diff --git a/Cargo.toml b/Cargo.toml
index ab77c84..9c9733e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,7 +7,7 @@ description = "'Static functions': compressed maps with the keys removed"
 readme = "README.md"
 repository = "https://github.com/bitwiseshiftleft/compressed_map"
 categories = ["data-structures", "compression"]
-include = ["/src", "/benches", "LICENSE.txt", "build.rs"]
+include = ["/src", "/benches", "LICENSE.txt", "TODO.md", "README.md", "build.rs"]
 build = "build.rs" # for cbindgen
 
 [lib]
diff --git a/README.md b/README.md
index 9de2c3b..4dbe67b 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,12 @@ This implementation is still research-grade.  Don't deploy it in production.
 In particular, it depends on `bincode` version 2.0.0-RC.1, which may have
 significant changes before release.
 
+The C FFI is currently incomplete, and I might change the type names
+to be namespaced and/or to be less ridiculous.  Let me know (via issues)
+if there's something you want added or changed in the C FFI.  Currently,
+it does not expose the full functionality of the Rust side, especially
+regarding build options.
+
 ## Static functions, aka CompressedMap
 
 The static function problem is to compress a map `M` of type `K -> V`.
diff --git a/TODO.md b/TODO.md
index 9632971..3e2f717 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,7 +1,13 @@
-# Release items
+# C FFI items
 
 * Complete the C interface / dylib: deserialize, save/load file, map with bytes output
-* Test CFFI
+* Test compressed maps in CFFI
+* Test (de)serialization in CFFI
+* Test that CFFI doesn't leak memory
+* Rename the C FFI types?
+
+# Other v0.2 release items
+
 * Test on Armv7 and x86
 * Demo apps
 
diff --git a/examples/ffi.c b/examples/ffi.c
index 7fcbc68..d3eded0 100644
--- a/examples/ffi.c
+++ b/examples/ffi.c
@@ -1,3 +1,11 @@
+/*
+ * @file ffi.c
+ * @author Mike Hamburg
+ * @copyright 2020-2022 Rambus Inc.
+ *
+ * Tests / examples for C FFI.
+ */
+
 #include "compressed_map.h"
 #include <stdlib.h>
 #include <assert.h>
@@ -10,26 +18,17 @@ double now() {
     return tv.tv_sec + tv.tv_usec * 1.0e-6;
 }
 
-int main(int argc, char **argv) {
-    (void)argv[argc];
-
-    int nitems = 1000000;
-    if (argc > 1) {
-        nitems = atoll(argv[1]);
-    }
-
-    uint64_t *keys   = calloc(nitems, sizeof(*keys));
-    uint64_t *values = calloc(nitems, sizeof(*values));
+void test_u64_u64(uint64_t *keys, uint64_t *values, int nitems) {
+    double start, end;
+    printf("********** Map u64 -> u64 **********\n");
 
     // Build hash map
-    srandom(0);
     HashMap_u64__u64 *hash = cmap_hashmap_u64_u64_new();
-    double start = now();
+    start = now();
     for (int i=0; i<nitems; i++) {
-        keys[i] = random();
-        cmap_hashmap_u64_u64_insert(hash,keys[i],random());
+        cmap_hashmap_u64_u64_insert(hash,keys[i],values[i]);
     }
-    double end = now();
+    end = now();
     size_t hashmap_len = cmap_hashmap_u64_u64_len(hash);
     assert(hashmap_len <= nitems);
     assert(hashmap_len >= nitems * 0.9);
@@ -65,15 +64,179 @@ int main(int argc, char **argv) {
         if (ret != values[i]) {
             printf("Fail: lookup[0x%llx] should have been 0x%llx; got 0x%llx\n",
                 (long long)keys[i], (long long)values[i], (long long)ret);
-            return 1;
+            exit(1);
         }
     }
     end = now();
-    printf("Query compressed_random_map of %lld items: %0.3fs = %0.1f ns/item\n",
+    printf("Query compressed_random_map of %lld items: %0.3fs = %0.1f ns/item\n\n",
         (long long)hashmap_len, end-start, (end-start)*1e9/hashmap_len);
     
