How to convert variable to RDA format in memory - r

Question

Currently, I convert data table into rda format by using save() like so
save(data_table,file="data.rda")
But I don't want to write to disk to get .rda format of the variable.
Instead, I would like to have the output(rda bytes) be written straight into a variable.
If it were in other programming languages, It would be something like
Switching from
FileStream fs = new FileStream("data.rda","w")
Save(data_table,fs)
to
byte[] buffer = new byte[data_table.getBytes()]
Save(data_table,buffer);
Is there a way to do something like this in R?

Answer 1

This is possible with raw connections
rc <- rawConnection(raw(0),"wb")
save(iris,file=rc)
v1 <- rawConnectionValue(rc)
close(rc)
head(v1,80)
#> [1] 52 44 58 32 0a 58 0a 00 00 00 02 00 03 01 01 00 02 03 00 00
#> [21] 00 04 02 00 00 00 01 00 04 00 09 00 00 00 04 69 72 69 73 00
#> [41] 00 03 13 00 00 00 05 00 00 00 0e 00 00 00 96 40 14 66 66 66
#> [61] 66 66 66 40 13 99 99 99 99 99 9a 40 12 cc cc cc cc cc cd 40
Compare to writing to a temporary file and reading back
save(iris,file="temp.rda",compress=FALSE)
v2 = readBin("temp.rda", raw(), file.info("temp.rda")[1,"size"])
identical(v1,v2)
#> [1] TRUE
Note that writing to file by default uses compression and writing to a raw connection by default does not, hence the compress=FALSE argument.
See also serialize, which may be more suitable, depending on your purpose
v3 <- serialize(iris,NULL)
Note that identical(v1,v3)==FALSE. Indeed, v3 is identical instead to using saveRDS in place of save above. The encoding/content is similar
head(v3,80)
#> [1] 58 0a 00 00 00 02 00 03 01 01 00 02 03 00 00 00 03 13 00 00
#> [21] 00 05 00 00 00 0e 00 00 00 96 40 14 66 66 66 66 66 66 40 13
#> [41] 99 99 99 99 99 9a 40 12 cc cc cc cc cc cd 40 12 66 66 66 66
#> [61] 66 66 40 14 00 00 00 00 00 00 40 15 99 99 99 99 99 9a 40 12
And it is easy to recover the data
identical(unserialize(v3),iris)
#> [1] TRUE