| /* |
| * Copyright (C) 2010 The Guava Authors |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except |
| * in compliance with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software distributed under the License |
| * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express |
| * or implied. See the License for the specific language governing permissions and limitations under |
| * the License. |
| */ |
| |
| package com.google.common.base; |
| |
| import static com.google.common.base.Preconditions.checkArgument; |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| import com.google.common.annotations.GwtCompatible; |
| |
| /** |
| * Static methods pertaining to ASCII characters (those in the range of values {@code 0x00} through |
| * {@code 0x7F}), and to strings containing such characters. |
| * |
| * <p>ASCII utilities also exist in other classes of this package: |
| * |
| * <ul> |
| * <!-- TODO(kevinb): how can we make this not produce a warning when building gwt javadoc? --> |
| * <li>{@link Charsets#US_ASCII} specifies the {@code Charset} of ASCII characters. |
| * <li>{@link CharMatcher#ascii} matches ASCII characters and provides text processing methods |
| * which operate only on the ASCII characters of a string. |
| * </ul> |
| * |
| * @author Catherine Berry |
| * @author Gregory Kick |
| * @since 7.0 |
| */ |
| @GwtCompatible |
| public final class Ascii { |
| |
| private Ascii() {} |
| |
| /* The ASCII control characters, per RFC 20. */ |
| /** |
| * Null ('\0'): The all-zeros character which may serve to accomplish time fill and media fill. |
| * Normally used as a C string terminator. |
| * |
| * <p>Although RFC 20 names this as "Null", note that it is distinct from the C/C++ "NULL" |
| * pointer. |
| * |
| * @since 8.0 |
| */ |
| public static final byte NUL = 0; |
| |
| /** |
| * Start of Heading: A communication control character used at the beginning of a sequence of |
| * characters which constitute a machine-sensible address or routing information. Such a sequence |
| * is referred to as the "heading." An STX character has the effect of terminating a heading. |
| * |
| * @since 8.0 |
| */ |
| public static final byte SOH = 1; |
| |
| /** |
| * Start of Text: A communication control character which precedes a sequence of characters that |
| * is to be treated as an entity and entirely transmitted through to the ultimate destination. |
| * Such a sequence is referred to as "text." STX may be used to terminate a sequence of characters |
| * started by SOH. |
| * |
| * @since 8.0 |
| */ |
| public static final byte STX = 2; |
| |
| /** |
| * End of Text: A communication control character used to terminate a sequence of characters |
| * started with STX and transmitted as an entity. |
| * |
| * @since 8.0 |
| */ |
| public static final byte ETX = 3; |
| |
| /** |
| * End of Transmission: A communication control character used to indicate the conclusion of a |
| * transmission, which may have contained one or more texts and any associated headings. |
| * |
| * @since 8.0 |
| */ |
| public static final byte EOT = 4; |
| |
| /** |
| * Enquiry: A communication control character used in data communication systems as a request for |
| * a response from a remote station. It may be used as a "Who Are You" (WRU) to obtain |
| * identification, or may be used to obtain station status, or both. |
| * |
| * @since 8.0 |
| */ |
| public static final byte ENQ = 5; |
| |
| /** |
| * Acknowledge: A communication control character transmitted by a receiver as an affirmative |
| * response to a sender. |
| * |
| * @since 8.0 |
| */ |
| public static final byte ACK = 6; |
| |
| /** |
| * Bell ('\a'): A character for use when there is a need to call for human attention. It may |
| * control alarm or attention devices. |
| * |
| * @since 8.0 |
| */ |
| public static final byte BEL = 7; |
| |
| /** |
| * Backspace ('\b'): A format effector which controls the movement of the printing position one |
| * printing space backward on the same printing line. (Applicable also to display devices.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte BS = 8; |
| |
| /** |
| * Horizontal Tabulation ('\t'): A format effector which controls the movement of the printing |
| * position to the next in a series of predetermined positions along the printing line. |
| * (Applicable also to display devices and the skip function on punched cards.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte HT = 9; |
