[Rd] Get memory address of an R data frame

[Tomas Kalibera]

On 1/9/20 1:03 PM, Ezra Tucker wrote:
> Hi Lille,
>
> Is it possible you're looking for tracemem() or inspect() ?

Please note these functions are only for debugging. They should never be 
called from programs or packages. One should never try to manipulate 
pointers from R directly or even hold them (except for what "external 
pointer" objects allow and is described in Writing R Extensions).

Tomas
>
>> x <- data.frame(z = 1:10)> tracemem(x)[1] "<0x55aa743e0bc0>"
>> x[1] <- 2Ltracemem[0x55aa743e0bc0 -> 0x55aa778f6ad0]:
> tracemem[0x55aa778f6ad0 -> 0x55aa778f6868]: [<-.data.frame [<-
> tracemem[0x55aa778f6868 -> 0x55aa778f5b48]: [<-.data.frame [<-
>
>> .Internal(inspect(x)) @55aa743e0bc0 19 VECSXP g0c1
> [OBJ,MARK,NAM(7),TR,ATT] (len=1, tl=0) @55aa7440d420 13 INTSXP g0c0
> [MARK,NAM(7)] 1 : 10 (compact) ATTRIB: @55aa743f9ea0 02 LISTSXP g0c0 [MARK]
> TAG: @55aa72ac98a0 01 SYMSXP g0c0 [MARK,NAM(7),LCK,gp=0x6000] "names" (has
> value) @55aa743e0fb0 16 STRSXP g0c1 [MARK,NAM(7)] (len=1, tl=0)
> @55aa72be1c70 09 CHARSXP g0c1 [MARK,gp=0x61] [ASCII] [cached] "z" TAG:
> @55aa72ac9d70 01 SYMSXP g0c0 [MARK,NAM(7),LCK,gp=0x4000] "class" (has
> value) @55aa73ca59b8 16 STRSXP g0c1 [MARK,NAM(7)] (len=1, tl=0)
> @55aa72b562b8 09 CHARSXP g0c2 [MARK,gp=0x61,ATT] [ASCII] [cached]
> "data.frame" TAG: @55aa72ac9670 01 SYMSXP g0c0 [MARK,NAM(7),LCK,gp=0x4000]
> "row.names" (has value) @55aa743e1c98 13 INTSXP g0c1 [MARK,NAM(7)] (len=2,
> tl=0) -2147483648,-10
>
>
>
> On Thu, Jan 9, 2020 at 6:48 AM lille stor <lille.stor using gmx.com> wrote:
>
>> Hello,
>>
>> I would like for my C function to be able to manipulate some values stored
>> in an R data frame.
>>
>> To achieve this, a need the (real) memory address where the R data frame
>> stores its data (hopefully in a contiguous way). Then, from R, I call the C
>> function and passing this memory address as a parameter.
>>
>> The question: how can we get the memory address of the R data frame?
>>
>> Thank you!
>>
>> L.
>>
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>>
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