Merge pull request #3243 from Sonicadvance1/loadfile_unsized

FEXCore/FileLoading: Updates helper to load file that is backed by memory

FEXCore/Source/Utils/FileLoading.cpp

@@ -24,24 +24,48 @@ static bool LoadFileImpl(T &Data, const fextl::string &Filepath, size_t FixedSiz
   size_t FileSize{};
   if (FixedSize == 0) {
     struct stat buf;
-    if (fstat(FD, &buf) != 0) {
-      close(FD);
-      return false;
+    if (fstat(FD, &buf) == 0) {
+      FileSize = buf.st_size;
     }
-
-    FileSize = buf.st_size;
   }
   else {
     FileSize = FixedSize;
   }
 
   ssize_t Read = -1;
-  if (FileSize > 0) {
+  bool LoadedFile{};
+  if (FileSize) {
+    // File size is known upfront
     Data.resize(FileSize);
     Read = pread(FD, &Data.at(0), FileSize, 0);
+
+    LoadedFile = Read == FileSize;
+  }
+  else {
+    // The file is either empty or its size is unknown (e.g. procfs data).
+    // Try reading in chunks instead
+    ssize_t CurrentOffset = 0;
+    constexpr size_t READ_SIZE = 4096;
+    Data.resize(READ_SIZE);
+
+    while ((Read = pread(FD, &Data.at(CurrentOffset), READ_SIZE, CurrentOffset)) == READ_SIZE) {
+      CurrentOffset += Read;
+      Data.resize(CurrentOffset + Read);
+    }
+
+    if (Read == -1) {
+      Data.clear();
+      close(FD);
+      return false;
+    }
+
+    // Final resize to ensure there is no garbage data past the end.
+    Data.resize(CurrentOffset + Read);
+
+    LoadedFile = true;
   }
   close(FD);
-  return Read == FileSize;
+  return LoadedFile;
 }
 
 ssize_t LoadFileToBuffer(const fextl::string &Filepath, std::span<char> Buffer) {

FEXCore/unittests/APITests/FileLoading.cpp

@@ -0,0 +1,22 @@
+#include <FEXCore/Utils/FileLoading.h>
+#include <catch2/catch.hpp>
+
+TEST_CASE("LoadFile-Doesn'tExist") {
+  fextl::string MapsFile;
+  auto Read = FEXCore::FileLoading::LoadFile(MapsFile, "/tmp/a/b/c/d/e/z");
+  REQUIRE(MapsFile.size() == 0);
+  REQUIRE(Read == false);
+}
+
+TEST_CASE("LoadFile-procfs") {
+  fextl::string MapsFile;
+  FEXCore::FileLoading::LoadFile(MapsFile, "/proc/self/maps");
+  REQUIRE(MapsFile.size() != 0);
+}
+
+TEST_CASE("LoadFile-Buffer") {
+  fextl::string MapsFile;
+  MapsFile.resize(16);
+  auto Read = FEXCore::FileLoading::LoadFileToBuffer("/proc/self/maps", MapsFile);
+  REQUIRE(MapsFile.size() == Read);
+}