| |
| /** |
| * Line Feed ('\n'): A format effector which controls the movement of the printing position to the |
| * next printing line. (Applicable also to display devices.) Where appropriate, this character may |
| * have the meaning "New Line" (NL), a format effector which controls the movement of the printing |
| * point to the first printing position on the next printing line. Use of this convention requires |
| * agreement between sender and recipient of data. |
| * |
| * @since 8.0 |
| */ |
| public static final byte LF = 10; |
| |
| /** |
| * Alternate name for {@link #LF}. ({@code LF} is preferred.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte NL = 10; |
| |
| /** |
| * Vertical Tabulation ('\v'): A format effector which controls the movement of the printing |
| * position to the next in a series of predetermined printing lines. (Applicable also to display |
| * devices.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte VT = 11; |
| |
| /** |
| * Form Feed ('\f'): A format effector which controls the movement of the printing position to the |
| * first pre-determined printing line on the next form or page. (Applicable also to display |
| * devices.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte FF = 12; |
| |
| /** |
| * Carriage Return ('\r'): A format effector which controls the movement of the printing position |
| * to the first printing position on the same printing line. (Applicable also to display devices.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte CR = 13; |
| |
| /** |
| * Shift Out: A control character indicating that the code combinations which follow shall be |
| * interpreted as outside of the character set of the standard code table until a Shift In |
| * character is reached. |
| * |
| * @since 8.0 |
| */ |
| public static final byte SO = 14; |
| |
| /** |
| * Shift In: A control character indicating that the code combinations which follow shall be |
| * interpreted according to the standard code table. |
| * |
| * @since 8.0 |
| */ |
| public static final byte SI = 15; |
| |
| /** |
| * Data Link Escape: A communication control character which will change the meaning of a limited |
| * number of contiguously following characters. It is used exclusively to provide supplementary |
| * controls in data communication networks. |
| * |
| * @since 8.0 |
| */ |
| public static final byte DLE = 16; |
| |
| /** |
| * Device Control 1. Characters for the control of ancillary devices associated with data |
| * processing or telecommunication systems, more especially switching devices "on" or "off." (If a |
| * single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the |
| * preferred assignment.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte DC1 = 17; // aka XON |
| |
| /** |
| * Transmission On: Although originally defined as DC1, this ASCII control character is now better |
| * known as the XON code used for software flow control in serial communications. The main use is |
| * restarting the transmission after the communication has been stopped by the XOFF control code. |
| * |
| * @since 8.0 |
| */ |
| public static final byte XON = 17; // aka DC1 |
| |
| /** |
| * Device Control 2. Characters for the control of ancillary devices associated with data |
| * processing or telecommunication systems, more especially switching devices "on" or "off." (If a |
| * single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the |
| * preferred assignment.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte DC2 = 18; |
| |
| /** |
| * Device Control 3. Characters for the control of ancillary devices associated with data |
| * processing or telecommunication systems, more especially switching devices "on" or "off." (If a |
| * single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the |
| * preferred assignment.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte DC3 = 19; // aka XOFF |
| |
| /** |
| * Transmission off. See {@link #XON} for explanation. |
| * |
| * @since 8.0 |
| */ |
| public static final byte XOFF = 19; // aka DC3 |
| |
| /** |
| * Device Control 4. Characters for the control of ancillary devices associated with data |
| * processing or telecommunication systems, more especially switching devices "on" or "off." (If a |
| * single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the |
