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asset_v1.h
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1 //
2 // Copyright 2021 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 //
18 // Unless required by applicable law or agreed to in writing, software
19 // distributed under the Apache License with the above modification is
20 // distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
21 // KIND, either express or implied. See the Apache License for the specific
22 // language governing permissions and limitations under the Apache License.
23 //
24 #ifndef INCLUDE_AR_ASSET
25 #error This file should not be included directly. Include asset.h instead.
26 #endif
27 
28 #ifndef PXR_USD_AR_ASSET_V1_H
29 #define PXR_USD_AR_ASSET_V1_H
30 
31 /// \file ar/asset_v1.h
32 
33 #include "pxr/pxr.h"
34 #include "pxr/usd/ar/api.h"
35 
36 #include <cstdio>
37 #include <memory>
38 #include <utility>
39 
41 
42 /// \class ArAsset
43 ///
44 /// Interface for accessing the contents of an asset.
45 ///
46 /// \see ArResolver::OpenAsset for how to retrieve instances of this object.
47 class ArAsset {
48 public:
49  AR_API
50  virtual ~ArAsset();
51 
52  ArAsset(const ArAsset&) = delete;
53 
54  ArAsset& operator=(const ArAsset&) = delete;
55 
56  /// Returns size of the asset.
57  AR_API
58  virtual size_t GetSize() = 0;
59 
60  /// Returns a pointer to a buffer with the contents of the asset,
61  /// with size given by GetSize(). Returns an invalid std::shared_ptr
62  /// if the contents could not be retrieved.
63  ///
64  /// The data in the returned buffer must remain valid while there are
65  /// outstanding copies of the returned std::shared_ptr. Note that the
66  /// deleter stored in the std::shared_ptr may contain additional data
67  /// needed to maintain the buffer's validity.
68  AR_API
69  virtual std::shared_ptr<const char> GetBuffer() = 0;
70 
71  /// Read \p count bytes at \p offset from the beginning of the asset
72  /// into \p buffer. Returns number of bytes read, or 0 on error.
73  ///
74  /// Implementers should range-check calls and return zero for out-of-bounds
75  /// reads.
76  AR_API
77  virtual size_t Read(void* buffer, size_t count, size_t offset) = 0;
78 
79  /// Returns a read-only FILE* handle and offset for this asset if
80  /// available, or (nullptr, 0) otherwise.
81  ///
82  /// The returned handle must remain valid for the lifetime of this
83  /// ArAsset object. The returned offset is the offset from the beginning
84  /// of the FILE* where the asset's contents begins.
85  ///
86  /// This function is marked unsafe because the handle may wind up
87  /// being used in multiple threads depending on the underlying
88  /// resolver implementation. For instance, a resolver may cache
89  /// and return ArAsset objects with the same FILE* to multiple
90  /// threads.
91  ///
92  /// Clients MUST NOT use this handle with functions that cannot be
93  /// called concurrently on the same file descriptor, e.g. read,
94  /// fread, fseek, etc. See ArchPRead for a function that can be used
95  /// to read data from this handle safely.
96  AR_API
97  virtual std::pair<FILE*, size_t> GetFileUnsafe() = 0;
98 
99 protected:
100  AR_API
101  ArAsset();
102 };
103 
105 
106 #endif // PXR_USD_AR_ASSET_V1_H
ArAsset & operator=(const ArAsset &)=delete
#define AR_API
Definition: api.h:40
GLuint buffer
Definition: glcorearb.h:659
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.
virtual AR_API ~ArAsset()
AR_API ArAsset()
GLint GLsizei count
Definition: glcorearb.h:404
PXR_NAMESPACE_CLOSE_SCOPE PXR_NAMESPACE_OPEN_SCOPE
Definition: path.h:1375
#define PXR_NAMESPACE_CLOSE_SCOPE
Definition: pxr.h:91
virtual AR_API std::pair< FILE *, size_t > GetFileUnsafe()=0
GLintptr offset
Definition: glcorearb.h:664