diff --git a/scripts/hiddenapi/signature_patterns.py b/scripts/hiddenapi/signature_patterns.py
index 0acb2a0..e75ee95 100755
--- a/scripts/hiddenapi/signature_patterns.py
+++ b/scripts/hiddenapi/signature_patterns.py
@@ -13,8 +13,10 @@
 # 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.
-"""Generate a set of signature patterns from the modular flags generated by a
-bootclasspath_fragment that can be used to select a subset of monolithic flags
+"""Generate a set of signature patterns for a bootclasspath_fragment.
+
+The patterns are generated from the modular flags produced by the
+bootclasspath_fragment and are used to select a subset of the monolithic flags
 against which the modular flags can be compared.
 """
 
@@ -22,33 +24,122 @@
 import csv
 import sys
 
+
 def dict_reader(csvfile):
     return csv.DictReader(
-        csvfile, delimiter=',', quotechar='|', fieldnames=['signature']
-    )
+        csvfile, delimiter=',', quotechar='|', fieldnames=['signature'])
 
 
-def produce_patterns_from_file(file):
+def dotPackageToSlashPackage(pkg):
+    return pkg.replace('.', '/')
+
+
+def slashPackageToDotPackage(pkg):
+    return pkg.replace('/', '.')
+
+
+def isSplitPackage(splitPackages, pkg):
+    return splitPackages and (pkg in splitPackages or '*' in splitPackages)
+
+
+def matchedByPackagePrefixPattern(packagePrefixes, prefix):
+    for packagePrefix in packagePrefixes:
+        if prefix == packagePrefix:
+            return packagePrefix
+        elif prefix.startswith(packagePrefix) and prefix[len(
+                packagePrefix)] == '/':
+            return packagePrefix
+    return False
+
+
+def validate_package_prefixes(splitPackages, packagePrefixes):
+    # If there are no package prefixes then there is no possible conflict
+    # between them and the split packages.
+    if len(packagePrefixes) == 0:
+        return
+
+    # Check to make sure that the split packages and package prefixes do not
+    # overlap.
+    errors = []
+    for splitPackage in splitPackages:
+        if splitPackage == '*':
+            # A package prefix matches a split package.
+            packagePrefixesForOutput = ', '.join(
+                map(slashPackageToDotPackage, packagePrefixes))
+            errors.append(
+                'split package "*" conflicts with all package prefixes %s\n'
+                '    add split_packages:[] to fix' % packagePrefixesForOutput)
+        else:
+            packagePrefix = matchedByPackagePrefixPattern(
+                packagePrefixes, splitPackage)
+            if packagePrefix:
+                # A package prefix matches a split package.
+                splitPackageForOutput = slashPackageToDotPackage(splitPackage)
+                packagePrefixForOutput = slashPackageToDotPackage(packagePrefix)
+                errors.append(
+                    'split package %s is matched by package prefix %s' %
+                    (splitPackageForOutput, packagePrefixForOutput))
+    return errors
+
+
+def validate_split_packages(splitPackages):
+    errors = []
+    if '*' in splitPackages and len(splitPackages) > 1:
+        errors.append('split packages are invalid as they contain both the'
+                      ' wildcard (*) and specific packages, use the wildcard or'
+                      ' specific packages, not a mixture')
+    return errors
+
+
+def produce_patterns_from_file(file, splitPackages=None, packagePrefixes=None):
     with open(file, 'r') as f:
-        return produce_patterns_from_stream(f)
+        return produce_patterns_from_stream(f, splitPackages, packagePrefixes)
 
