README.md

In libdeflate: DEFLATE Compression and Static Library

libdeflate

High‑performance DEFLATE compression for R, wrapping Eric Biggers’ libdeflate C library.

The installed package includes a static copy of the C library (along with CMake config files) so you can use DEFLATE compression in your package without requiring the user to separately install libdeflate as a system dependency. The package also includes a minimal R API that allows for compression and decompression of raw vectors, which can serve as an implementation reference for any downstream libraries.

Installation

# once released on CRAN
install.packages("libdeflate")

# development version
remotes::install_github("tylermorganwall/libdeflate")

No external libraries are required—the libdeflate static library is built and installed during the R package install.

Example

library(libdeflate)

raw_in  = charToRaw("Example data payload, 123412341234123412341234")

print(raw_in)

##  [1] 45 78 61 6d 70 6c 65 20 64 61 74 61 20 70 61 79 6c 6f 61 64 2c 20 31 32 33 34 31 32 33 34 31 32 33 34 31 32 33 34
## [39] 31 32 33 34 31 32 33 34

length(raw_in)

## [1] 46

cmp     = alloc_compressor(level = 6L)      # create compressor @ default level
raw_cmp = deflate_compress(cmp, raw_in)     # compress

print(raw_cmp)

##  [1] 73 ad 48 cc 2d c8 49 55 48 49 2c 49 54 28 48 ac cc c9 4f 4c d1 51 30 34 32 36 c1 86 01

length(raw_cmp)

## [1] 29

dcmp    = alloc_decompressor()              # create decompressor
raw_out = deflate_decompress(dcmp, raw_cmp, length(raw_in))

print(raw_out)

##  [1] 45 78 61 6d 70 6c 65 20 64 61 74 61 20 70 61 79 6c 6f 61 64 2c 20 31 32 33 34 31 32 33 34 31 32 33 34 31 32 33 34
## [39] 31 32 33 34 31 32 33 34

print(rawToChar(raw_out)) # round‑trip successful

## [1] "Example data payload, 123412341234123412341234"

R API

| Function | Purpose | Key arguments | |----------|---------|---------------| | alloc_compressor(level = 6L) | Allocate a compression context. | level ∈ 0…12 (0 = none, 6 = default, 12 = max) | | deflate_compress(compressor, input) | Compress a raw vector. | compressor, input (coerced to raw) | | alloc_decompressor() | Allocate a decompression context. | – | | deflate_decompress(decompressor, input, out_len) | Inflate a DEFLATE stream. | decompressor, input, out_len (expected size) |

All four functions are simple .Call() wrappers around the C API; see the @examples in their help pages for typical workflows.

Using the bundled static library in your own packages

The package installs

lib/<R_ARCH>/libdeflate.a        # static archive
lib/<R_ARCH>/cmake/libdeflate/*  # CMake config files
include/libdeflate.h             # public header

R_ARCH can be obtained in R via Sys.info()[["machine"]].

Makevars‑style linkage

## configure
DEFLATE_DIR=$(Rscript -e 'cat(system.file("lib", Sys.info()[["machine"]], package = "libdeflate"))')
CPPFLAGS += -I$(DEFLATE_DIR)/../include
PKG_LIBS += -L$(DEFLATE_DIR) -ldeflate

CMake consumers

Call this R code in your configure step to determine the location of the CMake config files:

DEFLATE_LIB_ARCH = normalizePath(sprintf(
  "%s/%s",
  system.file(
    "lib",
    package = "libdeflate",
    mustWork = TRUE
  ),
  Sys.info()[["machine"]]
))

DEFLATE_CMAKE_CONFIG = file.path(DEFLATE_LIB_ARCH, "cmake", "libdeflate")

Minimal C wrapper (see r-api.c in package source)

// File: src/r-api.c
#define R_NO_REMAP
#include <R.h>
#include <Rinternals.h>
#include <libdeflate.h>

SEXP C_alloc_compressor(SEXP level_SEXP) {
    int level = INTEGER(level_SEXP)[0];
    struct libdeflate_compressor *c = libdeflate_alloc_compressor(level);
    if(!c) Rf_error("libdeflate_alloc_compressor(%d) failed", level);
    SEXP ext = PROTECT(R_MakeExternalPtr(c, R_NilValue, R_NilValue));
    R_RegisterCFinalizerEx(ext, compressor_finalizer, TRUE);
    UNPROTECT(1);
    return ext;
}

libdeflate documentation built on June 29, 2025, 5:07 p.m.