| 1: | public class In {
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| 2: |
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| 3: | /** End of file indicator returned by read() or peek() when no more
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| 4: | characters can be read.
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| 5: | */
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| 6: | public static final char eof = '\uffff';
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| 7: |
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| 8: | private static final int empty = '\ufffe';
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| 9: |
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| 10: | private static final char eofChar = '\u0005'; // ctrl E
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| 11: | private static InputStream in;
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| 12: | private static LinkedList inputStack, bufferStack;
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| 13: | private static boolean done; // true if recent operation was successful
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| 14: | private static char buf; // last read character
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| 15: | private static char[] LS; // line separator (eol)
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| 16: |
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| 17: | private static char charAfterWhiteSpace() {
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| 18: | char c;
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| 19: | do c = read(); while (done && c <= ' ');
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| 20: | return c;
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| 21: | }
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| 22: |
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| 23: | private static String readDigits() {
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| 24: | StringBuffer b = new StringBuffer();
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| 25: | char c = charAfterWhiteSpace();
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| 26: | if (done && c == '-') {
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| 27: | b.append(c);
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| 28: | c = read();
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| 29: | }
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| 30: | while (done && Character.isDigit(c)) {
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| 31: | b.append(c);
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| 32: | c = read();
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| 33: | }
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| 34: | buf = c;
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| 35: | return b.toString();
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| 36: | }
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| 37: |
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| 38: | private static String readFloatDigits() {
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| 39: | StringBuffer b = new StringBuffer();
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| 40: | char c = charAfterWhiteSpace();
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| 41: | if (done && (c == '+' || c == '-')) {
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| 42: | b.append(c);
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| 43: | c = read();
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| 44: | }
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| 45: | while (done && Character.isDigit(c)) {
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| 46: | b.append(c);
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| 47: | c = read();
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| 48: | }
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| 49: | if (done && (c == '.')) {
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| 50: | b.append(c);
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| 51: | c = read();
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| 52: | while (done && Character.isDigit(c)) {
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| 53: | b.append(c);
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| 54: | c = read();
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| 55: | }
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| 56: | }
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| 57: | if (done && (c == 'e' || c == 'E')) {
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| 58: | b.append(c);
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| 59: | c = read();
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| 60: | if (done && (c == '+' || c == '-')) {
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| 61: | b.append(c);
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| 62: | c = read();
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| 63: | }
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| 64: | while (done && Character.isDigit(c)) {
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| 65: | b.append(c);
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| 66: | c = read();
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| 67: | }
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| 68: | }
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| 69: | buf = c;
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| 70: | return b.toString();
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| 71: | }
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| 72: |
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| 73: |
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| 74: | /** Read a raw character (byte).
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| 75: | If an attempt is made to read beyond the end of the file,
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| 76: | eof is returned and done() yields false. Otherwise the read byte
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| 77: | is in the range 0..255.
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| 78: | */
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| 79: | public static char read() {
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| 80: | char c;
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| 81: | if (buf != empty) {
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| 82: | c = buf;
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| 83: | if (buf != eof) buf = empty;
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| 84: | } else {
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| 85: | try {
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| 86: | c = (char)in.read();
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| 87: | } catch (IOException e) {
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| 88: | done = false;
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| 89: | c = eof; buf = eof;
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| 90: | }
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| 91: | }
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| 92: | if (c == eofChar && inputStack.size() == 0) { c = eof; buf = eof; }
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| 93: | done = c != eof;
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| 94: | return c;
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| 95: | }
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| 96: |
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| 97: | /** Current available raw characters.
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| 98: | In case of an error 0 is returned and done() yields false.
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| 99: | */
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| 100: | public static int available() {
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| 101: | int avail;
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| 102: |
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| 103: | try {
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| 104: | avail = in.available();
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| 105: | } catch(IOException exc) {
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| 106: | avail = 0;
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| 107: | done = false;
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| 108: | }
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| 109: |
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| 110: | return avail;
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| 111: | }
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| 112: |
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| 113: | /** Read a character, but skip white spaces (byte).
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| 114: | If an attempt is made to read beyond the end of the file,
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| 115: | eof is returned and done() yields false. Otherwise the read byte
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| 116: | is in the range 0..255.
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| 117: | */
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| 118: | public static char readChar() {
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| 119: | return charAfterWhiteSpace();
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| 120: | }
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| 121: |
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| 122: | /** Read a boolean value.
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| 123: | This method skips white space and tries to read an identifier. If its value
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| 124: | is "true" the method returns true otherwise false. If the identifier is neither
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| 125: | "true" nor "false" done() yields false.
