[External] readChar() could read the whole file by default?

My opinion is that the proposed feature would be greatly appreciated by users.
I had always wondered if I was the only one doing paste(readLines(f),
collapse="\n") all the time.
It would be great to have the proposed, more straightforward way to
read the whole file as a string: readChar("my_file.txt", -1) or even
better readChar("my_file.txt")
Thanks for your detailed analysis Michael.

On Fri, Jan 26, 2024 at 2:05?PM luke-tierney--- via R-devel
<r-devel at r-project.org> wrote:

On Fri, 26 Jan 2024, Michael Chirico wrote:

I am curious why readLines() has a default (n=-1L) to read the full
file while readChar() has no default for nchars= (i.e., readChar(file)
is an error). Is there a technical reason for this?

I often[1] see code like paste(readLines(f), collapse="\n") which
would be better served by readChar(), especially given issues with the
global string cache I've come across[2]. But lacking the default, the
replacement might come across less clean.

The string cache seems like a very dark pink herring to me. The fact
that the lines are allocated on the heap might create an issue; the
cache isn't likely to add much to that. In any case I would need to
see a realistic example to convince me this is worth addressing on
performance grounds.

I don't see any reason in principle not to have readChar and readBin
read the entire file if n = -1 (others might) but someone would need
to write a patch to implement that.

Best,

luke

For my own purposes the incantation readChar(file, file.size(file)) is
ubiquitous. Taking CRAN code[3] as a sample[4], 41% of readChar()
calls use either readChar(f, file.info(f)$size) or readChar(f,
file.size(f))[5].

Thanks for the consideration and feedback,
Mike C

[1] e.g. a quick search shows O(100) usages in CRAN packages:
https://github.com/search?q=org%3Acran+%2Fpaste%5B%28%5D%5Cs*readLines%5B%28%5D.*%5B%29%5D%2C%5Cs*collapse%5Cs*%3D%5Cs*%5B%27%22%5D%5B%5C%5C%5D%2F+lang%3AR&type=code,
and O(1000) usages generally on GitHub:
https://github.com/search?q=lang%3AR+%2Fpaste%5B%28%5D%5Cs*readLines%5B%28%5D.*%5B%29%5D%2C%5Cs*collapse%5Cs*%3D%5Cs*%5B%27%22%5D%5B%5C%5C%5D%2F+lang%3AR&type=code
[2] AIUI the readLines() approach "pollutes" the global string cache
with potentially 1000s/10000s of strings for each line, only to get
them gc()'d after combining everything with paste(collapse="\n")
[3] The mirror on GitHub, which includes archived packages as well as
current (well, eventually-consistent) versions.
[4] Note that usage in packages is likely not representative of usage
in scripts, e.g. I often saw readChar(f, 1), or eol-finders like
readChar(f, 500) + grep("[\n\r]"), which makes more sense to me as
something to find in package internals than in analysis scripts. FWIW
I searched an internal codebase (scripts and packages) and found 70%
of usages reading the full file.
[5] repro: https://gist.github.com/MichaelChirico/247ea9500460dca239f031e74bdcf76b
requires GitHub PAT in env GITHUB_PAT for API permissions.

--
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
     Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney at uiowa.edu
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