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//===--- StringParser.swift -----------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
/// A simple utility to parse a string.
public struct StringParser {
private var s: Substring
private let originalLength: Int
private mutating func consumeWhitespace() {
s = s.drop { $0.isWhitespace }
}
public init(_ string: String) {
s = Substring(string)
originalLength = string.count
}
public mutating func isEmpty() -> Bool {
consumeWhitespace()
return s.isEmpty
}
public mutating func consume(_ str: String) -> Bool {
consumeWhitespace()
if !s.starts(with: str) { return false }
s = s.dropFirst(str.count)
return true
}
public mutating func consumeInt(withWhiteSpace: Bool = true) -> Int? {
if withWhiteSpace {
consumeWhitespace()
}
var intStr = ""
s = s.drop {
if $0.isNumber {
intStr.append($0)
return true
}
return false
}
return Int(intStr)
}
public mutating func consumeIdentifier() -> String? {
consumeWhitespace()
var name = ""
s = s.drop {
if $0.isLetter {
name.append($0)
return true
}
return false
}
return name.isEmpty ? nil : name
}
public func throwError(_ message: StaticString) throws -> Never {
throw ParsingError(message: message, position: originalLength - s.count)
}
}
public struct ParsingError : Error {
public let message: StaticString
public let position: Int
}
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