# This file is a part of Julia. License is MIT: https://julialang.org/license

# definitions related to C interface

import Core.Intrinsics: cglobal, bitcast

"""
    cfunction(function::Function, ReturnType::Type, ArgumentTypes::Type)

Generate C-callable function pointer from Julia function. Type annotation of the return
value in the callback function is a must for situations where Julia cannot infer the return
type automatically.

# Examples
```julia-repl
julia> function foo(x::Int, y::Int)
           return x + y
       end

julia> cfunction(foo, Int, Tuple{Int,Int})
Ptr{Void} @0x000000001b82fcd0
```
"""
cfunction(f, r, a) = ccall(:jl_function_ptr, Ptr{Void}, (Any, Any, Any), f, r, a)

if ccall(:jl_is_char_signed, Ref{Bool}, ())
    const Cchar = Int8
else
    const Cchar = UInt8
end
"""
    Cchar

Equivalent to the native `char` c-type.
"""
Cchar

if is_windows()
    const Clong = Int32
    const Culong = UInt32
    const Cwchar_t = UInt16
else
    const Clong = Int
    const Culong = UInt
    const Cwchar_t = Int32
end

"""
    Clong

Equivalent to the native `signed long` c-type.
"""
Clong

"""
    Culong

Equivalent to the native `unsigned long` c-type.
"""
Culong

"""
    Cwchar_t

Equivalent to the native `wchar_t` c-type ([`Int32`](@ref)).
"""
Cwchar_t

if !is_windows()
    const sizeof_mode_t = ccall(:jl_sizeof_mode_t, Cint, ())
    if sizeof_mode_t == 2
        const Cmode_t = Int16
    elseif sizeof_mode_t == 4
        const Cmode_t = Int32
    elseif sizeof_mode_t == 8
        const Cmode_t = Int64
    end
end

# construction from typed pointers
convert(::Type{Cstring}, p::Ptr{<:Union{Int8,UInt8}}) = bitcast(Cstring, p)
convert(::Type{Cwstring}, p::Ptr{Cwchar_t}) = bitcast(Cwstring, p)
convert(::Type{Ptr{T}}, p::Cstring) where {T<:Union{Int8,UInt8}} = bitcast(Ptr{T}, p)
convert(::Type{Ptr{Cwchar_t}}, p::Cwstring) = bitcast(Ptr{Cwchar_t}, p)

# construction from untyped pointers
convert(::Type{T}, p::Ptr{Void}) where {T<:Union{Cstring,Cwstring}} = bitcast(T, p)

pointer(p::Cstring) = convert(Ptr{UInt8}, p)
pointer(p::Cwstring) = convert(Ptr{Cwchar_t}, p)

# comparisons against pointers (mainly to support `cstr==C_NULL`)
==(x::Union{Cstring,Cwstring}, y::Ptr) = pointer(x) == y
==(x::Ptr, y::Union{Cstring,Cwstring}) = x == pointer(y)

unsafe_string(s::Cstring) = unsafe_string(convert(Ptr{UInt8}, s))

# convert strings to String etc. to pass as pointers
cconvert(::Type{Cstring}, s::String) = s
cconvert(::Type{Cstring}, s::AbstractString) =
    cconvert(Cstring, String(s)::String)

function cconvert(::Type{Cwstring}, s::AbstractString)
    v = transcode(Cwchar_t, Vector{UInt8}(String(s)))
    !isempty(v) && v[end] == 0 || push!(v, 0)
    return v
end

eltype(::Type{Cstring}) = UInt8
eltype(::Type{Cwstring}) = Cwchar_t

containsnul(p::Ptr, len) =
    C_NULL != ccall(:memchr, Ptr{Cchar}, (Ptr{Cchar}, Cint, Csize_t), p, 0, len)
containsnul(s::String) = containsnul(unsafe_convert(Ptr{Cchar}, s), sizeof(s))
containsnul(s::AbstractString) = '\0' in s

function unsafe_convert(::Type{Cstring}, s::Union{String,Vector{UInt8}})
    p = unsafe_convert(Ptr{Cchar}, s)
    containsnul(p, sizeof(s)) &&
        throw(ArgumentError("embedded NULs are not allowed in C strings: $(repr(s))"))
    return Cstring(p)
end

function unsafe_convert(::Type{Cwstring}, v::Vector{Cwchar_t})
    for i = 1:length(v)-1
        v[i] == 0 &&
            throw(ArgumentError("embedded NULs are not allowed in C strings: $(repr(v))"))
    end
    v[end] == 0 ||
        throw(ArgumentError("C string data must be NUL terminated: $(repr(v))"))
    p = unsafe_convert(Ptr{Cwchar_t}, v)
    return Cwstring(p)
end

# symbols are guaranteed not to contain embedded NUL
convert(::Type{Cstring}, s::Symbol) = Cstring(unsafe_convert(Ptr{Cchar}, s))

if is_windows()
"""
    Base.cwstring(s)

Converts a string `s` to a NUL-terminated `Vector{Cwchar_t}`, suitable for passing to C
functions expecting a `Ptr{Cwchar_t}`. The main advantage of using this over the implicit
conversion provided by `Cwstring` is if the function is called multiple times with the
same argument.

