base64: some optimizations

* Add a test for the base64 encoding/decoding of long strings (i.e. mainly memory allocation).

* Make vlib/encoding/base64/base64_memory_test.v resemble more test.v from https://github.com/kostya/benchmarks .

* base64: some optimizations, also add base64.encode_in_buffer and base64.decode_in_buffer .

* Fix tests passing static strings.

* Reduce time needed for base64_memory_test.v .

* Optimize encoding.base64.Index access too (it is static), which speeds up decoding.

vlib/encoding/base64/base64.v

@@ -5,16 +5,50 @@
 module base64
 
 const (
-	Index = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	Index = [int(0), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 	62, 63, 62, 62, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0,
 	0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
 	17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 63, 0, 26, 27, 28, 29,
 	30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
-	47, 48, 49, 50, 51]
+	47, 48, 49, 50, 51]!!
+
+	EndingTable = [0, 2, 1]
+	EncodingTable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
 )
 
+/**
+ * decode - expects a base64 encoded string. Returns its decoded version.
+ * @param data - the encoded input string.
+ * @return the decoded version of the input string data.
+ * NB: if you need to decode many strings repeatedly, take a look at decode_in_buffer too.
+ */
 pub fn decode(data string) string {
+	buffer := malloc( data.len * 3 / 4 )
+	return tos(buffer, decode_in_buffer(data, mut buffer) )
+}
+
+/**
+ * decode - expects a string. Returns its base64 encoded version.
+ * @param data - the input string.
+ * @return the base64 encoded version of the input string. 
+ * NB: base64 encoding returns a string that is ~ 4/3 larger than the input.
+ * NB: if you need to encode many strings repeatedly, take a look at encode_in_buffer too.
+ */
+pub fn encode(data string) string {
+	buffer := malloc( 4 * ((data.len + 2) / 3) )
+	return tos(buffer, encode_in_buffer(data, mut buffer))
+}
+
+/**
+ * decode_in_buffer - expects a string reference, and a buffer in which to store its decoded version.
+ * @param data - a reference/pointer to the input string that will be decoded.
+ * @param buffer - a reference/pointer to the buffer that will hold the result. 
+ * The buffer should be large enough (i.e. 3/4 of the data.len, or larger) to hold the decoded data.
+ * @return the actual size of the decoded data in the buffer.
+ * NB: this function does NOT allocate new memory, and is suitable for handling very large strings.
+ */
+pub fn decode_in_buffer(data &string, buffer mut byteptr) int {
 	mut padding := 0
 	if data.ends_with('=') {
 		if data.ends_with('==') {
@@ -29,52 +63,67 @@ pub fn decode(data string) string {
 
 	mut i := 0
 	mut j := 0
-	mut str := malloc(output_length)
+	mut b := &byte(0)
+	mut d := &byte(0)
+	unsafe{
+		d = byteptr(data.str)
+		b = byteptr(buffer)
+	}
 
 	for i < input_length {
 		mut char_a := 0
 		mut char_b := 0
 		mut char_c := 0
 		mut char_d := 0
-
 		if i < input_length {
-			char_a = Index[int(data[i])]
+			char_a = Index[d[i]]
 			i++
 		}
 		if i < input_length {
-			char_b = Index[int(data[i])]
+			char_b = Index[d[i]]
 			i++
 		}
 		if i < input_length {
-			char_c = Index[int(data[i])]
+			char_c = Index[d[i]]
 			i++
 		}
 		if i < input_length {
-			char_d = Index[int(data[i])]
+			char_d = Index[d[i]]
 			i++
 		}
 
 		decoded_bytes := (char_a << 18) | (char_b << 12) | (char_c << 6) | (char_d << 0)
-		str[j] = decoded_bytes >> 16
-		str[j+1] = (decoded_bytes >> 8) & 0xff
-		str[j+2] = (decoded_bytes >> 0) & 0xff
-
+		b[j]   = decoded_bytes >> 16
+		b[j+1] = (decoded_bytes >> 8) & 0xff
+		b[j+2] = (decoded_bytes >> 0) & 0xff
 		j += 3
 	}
-	return tos(str, output_length)
+	return output_length
 }
 
