Add script for updating fuzztest corpus from oss-fuzz.
diff --git a/tests/fuzztest/update_corpus.sh b/tests/fuzztest/update_corpus.sh
new file mode 100755
index 0000000..a0273cc
--- /dev/null
+++ b/tests/fuzztest/update_corpus.sh
@@ -0,0 +1,47 @@
+#!/bin/bash
+
+# This script is used to update corpus.zip and regressions.zip from the
+# Google oss-fuzz project. To actually run this requires access rights to the
+# nanopb oss-fuzz storage.
+#
+# The oss-fuzz project uses separate fuzzer test cases for better performance
+# with coverage based fuzzers. This script merges the corpus to a single one
+# for the combined fuzztest test case.
+
+set -x
+set -e
+mkdir tmp-corpusupdate
+cd tmp-corpusupdate
+
+gsutil cp gs://nanopb-backup.clusterfuzz-external.appspot.com/corpus/libFuzzer/nanopb_fuzztest_proto2_static/latest.zip proto2_static.zip
+gsutil cp gs://nanopb-backup.clusterfuzz-external.appspot.com/corpus/libFuzzer/nanopb_fuzztest_proto2_pointer/latest.zip proto2_pointer.zip
+gsutil cp gs://nanopb-backup.clusterfuzz-external.appspot.com/corpus/libFuzzer/nanopb_fuzztest_proto3_static/latest.zip proto3_static.zip
+gsutil cp gs://nanopb-backup.clusterfuzz-external.appspot.com/corpus/libFuzzer/nanopb_fuzztest_proto3_pointer/latest.zip proto3_pointer.zip
+gsutil cp gs://nanopb-backup.clusterfuzz-external.appspot.com/corpus/libFuzzer/nanopb_fuzztest_io_errors/latest.zip io_errors.zip
+
+unzip -nd corpus ../corpus.zip # Unzip old corpus
+unzip -nd new_corpus proto2_static.zip
+unzip -nd new_corpus proto2_pointer.zip
+unzip -nd new_corpus proto3_static.zip
+unzip -nd new_corpus proto3_pointer.zip
+unzip -nd new_corpus io_errors.zip
+
+# Build fuzztest with libfuzzer to merge corpuses
+CCFLAGS="-DLLVMFUZZER -fsanitize=address -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link"
+LINKFLAGS="-std=c++11 -O1 -fsanitize=address -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link -stdlib=libc++"
+LINKLIBS="-fsanitize=fuzzer"
+
+scons -u CC=clang LINK=clang++ \
+ BUILDDIR=fuzztest/tmp-corpusupdate/build build/fuzztest/fuzztest \
+ "CCFLAGS=$CCFLAGS" "LINKFLAGS=$LINKFLAGS" "LINKLIBS=$LINKLIBS"
+
+# Copy any files with new features into corpus directory
+build/fuzztest/fuzztest corpus new_corpus -merge=1
+
+# Add files to end of the zips. This should work relatively efficiently
+# with gits binary diff feature.
+(cd corpus; zip -u ../../corpus.zip ./*)
+(cd new_corpus/regressions; zip -u ../../regressions.zip *)
+
+cd ..
+rm -rf tmp-corpusupdate
