compression.gdsn {gdsfmt} | R Documentation

## Modify compression mode

### Description

Modifie the compression mode of data field in the GDS node.

### Usage

    compression.gdsn(node,
        compress=c("", "ZIP", "ZIP_RA", "LZMA", "LZMA_RA", "LZ4", "LZ4_RA"))

### Arguments

`node` | an object of class `gdsn.class`, a GDS node
`compress` | the compression method can be "" (no compression), "ZIP", "ZIP.fast", "ZIP.def", "ZIP.max" or "ZIP.none" (original zlib); "ZIP_RA", "ZIP_RA.fast", "ZIP_RA.def", "ZIP_RA.max" or "ZIP_RA.none" (zlib with efficient random access); "LZ4", "LZ4.none", "LZ4.fast", "LZ4.hc" or "LZ4.max" (LZ4 compression/decompression library); "LZ4_RA", "LZ4_RA.none", "LZ4_RA.fast", "LZ4_RA.hc" or "LZ4_RA.max" (with efficient random access). "LZMA", "LZMA.fast", "LZMA.def", "LZMA.max", "LZMA_RA", "LZMA_RA.fast", "LZMA_RA.def", "LZMA_RA.max" (lzma compression/decompression algorithm). See details

### Details

Z compression algorithm (http://www.zlib.net/) can be used to deflate the data stored in the GDS file. "ZIP" option is equivalent to "ZIP.def". "ZIP.fast", "ZIP.def" and "ZIP.max" correspond to different compression levels.

To support efficient random access of Z stream, "ZIP_RA", "ZIP_RA.fast", "ZIP_RA.def" or "ZIP_RA.max" should be specified. "ZIP_RA" option is equivalent to "ZIP_RA.def:256K". The block size can be specified by following colon, and "16K", "32K", "64K", "128K", "256K", "512K", "1M", "2M", "4M" and "8M" are allowed, like "ZIP_RA:64K". The compression algorithm tries to keep each independent compressed data block to be about of the specified block size, like 64K.

LZ4 fast lossless compression algorithm is allowed when `compress="LZ4"` (http://code.google.com/p/lz4/). Three compression levels can be specified, "LZ4.fast" (LZ4 fast mode), "LZ4.hc" (LZ4 high compression mode), "LZ4.max" (maximize the compression ratio). The block size can be specified by following colon, and "64K", "256K", "1M" and "4M" are allowed according to LZ4 frame format. "LZ4" is equivalent to "LZ4.hc:256K".

To support efficient random access of LZ4 stream, "LZ4_RA", "LZ4_RA.fast", "LZ4_RA.hc" or "ZIP_RA.max" should be specified. "LZ4_RA" option is equivalent to "LZ4_RA.hc:256K". The block size can be specified by following colon, and "16K", "32K", "64K", "128K", "256K", "512K", "1M", "2M", "4M" and "8M" are allowed, like "LZ4_RA:64K". The compression algorithm tries to keep each independent compressed data block to be about of the specified block size, like 64K.

LZMA compression algorithm (http://tukaani.org/xz/) is available since gdsfmt_v1.7.18, which has a higher compression ratio than ZIP algorithm. "LZMA", "LZMA.fast", "LZMA.def" and "LZMA.max" available. To support efficient random access of LZMA stream, "LZMA_RA", "LZMA_RA.fast", "LZMA_RA.def" and "LZMA_RA.max" can be used. The block size can be specified by following colon. "LZMA_RA" is equivalent to "LZMA_RA.def:256K".

compression 1 | compression 2 | command line
ZIP | ZIP_RA | `gzip -6`
ZIP.fast | ZIP_RA.fast | `gzip --fast`
ZIP.def | ZIP_RA.def | `gzip -6`
ZIP.max | ZIP_RA.max | `gzip --best`
LZ4 | LZ4_RA | `LZ4 HC -6`
LZ4.min | LZ4_RA.min | `LZ4 fast 0`
LZ4.fast | LZ4_RA.fast | `LZ4 fast 2`
LZ4.hc | LZ4_RA.hc | `LZ4 HC -6`
LZ4.max | LZ4_RA.max | `LZ4 HC -9`
LZMA | LZMA_RA | `xz -6`
LZMA.min | LZMA_RA.min | `xz -0`
LZMA.fast | LZMA_RA.fast | `xz -2`
LZMA.def | LZMA_RA.def | `xz -6`
LZMA.max | LZMA_RA.max | `xz -9e`
LZMA.ultra | LZMA_RA.ultra | `xz --lzma2=dict=512Mi`
LZMA.ultra_max | LZMA_RA.ultra_max | `xz --lzma2=dict=1536Mi`

### Value

Return `node`.

### Author(s)

Xiuwen Zheng

### References

http://github.com/zhengxwen/gdsfmt, http://zlib.net/

### See Also

`readmode.gdsn`, `add.gdsn`

### Examples

    # cteate a GDS file
    f <- createfn.gds("test.gds")

    n <- add.gdsn(f, "int.matrix", matrix(1:50*100, nrow=100, ncol=50))
    n

    compression.gdsn(n, "ZIP")

    # close the GDS file
    closefn.gds(f)

    # delete the temporary file
    unlink("test.gds", force=TRUE)

[Package gdsfmt version 1.26.1 Index]