]
 fn test_zstd_compression() {
     // gdal_translate -co COMPRESS=ZSTD -co ZSTD_LEVEL=20 int16.tif int16_zstd.tif
     test_image_sum_i16("int16_zstd.tif", ColorType::Gray(16), 354396);