125 lines
4.5 KiB
Julia
125 lines
4.5 KiB
Julia
# This file is a part of Julia. License is MIT: https://julialang.org/license
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"""
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Ref{T}
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An object that safely references data of type `T`. This type is guaranteed to point to
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valid, Julia-allocated memory of the correct type. The underlying data is protected from
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freeing by the garbage collector as long as the `Ref` itself is referenced.
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When passed as a `ccall` argument (either as a `Ptr` or `Ref` type), a `Ref` object will be
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converted to a native pointer to the data it references.
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There is no invalid (NULL) `Ref`.
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"""
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Ref
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# C NUL-terminated string pointers; these can be used in ccall
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# instead of Ptr{Cchar} and Ptr{Cwchar_t}, respectively, to enforce
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# a check for embedded NUL chars in the string (to avoid silent truncation).
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if Int === Int64
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primitive type Cstring 64 end
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primitive type Cwstring 64 end
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else
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primitive type Cstring 32 end
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primitive type Cwstring 32 end
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end
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### General Methods for Ref{T} type
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eltype(x::Type{Ref{T}}) where {T} = T
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convert(::Type{Ref{T}}, x::Ref{T}) where {T} = x
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# create Ref objects for general object conversion
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unsafe_convert(::Type{Ref{T}}, x::Ref{T}) where {T} = unsafe_convert(Ptr{T}, x)
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unsafe_convert(::Type{Ref{T}}, x) where {T} = unsafe_convert(Ptr{T}, x)
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### Methods for a Ref object that can store a single value of any type
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mutable struct RefValue{T} <: Ref{T}
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x::T
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RefValue{T}() where {T} = new()
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RefValue{T}(x) where {T} = new(x)
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end
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RefValue(x::T) where {T} = RefValue{T}(x)
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isassigned(x::RefValue) = isdefined(x, :x)
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Ref(x::Ref) = x
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Ref(x::Any) = RefValue(x)
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Ref(x::Ptr{T}, i::Integer=1) where {T} = x + (i-1)*Core.sizeof(T)
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Ref(x, i::Integer) = (i != 1 && error("Object only has one element"); Ref(x))
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Ref{T}() where {T} = RefValue{T}() # Ref{T}()
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Ref{T}(x) where {T} = RefValue{T}(x) # Ref{T}(x)
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convert(::Type{Ref{T}}, x) where {T} = RefValue{T}(x)
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function unsafe_convert(P::Type{Ptr{T}}, b::RefValue{T}) where T
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if isbits(T)
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return convert(P, data_pointer_from_objref(b))
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else
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return convert(P, data_pointer_from_objref(b.x))
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end
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end
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function unsafe_convert(P::Type{Ptr{Any}}, b::RefValue{Any})
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return convert(P, data_pointer_from_objref(b))
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end
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unsafe_convert(::Type{Ptr{Void}}, b::RefValue{T}) where {T} = convert(Ptr{Void}, unsafe_convert(Ptr{T}, b))
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### Methods for a Ref object that is backed by an array at index i
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struct RefArray{T,A<:AbstractArray{T},R} <: Ref{T}
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x::A
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i::Int
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roots::R # should be either ::Void or ::Any
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RefArray{T,A,R}(x,i,roots=nothing) where {T,A<:AbstractArray{T},R} = new(x,i,roots)
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end
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RefArray(x::AbstractArray{T}, i::Int, roots::Any) where {T} = RefArray{T,typeof(x),Any}(x, i, roots)
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RefArray(x::AbstractArray{T}, i::Int=1, roots::Void=nothing) where {T} = RefArray{T,typeof(x),Void}(x, i, nothing)
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convert(::Type{Ref{T}}, x::AbstractArray{T}) where {T} = RefArray(x, 1)
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Ref(x::AbstractArray, i::Integer=1) = RefArray(x, i)
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function unsafe_convert(P::Type{Ptr{T}}, b::RefArray{T}) where T
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if isbits(T)
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convert(P, pointer(b.x, b.i))
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else
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convert(P, data_pointer_from_objref(b.x[b.i]))
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end
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end
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function unsafe_convert(P::Type{Ptr{Any}}, b::RefArray{Any})
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return convert(P, pointer(b.x, b.i))
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end
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unsafe_convert(::Type{Ptr{Void}}, b::RefArray{T}) where {T} = convert(Ptr{Void}, unsafe_convert(Ptr{T}, b))
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# convert Arrays to pointer arrays for ccall
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function Ref{P}(a::Array{<:Union{Ptr,Cwstring,Cstring}}) where P<:Union{Ptr,Cwstring,Cstring}
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return RefArray(a) # effectively a no-op
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end
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function Ref{P}(a::Array{T}) where P<:Union{Ptr,Cwstring,Cstring} where T
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if (!isbits(T) && T <: eltype(P))
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# this Array already has the right memory layout for the requested Ref
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return RefArray(a,1,false) # root something, so that this function is type-stable
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else
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ptrs = Vector{P}(length(a)+1)
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roots = Vector{Any}(length(a))
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for i = 1:length(a)
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root = cconvert(P, a[i])
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ptrs[i] = unsafe_convert(P, root)::P
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roots[i] = root
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end
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ptrs[length(a)+1] = C_NULL
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return RefArray(ptrs,1,roots)
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end
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end
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cconvert(::Type{Ptr{P}}, a::Array{<:Ptr}) where {P<:Ptr} = a
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cconvert(::Type{Ref{P}}, a::Array{<:Ptr}) where {P<:Ptr} = a
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cconvert(::Type{Ptr{P}}, a::Array) where {P<:Union{Ptr,Cwstring,Cstring}} = Ref{P}(a)
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cconvert(::Type{Ref{P}}, a::Array) where {P<:Union{Ptr,Cwstring,Cstring}} = Ref{P}(a)
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###
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getindex(b::RefValue) = b.x
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getindex(b::RefArray) = b.x[b.i]
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setindex!(b::RefValue, x) = (b.x = x; b)
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setindex!(b::RefArray, x) = (b.x[b.i] = x; b)
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###
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