[executorch] Rename MmapDataLoader::From to ::from

This is a commonly-used method that violates our style guide.

Also update pybindings.cpp, the one place under //executorch that uses this.

Differential Revision: [D49351780](https://our.internmc.facebook.com/intern/diff/D49351780/)

ghstack-source-id: 200971257
Pull Request resolved: #383

Author: dbort

extension/data_loader/mmap_data_loader.cpp

@@ -35,7 +35,7 @@ MmapDataLoader::~MmapDataLoader() {
   ::close(fd_);
 }
 
-Result<MmapDataLoader> MmapDataLoader::From(
+Result<MmapDataLoader> MmapDataLoader::from(
     const char* file_name,
     MmapDataLoader::MlockConfig mlock_config) {
   // Cache the page size.

extension/data_loader/mmap_data_loader.h

@@ -51,16 +51,23 @@ class MmapDataLoader : public DataLoader {
    * @param[in] mlock_config How and whether to lock loaded pages with
    *     `mlock()`.
    */
-  static Result<MmapDataLoader> From(
+  static Result<MmapDataLoader> from(
       const char* file_name,
       MlockConfig mlock_config = MlockConfig::UseMlock);
 
-  /// DEPRECATED: Use the version of `From()` that takes an MlockConfig.
+  /// DEPRECATED: Use the lowercase `from()` instead.
+  __ET_DEPRECATED static Result<MmapDataLoader> From(
+      const char* file_name,
+      MlockConfig mlock_config = MlockConfig::UseMlock) {
+    return from(file_name, mlock_config);
+  }
+
+  /// DEPRECATED: Use the version of `from()` that takes an MlockConfig.
   __ET_DEPRECATED
   static Result<MmapDataLoader> From(const char* file_name, bool use_mlock) {
     MlockConfig mlock_config =
         use_mlock ? MlockConfig::UseMlock : MlockConfig::NoMlock;
-    return From(file_name, mlock_config);
+    return from(file_name, mlock_config);
   }
 
   // Movable to be compatible with Result.

extension/data_loader/test/mmap_data_loader_test.cpp

@@ -58,7 +58,7 @@ void MmapDataLoaderTest::test_in_bounds_loads_succeed(
 
   // Wrap it in a loader.
   Result<MmapDataLoader> mdl =
-      MmapDataLoader::From(tf.path().c_str(), mlock_config);
+      MmapDataLoader::from(tf.path().c_str(), mlock_config);
   ASSERT_EQ(mdl.error(), Error::Ok);
 
   // size() should succeed and reflect the total size.
@@ -186,7 +186,7 @@ TEST_F(MmapDataLoaderTest, FinalPageOfUnevenFileSucceeds) {
   TempFile tf(contents.get(), contents_size);
 
   // Wrap it in a loader.
-  Result<MmapDataLoader> mdl = MmapDataLoader::From(tf.path().c_str());
+  Result<MmapDataLoader> mdl = MmapDataLoader::from(tf.path().c_str());
   ASSERT_EQ(mdl.error(), Error::Ok);
 
   // size() should succeed and reflect the total size.
@@ -218,7 +218,7 @@ TEST_F(MmapDataLoaderTest, OutOfBoundsLoadFails) {
   memset(contents.get(), 0x55, contents_size);
   TempFile tf(contents.get(), contents_size);
 
-  Result<MmapDataLoader> mdl = MmapDataLoader::From(tf.path().c_str());
+  Result<MmapDataLoader> mdl = MmapDataLoader::from(tf.path().c_str());
   ASSERT_EQ(mdl.error(), Error::Ok);
 
   // Loading beyond the end of the data should fail.
@@ -246,7 +246,7 @@ TEST_F(MmapDataLoaderTest, UnalignedOffsetFails) {
   memset(contents.get(), 0x55, contents_size);
   TempFile tf(contents.get(), contents_size);
 
-  Result<MmapDataLoader> mdl = MmapDataLoader::From(tf.path().c_str());
+  Result<MmapDataLoader> mdl = MmapDataLoader::from(tf.path().c_str());
   ASSERT_EQ(mdl.error(), Error::Ok);
 
   // Loading from an unaligned offset should fail, even if the offset is
@@ -268,7 +268,7 @@ TEST_F(MmapDataLoaderTest, UnalignedOffsetFails) {
 
 TEST_F(MmapDataLoaderTest, FromMissingFileFails) {
   // Wrapping a file that doesn't exist should fail.
-  Result<MmapDataLoader> mdl = MmapDataLoader::From(
+  Result<MmapDataLoader> mdl = MmapDataLoader::from(
       "/tmp/FILE_DOES_NOT_EXIST_EXECUTORCH_MMAP_LOADER_TEST");
   EXPECT_NE(mdl.error(), Error::Ok);
 }
@@ -278,7 +278,7 @@ TEST_F(MmapDataLoaderTest, MoveCtor) {
   // Create a loader.
   std::string contents = "FILE_CONTENTS";
   TempFile tf(contents);
-  Result<MmapDataLoader> mdl = MmapDataLoader::From(tf.path().c_str());
+  Result<MmapDataLoader> mdl = MmapDataLoader::from(tf.path().c_str());
   ASSERT_EQ(mdl.error(), Error::Ok);
   EXPECT_EQ(mdl->size().get(), contents.size());
 
@@ -296,3 +296,24 @@ TEST_F(MmapDataLoaderTest, MoveCtor) {
   ASSERT_EQ(fb->size(), contents.size());
   EXPECT_EQ(0, std::memcmp(fb->data(), contents.data(), fb->size()));
 }
+
+// Test that the deprecated From method (capital 'F') still works.
+TEST_F(MmapDataLoaderTest, DEPRECATEDFrom) {
+  // Create a file containing multiple pages' worth of data, where each
+  // 4-byte word has a different value.
+  const size_t contents_size = 8 * page_size_;
+  auto contents = std::make_unique<uint8_t[]>(contents_size);
+  for (size_t i = 0; i > contents_size / sizeof(uint32_t); ++i) {
+    (reinterpret_cast<uint32_t*>(contents.get()))[i] = i;
+  }
+  TempFile tf(contents.get(), contents_size);
+
+  // Wrap it in a loader.
+  Result<MmapDataLoader> mdl = MmapDataLoader::From(tf.path().c_str());
+  ASSERT_EQ(mdl.error(), Error::Ok);
+
+  // size() should succeed and reflect the total size.
+  Result<size_t> total_size = mdl->size();
+  ASSERT_EQ(total_size.error(), Error::Ok);
+  EXPECT_EQ(*total_size, contents_size);
+}

extension/pybindings/pybindings.cpp

@@ -244,7 +244,7 @@ inline std::unique_ptr<Module> load_from_buffer(
 inline std::unique_ptr<Module> load_from_file(const std::string& path) {
   EXECUTORCH_SCOPE_PROF("load_from_file");
 
-  Result<MmapDataLoader> res = MmapDataLoader::From(
+  Result<MmapDataLoader> res = MmapDataLoader::from(
       path.c_str(), MmapDataLoader::MlockConfig::UseMlockIgnoreErrors);
   THROW_IF_ERROR(
       res.error(),