v.util: simplify smart_quote more

vlib/v/util/quote.v

@@ -14,13 +14,34 @@ const double_quote = 34
 
 const double_escape = '\\\\'
 
-//[direct_array_access]
+[direct_array_access]
 pub fn smart_quote(str string, raw bool) string {
 	len := str.len
 	if len == 0 {
 		return ''
 	}
-	mut result := strings.new_builder(len)
+	if len < 256 {
+		mut is_pure := true
+		for i := 0; i < len; i++ {
+			ch := byte(str[i])
+			if (ch >= 37 && ch <= 90) || (ch >= 95 && ch <= 126)
+				|| (ch in [` `, `!`, `#`, `[`, `]`]) {
+				// safe punctuation + digits + big latin letters,
+				// small latin letters + more safe punctuation,
+				// important punctuation exceptions, that are not
+				// placed conveniently in a consequitive span in
+				// the ASCII table.
+				continue
+			}
+			is_pure = false
+			break
+		}
+		if is_pure {
+			return str
+		}
+	}
+	// ensure there is enough space for the potential expansion of several \\ or \n
+	mut result := strings.new_builder(len + 10)
 	mut pos := -1
 	mut last := byte(0)
 	mut current := byte(0)
@@ -35,85 +56,78 @@ pub fn smart_quote(str string, raw bool) string {
 		if pos >= len {
 			break
 		}
+		last = current
+		current = str[pos]
 		if pos + 1 < len {
 			next = str[pos + 1]
+		} else {
+			next = 0
 		}
-		current = str[pos]
-		// double quote
 		if current == util.double_quote {
 			current = 0
-			last = current
 			result.write_b(util.backslash)
 			result.write_b(util.double_quote)
 			continue
 		}
 		if current == util.backslash {
 			if raw {
-				last = current
 				result.write_string(util.double_escape)
 				continue
-			} else {
+			}
-				// escaped backslash - keep as is
 			if next == util.backslash {
+				// escaped backslash - keep as is
 				skip_next = true
-					last = current
 				result.write_string(util.double_escape)
 				continue
-				} else if next != 0 {
+			}
+			if next != 0 {
 				if raw {
 					skip_next = true
-						last = current
 					result.write_string(util.double_escape)
 					continue
-					} else if next in util.invalid_escapes {
+				}
+				if next in util.invalid_escapes {
 					skip_next = true
-						last = current
 					result.write_b(next)
 					continue
-					} else {
+				}
 				// keep all valid escape sequences
 				skip_next = true
-						last = current
 				result.write_b(current)
 				result.write_b(next)
 				continue
 			}
 		}
-			}
-		}
-		// keep newlines in string
 		if current == util.backslash_n {
+			// keep newlines in string
 			current = 0
-			last = current
 			result.write_b(util.backslash)
 			result.write_b(`n`)
 			continue
-		} else if current == util.backslash_r && next == util.backslash_n {
+		}
+		if current == util.backslash_r && next == util.backslash_n {
 			result.write_b(current)
 			result.write_b(next)
 			current = 0
 			skip_next = true
-			last = current
 			continue
 		}
-		// Dolar sign
+		if !raw {
-		if !raw && current == `$` {
+			if current == `$` {
 				if last == util.backslash {
 					result.write_b(last)
 					result.write_b(current)
-				last = current
 					continue
 				}
 			}
+			if current == util.backslash_r && next == util.backslash_n {
 				// Windows style new line \r\n
-		if !raw && current == util.backslash_r && next == util.backslash_n {
 				skip_next = true
 				result.write_b(util.backslash)
 				result.write_b(`n`)
-			last = current
 				continue
 			}
-		last = current
+		}
 		result.write_b(current)
 	}
 	return result.str()