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asset.h
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1 //
2 // Copyright 2018 Pixar
3 //
4 // Licensed under the Apache License, Version 2.0 (the "Apache License")
5 // with the following modification; you may not use this file except in
6 // compliance with the Apache License and the following modification to it:
7 // Section 6. Trademarks. is deleted and replaced with:
8 //
9 // 6. Trademarks. This License does not grant permission to use the trade
10 // names, trademarks, service marks, or product names of the Licensor
11 // and its affiliates, except as required to comply with Section 4(c) of
12 // the License and to reproduce the content of the NOTICE file.
13 //
14 // You may obtain a copy of the Apache License at
15 //
16 // http://www.apache.org/licenses/LICENSE-2.0
17 //
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19 // distributed under the Apache License with the above modification is
20 // distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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22 // language governing permissions and limitations under the Apache License.
23 //
24 #ifndef PXR_USD_AR_ASSET_H
25 #define PXR_USD_AR_ASSET_H
26 
27 /// \file ar/asset.h
28 
29 #include "pxr/pxr.h"
30 #include "pxr/usd/ar/api.h"
31 
32 #include <cstdio>
33 #include <memory>
34 #include <utility>
35 
37 
38 /// \class ArAsset
39 ///
40 /// Interface for accessing the contents of an asset.
41 ///
42 /// \see ArResolver::OpenAsset for how to retrieve instances of this object.
43 class ArAsset {
44 public:
45  AR_API
46  virtual ~ArAsset();
47 
48  ArAsset(const ArAsset&) = delete;
49 
50  ArAsset& operator=(const ArAsset&) = delete;
51 
52  /// Returns size of the asset.
53  AR_API
54  virtual size_t GetSize() = 0;
55 
56  /// Returns a pointer to a buffer with the contents of the asset,
57  /// with size given by GetSize(). Returns an invalid std::shared_ptr
58  /// if the contents could not be retrieved.
59  ///
60  /// The data in the returned buffer must remain valid while there are
61  /// outstanding copies of the returned std::shared_ptr. Note that the
62  /// deleter stored in the std::shared_ptr may contain additional data
63  /// needed to maintain the buffer's validity.
64  AR_API
65  virtual std::shared_ptr<const char> GetBuffer() = 0;
66 
67  /// Read \p count bytes at \p offset from the beginning of the asset
68  /// into \p buffer. Returns number of bytes read, or 0 on error.
69  AR_API
70  virtual size_t Read(void* buffer, size_t count, size_t offset) = 0;
71 
72  /// Returns a read-only FILE* handle and offset for this asset if
73  /// available, or (nullptr, 0) otherwise.
74  ///
75  /// The returned handle must remain valid for the lifetime of this
76  /// ArAsset object. The returned offset is the offset from the beginning
77  /// of the FILE* where the asset's contents begins.
78  ///
79  /// This function is marked unsafe because the handle may wind up
80  /// being used in multiple threads depending on the underlying
81  /// resolver implementation. For instance, a resolver may cache
82  /// and return ArAsset objects with the same FILE* to multiple
83  /// threads.
84  ///
85  /// Clients MUST NOT use this handle with functions that cannot be
86  /// called concurrently on the same file descriptor, e.g. read,
87  /// fread, fseek, etc. See ArchPRead for a function that can be used
88  /// to read data from this handle safely.
89  AR_API
90  virtual std::pair<FILE*, size_t> GetFileUnsafe() = 0;
91 
92 protected:
93  AR_API
94  ArAsset();
95 };
96 
98 
99 #endif // PXR_USD_AR_ASSET_H
ArAsset & operator=(const ArAsset &)=delete
Definition: asset.h:43
#define AR_API
Definition: api.h:40
virtual AR_API size_t Read(void *buffer, size_t count, size_t offset)=0
virtual AR_API std::shared_ptr< const char > GetBuffer()=0
virtual AR_API size_t GetSize()=0
Returns size of the asset.
GLuint buffer
Definition: glew.h:1680
virtual AR_API ~ArAsset()
AR_API ArAsset()
PXR_NAMESPACE_CLOSE_SCOPE PXR_NAMESPACE_OPEN_SCOPE
Definition: path.h:1346
GLuint GLuint GLsizei count
Definition: glew.h:1253
#define PXR_NAMESPACE_CLOSE_SCOPE
Definition: pxr.h:91
virtual AR_API std::pair< FILE *, size_t > GetFileUnsafe()=0
GLintptr offset
Definition: glew.h:1682