| * preferred assignment.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte DC4 = 20; |
| |
| /** |
| * Negative Acknowledge: A communication control character transmitted by a receiver as a negative |
| * response to the sender. |
| * |
| * @since 8.0 |
| */ |
| public static final byte NAK = 21; |
| |
| /** |
| * Synchronous Idle: A communication control character used by a synchronous transmission system |
| * in the absence of any other character to provide a signal from which synchronism may be |
| * achieved or retained. |
| * |
| * @since 8.0 |
| */ |
| public static final byte SYN = 22; |
| |
| /** |
| * End of Transmission Block: A communication control character used to indicate the end of a |
| * block of data for communication purposes. ETB is used for blocking data where the block |
| * structure is not necessarily related to the processing format. |
| * |
| * @since 8.0 |
| */ |
| public static final byte ETB = 23; |
| |
| /** |
| * Cancel: A control character used to indicate that the data with which it is sent is in error or |
| * is to be disregarded. |
| * |
| * @since 8.0 |
| */ |
| public static final byte CAN = 24; |
| |
| /** |
| * End of Medium: A control character associated with the sent data which may be used to identify |
| * the physical end of the medium, or the end of the used, or wanted, portion of information |
| * recorded on a medium. (The position of this character does not necessarily correspond to the |
| * physical end of the medium.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte EM = 25; |
| |
| /** |
| * Substitute: A character that may be substituted for a character which is determined to be |
| * invalid or in error. |
| * |
| * @since 8.0 |
| */ |
| public static final byte SUB = 26; |
| |
| /** |
| * Escape: A control character intended to provide code extension (supplementary characters) in |
| * general information interchange. The Escape character itself is a prefix affecting the |
| * interpretation of a limited number of contiguously following characters. |
| * |
| * @since 8.0 |
| */ |
| public static final byte ESC = 27; |
| |
| /** |
| * File Separator: These four information separators may be used within data in optional fashion, |
| * except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then |
| * RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are |
| * not specified.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte FS = 28; |
| |
| /** |
| * Group Separator: These four information separators may be used within data in optional fashion, |
| * except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then |
| * RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are |
| * not specified.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte GS = 29; |
| |
| /** |
| * Record Separator: These four information separators may be used within data in optional |
| * fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then |
| * GS, then RS, and US is least inclusive. (The content and length of a File, Group, Record, or |
| * Unit are not specified.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte RS = 30; |
| |
| /** |
| * Unit Separator: These four information separators may be used within data in optional fashion, |
| * except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then |
| * RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are |
| * not specified.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte US = 31; |
| |
| /** |
| * Space: A normally non-printing graphic character used to separate words. It is also a format |
| * effector which controls the movement of the printing position, one printing position forward. |
| * (Applicable also to display devices.) |
| * |
| * @since 8.0 |
| */ |
| public static final byte SP = 32; |
| |
| /** |
| * Alternate name for {@link #SP}. |
| * |
| * @since 8.0 |
| */ |
| public static final byte SPACE = 32; |
| |
| /** |
| * Delete: This character is used primarily to "erase" or "obliterate" erroneous or unwanted |
| * characters in perforated tape. |
| * |
| * @since 8.0 |
| */ |
| public static final byte DEL = 127; |
| |
| /** |
| * The minimum value of an ASCII character. |
| * |
| * @since 9.0 (was type {@code int} before 12.0) |
| */ |
| public static final char MIN = 0; |
| |
| /** |
| * The maximum value of an ASCII character. |
| * |
| * @since 9.0 (was type {@code int} before 12.0) |
| */ |
