1 //===-- LibCxxBitset.cpp --------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "LibCxx.h"
10 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
11 #include "lldb/DataFormatters/FormattersHelpers.h"
12 #include "lldb/Target/Target.h"
13 
14 using namespace lldb;
15 using namespace lldb_private;
16 
17 namespace {
18 
19 class BitsetFrontEnd : public SyntheticChildrenFrontEnd {
20 public:
21   BitsetFrontEnd(ValueObject &valobj);
22 
23   size_t GetIndexOfChildWithName(ConstString name) override {
24     return formatters::ExtractIndexFromString(name.GetCString());
25   }
26 
27   bool MightHaveChildren() override { return true; }
28   bool Update() override;
29   size_t CalculateNumChildren() override { return m_elements.size(); }
30   ValueObjectSP GetChildAtIndex(size_t idx) override;
31 
32 private:
33   // The lifetime of a ValueObject and all its derivative ValueObjects
34   // (children, clones, etc.) is managed by a ClusterManager. These
35   // objects are only destroyed when every shared pointer to any of them
36   // is destroyed, so we must not store a shared pointer to any ValueObject
37   // derived from our backend ValueObject (since we're in the same cluster).
38   // Value objects created from raw data (i.e. in a different cluster) must
39   // be referenced via shared pointer to keep them alive, however.
40   std::vector<ValueObjectSP> m_elements;
41   ValueObject* m_first = nullptr;
42   CompilerType m_bool_type;
43   ByteOrder m_byte_order = eByteOrderInvalid;
44   uint8_t m_byte_size = 0;
45 };
46 } // namespace
47 
48 BitsetFrontEnd::BitsetFrontEnd(ValueObject &valobj)
49     : SyntheticChildrenFrontEnd(valobj) {
50   m_bool_type = valobj.GetCompilerType().GetBasicTypeFromAST(eBasicTypeBool);
51   if (auto target_sp = m_backend.GetTargetSP()) {
52     m_byte_order = target_sp->GetArchitecture().GetByteOrder();
53     m_byte_size = target_sp->GetArchitecture().GetAddressByteSize();
54     Update();
55   }
56 }
57 
58 bool BitsetFrontEnd::Update() {
59   m_elements.clear();
60   m_first = nullptr;
61 
62   TargetSP target_sp = m_backend.GetTargetSP();
63   if (!target_sp)
64     return false;
65   size_t capping_size = target_sp->GetMaximumNumberOfChildrenToDisplay();
66 
67   size_t size = 0;
68   if (auto arg = m_backend.GetCompilerType().GetIntegralTemplateArgument(0))
69     size = arg->value.getLimitedValue(capping_size);
70 
71   m_elements.assign(size, ValueObjectSP());
72 
73   m_first = m_backend.GetChildMemberWithName(ConstString("__first_"), true).get();
74   return false;
75 }
76 
77 ValueObjectSP BitsetFrontEnd::GetChildAtIndex(size_t idx) {
78   if (idx >= m_elements.size() || !m_first)
79     return ValueObjectSP();
80 
81   if (m_elements[idx])
82     return m_elements[idx];
83 
84   ExecutionContext ctx = m_backend.GetExecutionContextRef().Lock(false);
85   CompilerType type;
86   ValueObjectSP chunk;
87   // For small bitsets __first_ is not an array, but a plain size_t.
88   if (m_first->GetCompilerType().IsArrayType(&type)) {
89     llvm::Optional<uint64_t> bit_size =
90         type.GetBitSize(ctx.GetBestExecutionContextScope());
91     if (!bit_size || *bit_size == 0)
92       return {};
93     chunk = m_first->GetChildAtIndex(idx / *bit_size, true);
94   } else {
95     type = m_first->GetCompilerType();
96     chunk = m_first->GetSP();
97   }
98   if (!type || !chunk)
99     return {};
100 
101   llvm::Optional<uint64_t> bit_size =
102       type.GetBitSize(ctx.GetBestExecutionContextScope());
103   if (!bit_size || *bit_size == 0)
104     return {};
105   size_t chunk_idx = idx % *bit_size;
106   uint8_t value = !!(chunk->GetValueAsUnsigned(0) & (uint64_t(1) << chunk_idx));
107   DataExtractor data(&value, sizeof(value), m_byte_order, m_byte_size);
108 
109   m_elements[idx] = CreateValueObjectFromData(llvm::formatv("[{0}]", idx).str(),
110                                               data, ctx, m_bool_type);
111 
112   return m_elements[idx];
113 }
114 
115 SyntheticChildrenFrontEnd *formatters::LibcxxBitsetSyntheticFrontEndCreator(
116     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
117   if (valobj_sp)
118     return new BitsetFrontEnd(*valobj_sp);
119   return nullptr;
120 }
121