Initial project import

tools/v/vlib/encoding/xml/entity.v

@@ -0,0 +1,82 @@
+module xml
+
+import strings
+
+pub const default_entities = {
+	'lt':   '<'
+	'gt':   '>'
+	'amp':  '&'
+	'apos': "'"
+	'quot': '"'
+}
+
+pub const default_entities_reverse = {
+	'<': 'lt'
+	'>': 'gt'
+	'&': 'amp'
+	"'": 'apos'
+	'"': 'quot'
+}
+
+@[params]
+pub struct EscapeConfig {
+pub:
+	reverse_entities map[string]string = default_entities_reverse
+}
+
+// escape_text replaces all entities in the given string with their respective
+// XML entity strings. See default_entities, which can be overridden.
+pub fn escape_text(content string, config EscapeConfig) string {
+	mut flattened_entities := []string{cap: 2 * config.reverse_entities.len}
+
+	for target, replacement in config.reverse_entities {
+		flattened_entities << target
+		flattened_entities << '&' + replacement + ';'
+	}
+
+	return content.replace_each(flattened_entities)
+}
+
+@[params]
+pub struct UnescapeConfig {
+pub:
+	entities map[string]string = default_entities
+}
+
+// unescape_text replaces all entities in the given string with their respective
+// original characters or strings. See default_entities_reverse, which can be overridden.
+pub fn unescape_text(content string, config UnescapeConfig) !string {
+	mut buffer := strings.new_builder(content.len)
+	mut index := 0
+	runes := content.runes()
+	for index < runes.len {
+		match runes[index] {
+			`&` {
+				mut offset := 1
+				mut entity_buf := strings.new_builder(8)
+				for index + offset < runes.len && runes[index + offset] != `;` {
+					entity_buf.write_rune(runes[index + offset])
+					offset++
+				}
+				// Did we reach the end of the string?
+				if index + offset == runes.len {
+					return error('Unexpected end of string while parsing entity.')
+				}
+				// Did we find a valid entity?
+				entity := entity_buf.str()
+				if entity in config.entities {
+					buffer.write_string(config.entities[entity])
+					index += offset
+				} else {
+					return error('Unknown entity: ' + entity)
+				}
+			}
+			else {
+				buffer.write_rune(runes[index])
+			}
+		}
+
+		index++
+	}
+	return buffer.str()
+}