| public static final char MAX = 127; |
| |
| /** A bit mask which selects the bit encoding ASCII character case. */ |
| private static final char CASE_MASK = 0x20; |
| |
| /** |
| * Returns a copy of the input string in which all {@linkplain #isUpperCase(char) uppercase ASCII |
| * characters} have been converted to lowercase. All other characters are copied without |
| * modification. |
| */ |
| public static String toLowerCase(String string) { |
| int length = string.length(); |
| for (int i = 0; i < length; i++) { |
| if (isUpperCase(string.charAt(i))) { |
| char[] chars = string.toCharArray(); |
| for (; i < length; i++) { |
| char c = chars[i]; |
| if (isUpperCase(c)) { |
| chars[i] = (char) (c ^ CASE_MASK); |
| } |
| } |
| return String.valueOf(chars); |
| } |
| } |
| return string; |
| } |
| |
| /** |
| * Returns a copy of the input character sequence in which all {@linkplain #isUpperCase(char) |
| * uppercase ASCII characters} have been converted to lowercase. All other characters are copied |
| * without modification. |
| * |
| * @since 14.0 |
| */ |
| public static String toLowerCase(CharSequence chars) { |
| if (chars instanceof String) { |
| return toLowerCase((String) chars); |
| } |
| char[] newChars = new char[chars.length()]; |
| for (int i = 0; i < newChars.length; i++) { |
| newChars[i] = toLowerCase(chars.charAt(i)); |
| } |
| return String.valueOf(newChars); |
| } |
| |
| /** |
| * If the argument is an {@linkplain #isUpperCase(char) uppercase ASCII character} returns the |
| * lowercase equivalent. Otherwise returns the argument. |
| */ |
| public static char toLowerCase(char c) { |
| return isUpperCase(c) ? (char) (c ^ CASE_MASK) : c; |
| } |
| |
| /** |
| * Returns a copy of the input string in which all {@linkplain #isLowerCase(char) lowercase ASCII |
| * characters} have been converted to uppercase. All other characters are copied without |
| * modification. |
| */ |
| public static String toUpperCase(String string) { |
| int length = string.length(); |
| for (int i = 0; i < length; i++) { |
| if (isLowerCase(string.charAt(i))) { |
| char[] chars = string.toCharArray(); |
| for (; i < length; i++) { |
| char c = chars[i]; |
| if (isLowerCase(c)) { |
| chars[i] = (char) (c ^ CASE_MASK); |
| } |
| } |
| return String.valueOf(chars); |
| } |
| } |
| return string; |
| } |
| |
| /** |
| * Returns a copy of the input character sequence in which all {@linkplain #isLowerCase(char) |
| * lowercase ASCII characters} have been converted to uppercase. All other characters are copied |
| * without modification. |
| * |
| * @since 14.0 |
| */ |
| public static String toUpperCase(CharSequence chars) { |
| if (chars instanceof String) { |
| return toUpperCase((String) chars); |
| } |
| char[] newChars = new char[chars.length()]; |
| for (int i = 0; i < newChars.length; i++) { |
| newChars[i] = toUpperCase(chars.charAt(i)); |
| } |
| return String.valueOf(newChars); |
| } |
| |
| /** |
| * If the argument is a {@linkplain #isLowerCase(char) lowercase ASCII character} returns the |
| * uppercase equivalent. Otherwise returns the argument. |
| */ |
| public static char toUpperCase(char c) { |
| return isLowerCase(c) ? (char) (c ^ CASE_MASK) : c; |
| } |
| |
| /** |
| * Indicates whether {@code c} is one of the twenty-six lowercase ASCII alphabetic characters |
| * between {@code 'a'} and {@code 'z'} inclusive. All others (including non-ASCII characters) |
| * return {@code false}. |
| */ |
| public static boolean isLowerCase(char c) { |
| // Note: This was benchmarked against the alternate expression "(char)(c - 'a') < 26" (Nov '13) |
| // and found to perform at least as well, or better. |
| return (c >= 'a') && (c <= 'z'); |
| } |
| |
| /** |
| * Indicates whether {@code c} is one of the twenty-six uppercase ASCII alphabetic characters |
| * between {@code 'A'} and {@code 'Z'} inclusive. All others (including non-ASCII characters) |
| * return {@code false}. |
| */ |
| public static boolean isUpperCase(char c) { |
| return (c >= 'A') && (c <= 'Z'); |
| } |
| |
| /** |
| * Truncates the given character sequence to the given maximum length. If the length of the |
| * sequence is greater than {@code maxLength}, the returned string will be exactly {@code |
| * maxLength} chars in length and will end with the given {@code truncationIndicator}. Otherwise, |
| * the sequence will be returned as a string with no changes to the content. |
| * |
| * <p>Examples: |
