From 285222d4907ebd45efe1a2f17ff9ce8f60d9250f Mon Sep 17 00:00:00 2001
From: Brad Davis <bdavis@saintandreas.org>
Date: Fri, 17 Feb 2017 12:49:55 -0800
Subject: [PATCH] Add view storage

---
 libraries/shared/src/shared/Storage.cpp | 29 +++++++++----------------
 libraries/shared/src/shared/Storage.h   | 21 +++++++++++++-----
 2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/libraries/shared/src/shared/Storage.cpp b/libraries/shared/src/shared/Storage.cpp
index fe17d678c7..d3f1f3c5d3 100644
--- a/libraries/shared/src/shared/Storage.cpp
+++ b/libraries/shared/src/shared/Storage.cpp
@@ -12,8 +12,16 @@
 
 using namespace storage;
 
+ViewStoragePointer Storage::createView(size_t viewSize, size_t offset) const {
+    auto selfSize = size();
+    if ((viewSize + offset) > selfSize) {
+        throw std::runtime_error("Unable to map file");
+    }
+    return ViewStoragePointer(new ViewStorage(viewSize, data() + offset));
+}
+
 MemoryStoragePointer Storage::toMemoryStorage() const {
-    return std::make_unique<MemoryStorage>(size(), data());
+    return MemoryStoragePointer(new MemoryStorage(size(), data()));
 }
 
 FileStoragePointer Storage::toFileStorage(const QString& filename) const {
@@ -25,14 +33,6 @@ MemoryStorage::MemoryStorage(size_t size, const uint8_t* data) {
     memcpy(_data.data(), data, size);
 }
 
-const uint8_t* MemoryStorage::data() const {
-    return _data.data();
-}
-
-size_t MemoryStorage::size() const {
-    return _data.size();
-}
-
 FileStoragePointer FileStorage::create(const QString& filename, size_t size, const uint8_t* data) {
     QFile file(filename);
     if (!file.open(QFile::ReadWrite | QIODevice::Truncate)) {
@@ -52,7 +52,7 @@ FileStoragePointer FileStorage::create(const QString& filename, size_t size, con
         }
     }
     file.close();
-    return std::make_unique<FileStorage>(filename);
+    return FileStoragePointer(new FileStorage(filename));
 }
 
 FileStorage::FileStorage(const QString& filename) : _file(filename) {
@@ -75,12 +75,3 @@ FileStorage::~FileStorage() {
         _file.close();
     }
 }
-
-
-const uint8_t* FileStorage::data() const {
-    return _mapped;
-}
-
-size_t FileStorage::size() const {
-    return _file.size();
-}
diff --git a/libraries/shared/src/shared/Storage.h b/libraries/shared/src/shared/Storage.h
index 3198172b06..8096b631ed 100644
--- a/libraries/shared/src/shared/Storage.h
+++ b/libraries/shared/src/shared/Storage.h
@@ -23,13 +23,15 @@ namespace storage {
     using MemoryStoragePointer = std::unique_ptr<MemoryStorage>;
     class FileStorage;
     using FileStoragePointer = std::unique_ptr<FileStorage>;
+    class ViewStorage;
+    using ViewStoragePointer = std::unique_ptr<ViewStorage>;
 
     class Storage {
     public:
         virtual ~Storage() {}
         virtual const uint8_t* data() const = 0;
         virtual size_t size() const = 0;
-
+        ViewStoragePointer createView(size_t size, size_t offset = 0) const;
         FileStoragePointer toFileStorage(const QString& filename) const;
         MemoryStoragePointer toMemoryStorage() const;
     };
@@ -37,8 +39,8 @@ namespace storage {
     class MemoryStorage : public Storage {
     public:
         MemoryStorage(size_t size, const uint8_t* data);
-        const uint8_t* data() const override;
-        size_t size() const override;
+        const uint8_t* data() const override { return _data.data(); }
+        size_t size() const override { return _data.size(); }
     private:
         std::vector<uint8_t> _data;
     };
@@ -52,13 +54,22 @@ namespace storage {
         FileStorage(const FileStorage& other) = delete;
         FileStorage& operator=(const FileStorage& other) = delete;
 
-        const uint8_t* data() const override;
-        size_t size() const override;
+        const uint8_t* data() const override { return _mapped; }
+        size_t size() const override { return _file.size(); }
     private:
         QFile _file;
         uint8_t* _mapped { nullptr };
     };
 
+    class ViewStorage : public Storage {
+    public:
+        ViewStorage(size_t size, const uint8_t* data) : _size(size), _data(data) {}
+        const uint8_t* data() const override { return _data; }
+        size_t size() const override { return _size; }
+    private:
+        const size_t _size;
+        const uint8_t* _data;
+    };
 
 }