1 files changed, 22 insertions, 11 deletions

diff --git a/tools/aapt2/optimize/ResourcePathShortener.cpp b/tools/aapt2/optimize/ResourcePathShortener.cpp
index c5df3dd00db9..7ff9bf5aa8df 100644
--- a/tools/aapt2/optimize/ResourcePathShortener.cpp
+++ b/tools/aapt2/optimize/ResourcePathShortener.cpp
@@ -16,13 +16,14 @@
 
 #include "optimize/ResourcePathShortener.h"
 
-#include <math.h>
+#include <set>
 #include <unordered_set>
 
 #include "androidfw/StringPiece.h"
 
 #include "ResourceTable.h"
 #include "ValueVisitor.h"
+#include "util/Util.h"
 
 
 static const std::string base64_chars =
@@ -50,18 +51,15 @@ std::string ShortenFileName(const android::StringPiece& file_path, int output_le
 }
 
 
-// Calculate the optimal hash length such that an average of 10% of resources
-// collide in their shortened path.
+// Return the optimal hash length such that at most 10% of resources collide in
+// their shortened path.
 // Reference: http://matt.might.net/articles/counting-hash-collisions/
 int OptimalShortenedLength(int num_resources) {
-  int num_chars = 2;
-  double N = 64*64; // hash space when hash is 2 chars long
-  double max_collisions = num_resources * 0.1;
-  while (num_resources - N + N * pow((N - 1) / N, num_resources) > max_collisions) {
-    N *= 64;
-    num_chars++;
+  if (num_resources > 4000) {
+    return 3;
+  } else {
+    return 2;
   }
-  return num_chars;
 }
 
 std::string GetShortenedPath(const android::StringPiece& shortened_filename,
@@ -74,10 +72,19 @@ std::string GetShortenedPath(const android::StringPiece& shortened_filename,
   return shortened_path;
 }
 
+// implement custom comparator of FileReference pointers so as to use the
+// underlying filepath as key rather than the integer address. This is to ensure
+// determinism of output for colliding files.
+struct PathComparator {
+    bool operator() (const FileReference* lhs, const FileReference* rhs) const {
+        return lhs->path->compare(*rhs->path);
+    }
+};
+
 bool ResourcePathShortener::Consume(IAaptContext* context, ResourceTable* table) {
   // used to detect collisions
   std::unordered_set<std::string> shortened_paths;
-  std::unordered_set<FileReference*> file_refs;
+  std::set<FileReference*, PathComparator> file_refs;
   for (auto& package : table->packages) {
     for (auto& type : package->types) {
       for (auto& entry : type->entries) {
@@ -95,6 +102,10 @@ bool ResourcePathShortener::Consume(IAaptContext* context, ResourceTable* table)
     android::StringPiece res_subdir, actual_filename, extension;
     util::ExtractResFilePathParts(*file_ref->path, &res_subdir, &actual_filename, &extension);
 
+    // Android detects ColorStateLists via pathname, skip res/color*
+    if (util::StartsWith(res_subdir, "res/color"))
+      continue;
+
     std::string shortened_filename = ShortenFileName(*file_ref->path, num_chars);
     int collision_count = 0;
     std::string shortened_path = GetShortenedPath(shortened_filename, extension, collision_count);