| * |
| * <pre>{@code |
| * Ascii.truncate("foobar", 7, "..."); // returns "foobar" |
| * Ascii.truncate("foobar", 5, "..."); // returns "fo..." |
| * }</pre> |
| * |
| * <p><b>Note:</b> This method <i>may</i> work with certain non-ASCII text but is not safe for use |
| * with arbitrary Unicode text. It is mostly intended for use with text that is known to be safe |
| * for use with it (such as all-ASCII text) and for simple debugging text. When using this method, |
| * consider the following: |
| * |
| * <ul> |
| * <li>it may split surrogate pairs |
| * <li>it may split characters and combining characters |
| * <li>it does not consider word boundaries |
| * <li>if truncating for display to users, there are other considerations that must be taken |
| * into account |
| * <li>the appropriate truncation indicator may be locale-dependent |
| * <li>it is safe to use non-ASCII characters in the truncation indicator |
| * </ul> |
| * |
| * |
| * @throws IllegalArgumentException if {@code maxLength} is less than the length of {@code |
| * truncationIndicator} |
| * @since 16.0 |
| */ |
| public static String truncate(CharSequence seq, int maxLength, String truncationIndicator) { |
| checkNotNull(seq); |
| |
| // length to truncate the sequence to, not including the truncation indicator |
| int truncationLength = maxLength - truncationIndicator.length(); |
| |
| // in this worst case, this allows a maxLength equal to the length of the truncationIndicator, |
| // meaning that a string will be truncated to just the truncation indicator itself |
| checkArgument( |
| truncationLength >= 0, |
| "maxLength (%s) must be >= length of the truncation indicator (%s)", |
| maxLength, |
| truncationIndicator.length()); |
| |
| if (seq.length() <= maxLength) { |
| String string = seq.toString(); |
| if (string.length() <= maxLength) { |
| return string; |
| } |
| // if the length of the toString() result was > maxLength for some reason, truncate that |
| seq = string; |
| } |
| |
| return new StringBuilder(maxLength) |
| .append(seq, 0, truncationLength) |
| .append(truncationIndicator) |
| .toString(); |
| } |
| |
| /** |
| * Indicates whether the contents of the given character sequences {@code s1} and {@code s2} are |
| * equal, ignoring the case of any ASCII alphabetic characters between {@code 'a'} and {@code 'z'} |
| * or {@code 'A'} and {@code 'Z'} inclusive. |
| * |
| * <p>This method is significantly faster than {@link String#equalsIgnoreCase} and should be used |
| * in preference if at least one of the parameters is known to contain only ASCII characters. |
| * |
| * <p>Note however that this method does not always behave identically to expressions such as: |
| * |
| * <ul> |
| * <li>{@code string.toUpperCase().equals("UPPER CASE ASCII")} |
| * <li>{@code string.toLowerCase().equals("lower case ascii")} |
| * </ul> |
| * |
| * <p>due to case-folding of some non-ASCII characters (which does not occur in {@link |
| * String#equalsIgnoreCase}). However in almost all cases that ASCII strings are used, the author |
| * probably wanted the behavior provided by this method rather than the subtle and sometimes |
| * surprising behavior of {@code toUpperCase()} and {@code toLowerCase()}. |
| * |
| * @since 16.0 |
| */ |
| public static boolean equalsIgnoreCase(CharSequence s1, CharSequence s2) { |
| // Calling length() is the null pointer check (so do it before we can exit early). |
| int length = s1.length(); |
| if (s1 == s2) { |
| return true; |
| } |
| if (length != s2.length()) { |
| return false; |
| } |
| for (int i = 0; i < length; i++) { |
| char c1 = s1.charAt(i); |
| char c2 = s2.charAt(i); |
| if (c1 == c2) { |
| continue; |
| } |
| int alphaIndex = getAlphaIndex(c1); |
| // This was also benchmarked using '&' to avoid branching (but always evaluate the rhs), |
| // however this showed no obvious improvement. |
| if (alphaIndex < 26 && alphaIndex == getAlphaIndex(c2)) { |
| continue; |
| } |
| return false; |
| } |
| return true; |
| } |
| |
| /** |
| * Returns the non-negative index value of the alpha character {@code c}, regardless of case. Ie, |
| * 'a'/'A' returns 0 and 'z'/'Z' returns 25. Non-alpha characters return a value of 26 or greater. |
| */ |
| private static int getAlphaIndex(char c) { |
| // Fold upper-case ASCII to lower-case and make zero-indexed and unsigned (by casting to char). |
| return (char) ((c | CASE_MASK) - 'a'); |
| } |
| } |