org.apache.lucene.util

## Class UnicodeUtil

- java.lang.Object
- - org.apache.lucene.util.UnicodeUtil

-     public final class UnicodeUtil
      extends Object

  Class to encode java's UTF16 char[] into UTF8 byte[] without always allocating a new byte[] as String.getBytes(StandardCharsets.UTF_8) does.
  NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static BytesRef` | `BIG_TERM` A binary term consisting of a number of 0xff bytes, likely to be bigger than other terms (e.g.
    `static int` | `MAX_UTF8_BYTES_PER_CHAR` Maximum number of UTF8 bytes per UTF16 character.
    `static int` | `UNI_REPLACEMENT_CHAR`
    `static int` | `UNI_SUR_HIGH_END`
    `static int` | `UNI_SUR_HIGH_START`
    `static int` | `UNI_SUR_LOW_END`
    `static int` | `UNI_SUR_LOW_START`

  - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static int` | `calcUTF16toUTF8Length(CharSequence s, int offset, int len)` Calculates the number of UTF8 bytes necessary to write a UTF16 string.
    `static int` | `codePointCount(BytesRef utf8)` Returns the number of code points in this UTF8 sequence.
    `static int` | `maxUTF8Length(int utf16Length)` Returns the maximum number of utf8 bytes required to encode a utf16 (e.g., java char[], String)
    `static String` | `newString(int[] codePoints, int offset, int count)` Cover JDK 1.5 API.
    `static String` | `toHexString(String s)`
    `static int` | `UTF16toUTF8(char[] source, int offset, int length, byte[] out)` Encode characters from a char[] source, starting at offset for length chars.
    `static int` | `UTF16toUTF8(CharSequence s, int offset, int length, byte[] out)` Encode characters from this String, starting at offset for length characters.
    `static int` | `UTF16toUTF8(CharSequence s, int offset, int length, byte[] out, int outOffset)` Encode characters from this String, starting at offset for length characters.
    `static int` | `UTF8toUTF16(byte[] utf8, int offset, int length, char[] out)` Interprets the given byte array as UTF-8 and converts to UTF-16.
    `static int` | `UTF8toUTF16(BytesRef bytesRef, char[] chars)` Utility method for `UTF8toUTF16(byte[], int, int, char[])`
    `static int` | `UTF8toUTF32(BytesRef utf8, int[] ints)` This method assumes valid UTF8 input.
    `static boolean` | `validUTF16String(char[] s, int size)`
    `static boolean` | `validUTF16String(CharSequence s)`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### BIG_TERM

          public static final BytesRef BIG_TERM

      A binary term consisting of a number of 0xff bytes, likely to be bigger than other terms (e.g. collation keys) one would normally encounter, and definitely bigger than any UTF-8 terms.

      WARNING: This is not a valid UTF8 Term

    - #### UNI_SUR_HIGH_START

          public static final int UNI_SUR_HIGH_START

      See Also:
        Constant Field Values

    - #### UNI_SUR_HIGH_END

          public static final int UNI_SUR_HIGH_END

      See Also:
        Constant Field Values

    - #### UNI_SUR_LOW_START

          public static final int UNI_SUR_LOW_START

      See Also:
        Constant Field Values

    - #### UNI_SUR_LOW_END

          public static final int UNI_SUR_LOW_END

      See Also:
        Constant Field Values

    - #### UNI_REPLACEMENT_CHAR

          public static final int UNI_REPLACEMENT_CHAR

      See Also:
        Constant Field Values

    - #### MAX_UTF8_BYTES_PER_CHAR

          public static final int MAX_UTF8_BYTES_PER_CHAR

      Maximum number of UTF8 bytes per UTF16 character.
      See Also:
        Constant Field Values

  - ### Method Detail

    - #### UTF16toUTF8

          public static int UTF16toUTF8(char[] source,
                                        int offset,
                                        int length,
                                        byte[] out)

      Encode characters from a char[] source, starting at offset for length chars. It is the responsibility of the caller to make sure that the destination array is large enough.

    - #### UTF16toUTF8

          public static int UTF16toUTF8(CharSequence s,
                                        int offset,
                                        int length,
                                        byte[] out)

      Encode characters from this String, starting at offset for length characters. It is the responsibility of the caller to make sure that the destination array is large enough.

    - #### UTF16toUTF8

          public static int UTF16toUTF8(CharSequence s,
                                        int offset,
                                        int length,
                                        byte[] out,
                                        int outOffset)

      Encode characters from this String, starting at offset for length characters. Output to the destination array will begin at `outOffset`. It is the responsibility of the caller to make sure that the destination array is large enough.

      note this method returns the final output offset (outOffset + number of bytes written)

    - #### calcUTF16toUTF8Length

          public static int calcUTF16toUTF8Length(CharSequence s,
                                                  int offset,
                                                  int len)

      Calculates the number of UTF8 bytes necessary to write a UTF16 string.
      Returns:
        the number of bytes written

    - #### validUTF16String

          public static boolean validUTF16String(CharSequence s)

    - #### validUTF16String

          public static boolean validUTF16String(char[] s,
                                                 int size)

    - #### codePointCount

          public static int codePointCount(BytesRef utf8)

      Returns the number of code points in this UTF8 sequence.

      This method assumes valid UTF8 input. This method does not perform full UTF8 validation, it will check only the first byte of each codepoint (for multi-byte sequences any bytes after the head are skipped).

      Throws:
        `IllegalArgumentException` - If invalid codepoint header byte occurs or the content is prematurely truncated.

    - #### UTF8toUTF32

          public static int UTF8toUTF32(BytesRef utf8,
                                        int[] ints)

      This method assumes valid UTF8 input. This method does not perform full UTF8 validation, it will check only the first byte of each codepoint (for multi-byte sequences any bytes after the head are skipped). It is the responsibility of the caller to make sure that the destination array is large enough.

      Throws:
        `IllegalArgumentException` - If invalid codepoint header byte occurs or the content is prematurely truncated.

    - #### newString

          public static String newString(int[] codePoints,
                                         int offset,
                                         int count)

      Cover JDK 1.5 API. Create a String from an array of codePoints.
      Parameters:
        `codePoints` - The code array
        `offset` - The start of the text in the code point array
        `count` - The number of code points
      Returns:
        a String representing the code points between offset and count
      Throws:
        `IllegalArgumentException` - If an invalid code point is encountered
        `IndexOutOfBoundsException` - If the offset or count are out of bounds.

    - #### toHexString

          public static String toHexString(String s)

    - #### UTF8toUTF16

          public static int UTF8toUTF16(byte[] utf8,
                                        int offset,
                                        int length,
                                        char[] out)

      Interprets the given byte array as UTF-8 and converts to UTF-16. It is the responsibility of the caller to make sure that the destination array is large enough.

      NOTE: Full characters are read, even if this reads past the length passed (and can result in an ArrayOutOfBoundsException if invalid UTF-8 is passed). Explicit checks for valid UTF-8 are not performed.

    - #### maxUTF8Length

          public static int maxUTF8Length(int utf16Length)

      Returns the maximum number of utf8 bytes required to encode a utf16 (e.g., java char[], String)

    - #### UTF8toUTF16

          public static int UTF8toUTF16(BytesRef bytesRef,
                                        char[] chars)

      Utility method for `UTF8toUTF16(byte[], int, int, char[])`
      See Also:
        `UTF8toUTF16(byte[], int, int, char[])`

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