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stdlib: move String.{lowercaseString,uppercaseString} to the core

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library

Swift SVN r23936
This commit is contained in:
Dmitri Hrybenko
2014-12-15 09:47:03 +00:00
parent 397d2fb8c3
commit e87bcff79d
8 changed files with 290 additions and 155 deletions
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78
stdlib/objc/Foundation/ExtraStringAPIs.swift
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@@ -10,84 +10,6 @@
//
//===----------------------------------------------------------------------===//
// FIXME: these properties should be implemented in the core library.
// <rdar://problem/17550602> [unicode] Implement case folding
extension String {
/// A "table" for which ASCII characters need to be upper cased.
/// To determine which bit corresponds to which ASCII character, subtract 1
/// from the ASCII value of that character and divide by 2. The bit is set iff
/// that character is a lower case character.
internal var _asciiLowerCaseTable: UInt64 {
@inline(__always)
get {
return 0b0001_1111_1111_1111_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000
}
}
/// The same table for upper case characters.
internal var _asciiUpperCaseTable: UInt64 {
@inline(__always)
get {
return 0b0000_0000_0000_0000_0001_1111_1111_1111_0000_0000_0000_0000_0000_0000_0000_0000
}
}
public var lowercaseString: String {
if self._core.isASCII {
let length = self._core.count
let source = self._core.startASCII
var buffer = _StringBuffer(
capacity: length, initialSize: length, elementWidth: 1)
var dest = UnsafeMutablePointer<UInt8>(buffer.start)
for i in 0..<length {
// For each character in the string, we lookup if it should be shifted
// in our ascii table, then we return 0x20 if it should, 0x0 if not.
// This code is equivalent to:
// switch source[i] {
// case let x where (x >= 0x41 && x <= 0x5a):
// dest[i] = x &+ 0x20
// case let x:
// dest[i] = x
// }
let value = source[i]
let isUpper =
_asciiUpperCaseTable >>
UInt64(((value &- 1) & 0b0111_1111) >> 1)
let add = (isUpper & 0x1) << 5
// Since we are left with either 0x0 or 0x20, we can safely truncate to
// a UInt8 and add to our ASCII value (this will not overflow numbers in
// the ASCII range).
dest[i] = value &+ UInt8(truncatingBitPattern: add)
}
return String(_storage: buffer)
}
return _ns.lowercaseString
}
public var uppercaseString: String {
if self._core.isASCII {
let length = self._core.count
let source = self._core.startASCII
var buffer = _StringBuffer(
capacity: length, initialSize: length, elementWidth: 1)
var dest = UnsafeMutablePointer<UInt8>(buffer.start)
for i in 0..<length {
// See the comment above in lowercaseString.
let value = source[i]
let isLower =
_asciiLowerCaseTable >>
UInt64(((value &- 1) & 0b0111_1111) >> 1)
let add = (isLower & 0x1) << 5
dest[i] = value &- UInt8(truncatingBitPattern: add)
}
return String(_storage: buffer)
}
return _ns.uppercaseString
}
}
extension String.UTF16View.Index : RandomAccessIndexType {
public func distanceTo(x: String.UTF16View.Index) -> Int {
return x._offset - _offset