gzip: Perform in-memory gzip compression

In statwonk/Rcompression: In-memory decompression for GNU zip and bzip2 formats.

Description

This function compresses the content using the GZIP compression format and returns the resulting compressed content. It does this within memory rather than writing to file. This content can then be passed to other functions to be used in other contexts, e.g. sent to a Web server as part of a request, inserted into an HTML document via base64 encoding.

Usage

gzip(content, level = 1, windowBits = (15 + 16), memLevel = 9, strategy = 0L, 
      size = length(content) * 1.01 + 12)

Arguments

content	the content to be compressed. This should be either a raw vector or a character vector which will be collapsed to a single string.
level	the compression level, a number between 1 and 9
windowBits	integer between 24 and 31. Larger values result in better compression at the expense of memory usage. This is a value between 8 and 15 with 16 added on to cause GZIP compression to be used.
memLevel	a value between 1 and 9 that controls the tradeoff of memory and speed used in the process of compression. Larger values use more memory with better speed.
strategy	an integer, this should be 0 for the default strategy. filter, huffman and rle strategies are also available.
size	a number, the size to use as the best guess for the size of the result. The output buffer will grow as necessary, but this provides an opportunity to specify an initial guees.

Details

This uses the zlib library.

Value

A raw object containing the compressed information. Note that this cannot currently be uncompressed with the gunzip function but can be decompressed with the gzip application.

Author(s)

Duncan Temple Lang

References

http://www.gzip.org

See Also

compress

Examples

txt = paste(rep("This is a string", 40), collapse = "\n")
v = gzip(txt)
f = tempfile()
writeBin(v, f)
readLines(gzfile(f))


dev = paste(tempfile(), "pdf", sep = ".")
pdf(dev)
plot(1:10)
dev.off()
vals = readBinaryFile(dev)
writeBin(gzip(vals), paste(dev, "gz", sep = "."))

statwonk/Rcompression documentation built on May 30, 2019, 10:43 a.m.