qmail.eclass: simplify is_prime()

The previous algorithm would scan for all primes for a given number, which
takes needlessly long.

Signed-off-by: Rolf Eike Beer <eike@sf-mail.de>
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/eclass/tests/qmail.sh b/eclass/tests/qmail.sh
new file mode 100755
index 000000000000..3520ed2a9d5b
--- /dev/null
+++ b/eclass/tests/qmail.sh
@@ -0,0 +1,52 @@
+#!/bin/bash
+# Copyright 2020-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+source tests-common.sh
+
+inherit qmail
+
+# some numbers are blocked because they are to small even if prime
+test_low_numbers() {
+	tbegin "low numbers"
+
+	for i in $(seq 0 6); do
+		if is_prime ${i}; then
+			return tend 1 "${i} badly accepted"
+		fi
+	done
+
+	tend 0
+}
+
+# test a given number for being prime
+check_prime_number() {
+	# use factor from coreutils to count the factors
+	if [[ $(factor $1 | cut -d: -f2 | wc -w) == 1 ]]; then
+		return $(is_prime $1)
+	else
+		return $(is_prime $1 && false || true)
+	fi
+}
+
+test_primes() {
+	tbegin "factorizations from ${1} to ${2}"
+
+	for i in $(seq ${1:?} ${2:?}); do
+		if ! check_prime_number $i; then
+			tend 1 "${i} returned bad factorization"
+			return 1
+		fi
+	done
+
+	tend 0
+}
+
+test_low_numbers
+test_primes 7 99
+for i in $(seq 100 100 1000); do
+	test_primes $i $((i + 99))
+done
+
+texit