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Tarsnap
libcperciva
C2016–2025
Tarsnap / libcperciva

libcperciva

BSD-licensed C99/POSIX library code shared between tarsnap, scrypt, kivaloo, spiped, and bsdiff.

Libraries & SDKs
Explore on GitHubRead Hacker News discussions
5Distinct people
12Mentions
0Explicit recommenders
116GitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

BSD-licensed C99/POSIX library code shared between tarsnap, scrypt, kivaloo, spiped, and bsdiff.

GitHub

Where it is used

No documented product use has been verified yet.

What people are saying

No recommendation phrase was found in the indexed comments.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

No other repository is repeatedly linked in the same discussions.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 3:56:07 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year12 dated mentions

Observed mentions: 2016-01-18 09:39:53 UTC to 2025-05-13 21:04:07 UTC.

012342016-01-01 00:00:00 UTC to 2017-01-01 00:00:00 UTC (exclusive): 4 mentions; 1 submissions, 3 comments20162017-01-01 00:00:00 UTC to 2018-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2018-01-01 00:00:00 UTC to 2019-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments20202021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2025

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20162016-01-01 00:00:00 UTC2017-01-01 00:00:00 UTC413
20172017-01-01 00:00:00 UTC2018-01-01 00:00:00 UTC101
20182018-01-01 00:00:00 UTC2019-01-01 00:00:00 UTC000
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC101
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC202
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC202
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC000
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC101
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC000
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC101

What Hacker News says

12 sources
cperciva·Jan 30, 2020
While I'm not a fan of the specific changes shown in this article, I do agree with the principle of "remove boilerplate when possible". I found that the largest amount of boilerplate I ever wrote was in main() to parse the command line, and to that end I wrote a "magic getopt", which handles both short and long options in-line without external tables (https://www.daemonology.net/blog/2015-12-06-magic-getopt.htm... ); and PARSENUM, which handles the common cases of parsing human-readable values while appropriately checking for overflow (https://github.com/Tarsnap/libcperciva/blob/master/util/pars...).
In Let's Destroy C
cperciva·Mar 16, 2017
Avoid magic. Do not use macros. Disagree. Use magic, especially macros, in ways such that your code becomes easier, not harder, to understand. A few examples from my own code: 1. My "elastic arrays" (https://github.com/Tarsnap/libcperciva/blob/master/datastruc... and .c) allow me to write ELASTICARRAY_DECL(STRLIST, strlist, const char *); and get a data structure STRLIST which contains an arbitrary number of strings and functions strlist_init, strlist_append, strlist_get, strlist_free, etc. for accessing the array. Compared to the non-macro approach of keeping track of the array size and resizing as needed, this makes code vastly simpler. (Of course, this sort of data structure is built into most non-C languages already.) 2. My "magic getopt" (https://github.com/Tarsnap/libcperciva/commit/53d00e5bd0478f...) allows me to something
Read the rest
which looks and behaves just like a standard UNIX getopt loop, except with support for --long options. Yes, the implementation is mildly insane (and needs to work around a bug in clang!), but it allows for code which is vastly simpler than other getopt-with-long-options alternatives. 3. My "cpu features support" framework (https://github.com/Tarsnap/libcperciva/blob/master/cpusuppor...) makes use of both macros and some tricky edge cases of C object linkage rules, but makes it trivial for me to add support for new CPU features. 4. Soon to be released, the PARSENUM macro (WIP: https://github.com/Tarsnap/libcperciva/blob/parsenum-additio...) which allows me to write PARSENUM(&n, "1234"); PARSENUM(&x, "123.456"); PARSENUM(&s, "123", 0, 1000); where the first argument is a pointer to a variable of any integer or floating-point type to which is assigned the numeric value of the string in the second argument; for floating-point values and unsigned integers, the two-argument form range-checks the value against the bounds of the type, while the four-argument form range-checks against the provided bounds. (Basically, this is strtonum on steroids.) In all of these cases, you will never need to understand how these macros work. Instead, you can simply treat them as language extensions which allow you to write cleaner and simpler code.
In Principles for C programming
cperciva·Sep 12, 2016
Grepping my checked-out source trees quickly: 1. spiped re-binds SIGINT if it is launched as pid 1, in order to work around a Docker bug: https://github.com/Tarsnap/spiped/blob/master/spiped/main.c#... 2. In my POSIX-violation-workarounds script, ironically enough, I work around a bug in bash which makes 'command -p sh' run with the incorrect path (this has since been fixed, but continues to be present in older installed versions of bash): https://github.com/Tarsnap/spiped/commit/e3968941c9c1b20c63d... 3. In my getopt code, I use a (non-C99-compliant) computed goto in order to work around a bug in LLVM's handling of sigsetjmp/siglongjmp: https://github.com/Tarsnap/libcperciva/commit/92e666e59503de... 4. Many years ago, I added a spurious 'volatile' into some Tarsnap code in order to prevent a buggy LLVM optimization step from running (it
Read the rest
was making the Tarsnap build hang on on OS X 10.7): https://github.com/Tarsnap/tarsnap/blob/master/tar/multitape...
In Ask HN: Strange bug workarounds?
seiji·Mar 13, 2016
allocate a separate list node for each piece of data So many programmers don't even consider "overhead" of data when writing things. But, most of the time it doesn't matter. Do you need a list of ten things? Great. Do whatever. Do you need a list of a billion things? Then you need to rethink everything from the bottom up. when all you need is just a pointer to realloc Wrong! https://github.com/Tarsnap/libcperciva/commit/cabe5fca76f6c3...
In Collections-C, generic data structures for C

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