lib: add StrToNum

2 files changed, 70 insertions, 0 deletions

diff --git a/lib/str.go b/lib/str.go
index 857268d..2f6ece4 100644
--- a/lib/str.go
+++ b/lib/str.go
@@ -153,3 +153,31 @@ func StrHas(s, n string) bool {
 	}
 	return false
 }
+
+// Converts a string to an integer.
+func StrToNum(s string) (int, error) {
+	var negative bool
+	var n int
+
+	if len(s) < 1 {
+		return 0, CPError{"invalid number"}
+	}
+	if s[0] == '-' {
+		negative = true
+		s = s[1:]
+	}
+	u := 1
+	for i := len(s) - 1; i >= 0; i-- {
+		b := s[i]
+		if b >= '0' && b <= '9' {
+			n += int(b-48) * u
+			u *= 10
+		} else {
+			return 0, CPError{"invalid number"}
+		}
+	}
+	if negative {
+		n *= -1
+	}
+	return n, nil
+}
diff --git a/lib/str_test.go b/lib/str_test.go
new file mode 100644
index 0000000..1b1bb60
--- /dev/null
+++ b/lib/str_test.go
@@ -0,0 +1,42 @@
+// Copyright © 2022 siddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+import "testing"
+
+func TestStrToNum(t *testing.T) {
+	// Test 1
+	s1 := "29283329"
+	n1, err := StrToNum(s1)
+	if err != nil {
+		t.Errorf("test 1 failed: %v\n", err)
+	}
+	if n1 != 29283329 {
+		t.Errorf("test 1 failed: %v != %v\n", s1, n1)
+	}
+
+	// Test 2
+	s2 := "-83729282"
+	n2, err := StrToNum(s2)
+	if err != nil {
+		t.Errorf("test 2 failed: %v\n", err)
+	}
+	if n2 != -83729282 {
+		t.Errorf("test 2 failed: %v != %v\n", s2, n2)
+	}
+
+	// Test 3
+	s3 := "887232.2323"
+	_, err = StrToNum(s3)
+	if err == nil {
+		t.Errorf("test 3 failed\n")
+	}
+
+	// Test 4
+	s4 := "332e323"
+	_, err = StrToNum(s4)
+	if err == nil {
+		t.Errorf("test 4 failed\n")
+	}
+}