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//===-- LibCxxSpan.cpp ----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "LibCxx.h"
#include "lldb/DataFormatters/FormattersHelpers.h"
#include "lldb/Utility/ConstString.h"
#include "lldb/ValueObject/ValueObject.h"
#include "llvm/ADT/APSInt.h"
#include <optional>
using namespace lldb;
using namespace lldb_private;
using namespace lldb_private::formatters;
namespace lldb_private {
namespace formatters {
class LibcxxStdSpanSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
public:
LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);
~LibcxxStdSpanSyntheticFrontEnd() override = default;
llvm::Expected<uint32_t> CalculateNumChildren() override;
lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;
/// Determines properties of the std::span<> associated with this object
//
// std::span can either be instantiated with a compile-time known
// extent or a std::dynamic_extent (this is the default if only the
// type template argument is provided). The layout of std::span
// depends on whether the extent is dynamic or not. For static
// extents (e.g., std::span<int, 9>):
//
// (std::__1::span<const int, 9>) s = {
// __data = 0x000000016fdff494
// }
//
// For dynamic extents, e.g., std::span<int>, the layout is:
//
// (std::__1::span<const int, 18446744073709551615>) s = {
// __data = 0x000000016fdff494
// __size = 6
// }
//
// This function checks for a '__size' member to determine the number
// of elements in the span. If no such member exists, we get the size
// from the only other place it can be: the template argument.
lldb::ChildCacheState Update() override;
llvm::Expected<size_t> GetIndexOfChildWithName(ConstString name) override;
private:
ValueObject *m_start = nullptr; ///< First element of span. Held, not owned.
CompilerType m_element_type{}; ///< Type of span elements.
size_t m_num_elements = 0; ///< Number of elements in span.
uint32_t m_element_size = 0; ///< Size in bytes of each span element.
};
lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::
LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
: SyntheticChildrenFrontEnd(*valobj_sp) {
if (valobj_sp)
Update();
}
llvm::Expected<uint32_t> lldb_private::formatters::
LibcxxStdSpanSyntheticFrontEnd::CalculateNumChildren() {
return m_num_elements;
}
lldb::ValueObjectSP
lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::GetChildAtIndex(
uint32_t idx) {
if (!m_start)
return {};
uint64_t offset = idx * m_element_size;
offset = offset + m_start->GetValueAsUnsigned(0);
StreamString name;
name.Printf("[%" PRIu64 "]", (uint64_t)idx);
return CreateValueObjectFromAddress(name.GetString(), offset,
m_backend.GetExecutionContextRef(),
m_element_type);
}
lldb::ChildCacheState
lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::Update() {
// Get element type.
ValueObjectSP data_type_finder_sp = GetChildMemberWithName(
m_backend, {ConstString("__data_"), ConstString("__data")});
if (!data_type_finder_sp)
return lldb::ChildCacheState::eRefetch;
m_element_type = data_type_finder_sp->GetCompilerType().GetPointeeType();
// Get element size.
llvm::Expected<uint64_t> size_or_err = m_element_type.GetByteSize(nullptr);
if (!size_or_err)
LLDB_LOG_ERRORV(GetLog(LLDBLog::DataFormatters), size_or_err.takeError(),
"{0}");
else {
m_element_size = *size_or_err;
// Get data.
if (m_element_size > 0) {
m_start = data_type_finder_sp.get();
}
// Get number of elements.
if (auto size_sp = GetChildMemberWithName(
m_backend, {ConstString("__size_"), ConstString("__size")})) {
m_num_elements = size_sp->GetValueAsUnsigned(0);
} else if (auto arg =
m_backend.GetCompilerType().GetIntegralTemplateArgument(1)) {
m_num_elements = arg->value.GetAPSInt().getLimitedValue();
}
}
return lldb::ChildCacheState::eReuse;
}
llvm::Expected<size_t> lldb_private::formatters::
LibcxxStdSpanSyntheticFrontEnd::GetIndexOfChildWithName(ConstString name) {
if (!m_start)
return llvm::createStringError("Type has no child named '%s'",
name.AsCString());
auto optional_idx = formatters::ExtractIndexFromString(name.GetCString());
if (!optional_idx) {
return llvm::createStringError("Type has no child named '%s'",
name.AsCString());
}
return *optional_idx;
}
lldb_private::SyntheticChildrenFrontEnd *
LibcxxStdSpanSyntheticFrontEndCreator(CXXSyntheticChildren *,
lldb::ValueObjectSP valobj_sp) {
if (!valobj_sp)
return nullptr;
CompilerType type = valobj_sp->GetCompilerType();
if (!type.IsValid() || type.GetNumTemplateArguments() != 2)
return nullptr;
return new LibcxxStdSpanSyntheticFrontEnd(valobj_sp);
}
} // namespace formatters
} // namespace lldb_private
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