-const (
-	EncodingTable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
-)
-
-pub fn encode(data string) string {
+/**
+ * encode_in_buffer - expects a string reference, and a buffer in which to store its base64 encoded version.
+ * @param data - a reference/pointer to the input string.
+ * @param buffer - a reference/pointer to the buffer that will hold the result. 
+ * The buffer should be large enough (i.e. 4/3 of the data.len, or larger) to hold the encoded data.
+ * @return the actual size of the encoded data in the buffer.
+ * NB: this function does NOT allocate new memory, and is suitable for handling very large strings.
+ */
+pub fn encode_in_buffer(data &string, buffer mut byteptr) int {
 	input_length := data.len
 	output_length := 4 * ((input_length + 2) / 3)
 
 	mut i := 0
 	mut j := 0
-	mut str := malloc(output_length)
+
+	mut d	   := &byte(0)
+	mut b	   := &byte(0)
+	mut etable := &byte(0)
+	unsafe{
+		d = &byte(data.str)
+		b = &byte(buffer)
+		etable = &byte(EncodingTable.str)
+	}
 
 	for i < input_length {
 		mut octet_a := 0
@@ -82,31 +131,30 @@ pub fn encode(data string) string {
 		mut octet_c := 0
 
 		if i < input_length {
-			octet_a = int(data[i])
+			octet_a = int(d[i])
 			i++
 		}
 		if i < input_length {
-			octet_b = int(data[i])
+			octet_b = int(d[i])
 			i++
 		}
 		if i < input_length {
-			octet_c = int(data[i])
+			octet_c = int(d[i])
 			i++
 		}
 
-		triple := ((octet_a << 0x10) + (octet_b << 0x08) + octet_c)
+		triple := ((int(octet_a) << 0x10) + (int(octet_b) << 0x08) + int(octet_c))
 
-		str[j+0] = EncodingTable[(triple >> 3 * 6) & 63] // 63 is 0x3F
-		str[j+1] = EncodingTable[(triple >> 2 * 6) & 63]
-		str[j+2] = EncodingTable[(triple >> 1 * 6) & 63]
-		str[j+3] = EncodingTable[(triple >> 0 * 6) & 63]
+		b[j]   = etable[ (triple >> 3 * 6) & 63 ]  // 63 is 0x3F
+		b[j+1] = etable[ (triple >> 2 * 6) & 63 ]
+		b[j+2] = etable[ (triple >> 1 * 6) & 63 ]
+		b[j+3] = etable[ (triple >> 0 * 6) & 63 ]
 		j += 4
 	}
 
-	mod_table := [0, 2, 1]
-	for i = 0; i < mod_table[input_length % 3]; i++ {
-		str[output_length - 1 - i] = `=`
+	padding_length := EndingTable[input_length % 3]
+	for i = 0; i < padding_length; i++ {
+		b[output_length - 1 - i] = `=`
 	}
-
-	return tos(str, output_length)
+	return output_length
 }

vlib/encoding/base64/base64_memory_test.v

@@ -0,0 +1,32 @@
+import encoding.base64
+
+fn test_long_encoding(){
+	repeats := 1000
+	input_size := 3000
+	
+	s_original := 'a'.repeat(input_size)
+	s_encoded := base64.encode(s_original)
+	s_decoded := base64.decode(s_encoded)
+	
+	assert s_encoded.len > s_original.len
+	assert s_original == s_decoded
+
+	mut s := 0
+	
+	ebuffer := malloc( s_encoded.len )
+	for i := 0; i < repeats; i++ {
+		resultsize := base64.encode_in_buffer(s_original, mut ebuffer)
+		s += resultsize
+		assert resultsize == s_encoded.len
+	}
+
+	dbuffer := malloc( s_decoded.len )
+	for i := 0; i < repeats; i++ {
+		resultsize := base64.decode_in_buffer(s_encoded, mut dbuffer)
+		s += resultsize
+		assert resultsize == s_decoded.len
+	}
+
+	println( 'Final s: $s' )
+	//	assert s == 39147008
+}

vlib/encoding/base64/base64_test.v

@@ -31,11 +31,16 @@ const (
 		TestPair{'asure.', 'YXN1cmUu'},
 		TestPair{'sure.', 'c3VyZS4='},
 	]
+	
+	man_pair = TestPair{
+		'Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.',
+		'TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4='
+	}
+		
 )
 
 fn test_decode() {
-	assert base64.decode('TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=')
-	== 'Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.'
+	assert base64.decode(man_pair.encoded) == man_pair.decoded
 
 	// Test for incorrect padding.
 	assert base64.decode('aGk') == 'hi'
@@ -52,8 +57,7 @@ fn test_decode() {
 }
 
 fn test_encode() {
-	assert base64.encode('Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.')
-	== 'TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4='
+	assert base64.encode(man_pair.decoded) == man_pair.encoded
 
 	for i, p in pairs {
 		got := base64.encode(p.decoded)