1 /*
2 * Copyright 2023 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #ifndef SkRasterPipelineContextUtils_DEFINED
9 #define SkRasterPipelineContextUtils_DEFINED
10
11 #include "src/base/SkArenaAlloc.h"
12 #include "src/base/SkUtils.h"
13
14 #include <cstring>
15 #include <type_traits>
16
17 namespace SkRPCtxUtils {
18
19 template <typename T>
20 using UnpackedType = typename std::conditional<sizeof(T) <= sizeof(void*), T, const T&>::type;
21
22 /**
23 * SkRPCtxUtils::Pack will check if the passed-in struct is small enough to fit directly in the
24 * context field. If so, it will return the data bit-casted into a void pointer. If not, it
25 * allocates a copy of the struct inside the alloc and then returns a pointer to the copy.
26 */
27 template <typename T>
Pack(const T & ctx,SkArenaAlloc * alloc)28 [[maybe_unused]] static void* Pack(const T& ctx, SkArenaAlloc* alloc) {
29 // If the context is small enough to fit in a pointer, bit-cast it; if not, alloc a copy.
30 if constexpr (sizeof(T) <= sizeof(void*)) {
31 return sk_bit_cast<void*>(ctx);
32 } else {
33 return alloc->make<T>(ctx);
34 }
35 }
36
37 /**
38 * SkRPCtxUtils::Unpack performs the reverse operation: either un-bitcasting the object back to its
39 * original form, or returning the pointer as-is, depending on the size of the type.
40 */
41 template <typename T>
Unpack(const T * ctx)42 [[maybe_unused]] static UnpackedType<T> Unpack(const T* ctx) {
43 // If the context struct fits in a pointer, reinterpret the bits; if it doesn't, return
44 // a reference. This can vary based on the architecture (32-bit pointers vs 64-bit) so we
45 // let the compiler decide which is right, rather than hard-coding it.
46 if constexpr (sizeof(T) <= sizeof(void*)) {
47 return sk_bit_cast<T>(ctx);
48 } else {
49 return *ctx;
50 }
51 }
52
53 } // namespace SkRPCtxUtils
54
55 #endif // SkRasterPipelineContextUtils_DEFINED
56