This is only available on Windows.
"""
function cwstring(s::AbstractString)
    bytes = Vector{UInt8}(String(s))
    0 in bytes && throw(ArgumentError("embedded NULs are not allowed in C strings: $(repr(s))"))
    return push!(transcode(UInt16, bytes), 0)
end
end

# transcoding between data in UTF-8 and UTF-16 for Windows APIs,
# and also UTF-32 for APIs using Cwchar_t on other platforms.

"""
    transcode(T, src)

Convert string data between Unicode encodings. `src` is either a
`String` or a `Vector{UIntXX}` of UTF-XX code units, where
`XX` is 8, 16, or 32. `T` indicates the encoding of the return value:
`String` to return a (UTF-8 encoded) `String` or `UIntXX`
to return a `Vector{UIntXX}` of UTF-`XX` data.   (The alias `Cwchar_t`
can also be used as the integer type, for converting `wchar_t*` strings
used by external C libraries.)

The `transcode` function succeeds as long as the input data can be
reasonably represented in the target encoding; it always succeeds for
conversions between UTF-XX encodings, even for invalid Unicode data.

Only conversion to/from UTF-8 is currently supported.
"""
function transcode end

transcode(::Type{T}, src::Vector{T}) where {T<:Union{UInt8,UInt16,UInt32,Int32}} = src
transcode(::Type{T}, src::String) where {T<:Union{Int32,UInt32}} = T[T(c) for c in src]
transcode(::Type{T}, src::Vector{UInt8}) where {T<:Union{Int32,UInt32}} = transcode(T, String(src))
function transcode(::Type{UInt8}, src::Vector{<:Union{Int32,UInt32}})
    buf = IOBuffer()
    for c in src; print(buf, Char(c)); end
    take!(buf)
end
transcode(::Type{String}, src::String) = src
transcode(T, src::String) = transcode(T, Vector{UInt8}(src))
transcode(::Type{String}, src) = String(transcode(UInt8, src))

function transcode(::Type{UInt16}, src::Vector{UInt8})
    dst = UInt16[]
    i, n = 1, length(src)
    n > 0 || return dst
    sizehint!(dst, 2n)
    a = src[1]
    while true
        if i < n && -64 <= a % Int8 <= -12 # multi-byte character
            b = src[i += 1]
            if -64 <= (b % Int8) || a == 0xf4 && 0x8f < b
                # invalid UTF-8 (non-continuation or too-high code point)
                push!(dst, a)
                a = b; continue
            elseif a < 0xe0 # 2-byte UTF-8
                push!(dst, xor(0x3080, UInt16(a) << 6, b))
            elseif i < n # 3/4-byte character
                c = src[i += 1]
                if -64 <= (c % Int8) # invalid UTF-8 (non-continuation)
                    push!(dst, a, b)
                    a = c; continue
                elseif a < 0xf0 # 3-byte UTF-8
                    push!(dst, xor(0x2080, UInt16(a) << 12, UInt16(b) << 6, c))
                elseif i < n
                    d = src[i += 1]
                    if -64 <= (d % Int8) # invalid UTF-8 (non-continuation)
                        push!(dst, a, b, c)
                        a = d; continue
                    elseif a == 0xf0 && b < 0x90 # overlong encoding
                        push!(dst, xor(0x2080, UInt16(b) << 12, UInt16(c) << 6, d))
                    else # 4-byte UTF-8
                        push!(dst, 0xe5b8 + (UInt16(a) << 8) + (UInt16(b) << 2) + (c >> 4),
                                   xor(0xdc80, UInt16(c & 0xf) << 6, d))
                    end
                else # too short
                    push!(dst, a, b, c)
                    break
                end
            else # too short
                push!(dst, a, b)
                break
            end
        else # ASCII or invalid UTF-8 (continuation byte or too-high code point)
            push!(dst, a)
        end
        i < n || break
        a = src[i += 1]
    end
    return dst
end

function transcode(::Type{UInt8}, src::Vector{UInt16})
    n = length(src)
    n == 0 && return UInt8[]

