r - 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。数据库列类型是 BYTEA (Postgres)。为了让我按预期使用它，它应该是 raw 类型。相反，它是 character 类型。我想在以下意义上将其转换为原始数据:

字符串表示为

\x1f8b080000000000

如果我使用charToRaw，它会被转换成数组

5c 78 31 66 38 62 30 38 

相反，我需要它是数组

1f 8b 08 00 00 00 00 00

我如何实现这一目标。

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

这适用于将您所描述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