     cmap_hashmap_u64_u64_free(hash);
     cmap_compressed_random_map_u64_u64_free(map);
+
+    // Build hashset
+    HashSet_u64 *hashset = cmap_hashset_u64_new();
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        cmap_hashset_u64_insert(hashset,keys[i]);
+    }
+    end = now();
+    hashmap_len = cmap_hashset_u64_len(hashset);
+    assert(hashmap_len <= nitems);
+    assert(hashmap_len >= nitems * 0.9);
+    printf("Build hashset of %lld / %lld items: %0.3fs = %0.1f ns/item\n",
+        (long long)hashmap_len, (long long)nitems, end-start, (end-start)*1e9/nitems);
+
+    // Test approx set build
+    start = now();
+    ApproxSet_u64 *aset = cmap_approxset_u64_build(hashset,8);
+    end = now();
+    printf("Build approxset of %lld items: %0.3fs = %0.1f ns/item\n",
+        (long long)hashmap_len, end-start, (end-start)*1e9/hashmap_len);
+    ser_size = cmap_approxset_u64_encode(aset,NULL,0);
+    printf("Size is %lld bytes = %0.1f bytes/item\n",
+        (long long)ser_size, (double)ser_size/hashmap_len);
+
+    // Test approxset queries
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        bool ret = cmap_approxset_u64_probably_contains(aset, keys[i]);
+        if (!ret) {
+            printf("Fail: approxset[0x%llx] should have been true\n", (long long)keys[i]);
+            exit(1);
+        }
+    }
+    end = now();
+    printf("Query approxset of %lld items: %0.3fs = %0.1f ns/item\n\n\n",
+        (long long)hashmap_len, end-start, (end-start)*1e9/hashmap_len);
+
+
+    cmap_hashset_u64_free(hashset);
+    cmap_approxset_u64_free(aset);
+}
+
+void test_bytes_u64(uint64_t *keys, uint64_t *values, int nitems) {
+    double start, end;
+    printf("********** Map bytes -> u64 **********\n");
+
+    // Build hash map
+    HashMap_Bytes__u64 *hash = cmap_hashmap_bytes_u64_new();
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        cmap_hashmap_bytes_u64_insert(hash,(uint8_t*)&keys[i],sizeof(keys[i]),values[i]);
+    }
+    end = now();
+    size_t hashmap_len = cmap_hashmap_bytes_u64_len(hash);
+    assert(hashmap_len <= nitems);
+    assert(hashmap_len >= nitems * 0.9);
+    printf("Build hashmap of %lld / %lld items: %0.3fs = %0.1f ns/item\n",
+        (long long)hashmap_len, (long long)nitems, end-start, (end-start)*1e9/nitems);
+
+    // Test hash map lookup, and build the values array
+    // (don't build it on the first pass because values might be overwritten for duplicate keys)
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        bool ret = cmap_hashmap_bytes_u64_get(hash,(uint8_t*)&keys[i],sizeof(keys[i]),&values[i]);
+        (void)ret;
+        assert(ret);
+    }
+    end = now();
+    printf("Lookup in hashmap of %lld / %lld items: %0.3fs = %0.1f ns/item\n",
+        (long long)hashmap_len, (long long)nitems, end-start, (end-start)*1e9/nitems);
+
+    // Test compressed map build
+    start = now();
+    CompressedRandomMap_Bytes__u64 *map = cmap_compressed_random_map_bytes_u64_build(hash);
+    end = now();
+    printf("Build compressed_random_map of %lld items: %0.3fs = %0.1f ns/item\n",
+        (long long)hashmap_len, end-start, (end-start)*1e9/hashmap_len);
+    size_t ser_size = cmap_compressed_random_map_bytes_u64_encode(map,NULL,0);
+    printf("Size is %lld bytes = %0.1f bytes/item\n",
+        (long long)ser_size, (double)ser_size/hashmap_len);
+
+    // Test compressed map queries
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        uint64_t ret = cmap_compressed_random_map_bytes_u64_query(map, (uint8_t*)&keys[i], sizeof(keys[i]));
+        if (ret != values[i]) {
+            printf("Fail: lookup[0x%llx] should have been 0x%llx; got 0x%llx\n",
+                (long long)keys[i], (long long)values[i], (long long)ret);
+            exit(1);
+        }
+    }
+    end = now();
+    printf("Query compressed_random_map of %lld items: %0.3fs = %0.1f ns/item\n\n",
+        (long long)hashmap_len, end-start, (end-start)*1e9/hashmap_len);
+    
+    cmap_hashmap_bytes_u64_free(hash);
+    cmap_compressed_random_map_bytes_u64_free(map);
+
+    // Build hashset
+    HashSet_Bytes *hashset = cmap_hashset_bytes_new();
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        cmap_hashset_bytes_insert(hashset,(uint8_t*)&keys[i],sizeof(keys[i]));
+    }
+    end = now();
+    hashmap_len = cmap_hashset_bytes_len(hashset);
+    assert(hashmap_len <= nitems);
+    assert(hashmap_len >= nitems * 0.9);
+    printf("Build hashset of %lld / %lld items: %0.3fs = %0.1f ns/item\n",
+        (long long)hashmap_len, (long long)nitems, end-start, (end-start)*1e9/nitems);
+
+    // Test approx set build
+    start = now();
+    ApproxSet_Bytes *aset = cmap_approxset_bytes_build(hashset,8);
+    end = now();
+    printf("Build approxset of %lld items: %0.3fs = %0.1f ns/item\n",
+        (long long)hashmap_len, end-start, (end-start)*1e9/hashmap_len);
+    ser_size = cmap_approxset_bytes_encode(aset,NULL,0);
+    printf("Size is %lld bytes = %0.1f bytes/item\n",
+        (long long)ser_size, (double)ser_size/hashmap_len);
+
+    // Test approxset queries
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        bool ret = cmap_approxset_bytes_probably_contains(aset, (uint8_t*)&keys[i], sizeof(keys[i]));
+        if (!ret) {
+            printf("Fail: approxset[0x%llx] should have been true\n", (long long)keys[i]);
+            exit(1);
+        }
+    }
+    end = now();
+    printf("Query approxset of %lld items: %0.3fs = %0.1f ns/item\n\n\n",
+        (long long)hashmap_len, end-start, (end-start)*1e9/hashmap_len);
+
+
+    cmap_hashset_bytes_free(hashset);
+    cmap_approxset_bytes_free(aset);
+}
+
+
+int main(int argc, char **argv) {
+    (void)argv[argc];
+
+    int nitems = 1000000;
+    if (argc > 1) {
+        nitems = atoll(argv[1]);
+    }
+
+    uint64_t *keys   = calloc(nitems, sizeof(*keys));
+    uint64_t *values = calloc(nitems, sizeof(*values));
+
+    double start, end;
+    srandom(0);
+    start = now();
+    for (int i=0; i<nitems; i++) {
+        keys[i] = random() ^ (uint64_t)random()<<21 ^ (uint64_t)random()<<42;
+        values[i] = random();
+    }
+    end = now();
+    printf("Randomize %lld items: %0.3fs = %0.1f ns/item\n\n",
+        (long long)nitems, end-start, (end-start)*1e9/nitems);
+
+    test_u64_u64(keys,values,nitems);
+    test_bytes_u64(keys,values,nitems);
     
     return 0;
 }