 
-def produce_patterns_from_stream(stream):
-    # Read in all the signatures into a list and remove member names.
+def produce_patterns_from_stream(stream,
+                                 splitPackages=None,
+                                 packagePrefixes=None):
+    splitPackages = set(splitPackages or [])
+    packagePrefixes = list(packagePrefixes or [])
+    # Read in all the signatures into a list and remove any unnecessary class
+    # and member names.
     patterns = set()
     for row in dict_reader(stream):
         signature = row['signature']
-        text = signature.removeprefix("L")
+        text = signature.removeprefix('L')
         # Remove the class specific member signature
-        pieces = text.split(";->")
+        pieces = text.split(';->')
         qualifiedClassName = pieces[0]
-        # Remove inner class names as they cannot be separated
-        # from the containing outer class.
-        pieces = qualifiedClassName.split("$", maxsplit=1)
-        pattern = pieces[0]
+        pieces = qualifiedClassName.rsplit('/', maxsplit=1)
+        pkg = pieces[0]
+        # If the package is split across multiple modules then it cannot be used
+        # to select the subset of the monolithic flags that this module
+        # produces. In that case we need to keep the name of the class but can
+        # discard any nested class names as an outer class cannot be split
+        # across modules.
+        #
+        # If the package is not split then every class in the package must be
+        # provided by this module so there is no need to list the classes
+        # explicitly so just use the package name instead.
+        if isSplitPackage(splitPackages, pkg):
+            # Remove inner class names.
+            pieces = qualifiedClassName.split('$', maxsplit=1)
+            pattern = pieces[0]
+        else:
+            # Add a * to ensure that the pattern matches the classes in that
+            # package.
+            pattern = pkg + '/*'
         patterns.add(pattern)
 
-    patterns = list(patterns) #pylint: disable=redefined-variable-type
+    # Remove any patterns that would be matched by a package prefix pattern.
+    patterns = list(
+        filter(lambda p: not matchedByPackagePrefixPattern(packagePrefixes, p),
+               patterns))
+    # Add the package prefix patterns to the list. Add a ** to ensure that each
+    # package prefix pattern will match the classes in that package and all
+    # sub-packages.
+    patterns = patterns + list(map(lambda x: x + '/**', packagePrefixes))
+    # Sort the patterns.
     patterns.sort()
     return patterns
 
@@ -56,24 +147,47 @@
 def main(args):
     args_parser = argparse.ArgumentParser(
         description='Generate a set of signature patterns '
-        'that select a subset of monolithic hidden API files.'
-    )
+        'that select a subset of monolithic hidden API files.')
     args_parser.add_argument(
         '--flags',
         help='The stub flags file which contains an entry for every dex member',
     )
+    args_parser.add_argument(
+        '--split-package',
+        action='append',
+        help='A package that is split across multiple bootclasspath_fragment modules'
+    )
+    args_parser.add_argument(
+        '--package-prefix',
+        action='append',
+        help='A package prefix unique to this set of flags')
     args_parser.add_argument('--output', help='Generated signature prefixes')
     args = args_parser.parse_args(args)
 
+    splitPackages = set(map(dotPackageToSlashPackage, args.split_package or []))
+    errors = validate_split_packages(splitPackages)
+
+    packagePrefixes = list(
+        map(dotPackageToSlashPackage, args.package_prefix or []))
+
+    if not errors:
+        errors = validate_package_prefixes(splitPackages, packagePrefixes)
+
+    if errors:
+        for error in errors:
+            print(error)
+        sys.exit(1)
+
     # Read in all the patterns into a list.
-    patterns = produce_patterns_from_file(args.flags)
+    patterns = produce_patterns_from_file(args.flags, splitPackages,
+                                          packagePrefixes)
 
     # Write out all the patterns.
     with open(args.output, 'w') as outputFile:
         for pattern in patterns:
             outputFile.write(pattern)
-            outputFile.write("\n")
+            outputFile.write('\n')
 
 
-if __name__ == "__main__":
+if __name__ == '__main__':
     main(sys.argv[1:])
diff --git a/scripts/hiddenapi/signature_patterns_test.py b/scripts/hiddenapi/signature_patterns_test.py
index 3babe54..b59dfd7 100755
--- a/scripts/hiddenapi/signature_patterns_test.py
+++ b/scripts/hiddenapi/signature_patterns_test.py
@@ -13,37 +13,99 @@
 # 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.
-
 """Unit tests for signature_patterns.py."""
 import io
 import unittest
 
