Update RenderEngineTest's buffer dumping file paths

Writing to `/data/file.ppm` was failing for me, even with `adb shell
setenforce 0`. Changing this to `/data/local/tmp/file.ppm` let the write
succeed, event without `adb shell setenforce 0`.

I chose `/data/local/tmp/` based on context clues from other tests, but
am happy with any directory, as long as we have write permission. After
feedback I've also changed the code to create the target directory if it
doesn't exist, which allows us to use `/data/local/tmp/RenderEngineTest`
and remove the `texture_out_` file name prefix.

Note: both `/data/` and `/data/local/tmp/` have the same permissions of
771, but they're owned by different users, `system` and `shell`
respectively.

I also tweaked the file name since tests parameterized by RenderEngine
type were appending e.g. `/0`.

Bug: N/A
Test: manual
Flag: EXEMPT test only
Change-Id: I3017b870ecb4d61cd90206128774d45b003e3cf0

1 files changed, 42 insertions, 9 deletions

diff --git a/libs/renderengine/tests/RenderEngineTest.cpp b/libs/renderengine/tests/RenderEngineTest.cpp
index a8a98236e2..3c59fb30b1 100644
--- a/libs/renderengine/tests/RenderEngineTest.cpp
+++ b/libs/renderengine/tests/RenderEngineTest.cpp
@@ -34,9 +34,12 @@
 #include <ui/ColorSpace.h>
 #include <ui/PixelFormat.h>
 
+#include <algorithm>
 #include <chrono>
 #include <condition_variable>
+#include <filesystem>
 #include <fstream>
+#include <system_error>
 
 #include "../skia/SkiaGLRenderEngine.h"
 #include "../skia/SkiaVkRenderEngine.h"
@@ -259,22 +262,51 @@ public:
 
     ~RenderEngineTest() {
         if (WRITE_BUFFER_TO_FILE_ON_FAILURE && ::testing::Test::HasFailure()) {
-            writeBufferToFile("/data/texture_out_");
+            writeBufferToFile("/data/local/tmp/RenderEngineTest/");
         }
         const ::testing::TestInfo* const test_info =
                 ::testing::UnitTest::GetInstance()->current_test_info();
         ALOGI("**** Tearing down after %s.%s\n", test_info->test_case_name(), test_info->name());
     }
 
-    void writeBufferToFile(const char* basename) {
-        std::string filename(basename);
-        filename.append(::testing::UnitTest::GetInstance()->current_test_info()->name());
-        filename.append(".ppm");
-        std::ofstream file(filename.c_str(), std::ios::binary);
+    // If called during e.g.
+    // `PerRenderEngineType/RenderEngineTest#drawLayers_fillBufferCheckersRotate90_colorSource/0`
+    // with a directory of `/data/local/tmp/RenderEngineTest`, then mBuffer will be dumped to
+    // `/data/local/tmp/RenderEngineTest/drawLayers_fillBufferCheckersRotate90_colorSource-0.ppm`
+    //
+    // Note: if `directory` does not exist, then its full path will be recursively created with 777
+    // permissions. If `directory` already exists but does not grant the executing user write
+    // permissions, then saving the buffer will fail.
+    //
+    // Since this is test-only code, no security considerations are made.
+    void writeBufferToFile(const filesystem::path& directory) {
+        const auto currentTestInfo = ::testing::UnitTest::GetInstance()->current_test_info();
+        LOG_ALWAYS_FATAL_IF(!currentTestInfo,
+                            "writeBufferToFile must be called during execution of a test");
+
+        std::string fileName(currentTestInfo->name());
+        // Test names may include the RenderEngine variant separated by '/', which would separate
+        // the file name into a subdirectory if not corrected.
+        std::replace(fileName.begin(), fileName.end(), '/', '-');
+        fileName.append(".ppm");
+
+        std::error_code err;
+        filesystem::create_directories(directory, err);
+        if (err.value()) {
+            ALOGE("Unable to create directory %s for writing %s (%d: %s)", directory.c_str(),
+                  fileName.c_str(), err.value(), err.message().c_str());
+            return;
+        }
+
+        // Append operator ("/") ensures exactly one "/" directly before the argument.
+        const filesystem::path filePath = directory / fileName;
+        std::ofstream file(filePath.c_str(), std::ios::binary);
         if (!file.is_open()) {
-            ALOGE("Unable to open file: %s", filename.c_str());
-            ALOGE("You may need to do: \"adb shell setenforce 0\" to enable "
-                  "surfaceflinger to write debug images");
+            ALOGE("Unable to open file: %s", filePath.c_str());
+            ALOGE("You may need to do: \"adb shell setenforce 0\" to enable surfaceflinger to "
+                  "write debug images, or the %s directory might not give the executing user write "
+                  "permission",
+                  directory.c_str());
             return;
         }
 
@@ -304,6 +336,7 @@ public:
             }
         }
         file.write(reinterpret_cast<char*>(outBuffer.data()), outBuffer.size());
+        ALOGI("Image of incorrect output written to %s", filePath.c_str());
         mBuffer->getBuffer()->unlock();
     }