    # Precompute m = sizeof(dst).   This involves annoying duplication
    # of the loop over the src array.   However, this is not just an
    # optimization: it is problematic for security reasons to grow
    # dst dynamically, because Base.winprompt uses this function to
    # convert passwords to UTF-8 and we don't want to make unintentional
    # copies of the password data.
    a = src[1]
    i, m = 1, 0
    while true
        if a < 0x80
            m += 1
        elseif a < 0x800 # 2-byte UTF-8
            m += 2
        elseif a & 0xfc00 == 0xd800 && i < length(src)
            b = src[i += 1]
            if (b & 0xfc00) == 0xdc00 # 2-unit UTF-16 sequence => 4-byte UTF-8
                m += 4
            else
                m += 3
                a = b; continue
            end
        else
            # 1-unit high UTF-16 or unpaired high surrogate
            # either way, encode as 3-byte UTF-8 code point
            m += 3
        end
        i < n || break
        a = src[i += 1]
    end

    dst = StringVector(m)
    a = src[1]
    i, j = 1, 0
    while true
        if a < 0x80 # ASCII
            dst[j += 1] = a % UInt8
        elseif a < 0x800 # 2-byte UTF-8
            dst[j += 1] = 0xc0 | ((a >> 6) % UInt8)
            dst[j += 1] = 0x80 | ((a % UInt8) & 0x3f)
        elseif a & 0xfc00 == 0xd800 && i < n
            b = src[i += 1]
            if (b & 0xfc00) == 0xdc00
                # 2-unit UTF-16 sequence => 4-byte UTF-8
                a += 0x2840
                dst[j += 1] = 0xf0 | ((a >> 8) % UInt8)
                dst[j += 1] = 0x80 | ((a % UInt8) >> 2)
                dst[j += 1] = xor(0xf0, ((a % UInt8) << 4) & 0x3f, (b >> 6) % UInt8)
                dst[j += 1] = 0x80 | ((b % UInt8) & 0x3f)
            else
                dst[j += 1] = 0xe0 | ((a >> 12) % UInt8)
                dst[j += 1] = 0x80 | (((a >> 6) % UInt8) & 0x3f)
                dst[j += 1] = 0x80 | ((a % UInt8) & 0x3f)
                a = b; continue
            end
        else
            # 1-unit high UTF-16 or unpaired high surrogate
            # either way, encode as 3-byte UTF-8 code point
            dst[j += 1] = 0xe0 | ((a >> 12) % UInt8)
            dst[j += 1] = 0x80 | (((a >> 6) % UInt8) & 0x3f)
            dst[j += 1] = 0x80 | ((a % UInt8) & 0x3f)
        end
        i < n || break
        a = src[i += 1]
    end
    return dst
end

# deferring (or un-deferring) ctrl-c handler for external C code that
# is not interrupt safe (see also issue #2622).  The sigatomic_begin/end
# functions should always be called in matched pairs, ideally via:
#            disable_sigint() do .. end
# reennable_sigint is provided so that immediate ctrl-c handling is
# re-enabled within a sigatomic region, e.g. inside a Julia callback function
# within a long-running C routine.
sigatomic_begin() = ccall(:jl_sigatomic_begin, Void, ())
sigatomic_end() = ccall(:jl_sigatomic_end, Void, ())

"""
    disable_sigint(f::Function)

Disable Ctrl-C handler during execution of a function on the current task,
for calling external code that may call julia code that is not interrupt safe.
Intended to be called using `do` block syntax as follows:

    disable_sigint() do
        # interrupt-unsafe code
        ...
    end

This is not needed on worker threads (`Threads.threadid() != 1`) since the
`InterruptException` will only be delivered to the master thread.
External functions that do not call julia code or julia runtime
automatically disable sigint during their execution.
"""
function disable_sigint(f::Function)
    sigatomic_begin()
    res = f()
    # Exception unwind sigatomic automatically
    sigatomic_end()
    res
end

"""
    reenable_sigint(f::Function)

Re-enable Ctrl-C handler during execution of a function.
Temporarily reverses the effect of `disable_sigint`.
"""
function reenable_sigint(f::Function)
    sigatomic_end()
    res = f()
    # Exception unwind sigatomic automatically
    sigatomic_begin()
    res
end

function ccallable(f::Function, rt::Type, argt::Type, name::Union{AbstractString,Symbol}=string(f))
    ccall(:jl_extern_c, Void, (Any, Any, Any, Cstring), f, rt, argt, name)
end

function expand_ccallable(rt, def)
    if isa(def,Expr) && (def.head === :(=) || def.head === :function)
        sig = def.args[1]
        if sig.head === :(::)
            if rt === nothing
                rt = sig.args[2]
            end
            sig = sig.args[1]
        end
        if rt === nothing
            error("@ccallable requires a return type")
        end
        if sig.head === :call
            name = sig.args[1]
            at = map(sig.args[2:end]) do a
                if isa(a,Expr) && a.head === :(::)
                    a.args[2]
                else
                    :Any
                end
            end
            return quote
                $(esc(def))
                ccallable($(esc(name)), $(esc(rt)), $(Expr(:curly, :Tuple, map(esc, at)...)), $(string(name)))
            end
        end
    end
    error("expected method definition in @ccallable")
end

macro ccallable(def)
    expand_ccallable(nothing, def)
end
macro ccallable(rt, def)
    expand_ccallable(rt, def)
end