KT-23356 Cross-platform function to convert CharArray slice to String

Signed-off-by: Valeriy Zhirnov <neonailol@gmail.com>

libraries/stdlib/common/src/kotlin/TextH.kt

@@ -90,6 +90,20 @@ expect fun Char.isLowSurrogate(): Boolean
 
 // From string.kt
 
+
+/**
+ * Converts the characters in the specified array to a string.
+ */
+@SinceKotlin("1.2")
+public expect fun String(chars: CharArray): String
+
+/**
+ * Converts the characters from a portion of the specified array to a string.
+ */
+@SinceKotlin("1.2")
+public expect fun String(chars: CharArray, offset: Int, length: Int): String
+
+
 internal expect fun String.nativeIndexOf(str: String, fromIndex: Int): Int
 internal expect fun String.nativeLastIndexOf(str: String, fromIndex: Int): Int
 

libraries/stdlib/js/src/kotlin/string.kt

@@ -7,6 +7,24 @@ package kotlin.text
 
 import kotlin.js.RegExp
 
+/**
+ * Converts the characters in the specified array to a string.
+ */
+@SinceKotlin("1.2")
+@kotlin.internal.InlineOnly
+public actual inline fun String(chars: CharArray): String {
+    return js("String.fromCharCode").apply(null, chars)
+}
+
+/**
+ * Converts the characters from a portion of the specified array to a string.
+ */
+@SinceKotlin("1.2")
+public actual fun String(chars: CharArray, offset: Int, length: Int): String {
+    return String(chars.copyOfRange(offset, offset + length))
+}
+
+
 @kotlin.internal.InlineOnly
 public actual inline fun String.toUpperCase(): String = asDynamic().toUpperCase()
 

libraries/stdlib/jvm/src/kotlin/text/StringsJVM.kt

@@ -260,14 +260,14 @@ public inline fun String(bytes: ByteArray): String =
  * Converts the characters in the specified array to a string.
  */
 @kotlin.internal.InlineOnly
-public inline fun String(chars: CharArray): String =
+public actual inline fun String(chars: CharArray): String =
     java.lang.String(chars) as String
 
 /**
  * Converts the characters from a portion of the specified array to a string.
  */
 @kotlin.internal.InlineOnly
-public inline fun String(chars: CharArray, offset: Int, length: Int): String =
+public actual inline fun String(chars: CharArray, offset: Int, length: Int): String =
     java.lang.String(chars, offset, length) as String
 
 /**

libraries/stdlib/test/text/StringTest.kt

@@ -43,6 +43,28 @@ fun Char.isAsciiUpperCase() = this in 'A'..'Z'
 
 class StringTest {
 
+    @Test fun stringFromCharArrayFullSlice() {
+        val chars: CharArray = charArrayOf('K', 'o', 't', 'l', 'i', 'n')
+        assertEquals("Kotlin", String(chars, 0, chars.size))
+    }
+
+    @Test fun stringFromCharArraySlice() {
+        val chars: CharArray = charArrayOf('K', 'o', 't', 'l', 'i', 'n', ' ', 'r', 'u', 'l', 'e', 's')
+        assertEquals("rule", String(chars, 7, 4))
+    }
+
+    @Test fun stringFromCharArray() {
+        val chars: CharArray = charArrayOf('K', 'o', 't', 'l', 'i', 'n')
+        assertEquals("Kotlin", String(chars))
+    }
+
+    @Test fun stringFromCharArrayUnicodeSurrogatePairs() {
+        val chars: CharArray = charArrayOf('Ц', '月', '語', '\u016C', '\u138D', '\uD83C', '\uDC3A')
+        assertEquals("Ц月語Ŭᎍ🀺", String(chars))
+        assertEquals("月", String(chars, 1, 1))
+        assertEquals("Ŭᎍ🀺", String(chars, 3, 4))
+    }
+
     @Test fun isEmptyAndBlank() = withOneCharSequenceArg { arg1 ->
         class Case(val value: String?, val isNull: Boolean = false, val isEmpty: Boolean = false, val isBlank: Boolean = false)