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| 126: | */
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| 127: | public static boolean readBoolean() {
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| 128: | String s = readIdentifier();
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| 129: | done = true;
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| 130: | if (s.equals("true")) return true;
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| 131: | else { done = s.equals("false"); return false; }
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| 132: | }
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| 133: |
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| 134: | /** Read an identifier.
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| 135: | This method skips white space and tries to read an identifier starting
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| 136: | with a letter and continuing with letters or digits. If a token of this
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| 137: | structure could be read, it is returned otherwise the empty string is
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| 138: | returned and done() yields false.
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| 139: | */
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| 140: | public static String readIdentifier() {
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| 141: | StringBuffer b = new StringBuffer();
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| 142: | char c = charAfterWhiteSpace();
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| 143: | if (done && Character.isLetter(c)) {
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| 144: | b.append(c);
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| 145: | c = read();
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| 146: | while (done && (Character.isLetter(c) || Character.isDigit(c))) {
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| 147: | b.append(c);
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| 148: | c = read();
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| 149: | }
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| 150: | }
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| 151: | buf = c;
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| 152: | done = b.length() > 0;
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| 153: | return b.toString();
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| 154: | }
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| 155: |
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| 156: | /** Read a word.
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| 157: | This method skips white space and tries to read a word consisting of
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| 158: | all characters up to the next white space or to the end of the file.
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| 159: | If a token of this structure could be read, it is returned otherwise
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| 160: | an empty string is returned and done() yields false.
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| 161: | */
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| 162: | public static String readWord() {
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| 163: | StringBuffer b = new StringBuffer();
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| 164: | char c = charAfterWhiteSpace();
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| 165: | while (done && c > ' ') {
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| 166: | b.append(c);
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| 167: | c = read();
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| 168: | }
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| 169: | buf = c;
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| 170: | done = b.length() > 0;
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| 171: | return b.toString();
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| 172: | }
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| 173: |
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| 174: | /** Read a line of text.
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| 175: | This method reads the rest of the current line (including eol) and
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| 176: | returns it (excluding eol). A line may be empty.
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| 177: | */
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| 178: | public static String readLine() {
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| 179: | StringBuffer b = new StringBuffer();
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| 180: | char c = read();
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| 181: | while (done && c != LS[0]) {
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| 182: | b.append(c);
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| 183: | c = read();
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| 184: | }
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| 185: |
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| 186: | int i = 0;
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| 187: | while (c == LS[i]) {
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| 188: | ++i;
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| 189: | if (i >= LS.length) { break; }
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| 190: | c = read();
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| 191: | }
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| 192: |
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| 193: | if (i < LS.length) {
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| 194: | buf = c;
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| 195: | } else {
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| 196: | buf = empty;
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| 197: | }
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| 198: | if (b.length() > 0) done = true;
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| 199: | return b.toString();
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| 200: | }
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| 201: |
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| 202: | /** Read the whole file.
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| 203: | This method reads from the current position to the end of the
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| 204: | file and returns its text in a single large string. done() yields
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| 205: | always true.
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| 206: | */
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| 207: | public static String readFile() {
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| 208: | StringBuffer b = new StringBuffer();
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| 209: | char c = charAfterWhiteSpace();
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| 210: | while (done) {
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| 211: | b.append(c);
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| 212: | c = read();
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| 213: | }
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| 214: | buf = eof;
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| 215: | done = true;
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| 216: | return b.toString();
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| 217: | }
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| 218: |
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| 219: | /** Read a quote-delimited string.
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| 220: | This method skips white space and tries to read a string in the form "...".
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| 221: | It can be used to read pieces of text that contain white space.
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| 222: | */
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| 223: | public static String readString() {
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| 224: | StringBuffer b = new StringBuffer();
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| 225: | char c = charAfterWhiteSpace();
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| 226: | if (done && c == '"') {
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| 227: | c = read();
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| 228: | while (done && c != '"') {
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| 229: | b.append(c);
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| 230: | c = read();
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| 231: | }
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| 232: | if (c == '"') { c = read(); done = true; } else done = false;
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| 233: | } else done = false;
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| 234: | buf = c;
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| 235: | return b.toString();
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| 236: | }
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| 237: |
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| 238: | /** Read an integer.
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| 239: | This method skips white space and tries to read an integer. If the
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| 240: | text does not contain an integer or if the number is too big, the
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| 241: | value 0 is returned and the subsequent call of done() yields false.
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| 242: | An integer is a sequence of digits, possibly preceded by '-'.
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| 243: | */
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| 244: | public static int readInt() {
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| 245: | String s = readDigits();
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| 246: | try {
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| 247: | done = true;
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| 248: | return Integer.parseInt(s);
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| 249: | } catch (Exception e) {
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| 250: | done = false; return 0;
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| 251: | }
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| 252: | }
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| 253: |
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| 254: | /** Read a long integer.
