Add LoadFile function

Author: Kn99HN

include/flatbuffers/file_manager.h

@@ -20,6 +20,8 @@
 #include <set>
 #include <string>
 
+#include "flatbuffers/util.h"
+
 namespace flatbuffers {
 
 // A File interface to write data to file by default or
@@ -33,7 +35,7 @@ class FileManager {
                         const std::string &content) = 0;
 
   virtual bool LoadFile(const std::string &absolute_file_name,
-                        std::string *content) = 0;
+                        std::string *buf) = 0;
 
  private:
   // Copying is not supported.

src/file_binary_writer.cpp

@@ -31,6 +31,19 @@ class FileBinaryWriter : public FileManager {
     ofs.write(content.c_str(), content.size());
     return !ofs.bad();
   }
+
+  bool Loadfile(const std::string &absolute_file_name, std::string *output) {
+    if (DirExists(absolute_file_name.c_str())) return false;
+    std::ifstream ifs(absolute_file_name, std::ifstream::binary);
+    if (!ifs.is_open()) return false;
+    // The fastest way to read a file into a string.
+    ifs.seekg(0, std::ios::end);
+    auto size = ifs.tellg();
+    (*output).resize(static_cast<size_t>(size));
+    ifs.seekg(0, std::ios::beg);
+    ifs.read(&(*output)[0], (*output).size());
+    return !ifs.bad();
+  }
 };
 
 }  // namespace flatbuffers

src/file_name_saving_file_manager.cpp

@@ -27,14 +27,21 @@ class FileNameSavingFileManager : public FileManager {
   FileNameSavingFileManager(std::set<std::string> file_names)
       : file_names_(file_names) {}
 
-  bool SaveFile(const std::string &absolute_file_name, const std::string &content) override {
-    (void) content;
+  bool SaveFile(const std::string &absolute_file_name,
+                const std::string &content) override {
+    (void)content;
     auto pair = file_names_.insert(absolute_file_name);
     // pair.second indicates whether the insertion is
     // successful or not.
     return pair.second;
   }
 
+  bool Loadfile(const std::string &absolute_file_name, std::string *content) {
+    (void)absolute_file_name;
+    (void)content;
+    return false;
+  }
+
  private:
   std::set<std::string> file_names_;
 };

src/file_writer.cpp

@@ -31,6 +31,17 @@ class FileWriter : public FileManager {
     ofs.write(content.c_str(), content.size());
     return !ofs.bad();
   }
+
+  bool Loadfile(const std::string &absolute_file_name, std::string *output) {
+    if (DirExists(absolute_file_name.c_str())) return false;
+    std::ifstream ifs(absolute_file_name, std::ifstream::in);
+    if (!ifs.is_open()) return false;
+    // This is slower, but works correctly on all platforms for text files.
+    std::ostringstream oss;
+    oss << ifs.rdbuf();
+    *output = oss.str();
+    return !ifs.bad();
+  }
 };
 
 }  // namespace flatbuffers