update read/written bytes only on success

Author: samuel40791765

crypto/bio/bio.c

@@ -198,10 +198,11 @@ int BIO_read_ex(BIO *bio, void *data, size_t data_len, size_t *read_bytes) {
   }
 
   int ret = BIO_read(bio, data, read_len);
-  *read_bytes = ret;
   if (ret > 0) {
+    *read_bytes = ret;
     return 1;
   } else {
+    *read_bytes = 0;
     return 0;
   }
 }
@@ -268,12 +269,15 @@ int BIO_write_ex(BIO *bio, const void *data, size_t data_len, size_t *written_by
   }
 
   int ret = BIO_write(bio, data, write_len);
-  if (written_bytes != NULL) {
-    *written_bytes = ret;
-  }
   if (ret > 0) {
+    if (written_bytes != NULL) {
+      *written_bytes = ret;
+    }
     return 1;
   } else {
+    if (written_bytes != NULL) {
+      *written_bytes = 0;
+    }
     return 0;
   }
 }

crypto/bio/bio_test.cc

@@ -1091,8 +1091,12 @@ TEST(BIOTest, ReadWriteEx) {
 
   // Test that |BIO_write/read_ex| align with their non-ex counterparts, when
   // encountering NULL data.
+  written = 1;
   EXPECT_FALSE(BIO_write(bio.get(), nullptr, 0));
   EXPECT_FALSE(BIO_write_ex(bio.get(), nullptr, 0, &written));
+  EXPECT_EQ(written, (size_t)0);
+  read = 1;
   EXPECT_FALSE(BIO_read(bio.get(), nullptr, 0));
   EXPECT_FALSE(BIO_read_ex(bio.get(), nullptr, 0, &read));
+  EXPECT_EQ(read, (size_t)0);
 }