bench: add benchmark for FSChaCha20Poly1305

Add a benchmark for FSChaCha20Poly1305 encryption, so the overhead of key
generation and authentication can be observed for various message sizes.

src/bench/chacha20.cpp

@@ -5,6 +5,7 @@
 
 #include <bench/bench.h>
 #include <crypto/chacha20.h>
+#include <crypto/chacha20poly1305.h>
 
 /* Number of bytes to process per iteration */
 static const uint64_t BUFFER_SIZE_TINY  = 64;
@@ -23,6 +24,18 @@ static void CHACHA20(benchmark::Bench& bench, size_t buffersize)
     });
 }
 
+static void FSCHACHA20POLY1305(benchmark::Bench& bench, size_t buffersize)
+{
+    std::vector<std::byte> key(32);
+    FSChaCha20Poly1305 ctx(key, 224);
+    std::vector<std::byte> in(buffersize);
+    std::vector<std::byte> aad;
+    std::vector<std::byte> out(buffersize + FSChaCha20Poly1305::EXPANSION);
+    bench.batch(in.size()).unit("byte").run([&] {
+        ctx.Encrypt(in, aad, out);
+    });
+}
+
 static void CHACHA20_64BYTES(benchmark::Bench& bench)
 {
     CHACHA20(bench, BUFFER_SIZE_TINY);
@@ -38,6 +51,24 @@ static void CHACHA20_1MB(benchmark::Bench& bench)
     CHACHA20(bench, BUFFER_SIZE_LARGE);
 }
 
+static void FSCHACHA20POLY1305_64BYTES(benchmark::Bench& bench)
+{
+    FSCHACHA20POLY1305(bench, BUFFER_SIZE_TINY);
+}
+
+static void FSCHACHA20POLY1305_256BYTES(benchmark::Bench& bench)
+{
+    FSCHACHA20POLY1305(bench, BUFFER_SIZE_SMALL);
+}
+
+static void FSCHACHA20POLY1305_1MB(benchmark::Bench& bench)
+{
+    FSCHACHA20POLY1305(bench, BUFFER_SIZE_LARGE);
+}
+
 BENCHMARK(CHACHA20_64BYTES, benchmark::PriorityLevel::HIGH);
 BENCHMARK(CHACHA20_256BYTES, benchmark::PriorityLevel::HIGH);
 BENCHMARK(CHACHA20_1MB, benchmark::PriorityLevel::HIGH);
+BENCHMARK(FSCHACHA20POLY1305_64BYTES, benchmark::PriorityLevel::HIGH);
+BENCHMARK(FSCHACHA20POLY1305_256BYTES, benchmark::PriorityLevel::HIGH);
+BENCHMARK(FSCHACHA20POLY1305_1MB, benchmark::PriorityLevel::HIGH);