digest.gdsn {gdsfmt} | R Documentation

## create hash function digests

### Description

Create hash function digests for a GDS node.

### Usage

    digest.gdsn(node, algo=c("md5", "sha1", "sha256", "sha384", "sha512"),
        action=c("none", "Robject", "add", "add.Robj", "clear", "verify", "return"))

### Arguments

`node` | an object of class `gdsn.class`, a GDS node
`algo` | the algorithm to be used; currently available choices are "md5" (by default), "sha1", "sha256", "sha384", "sha512"
`action` | "none": nothing (by default); "Robject": convert to R object, i.e., raw, integer, double or character before applying hash digests; "add": add a barcode attribute; "add.Robj": add a barcode attribute generated from R object; "clear": remove all hash barcodes; "verify": verify data integrity if there is any hash code in the attributes, and stop if any fails; "return": compare the existing hash code in the attributes, and return `FALSE` if fails, `NA` if no hash code, and `TRUE` if the verification succeeds

### Details

The R package `digest` should be installed to perform hash function digests.

### Value

A character or `NA_character_` when the hash algorithm is not available.

### Author(s)

Xiuwen Zheng

### References

http://github.com/zhengxwen/gdsfmt

### Examples

    library(digest)
    library(tools)

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

    val <- as.raw(rep(1:128, 1024))
    n1 <- add.gdsn(f, "raw1", val)
    n2 <- add.gdsn(f, "int1", as.integer(val))
    n3 <- add.gdsn(f, "int2", as.integer(val), compress="ZIP", closezip=TRUE)

    digest.gdsn(n1)
    digest.gdsn(n1, action="Robject")
    digest.gdsn(n1, action="add")
    digest.gdsn(n1, action="add.Robj")
    writeBin(read.gdsn(n1, .useraw=TRUE), con="test1.bin")

    write.gdsn(n1, 0, start=1027, count=1)
    digest.gdsn(n1, action="add")
    digest.gdsn(n1, action="add.Robj")
    digest.gdsn(n1, "sha1", action="add")
    digest.gdsn(n1, "sha256", action="add")
    # digest.gdsn(n1, "sha384", action="add")  ## digest_0.6.11 does not work
    digest.gdsn(n1, "sha512", action="add")
    writeBin(read.gdsn(n1, .useraw=TRUE), con="test2.bin")

    print(n1, attribute=TRUE)
    digest.gdsn(n1, action="verify")

    digest.gdsn(n1, action="clear")
    print(n1, attribute=TRUE)

    digest.gdsn(n2)
    digest.gdsn(n2, action="Robject")

    # using R object
    digest.gdsn(n2) == digest.gdsn(n3)  # FALSE
    digest.gdsn(n2, action="Robject") == digest.gdsn(n3, action="Robject")  # TRUE

    # close the GDS file
    closefn.gds(f)

    # check with other program
    md5sum(c("test1.bin", "test2.bin"))

    # delete the temporary file
    unlink(c("test.gds", "test1.bin", "test2.bin"), force=TRUE)

[Package gdsfmt version 1.20.0 Index]