将原始字节作为R中的原始字节导入

Question

我已经从数据库中将一个字符串导入到R中.db列类型是BYTEA(Postgres).为了让我按预期使用它,它应该是类型raw.相反,它是类型character.我希望在以下意义上将其转换为raw:

字符串表示是

\x1f8b080000000000

如果我使用charToRaw,它将转换为数组

5c 78 31 66 38 62 30 38 

相反,我需要它作为数组

1f 8b 08 00 00 00 00 00

我怎么做到这一点.

编辑#1回复Chris

library(RPostgreSQL)
conn <- dbConnect(dbDriver("PostgreSQL"), dbname = "somename",
                  host = "1.2.3.4", port = 5432,
                  user = "someuser", password = pw)
some_value <- dbGetQuery(conn, "select value from schema.key_value where key like '%somekey%' limit 1")

some_value$value
# [1] "\\x1f8b080000000000000

Answer 1

这适用于将您描述的类型的单个字符串转换为原始向量。

## The string I think you're talking about
dat <- "\\x1f8b080000000000"
cat(dat, "\n")
## \x1f8b080000000000

## A function to convert one string to an array of raw
f <- function(x)  {
    ## Break into two-character segments
    x <- strsplit(x, "(?<=.{2})", perl=TRUE)[[1]]
    ## Remove the first element, "\\x"
    x <- x[-1]
    ## Complete the conversion
    as.raw(as.hexmode(x))
}

## Check that it works
f(dat)
##  [1] 1f 8b 08 00 00 00 00 00