-from signature_patterns import * #pylint: disable=unused-wildcard-import,wildcard-import
+from signature_patterns import *  #pylint: disable=unused-wildcard-import,wildcard-import
 
 
 class TestGeneratedPatterns(unittest.TestCase):
-    def produce_patterns_from_string(self, csvdata):
-        with io.StringIO(csvdata) as f:
-            return produce_patterns_from_stream(f)
 
-    def test_generate(self):
-        #pylint: disable=line-too-long
-        patterns = self.produce_patterns_from_string(
-            '''
+    csvFlags = """
 Ljava/lang/ProcessBuilder$Redirect$1;-><init>()V,blocked
 Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;,public-api
 Ljava/lang/Object;->hashCode()I,public-api,system-api,test-api
 Ljava/lang/Object;->toString()Ljava/lang/String;,blocked
-'''
-        )
-        #pylint: enable=line-too-long
+"""
+
+    def produce_patterns_from_string(self,
+                                     csv,
+                                     splitPackages=None,
+                                     packagePrefixes=None):
+        with io.StringIO(csv) as f:
+            return produce_patterns_from_stream(f, splitPackages,
+                                                packagePrefixes)
+
+    def test_generate_default(self):
+        patterns = self.produce_patterns_from_string(
+            TestGeneratedPatterns.csvFlags)
         expected = [
-            "java/lang/Character",
-            "java/lang/Object",
-            "java/lang/ProcessBuilder",
+            'java/lang/*',
         ]
         self.assertEqual(expected, patterns)
 
+    def test_generate_split_package(self):
+        patterns = self.produce_patterns_from_string(
+            TestGeneratedPatterns.csvFlags, splitPackages={'java/lang'})
+        expected = [
+            'java/lang/Character',
+            'java/lang/Object',
+            'java/lang/ProcessBuilder',
+        ]
+        self.assertEqual(expected, patterns)
+
+    def test_generate_split_package_wildcard(self):
+        patterns = self.produce_patterns_from_string(
+            TestGeneratedPatterns.csvFlags, splitPackages={'*'})
+        expected = [
+            'java/lang/Character',
+            'java/lang/Object',
+            'java/lang/ProcessBuilder',
+        ]
+        self.assertEqual(expected, patterns)
+
+    def test_generate_package_prefix(self):
+        patterns = self.produce_patterns_from_string(
+            TestGeneratedPatterns.csvFlags, packagePrefixes={'java/lang'})
+        expected = [
+            'java/lang/**',
+        ]
+        self.assertEqual(expected, patterns)
+
+    def test_generate_package_prefix_top_package(self):
+        patterns = self.produce_patterns_from_string(
+            TestGeneratedPatterns.csvFlags, packagePrefixes={'java'})
+        expected = [
+            'java/**',
+        ]
+        self.assertEqual(expected, patterns)
+
+    def test_split_package_wildcard_conflicts_with_other_split_packages(self):
+        errors = validate_split_packages({'*', 'java'})
+        expected = [
+            'split packages are invalid as they contain both the wildcard (*)'
+            ' and specific packages, use the wildcard or specific packages,'
+            ' not a mixture'
+        ]
+        self.assertEqual(expected, errors)
+
+    def test_split_package_wildcard_conflicts_with_package_prefixes(self):
+        errors = validate_package_prefixes({'*'}, packagePrefixes={'java'})
+        expected = [
+            'split package "*" conflicts with all package prefixes java\n'
+            '    add split_packages:[] to fix',
+        ]
+        self.assertEqual(expected, errors)
+
+    def test_split_package_conflict(self):
+        errors = validate_package_prefixes({'java/split'},
+                                           packagePrefixes={'java'})
+        expected = [
+            'split package java.split is matched by package prefix java',
+        ]
+        self.assertEqual(expected, errors)
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)