Mihaela Mihaljevic
f02ba8b8cf
Compile RELAX NG from both syntaxes and across documents: - A compact-syntax parser (lexer plus recursive descent) produces the same pattern algebra the XML syntax compiles to. It covers element and attribute declarations with name classes and namespace resolution, the , | & combinators and ? * + cardinality, text/empty/notAllowed, list and mixed, datatypes and value literals, grammars with start and named definitions (= |= &=), nested grammars, and include/external references. - The XML-syntax parser gains include (merging another grammar's definitions, with the include's own nested definitions overriding) and externalRef (resolving to an external schema's pattern), both through an injected loader. Both syntaxes reach the loader through a new schemaLoader parameter that returns nil by default, so compilation never touches the filesystem or network unless a loader is supplied. Closes #68
77 lines
3.0 KiB
Swift
77 lines
3.0 KiB
Swift
extension PureXML.Schema {
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/// One lexical token of the RELAX NG compact syntax.
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enum RNCToken: Equatable {
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case word(String)
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case string(String)
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case symbol(String)
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}
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/// Tokenizes RELAX NG compact-syntax source: NCName words (which may carry a
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/// single `:` prefix), quoted string literals, and punctuation, with `#`
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/// line comments skipped.
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enum RNCLexer {
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static func tokens(_ source: String) -> [RNCToken] {
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var tokens: [RNCToken] = []
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let characters = Array(source)
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var index = 0
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while index < characters.count {
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let character = characters[index]
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if character == "#" {
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while index < characters.count, characters[index] != "\n" {
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index += 1
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}
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} else if character.isWhitespace {
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index += 1
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} else if character == "\"" || character == "'" {
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index = readString(characters, index, quote: character, into: &tokens)
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} else if isNameStart(character) {
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index = readWord(characters, index, into: &tokens)
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} else {
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index = readSymbol(characters, index, into: &tokens)
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}
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}
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return tokens
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}
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private static func readString(_ characters: [Character], _ start: Int, quote: Character, into tokens: inout [RNCToken]) -> Int {
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var index = start + 1
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var value = ""
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while index < characters.count, characters[index] != quote {
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value.append(characters[index])
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index += 1
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}
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tokens.append(.string(value))
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return index + 1
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}
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private static func readWord(_ characters: [Character], _ start: Int, into tokens: inout [RNCToken]) -> Int {
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var index = start
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var value = ""
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while index < characters.count, isNameChar(characters[index]) {
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value.append(characters[index])
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index += 1
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}
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tokens.append(.word(value))
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return index
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}
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private static func readSymbol(_ characters: [Character], _ start: Int, into tokens: inout [RNCToken]) -> Int {
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let two = start + 1 < characters.count ? String(characters[start ... start + 1]) : ""
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if two == "|=" || two == "&=" {
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tokens.append(.symbol(two))
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return start + 2
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}
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tokens.append(.symbol(String(characters[start])))
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return start + 1
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}
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private static func isNameStart(_ character: Character) -> Bool {
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character.isLetter || character == "_"
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}
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private static func isNameChar(_ character: Character) -> Bool {
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character.isLetter || character.isNumber || character == "_" || character == "." || character == "-" || character == ":"
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}
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}
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}
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