Adapt alg_comp test to different zlib (latchset#142)

Different zlib implementations such as zlib-ng, QATzip and libnxz
provide API and ABI compatibility with madler's zlib. However, they do
not guarantee identical output.
This makes it very hard to compare the length or binary output of a
compressed stream.

Instead of doing that, this patch aims to compare the input against the
output of a compression and decompression cycle.

Fixes latchset#142.

tests/alg_comp.c

@@ -41,22 +41,23 @@ const struct {
     {}
 };
 
-typedef typeof(((jose_hook_alg_t *) NULL)->comp.inf) comp_func_t;
-
 static void
-test(const jose_hook_alg_t *a, comp_func_t func, bool iter,
-     const uint8_t *i, size_t il,
-     const uint8_t *o, size_t ol)
+test(const jose_hook_alg_t *a, bool iter,
+     const uint8_t *i, size_t il)
 {
     jose_io_auto_t *b = NULL;
+    jose_io_auto_t *c = NULL;
     jose_io_auto_t *z = NULL;
-    void *buf = NULL;
-    size_t len = 0;
+    void *buf1 = NULL;
+    void *buf2 = NULL;
+    size_t blen = 0;
+    size_t clen = 0;
 
-    b = jose_io_malloc(NULL, &buf, &len);
+    /* Test compression first. */
+    b = jose_io_malloc(NULL, &buf1, &blen);
     assert(b);
 
-    z = func(a, NULL, b);
+    z = a->comp.def(a, NULL, b);
     assert(z);
 
     if (iter) {
@@ -68,8 +69,26 @@ test(const jose_hook_alg_t *a, comp_func_t func, bool iter,
 
     assert(z->done(z));
 
-    assert(len == ol);
-    assert(memcmp(buf, o, ol) == 0);
+    /* Test decompression now. */
+    c = jose_io_malloc(NULL, &buf2, &clen);
+    assert(b);
+
+    z = a->comp.inf(a, NULL, c);
+    assert(z);
+
+    if (iter) {
+        uint8_t *m = buf1;
+        for (size_t j = 0; j < blen; j++)
+            assert(z->feed(z, &m[j], 1));
+    } else {
+        assert(z->feed(z, buf1, blen));
+    }
+
+    assert(z->done(z));
+
+    /* Compare the final output with the original input. */
+    assert(clen == il);
+    assert(memcmp(buf2, i, il) == 0);
 }
 
 int
@@ -93,20 +112,10 @@ main(int argc, char *argv[])
         assert(jose_b64_dec_buf(tests[i].def, strlen(tests[i].def),
                                 tst_def, sizeof(tst_def)) == sizeof(tst_def));
 
-        test(a, a->comp.def, false,
-             tst_inf, sizeof(tst_inf),
-             tst_def, sizeof(tst_def));
-
-        test(a, a->comp.inf, false,
-             tst_def, sizeof(tst_def),
+        test(a, false,
              tst_inf, sizeof(tst_inf));
 
-        test(a, a->comp.def, true,
-             tst_inf, sizeof(tst_inf),
-             tst_def, sizeof(tst_def));
-
-        test(a, a->comp.inf, true,
-             tst_def, sizeof(tst_def),
+        test(a, true,
              tst_inf, sizeof(tst_inf));
     }