These functions are for working with source files and more generally
with “source references” ("srcref"
), i.e., references to
source code. The resulting data is used for printing and source level
debugging, and is typically available in interactive R sessions,
namely when options(keep.source = TRUE)
.
srcfile(filename, encoding = getOption("encoding"), Enc = "unknown")
srcfilecopy(filename, lines, timestamp = Sys.time(), isFile = FALSE)
srcfilealias(filename, srcfile)
getSrcLines(srcfile, first, last)
srcref(srcfile, lloc)
# S3 method for srcfile
print(x, …)
# S3 method for srcfile
summary(object, …)
# S3 method for srcfile
open(con, line, …)
# S3 method for srcfile
close(con, …)
# S3 method for srcref
print(x, useSource = TRUE, …)
# S3 method for srcref
summary(object, useSource = FALSE, …)
# S3 method for srcref
as.character(x, useSource = TRUE, to = x, …)
.isOpen(srcfile)
The name of a file.
The character encoding to assume for the file.
The encoding with which to make strings: see the
encoding
argument of parse
.
A character vector of source lines. Other R objects will be coerced to character.
The timestamp to use on a copy of a file.
Is this srcfilecopy
known to come from a file system file?
A srcfile
object.
Line numbers.
A vector of four, six or eight values giving a source location; see ‘Details’.
An object of the appropriate class.
Whether to read the srcfile
to obtain the
text of a srcref
.
An optional second srcref
object to mark the end
of the character range.
Additional arguments to the methods; these will be ignored.
srcfile
returns a srcfile
object.
srcfilecopy
returns a srcfilecopy
object.
getSrcLines
returns a character vector of source code lines.
srcref
returns a srcref
object.
These functions and classes handle source code references.
The srcfile
function produces an object of class
srcfile
, which contains the name and directory of a source code
file, along with its timestamp, for use in source level debugging (not
yet implemented) and source echoing. The encoding of the file is
saved; see file
for a discussion of encodings, and
iconvlist
for a list of allowable encodings on your platform.
The srcfilecopy
function produces an object of the descendant
class srcfilecopy
, which saves the source lines in a character
vector. It copies the value of the isFile
argument, to help
debuggers identify whether this text comes from a real file in the
file system.
The srcfilealias
function produces an object of the descendant
class srcfilealias
, which gives an alternate name to another
srcfile. This is produced by the parser when a #line
directive
is used.
The getSrcLines
function reads the specified lines from
srcfile
.
The srcref
function produces an object of class
srcref
, which describes a range of characters in a
srcfile
.
The lloc
value gives the following values:
c(first_line, first_byte, last_line, last_byte, first_column, last_column, first_parsed, last_parsed)
Bytes (elements 2, 4) and
columns (elements 5, 6) may be different due to multibyte
characters. If only four values are given, the columns and bytes
are assumed to match. Lines (elements 1, 3) and parsed lines
(elements 7, 8) may differ if a #line
directive is used in
code: the former will respect the directive, the latter will just
count lines. If only 4 or 6 elements are given, the parsed lines
will be assumed to match the lines.
Methods are defined for print
, summary
, open
,
and close
for classes srcfile
and srcfilecopy
.
The open
method opens its internal file
connection at
a particular line; if it was already open, it will be repositioned
to that line.
Methods are defined for print
, summary
and
as.character
for class srcref
. The as.character
method will read the associated source file to obtain the text
corresponding to the reference. If the to
argument is given,
it should be a second srcref
that follows the first, in the
same file; they will be treated as one reference to the whole
range. The exact behaviour depends on the
class of the source file. If the source file inherits from
class srcfilecopy
, the lines are taken from the saved copy
using the “parsed” line counts. If not, an attempt
is made to read the file, and the original line numbers of the
srcref
record (i.e., elements 1 and 3) are used. If an error
occurs (e.g., the file no longer exists), text like
<srcref: "file" chars 1:1 to 2:10>
will be returned instead,
indicating the line:column
ranges of the first and last
character. The summary
method defaults to this type of
display.
Lists of srcref
objects may be attached to expressions as the
"srcref"
attribute. (The list of srcref
objects should be the same
length as the expression.) By default, expressions are printed by
print.default
using the associated srcref
. To
see deparsed code instead, call print
with argument
useSource = FALSE
. If a srcref
object
is printed with useSource = FALSE
, the <srcref: …>
record will be printed.
.isOpen
is intended for internal use: it checks whether the
connection associated with a srcfile
object is open.
getSrcFilename
for extracting information from a source
reference, or removeSource
to remove it from a
(non-primitive) function (aka ‘closure’).
# NOT RUN {
# has timestamp
src <- srcfile(system.file("DESCRIPTION", package = "base"))
summary(src)
getSrcLines(src, 1, 4)
ref <- srcref(src, c(1, 1, 2, 1000))
ref
print(ref, useSource = FALSE)
# }
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