string: remove strconv dep

vlib/builtin/string.v

@@ -4,6 +4,8 @@
 
 module builtin
 
+//import strconv
+
 /*
 NB: A V string should be/is immutable from the point of view of
     V user programs after it is first created. A V string is
@@ -41,7 +43,6 @@ NB: A V string should be/is immutable from the point of view of
     when used with modules using C functions (for example os and so on).
 */
 
-//import strconv
 
 pub struct string {
 //mut:
@@ -202,8 +203,23 @@ pub fn (s string) int() int {
 
 
 pub fn (s string) i64() i64 {
+	mut neg := false
+	mut i := 0
+	if s[0] == `-` {
+		neg = true
+		i++
+	}
+	else if s[0] == `+` {
+		i++
+	}
+	mut n := i64(0)
+	for C.isdigit(s[i]) {
+		n = i64(10) * n - i64(s[i] - `0`)
+		i++
+	}
+	return if neg { n } else { -n }
 	//return strconv.parse_int(s, 0, 64)
-	return C.atoll(*char(s.str))
+	//return C.atoll(*char(s.str))
 }
 
 pub fn (s string) f32() f32 {
@@ -215,12 +231,42 @@ pub fn (s string) f64() f64 {
 }
 
 pub fn (s string) u32() u32 {
-	return C.atol(*char(s.str))
+	mut neg := false
+	mut i := 0
+	if s[0] == `-` {
+		neg = true
+		i++
+	}
+	else if s[0] == `+` {
+		i++
+	}
+	mut n := u32(0)
+	for C.isdigit(s[i]) {
+		n = u32(10) * n - u32(s[i] - `0`)
+		i++
+	}
+	return if neg { n } else { -n }
+	//return C.atol(*char(s.str))
 	//return strconv.parse_uint(s, 0, 32)
 }
 
 pub fn (s string) u64() u64 {
-	return C.atoll(*char(s.str))
+	mut neg := false
+	mut i := 0
+	if s[0] == `-` {
+		neg = true
+		i++
+	}
+	else if s[0] == `+` {
+		i++
+	}
+	mut n := u64(0)
+	for C.isdigit(s[i]) {
+		n = u64(10) * n - u64(s[i] - `0`)
+		i++
+	}
+	return if neg { n } else { -n }
+	//return C.atoll(*char(s.str))
 	//return strconv.parse_uint(s, 0, 64)
 }