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| 255: | This method skips white space and tries to read a long integer. If the
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| 256: | text does not contain a number or if the number is too big, the
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| 257: | value 0 is returned and the subsequent call of done() yields false.
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| 258: | A long integer is a sequence of digits, possibly preceded by '-'.
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| 259: | */
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| 260: | public static long readLong() {
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| 261: | String s = readDigits();
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| 262: | try {
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| 263: | done = true;
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| 264: | return Long.parseLong(s);
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| 265: | } catch (Exception e) {
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| 266: | done = false; return 0;
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| 267: | }
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| 268: | }
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| 269: |
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| 270: | /** Read a float value.
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| 271: | This method skips white space and tries to read a float value. If the
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| 272: | text does not contain a float value or if the number is not well-formed,
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| 273: | the value 0f is returned and the subsequent call of done() yields false.
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| 274: | An float value is as specified in the Java language description. It may
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| 275: | be preceded by a '+' or a '-'.
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| 276: | */
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| 277: | public static float readFloat() {
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| 278: | String s = readFloatDigits();
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| 279: | try {
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| 280: | done = true;
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| 281: | return Float.parseFloat(s);
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| 282: | } catch (Exception e) {
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| 283: | done = false; return 0f;
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| 284: | }
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| 285: | }
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| 286: |
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| 287: | /** Read a double value.
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| 288: | This method skips white space and tries to read a double value. If the
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| 289: | text does not contain a double value or if the number is not well-formed,
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| 290: | the value 0.0 is returned and the subsequent call of done() yields false.
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| 291: | An double value is as specified in the Java language description. It may
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| 292: | be preceded by a '+' or a '-'.
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| 293: | */
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| 294: | public static double readDouble() {
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| 295: | String s = readFloatDigits();
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| 296: | try {
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| 297: | done = true;
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| 298: | return Double.parseDouble(s);
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| 299: | } catch (Exception e) {
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| 300: | done = false; return 0.0;
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| 301: | }
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| 302: | }
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| 303: |
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| 304: | /** Peek at the next character.
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| 305: | This method skips white space and returns the next character without removing
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| 306: | it from the input stream. It can be used to find out, what token comes next
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| 307: | in the input stream.
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| 308: | */
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| 309: | public static char peek() {
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| 310: | char c = charAfterWhiteSpace();
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| 311: | buf = c;
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| 312: | return c;
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| 313: | }
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| 314: |
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| 315: | /** Open a text file for reading
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| 316: | The text file with the name fn is opened as the new current input
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| 317: | file. When it is closed again, the previous input file is restored.
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| 318: | */
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| 319: | public static void open(String fn) {
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| 320: | try {
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| 321: | InputStream s = new FileInputStream(fn);
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| 322: | bufferStack.add(new Character(buf));
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| 323: | inputStack.add(in);
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| 324: | in = s;
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| 325: | done = true;
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| 326: | } catch (FileNotFoundException e) {
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| 327: | done = false;
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| 328: | }
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| 329: | buf = empty;
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| 330: | }
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| 331: |
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| 332: | /** Close the current input file.
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| 333: | The current input file is closed and the previous input file is
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| 334: | restored. Closing the keyboard input has no effect but causes
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| 335: | done() to yield false.
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| 336: | */
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| 337: | public static void close() {
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| 338: | try {
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| 339: | if (inputStack.size() > 0) {
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| 340: | in.close();
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| 341: | in = (InputStream) inputStack.removeLast();
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| 342: | buf = ((Character) bufferStack.removeLast()).charValue();
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| 343: | done = true;
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| 344: | } else {
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| 345: | done = false; buf = empty;
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| 346: | }
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| 347: | } catch (IOException e) {
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| 348: | done = false; buf = empty;
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| 349: | }
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| 350: | }
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| 351: |
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| 352: | /** Check if the previous operation was successful.
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| 353: | This method returns true if the previous read operation was able
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| 354: | to read a token of the requested structure. It can also be called
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| 355: | after open() and close() to check if these operations were successful.
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| 356: | If done() is called before any other operation it yields true.
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| 357: | */
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| 358: | public static boolean done() {
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| 359: | return done;
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| 360: | }
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| 361: |
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| 362: | static { // initializer
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| 363: | done = true;
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| 364: | in = System.in;
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| 365: | buf = empty;
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| 366: | inputStack = new LinkedList();
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| 367: | bufferStack = new LinkedList();
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| 368: | LS = System.getProperty("line.separator").toCharArray();
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| 369: | if (LS == null || LS.length == 0) {
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| 370: | LS = new char[] { '\n' };
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| 371: | }
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| 372: | } |
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