Add const XDR serialization

.github/workflows/rust.yml

@@ -17,7 +17,7 @@
 
   complete:
     if: always()
-    needs: [generate, fmt, readme, prepare, build, test, publish-dry-run]
+    needs: [generate, fmt, readme, prepare, build, test, fuzz-corpus, publish-dry-run]
     runs-on: ubuntu-latest
     steps:
     - if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
@@ -140,7 +140,23 @@
     - run: cargo version
     - run: cargo test ${{ matrix.feature-args }}
 
+  fuzz-corpus:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: stellar/actions/rust-cache@main
+    - uses: stellar/binaries@v55
+      with:
+        name: cargo-fuzz
+        version: 0.13.1
+    - run: rustup install nightly
+    - run: rustup default nightly
+    - name: Run fuzz corpus
+      run: make fuzz
+    - name: Check no diffs exist
+      run: git add -N . && git diff HEAD --exit-code
+
   publish-dry-run:
     if: github.event_name == 'push' || startsWith(github.head_ref, 'release/')
     strategy:
       matrix:

Cargo.toml

@@ -39,6 +39,7 @@ sha2 = { version = "0.10.9", optional = true }
 [dev-dependencies]
 serde_json = "1.0.89"
 bytes-lit = "0.0.5"
+rand = "0.9.0"
 
 [features]
 default = ["std"]
@@ -52,6 +53,7 @@ ms_close_time = []
 
 # Features available without any new dependencies.
 type_enum = []
+const = []
 
 # Features dependent on optional dependencies.
 base64 = ["std", "dep:base64"]

Makefile

@@ -1,3 +1,5 @@
+.PHONY: all test build doc install readme fuzz fuzz-reduce watch generate generate-files clean fmt publish
+
 export RUSTFLAGS=-Dwarnings -Dclippy::all -Dclippy::pedantic
 
 CARGO_HACK_ARGS=--feature-powerset --exclude-features default --group-features base64,serde,arbitrary,hex,rand
@@ -27,6 +29,16 @@ readme:
 		| jq -r '"# stellar-xdr\n\n" + .index[.root|tostring].docs' \
 		> README.md
 
+# Run the fuzz corpus.
+# Leak detection is disabled because the fuzzer tests the const impls that
+# contain &'static data and so their Arbitrary impls explicitly leak.
+fuzz:
+	ASAN_OPTIONS=detect_leaks=0 cargo +nightly fuzz run spec-entry -- -rss_limit_mb=0 -max_len=10240 -runs=0
+
+# Shrinks each corpus to the smallest set of inputs with the same coverage.
+fuzz-reduce:
+	ASAN_OPTIONS=detect_leaks=0 cargo +nightly fuzz cmin spec-entry -- -rss_limit_mb=0
+
 watch:
 	cargo watch --clear --watch-when-idle --shell '$(MAKE)'
 

README.md

@@ -61,6 +61,13 @@ only necessary to use utility functions that depend on serde_json.
 6. `hex` – Enables support for hex in string representations of some types.
 Automatically enabled when serde is enabled.
 7. `schemars` – Enables support for JSON Schema generation. (Experimental)
+8. `const` – Enables the `const` module, containing a form of every type
+that can be constructed and encoded to XDR in a const context. Types that
+own heap data have a borrowing counterpart in the module that wraps
+`&'static` slices instead; the rest are re-exports of the owned types.
+Every type in the module has `const_xdr_len` and `const_to_xdr` methods,
+so XDR can be encoded at compile time into a fixed-size array. Requires no
+additional dependencies and works without std or alloc. (Experimental)
 
 Features marked experimental may disappear at anytime, see breaking changes
 at anytime, or and may be minimal implementations instead of complete.

fuzz/.gitignore

@@ -0,0 +1,3 @@
+target
+artifacts
+coverage