matter_str-class: Out-of-Memory Strings

In matter: A framework for rapid prototyping with file-based data structures

Description

The matter_str class implements out-of-memory strings.

Usage

## Instance creation
matter_str(data, datamode = "uchar", paths = NULL,
            filemode = ifelse(all(file.exists(paths)), "r", "rw"),
            offset = c(0, cumsum(sizeof("uchar") * extent)[-length(extent)]),
            extent = nchar, nchar = 0, names = NULL, encoding = "unknown",
            chunksize = getOption("matter.default.chunksize"), ...)

## Additional methods documented below

Arguments

data	An optional character vector which will be initially written to the data in virtual memory if provided.
datamode	Must be "uchar" (or "raw") for strings.
paths	A 'character' vector of the paths to the files where the data are stored. If 'NULL', then a temporary file is created using tempfile.
filemode	The read/write mode of the files where the data are stored. This should be 'r' for read-only access, or 'rw' for read/write access.
offset	A vector giving the offsets in number of bytes from the beginning of each file in 'paths', specifying the start of the data to be accessed for each file.
extent	A vector giving the length of the data for each file in 'paths', specifying the number of elements of size 'datamode' to be accessed from each file.
nchar	A vector giving the length of each element of the character vector.
names	The names of the data elements.
encoding	The character encoding to use (if known).
chunksize	The (suggested) maximum number of elements which should be accessed at once by summary functions and linear algebra. Ignored when explicitly subsetting the dataset.
...	Additional arguments to be passed to constructor.

Value

An object of class matter_str.

Slots

data:

This slot stores the information about locations of the data in virtual memory and within the files.

datamode:

The storage mode of the accessed data when read into R. This is a 'character' vector of with possible values 'raw', 'logical', 'integer', 'numeric', or 'virtual'.

paths:

A 'character' vector of the paths to the files where the data are stored.

filemode:

The read/write mode of the files where the data are stored. This should be 'r' for read-only access, or 'rw' for read/write access.

chunksize:

The maximum number of elements which should be loaded into memory at once. Used by methods implementing summary statistics and linear algebra. Ignored when explicitly subsetting the dataset.

length:

The length of the data.

dim:

Either 'NULL' for vectors, or an integer vector of length one of more giving the maximal indices in each dimension for matrices and arrays.

names:

The names of the data elements for vectors.

dimnames:

Either 'NULL' or the names for the dimensions. If not 'NULL', then this should be a list of character vectors of the length given by 'dim' for each dimension. This is always 'NULL' for vectors.

ops:

Delayed operations to be applied on atoms.

encoding:

The character encoding of the strings.

Extends

matter

Creating Objects

matter_str instances can be created through matter_str() or matter().

Methods

Standard generic methods:

x[i], x[i] <- value:

Get or set the string elements of the vector.

lengths(x):

Get the number of characters (in bytes) of all string elements in the vector.

Author(s)

Kylie A. Bemis

See Also

matter

Examples

x <- matter_str(rep(c("hello", "world!"), 50))
x

matter documentation built on Nov. 8, 2020, 6:15 p.m.