blob

Overview

The goal of blob is to provide a simple S3 class to represent a vector of binary objects, aka blobs. The blob class is a lightweight wrapper around a list of raw vectors, suitable for inclusion in a data frame.

In most cases you will not need to use this package explicitly: it will be used transparently by packages that need to load BLOB columns from databases or binary file formats.

Goals and non-goals

blob aims to:

• Provide exactly one class, blob, built on vctrs::list_of(raw()), so that a vector of binary objects can live in a data frame column.
• Keep the constructors small and explicit: new_blob() for a list of raw vectors, blob() for individual ones, as_blob() for casting and validate_blob() for checking.
• Behave like a well-mannered vctrs vector, with vec_ptype2() and vec_cast() methods so that combining, subsetting and coercion follow the usual rules.
• Print each element by its size rather than its bytes, as blob[12 B] on its own and as <raw 12 B> in a tibble column.
• Stay cheap to depend on: only methods, rlang and vctrs are imported, and the pillar method is registered on load only if pillar is available.

It is explicitly not trying to:

• Be a package you reach for directly: in most cases it is used transparently by packages that load BLOB columns from databases or binary file formats.
• Produce or store the binary data itself: those packages hand over the raw vectors, and blob only holds them.
• Show or interpret the contents: formatting reports the size of each element, and nothing here decodes, parses or compresses a blob.
• Accept every input that could plausibly become bytes: casts exist for lists, lists of raw, raw vectors and character, and coercing an integer vector is deprecated.

Installation

# The easiest way to get blob is to install the whole tidyverse:
install.packages("tidyverse")

# Alternatively, install just blob:
install.packages("blob")

# Or the development version from GitHub:
# install.packages("pak")
# pak::pak("tidyverse/blob")
install.packages("blob", repos = c('https://tidyverse.r-universe.dev', 'https://cloud.r-project.org'))

Example

To create a blob, use blob(), new_blob() or as_blob():

library(blob)

x1 <- charToRaw("Good morning")
x2 <- as.raw(c(0x48, 0x65, 0x6c, 0x6c, 0x6f))

new_blob(list(x1, x2))
#> <blob[2]>
#> [1] blob[12 B] blob[5 B]
blob(x1, x2)
#> <blob[2]>
#> [1] blob[12 B] blob[5 B]

as_blob(c("Good morning", "Good evening"))
#> <blob[2]>
#> [1] blob[12 B] blob[12 B]

# Inside a tibble, `pillar_shaft.blob()` decides how the column looks.
tibble::tibble(x = blob(x1, x2))
#> # A tibble: 2 × 1
#>            x
#>       <blob>
#> 1 <raw 12 B>
#> 2  <raw 5 B>

---

Please note that the 'blob' project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.