deepcopy.jl
# This file is a part of Julia. License is MIT: https://julialang.org/license
# deep copying
# Note: deepcopy_internal(::Any, ::IdDict) is
# only exposed for specialization by libraries
"""
deepcopy(x)
Create a deep copy of `x`: everything is copied recursively, resulting in a fully
independent object. For example, deep-copying an array creates deep copies of all
the objects it contains and produces a new array with the consistent relationship
structure (e.g., if the first two elements are the same object in the original array,
the first two elements of the new array will also be the same `deepcopy`ed object).
Calling `deepcopy` on an object should generally
have the same effect as serializing and then deserializing it.
While it isn't normally necessary, user-defined types can override the default `deepcopy`
behavior by defining a specialized version of the function
`deepcopy_internal(x::T, dict::IdDict)` (which shouldn't otherwise be used),
where `T` is the type to be specialized for, and `dict` keeps track of objects copied
so far within the recursion. Within the definition, `deepcopy_internal` should be used
in place of `deepcopy`, and the `dict` variable should be
updated as appropriate before returning.
"""
function deepcopy(@nospecialize x)
isbitstype(typeof(x)) && return x
return deepcopy_internal(x, IdDict())::typeof(x)
end
deepcopy_internal(x::Union{Symbol,Core.MethodInstance,Method,GlobalRef,DataType,Union,UnionAll,Task,Regex},
stackdict::IdDict) = x
deepcopy_internal(x::Tuple, stackdict::IdDict) =
ntuple(i->deepcopy_internal(x[i], stackdict), length(x))
deepcopy_internal(x::Module, stackdict::IdDict) = error("deepcopy of Modules not supported")
function deepcopy_internal(x::SimpleVector, stackdict::IdDict)
if haskey(stackdict, x)
return stackdict[x]
end
y = Core.svec(Any[deepcopy_internal(x[i], stackdict) for i = 1:length(x)]...)
stackdict[x] = y
return y
end
function deepcopy_internal(x::String, stackdict::IdDict)
if haskey(stackdict, x)
return stackdict[x]
end
y = GC.@preserve x unsafe_string(pointer(x), sizeof(x))
stackdict[x] = y
return y
end
function deepcopy_internal(@nospecialize(x), stackdict::IdDict)
T = typeof(x)::DataType
nf = nfields(x)
if ismutable(x)
if haskey(stackdict, x)
return stackdict[x]
end
y = ccall(:jl_new_struct_uninit, Any, (Any,), T)
stackdict[x] = y
for i in 1:nf
if isdefined(x, i)
xi = getfield(x, i)
if !isbits(xi)
xi = deepcopy_internal(xi, stackdict)::typeof(xi)
end
ccall(:jl_set_nth_field, Cvoid, (Any, Csize_t, Any), y, i-1, xi)
end
end
elseif nf == 0 || isbitstype(T)
y = x
else
flds = Vector{Any}(undef, nf)
for i in 1:nf
if isdefined(x, i)
xi = getfield(x, i)
if !isbits(xi)
xi = deepcopy_internal(xi, stackdict)::typeof(xi)
end
flds[i] = xi
else
nf = i - 1 # rest of tail must be undefined values
break
end
end
y = ccall(:jl_new_structv, Any, (Any, Ptr{Any}, UInt32), T, flds, nf)
end
return y::T
end
function deepcopy_internal(x::Memory, stackdict::IdDict)
if haskey(stackdict, x)
return stackdict[x]::typeof(x)
end
_deepcopy_memory_t(x, eltype(x), stackdict)
end
function _deepcopy_memory_t(@nospecialize(x::Memory), T, stackdict::IdDict)
if isbitstype(T)
return (stackdict[x]=copy(x))
end
dest = typeof(x)(undef, length(x))
stackdict[x] = dest
xr = Core.memoryref(x)
dr = Core.memoryref(dest)
for i = 1:length(x)
xi = Core.memoryref(xr, i, false)
if Core.memoryref_isassigned(xi, :not_atomic, false)
xi = Core.memoryrefget(xi, :not_atomic, false)
if !isbits(xi)
xi = deepcopy_internal(xi, stackdict)::typeof(xi)
end
di = Core.memoryref(dr, i, false)
Core.memoryrefset!(di, xi, :not_atomic, false)
end
end
return dest
end
@eval function deepcopy_internal(x::Array{T, N}, stackdict::IdDict) where {T, N}
if haskey(stackdict, x)
return stackdict[x]::typeof(x)
end
stackdict[x] = $(Expr(:new, :(Array{T, N}), :(deepcopy_internal(x.ref, stackdict)), :(x.size)))
end
function deepcopy_internal(x::GenericMemoryRef, stackdict::IdDict)
if haskey(stackdict, x)
return stackdict[x]::typeof(x)
end
mem = getfield(x, :mem)
dest = GenericMemoryRef(deepcopy_internal(mem, stackdict)::typeof(mem))
i = memoryrefoffset(x)
i == 1 || (dest = Core.memoryref(dest, i, true))
return dest
end
function deepcopy_internal(x::Union{Dict,IdDict}, stackdict::IdDict)
if haskey(stackdict, x)
return stackdict[x]::typeof(x)
end
if isbitstype(eltype(x))
return (stackdict[x] = copy(x))
end
dest = empty(x)
stackdict[x] = dest
for (k, v) in x
dest[deepcopy_internal(k, stackdict)] = deepcopy_internal(v, stackdict)
end
dest
end
function deepcopy_internal(x::AbstractLock, stackdict::IdDict)
if haskey(stackdict, x)
return stackdict[x]
end
y = typeof(x)()
stackdict[x] = y
return y
end
function deepcopy_internal(x::GenericCondition, stackdict::IdDict)
if haskey(stackdict, x)
return stackdict[x]
end
y = typeof(x)(deepcopy_internal(x.lock, stackdict))
stackdict[x] = y
return y
end