rand: refactor string sampling functions to remove redundancy (#8830)

vlib/rand/rand.v

@@ -138,56 +138,45 @@ pub fn f64_in_range(min f64, max f64) f64 {
 }
 
 const (
-	chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
-)
-
-// string returns a string of length `len` containing random characters in range `[a-zA-Z]`.
-pub fn string(len int) string {
-	mut buf := unsafe {malloc(len)}
-	for i in 0 .. len {
-		unsafe {
-			buf[i] = rand.chars[intn(rand.chars.len)]
-		}
-	}
-	return unsafe { buf.vstring_with_len(len) }
-}
-
-
-const (
+	english_letters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
 	hex_chars       = 'abcdef0123456789'
-)
-
-// hex returns a hexadecimal number of length `len` containing random characters in range `[a-f0-9]`.
-pub fn hex(len int) string {
-	mut buf := unsafe {malloc(len)}
-	for i in 0 .. len {
-		unsafe {
-			buf[i] = rand.hex_chars[intn(rand.hex_chars.len)]
-		}
-	}
-	return unsafe { buf.vstring_with_len(len) }
-}
-
-const (
 	ascii_chars     = '!"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ\\^_`abcdefghijklmnopqrstuvwxyz{|}~'
 )
 
-// ascii returns a random string of the printable ASCII characters with length `len`.
-pub fn ascii(len int) string {
-	mut buf := unsafe {malloc(len)}
+// string_from_set returns a string of length `len` containing random characters sampled from the given `charset`
+pub fn string_from_set(charset string, len int) string {
+	if len == 0 {
+		return ''
+	}
+	mut buf := unsafe { malloc(len) }
 	for i in 0 .. len {
 		unsafe {
-			buf[i] = rand.ascii_chars[intn(rand.ascii_chars.len)]
+			buf[i] = charset[intn(charset.len)]
 		}
 	}
 	return unsafe { buf.vstring_with_len(len) }
 }
 
+// string returns a string of length `len` containing random characters in range `[a-zA-Z]`.
+pub fn string(len int) string {
+	return string_from_set(rand.english_letters, len)
+}
+
+// hex returns a hexadecimal number of length `len` containing random characters in range `[a-f0-9]`.
+pub fn hex(len int) string {
+	return string_from_set(rand.hex_chars, len)
+}
+
+// ascii returns a random string of the printable ASCII characters with length `len`.
+pub fn ascii(len int) string {
+	return string_from_set(rand.ascii_chars, len)
+}
+
 // uuid_v4 generates a random (v4) UUID
 // See https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_(random)
 pub fn uuid_v4() string {
 	buflen := 36
-	mut buf := unsafe {malloc(37)}
+	mut buf := unsafe { malloc(37) }
 	mut i_buf := 0
 	mut x := u64(0)
 	mut d := byte(0)
@@ -240,7 +229,7 @@ pub fn ulid() string {
 // ulid_at_millisecond does the same as `ulid` but takes a custom Unix millisecond timestamp via `unix_time_milli`.
 pub fn ulid_at_millisecond(unix_time_milli u64) string {
 	buflen := 26
-	mut buf := unsafe {malloc(27)}
+	mut buf := unsafe { malloc(27) }
 	mut t := unix_time_milli
 	mut i := 9
 	for i >= 0 {

vlib/rand/random_numbers_test.v

@@ -188,3 +188,83 @@ fn test_rand_byte() {
 	assert all[0] != all[255]
 	assert all[0] != all[128]
 }
+
+const (
+	string_count = 25
+)
+
+fn test_rand_string_from_set() {
+	sets := [
+		'0123456789',
+		'qwertyuiop',
+		'abcdefghijklmnopqrstuvwxyz',
+	]
+	for charset in sets {
+		for _ in 0 .. string_count {
+			len := rand.intn(rnd_count)
+			str := rand.string_from_set(charset, len)
+			assert str.len == len
+			for character in str {
+				position := charset.index(character.ascii_str()) or { -1 }
+				assert position > -1
+			}
+		}
+	}
+}
+
+fn test_rand_string() {
+	rand.seed([u32(0), 1])
+	outputs := [
+		'rzJfVBJgvAyCNpEdXIteDQezg',
+		'AJOeswgoelDOCfcrSUWzVPjeL',
+		'NQfKauQqsXYXSUMFPGnXXPJIn',
+		'vfBGUKbpLoBMQVYXfkvRplWih',
+		'aYHLjMJqvUJmJJHGxEnrEmQGl',
+		'rBJXkQZcembAteaRFoxXmECJo',
+		'HYVLfHmDOCTlSbiSzHrsAIaBH',
+		'zgOiwyISjLSdLGhLzJsSKHVBi',
+		'UiAtobWXGcHsEtgzuNatxfkoI',
+		'NisnYlffJgFEcIdcgzWcGjnHy',
+	]
+	for output in outputs {
+		assert rand.string(25) == output
+	}
+}
+
+fn test_rand_hex() {
+	rand.seed([u32(0), 1])
+	outputs := [
+		'fc30e495deee09e008e15ffc3',
+		'4320efa837788397fb59b28f4',
+		'4995210abf33b6765c240ce62',
+		'f3d20dbe0a8aa6b9c88cd1f6f',
+		'8d7d58b256ab00213dd519cf7',
+		'fa2251284bc20a21eff48127c',
+		'5fef90cdc0c37143117599092',
+		'2a6170531c76dfb50c54126bc',
+		'a686dfd536042d1c1a9afdaf4',
+		'7f12013f6e1177e2d63726de3',
+	]
+	for output in outputs {
+		assert rand.hex(25) == output
+	}
+}
+
+fn test_rand_ascii() {
+	rand.seed([u32(0), 1])
+	outputs := [
+		"2Z:&PeD'V;9=mn\$C>yKg'DIr%",
+		'Ub7ix,}>I=&#2QJki{%FHKv&K',
+		'1WStRylMO|p.R~qqRtr&AOEsd',
+		'yka<GPZ&m+r0^Zi!ShB*1dU~W',
+		'uDA?.zU2X,<DkKT#_-halW\\ki',
+		'fsx!@uRc?re/fSPXj`Y&\\BU}p',
+		'fI_qM"):2;CUno!<dX:Yv*FX$',
+		'FnA(Fr|D`WZVWEzp<k)O;auub',
+		"QRkxH!kjXh&/j{)uSe&{D'v?|",
+		"_CyaU\$z':#}At*v2|xDu6w=;1",
+	]
+	for output in outputs {
+		assert rand.ascii(25) == output
+	}
+}