Add fuzz/c/std/png_fuzzer.c
diff --git a/fuzz/c/std/png_fuzzer.c b/fuzz/c/std/png_fuzzer.c
new file mode 100644
index 0000000..33b4d2e
--- /dev/null
+++ b/fuzz/c/std/png_fuzzer.c
@@ -0,0 +1,80 @@
+// Copyright 2020 The Wuffs Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// ----------------
+
+// Silence the nested slash-star warning for the next comment's command line.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wcomment"
+
+/*
+This fuzzer (the fuzz function) is typically run indirectly, by a framework
+such as https://github.com/google/oss-fuzz calling LLVMFuzzerTestOneInput.
+
+When working on the fuzz implementation, or as a sanity check, defining
+WUFFS_CONFIG__FUZZLIB_MAIN will let you manually run fuzz over a set of files:
+
+gcc -DWUFFS_CONFIG__FUZZLIB_MAIN png_fuzzer.c
+./a.out ../../../test/data/*.png
+rm -f ./a.out
+
+It should print "PASS", amongst other information, and exit(0).
+*/
+
+#pragma clang diagnostic pop
+
+// Wuffs ships as a "single file C library" or "header file library" as per
+// https://github.com/nothings/stb/blob/master/docs/stb_howto.txt
+//
+// To use that single file as a "foo.c"-like implementation, instead of a
+// "foo.h"-like header, #define WUFFS_IMPLEMENTATION before #include'ing or
+// compiling it.
+#define WUFFS_IMPLEMENTATION
+
+// Defining the WUFFS_CONFIG__MODULE* macros are optional, but it lets users of
+// release/c/etc.c whitelist which parts of Wuffs to build. That file contains
+// the entire Wuffs standard library, implementing a variety of codecs and file
+// formats. Without this macro definition, an optimizing compiler or linker may
+// very well discard Wuffs code for unused codecs, but listing the Wuffs
+// modules we use makes that process explicit. Preprocessing means that such
+// code simply isn't compiled.
+#define WUFFS_CONFIG__MODULES
+#define WUFFS_CONFIG__MODULE__ADLER32
+#define WUFFS_CONFIG__MODULE__BASE
+#define WUFFS_CONFIG__MODULE__CRC32
+#define WUFFS_CONFIG__MODULE__DEFLATE
+#define WUFFS_CONFIG__MODULE__PNG
+#define WUFFS_CONFIG__MODULE__ZLIB
+
+// If building this program in an environment that doesn't easily accommodate
+// relative includes, you can use the script/inline-c-relative-includes.go
+// program to generate a stand-alone C file.
+#include "../../../release/c/wuffs-unsupported-snapshot.c"
+#include "../fuzzlib/fuzzlib.c"
+#include "../fuzzlib/fuzzlib_image_decoder.c"
+
+const char* //
+fuzz(wuffs_base__io_buffer* src, uint64_t hash) {
+ wuffs_png__decoder dec;
+ wuffs_base__status status = wuffs_png__decoder__initialize(
+ &dec, sizeof dec, WUFFS_VERSION,
+ (hash & 1) ? WUFFS_INITIALIZE__LEAVE_INTERNAL_BUFFERS_UNINITIALIZED : 0);
+ hash >>= 1;
+ if (!wuffs_base__status__is_ok(&status)) {
+ return wuffs_base__status__message(&status);
+ }
+ return fuzz_image_decoder(
+ src, hash,
+ wuffs_png__decoder__upcast_as__wuffs_base__image_decoder(&dec));
+}
