Merge pull request #908 from pushkarnk/substring-crash
diff --git a/Foundation/NSString.swift b/Foundation/NSString.swift
index 34badff..2fb666f 100644
--- a/Foundation/NSString.swift
+++ b/Foundation/NSString.swift
@@ -346,7 +346,49 @@
let start = _storage.utf16.startIndex
let min = start.advanced(by: range.location)
let max = start.advanced(by: range.location + range.length)
- return String(_storage.utf16[min..<max])!
+ if let substr = String(_storage.utf16[min..<max]) {
+ return substr
+ }
+ //If we come here, then the range has created unpaired surrogates on either end.
+ //An unpaired surrogate is replaced by OXFFFD - the Unicode Replacement Character.
+ //The CRLF ("\r\n") sequence is also treated like a surrogate pair, but its constinuent
+ //characters "\r" and "\n" can exist outside the pair!
+
+ let replacementCharacter = String(describing: UnicodeScalar(0xFFFD)!)
+ let CR: UInt16 = 13 //carriage return
+ let LF: UInt16 = 10 //new line
+
+ //make sure the range is of non-zero length
+ guard range.length > 0 else { return "" }
+
+ //if the range is pointing to a single unpaired surrogate
+ if range.length == 1 {
+ switch _storage.utf16[min] {
+ case CR: return "\r"
+ case LF: return "\n"
+ default: return replacementCharacter
+ }
+ }
+
+ //set the prefix and suffix characters
+ let prefix = _storage.utf16[min] == LF ? "\n" : replacementCharacter
+ let suffix = _storage.utf16[max.advanced(by: -1)] == CR ? "\r" : replacementCharacter
+
+ //if the range breaks a surrogate pair at the beginning of the string
+ if let substrSuffix = String(_storage.utf16[min.advanced(by: 1)..<max]) {
+ return prefix + substrSuffix
+ }
+
+ //if the range breaks a surrogate pair at the end of the string
+ if let substrPrefix = String(_storage.utf16[min..<max.advanced(by: -1)]) {
+ return substrPrefix + suffix
+ }
+
+ //the range probably breaks surrogate pairs at both the ends
+ guard min.advanced(by: 1) <= max.advanced(by: -1) else { return prefix + suffix }
+
+ let substr = String(_storage.utf16[min.advanced(by: 1)..<max.advanced(by: -1)])!
+ return prefix + substr + suffix
} else {
let buff = UnsafeMutablePointer<unichar>.allocate(capacity: range.length)
getCharacters(buff, range: range)
diff --git a/TestFoundation/TestNSString.swift b/TestFoundation/TestNSString.swift
index 0671f99..46974b0 100644
--- a/TestFoundation/TestNSString.swift
+++ b/TestFoundation/TestNSString.swift
@@ -95,6 +95,7 @@
("test_reflection", { _ in test_reflection }),
("test_replacingOccurrences", test_replacingOccurrences),
("test_getLineStart", test_getLineStart),
+ ("test_substringWithRange", test_substringWithRange),
]
}
@@ -1056,6 +1057,49 @@
XCTAssertEqual(outContentsEndIndex, twoLines.index(twoLines.startIndex, offsetBy: 11))
XCTAssertEqual(outEndIndex, twoLines.index(twoLines.startIndex, offsetBy: 12))
}
+
+ func test_emptyStringPrefixAndSuffix() {
+ let testString = "hello"
+ XCTAssertTrue(testString.hasPrefix(""))
+ XCTAssertTrue(testString.hasSuffix(""))
+ }
+
+ func test_substringWithRange() {
+ let trivial = NSString(string: "swift.org")
+ XCTAssertEqual(trivial.substring(with: NSMakeRange(0, 5)), "swift")
+
+ let surrogatePairSuffix = NSString(string: "Hurray🎉")
+ XCTAssertEqual(surrogatePairSuffix.substring(with: NSMakeRange(0, 7)), "Hurray�")
+
+ let surrogatePairPrefix = NSString(string: "🐱Cat")
+ XCTAssertEqual(surrogatePairPrefix.substring(with: NSMakeRange(1, 4)), "�Cat")
+
+ let singleChar = NSString(string: "😹")
+ XCTAssertEqual(singleChar.substring(with: NSMakeRange(0,1)), "�")
+
+ let crlf = NSString(string: "\r\n")
+ XCTAssertEqual(crlf.substring(with: NSMakeRange(0,1)), "\r")
+ XCTAssertEqual(crlf.substring(with: NSMakeRange(1,1)), "\n")
+ XCTAssertEqual(crlf.substring(with: NSMakeRange(1,0)), "")
+
+ let bothEnds1 = NSString(string: "😺😺")
+ XCTAssertEqual(bothEnds1.substring(with: NSMakeRange(1,2)), "��")
+
+ let s1 = NSString(string: "😺\r\n")
+ XCTAssertEqual(s1.substring(with: NSMakeRange(1,2)), "�\r")
+
+ let s2 = NSString(string: "\r\n😺")
+ XCTAssertEqual(s2.substring(with: NSMakeRange(1,2)), "\n�")
+
+ let s3 = NSString(string: "😺cats😺")
+ XCTAssertEqual(s3.substring(with: NSMakeRange(1,6)), "�cats�")
+
+ let s4 = NSString(string: "😺cats\r\n")
+ XCTAssertEqual(s4.substring(with: NSMakeRange(1,6)), "�cats\r")
+
+ let s5 = NSString(string: "\r\ncats😺")
+ XCTAssertEqual(s5.substring(with: NSMakeRange(1,6)), "\ncats�")
+ }
}
struct ComparisonTest {
