telodendria/man/man3/Util.3

.Dd $Mdocdate: February 15 2023 $
.Dt UTIL 3
.Os Telodendria Project
.Sh NAME
.Nm Util
.Nd Some misc. helper functions that don't need their own headers.
.Sh SYNOPSIS
.In Util.h
.Ft unsigned long
.Fn UtilServerTs "void"
.Ft unsigned long
.Fn UtilLastModified "char *"
.Ft int
.Fn UtilMkdir "const char *" "const mode_t"
.Ft int
.Fn UtilSleepMillis "long"
.Ft size_t
.Fn UtilParseBytes "char *"
.Ft ssize_t
.Fn UtilGetDelim "char **" "size_t *" "int" "FILE *"
.Ft ssize_t
.Fn UtilGetLine "char **" "size_t *" "FILE *"
.Sh DESCRIPTION
.Pp
This header holds a number of random functions related to strings,
time, and other tasks that don't require a full API, just one or
two functions. For the most part, the functions here are entirely
standalone, depending only on POSIX functions, however there are a
few that specifically utilize Telodendria APIs. Those are noted.
.Pp
.Fn UtilServerTs
gets the current time in milliseconds since the Unix epoch. This
uses
.Xr gettimeofday 2
and time_t, and converts it to a single number, which is then
returned to the caller. A note on the 2038 problem: as long as
sizeof(long) >= 8, that is, as long as the long datatype is 64 bits
or more, which it is on all modern 64-bit Unix-like operating
systems, then everything should be fine. Expect Telodendria on 32 bit
machines to break in 2038. I didn't want to try to hack together
some system to store larger numbers than the architecture supports.
We can always re-evaluate things over the next decade.
.Pp
.Fn UtilMkdir
behaves just like the system call
.Xr mkdir 2 ,
but it creates any intermediate directories if necessary, unlike
.Xr mkdir 2 .
.Pp
.Fn UtilSleepMillis
sleeps the calling thread for the given number of milliseconds. It
occurred to me that POSIX does not specify a super friendly way to
sleep, so this is a wrapper around the POSIX
.Xr nanosleep 2
designed to make its usage much, much simpler.
.Pp
.Fn UtilLastModified
uses
.Xr stat 2
to get the last modified time of the given file. This is used
primarily for caching file data.
.Pp
.Fn UtilParseBytes
is a highly specialized function used in parsing the configuration file.
It takes in a string which is supposed to represent a number of bytes.
It must consist of an integer, followed by an optional suffix of k, K, m, M,
g, or G, indicating the value is kilobytes, megabytes, or gigabytes.
.Pp
.Fn UtilGetDelim
and
.Fn UtilGetLine
work identically to the POSIX equivalents, documented in
.Xr getdelim 3 ,
except it assumes pointers were allocated using the Memory API, and it
uses the Memory API itself to reallocate necessary pointers.
.Sh RETURN VALUES
.Pp
.Fn UtilServerTs
and
.Fn UtilLastModified
return timestamps in the form of milliseconds since the Unix epoch as an unsigned
long. The Matrix specification requires timestamps be in milliseconds, so these
functions are designed to make that easy and convenient.
.Pp
.Fn UtilMkdir
returns 0 on success, and -1 on failure, just like
.Xr mkdir 2 .
It also sets errno as appropriate.
.Pp
.Fn UtilSleepMillis
returns the result of calling
.Xr nanosleep 2 .
.Pp
.Fn UtilParseBytes
returns a number of bytes, or 0 if there was an error parsing the byte string.
.Pp
.Fn UtilGetDelim
and
.Fn UtilGetLine
return the same value as their POSIX equivalents, documented in
.Xr getdelim 3 .