[[ This repository is archived.

This code is now maintained as the `tests/random_line_generator.c`
code in the https://github.com/ThePythonicCow/rawscan repository.

-- Paul Jackson, [email protected], 2 Nov 2019

]]

GenerateMillionLineTestData

Efficiently generate one million short random ASCII lines of text data

This program generates random short lines of ASCII text. Lines consist of zero to fifteen ASCII characters from a subset (the first 32 characters) of the RFC 4648 base64 set [A-Za-z0-9+/], each line (except perhaps the last) terminated by a newline ('\n').

Motivation:

The primary motivation for this command is to generate input test for a high performance "getline()" variant that I am currently working on, which will be called "rawscan_getline()", to be made available in both C (for now anyway just for gcc on Linux, where I have decades of experience) and Rust (as a Rust learning exercise for myself.)

Underlying technology:

This program is currently of use with the GNU C compiler on Linux systems, though it should be easily portable to other systems. It makes good use of Melissa E. O’Neill's delightful "PCG" pseudo random number generator: http://www.pcg-random.org/.

How to build and use:

The working source consists of a single C language source file.

Download and build

Download it, and compile it.

Minimal simple compile command:

gcc -o ran_len_line_gen ran_len_line_gen.c

Fancy optimized compile command:

gcc -fwhole-program -march=native -O3 -Wall -pedantic -Werror -o ran_len_line_gen ran_len_line_gen.c

Running the command

Then you can use this program to feed a million lines of test data into some other program. For example, to test how a command "foo" handles this particular input, at a shell prompt, pipe the output of the compiled ran_len_line_gen into the input of foo:

./ran_len_line_gen | foo

Command line option

Currently this command has one command line option, -n number, to change the number of lines output, from the default one million, to whatever positive number of lines you need.

Example output

Here's an example of using this command line option to obtain just ten lines of output, including showing exactly what those ten lines will be.

Running the command:

./ran_len_line_gen -n 10

at a shell prompt will produce the output:

AB
CDEFGHIJK
LMNOPQRSTUV
WXYZabcdefAB
CDEF
GHIJKLMNOPQRS
TUVW
XYZab
cdefABCDE
FGHIJKLMNOPQR

How to test:

The quite predictable default million line output has a sha256 sum of: 8f560d2518f0df1b0f309b7c34395d21ffd50648726e26ea37ea019b79acf6e9

To test this, build as above and run the following command at a shell prompt (assuming you have the command sha256sum installed):

./ran_len_line_gen | sha256sum

This command will output the string:

8f560d2518f0df1b0f309b7c34395d21ffd50648726e26ea37ea019b79acf6e9