A signature for a given file on disk. More...

#include <DataFileCache.h>

Public Member Functions
	CacheSignature ()=default
	CacheSignature (lldb_private::Module *module)
	Create a signature from a module.
	CacheSignature (lldb_private::ObjectFile *objfile)
	Create a signature from an object file.
void	Clear ()
bool	IsValid () const
	Return true only if the CacheSignature is valid.
bool	operator== (const CacheSignature &rhs) const
	Check if two signatures are the same.
bool	operator!= (const CacheSignature &rhs) const
	Check if two signatures differ.
bool	Encode (DataEncoder &encoder) const
	Encode this object into a data encoder object.
bool	Decode (const DataExtractor &data, lldb::offset_t *offset_ptr)
	Decode a serialized version of this object from data.

Public Attributes
std::optional< UUID >	m_uuid
	UUID of object file or module.
std::optional< std::time_t >	m_mod_time
	Modification time of file on disk.
std::optional< std::time_t >	m_obj_mod_time
	If this describes a .o file with a BSD archive, the BSD archive's modification time will be in m_mod_time, and the .o file's modification time will be in this m_obj_mod_time.

Detailed Description

A signature for a given file on disk.

There are two hashes for each file in the LLDB Index Cache. One hash uniquely identifies the binary, incorporating the name/filepath, triple, architecture – things that do not change as the same binary is recompiled with update code. ObjectFile::GetCacheHash() and Module::GetHash() provide these hashes.

The second hash, calculated in this class, is based on the mod date and UUID of the binary and does change on every recompile of the same binary.

The two hashes allow us to identify a file uniquely in the LLDB Index Cache and re-use the cache if the existing entry is a match for both. It also allows us to remove the entry for a previous build of a specific file, and save the new recompiled binary's symbol table in the LLDB Index Cache in its place.

Definition at line 117 of file DataFileCache.h.

Constructor & Destructor Documentation

◆ CacheSignature() [1/3]

lldb_private::CacheSignature::CacheSignature ( )

default

Referenced by operator!=(), and operator==().

◆ CacheSignature() [2/3]

CacheSignature::CacheSignature ( lldb_private::Module * module )

Create a signature from a module.

Definition at line 176 of file DataFileCache.cpp.

References Clear(), lldb_private::Module::GetModificationTime(), lldb_private::Module::GetObjectModificationTime(), lldb_private::UUID::IsValid(), m_mod_time, m_obj_mod_time, and m_uuid.

◆ CacheSignature() [3/3]

CacheSignature::CacheSignature ( lldb_private::ObjectFile * objfile )

Create a signature from an object file.

Definition at line 192 of file DataFileCache.cpp.

References Clear(), lldb_private::ObjectFile::GetFileSpec(), lldb_private::FileSystem::GetModificationTime(), lldb_private::ModuleChild::GetModule(), lldb_private::ObjectFile::GetUUID(), lldb_private::FileSystem::Instance(), lldb_private::UUID::IsValid(), m_mod_time, m_obj_mod_time, and m_uuid.

Member Function Documentation

◆ Clear()

void lldb_private::CacheSignature::Clear ( )

inline

Definition at line 135 of file DataFileCache.h.

References m_mod_time, m_obj_mod_time, and m_uuid.

Referenced by CacheSignature(), CacheSignature(), and Decode().

◆ Decode()

bool CacheSignature::Decode	(	const DataExtractor &	data,
		lldb::offset_t *	offset_ptr )

Decode a serialized version of this object from data.

Parameters

data	The decoder object that references the serialized data.
offset_ptr	A pointer that contains the offset from which the data will be decoded from that gets updated as data gets decoded.

Returns: True if the signature was successfully decoded, false otherwise.

Definition at line 242 of file DataFileCache.cpp.

References Clear(), eSignatureEnd, eSignatureModTime, eSignatureObjectModTime, eSignatureUUID, lldb_private::DataExtractor::GetData(), lldb_private::DataExtractor::GetU32(), lldb_private::DataExtractor::GetU8(), IsValid(), m_mod_time, m_obj_mod_time, and m_uuid.

Referenced by lldb_private::plugin::dwarf::ManualDWARFIndex::Decode(), and lldb_private::Symtab::Decode().

◆ Encode()

bool CacheSignature::Encode ( DataEncoder & encoder ) const

Encode this object into a data encoder object.

This allows this object to be serialized to disk. The CacheSignature object must have at least one member variable that has a value in order to be serialized so that we can match this data to when the cached file is loaded at a later time.

Parameters

encoder A data encoder object that serialized bytes will be encoded into.

Returns: True if a signature was encoded, and false if there were no member variables that had value. False indicates this data should not be cached to disk because we were unable to encode a valid signature.

Definition at line 220 of file DataFileCache.cpp.

References lldb_private::DataEncoder::AppendData(), lldb_private::DataEncoder::AppendU32(), lldb_private::DataEncoder::AppendU8(), eSignatureEnd, eSignatureModTime, eSignatureObjectModTime, eSignatureUUID, IsValid(), m_mod_time, m_obj_mod_time, and m_uuid.

Referenced by lldb_private::plugin::dwarf::ManualDWARFIndex::Encode(), and lldb_private::Symtab::Encode().

◆ IsValid()

bool lldb_private::CacheSignature::IsValid ( ) const

inline

Return true only if the CacheSignature is valid.

Cache signatures are considered valid only if there is a UUID in the file that can uniquely identify the file. Some build systems play with modification times of file so we can not trust them without using valid unique idenifier like the UUID being valid.

Definition at line 147 of file DataFileCache.h.

References m_uuid.

Referenced by Decode(), and Encode().

◆ operator!=()

bool lldb_private::CacheSignature::operator!= ( const CacheSignature & rhs ) const

inline

Check if two signatures differ.

Definition at line 156 of file DataFileCache.h.

References CacheSignature().

◆ operator==()

bool lldb_private::CacheSignature::operator== ( const CacheSignature & rhs ) const

inline

Check if two signatures are the same.

Definition at line 150 of file DataFileCache.h.

References CacheSignature(), m_mod_time, m_obj_mod_time, and m_uuid.

Member Data Documentation

◆ m_mod_time

std::optional<std::time_t> lldb_private::CacheSignature::m_mod_time

Modification time of file on disk.

Definition at line 121 of file DataFileCache.h.

Referenced by CacheSignature(), CacheSignature(), Clear(), Decode(), Encode(), and operator==().

◆ m_obj_mod_time

std::optional<std::time_t> lldb_private::CacheSignature::m_obj_mod_time

If this describes a .o file with a BSD archive, the BSD archive's modification time will be in m_mod_time, and the .o file's modification time will be in this m_obj_mod_time.

Definition at line 125 of file DataFileCache.h.

Referenced by CacheSignature(), CacheSignature(), Clear(), Decode(), Encode(), and operator==().

◆ m_uuid

std::optional<UUID> lldb_private::CacheSignature::m_uuid

UUID of object file or module.

Definition at line 119 of file DataFileCache.h.

Referenced by CacheSignature(), CacheSignature(), Clear(), Decode(), Encode(), IsValid(), and operator==().

The documentation for this struct was generated from the following files:

Public Member Functions

Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ CacheSignature() [1/3]

◆ CacheSignature() [2/3]

◆ CacheSignature() [3/3]

Member Function Documentation

◆ Clear()

◆ Decode()

◆ Encode()

◆ IsValid()

◆ operator!=()

◆ operator==()

Member Data Documentation

◆ m_mod_time

◆ m_obj_mod_time

◆ m_uuid