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/*
* Copyright (C) 2010 The Android Open Source Project
*
* 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 java.lang;
/**
* Converts integral types to strings. This class is public but hidden so that it can also be
* used by java.util.Formatter to speed up %d. This class is in java.lang so that it can take
* advantage of the package-private String constructor.
*
* The most important methods are appendInt/appendLong and intToString(int)/longToString(int).
* The former are used in the implementation of StringBuilder, StringBuffer, and Formatter, while
* the latter are used by Integer.toString and Long.toString.
*
* The append methods take AbstractStringBuilder rather than Appendable because the latter requires
* CharSequences, while we only have raw char[]s. Since much of the savings come from not creating
* any garbage, we can't afford temporary CharSequence instances.
*
* One day the performance advantage of the binary/hex/octal specializations will be small enough
* that we can lose the duplication, but until then this class offers the full set.
*
* @hide
*/
public final class IntegralToString {
/**
* When appending to an AbstractStringBuilder, this thread-local char[] lets us avoid
* allocation of a temporary array. (We can't write straight into the AbstractStringBuilder
* because it's almost as expensive to work out the exact length of the result as it is to
* do the formatting. We could try being conservative and "delete"-ing the unused space
* afterwards, but then we'd need to duplicate convertInt and convertLong rather than share
* the code.)
*/
private static final ThreadLocal BUFFER = new ThreadLocal() {
@Override protected char[] initialValue() {
return new char[20]; // Maximum length of a base-10 long.
}
};
/**
* These tables are used to special-case toString computation for
* small values. This serves three purposes: it reduces memory usage;
* it increases performance for small values; and it decreases the
* number of comparisons required to do the length computation.
* Elements of this table are lazily initialized on first use.
* No locking is necessary, i.e., we use the non-volatile, racy
* single-check idiom.
*/
private static final String[] SMALL_NONNEGATIVE_VALUES = new String[100];
private static final String[] SMALL_NEGATIVE_VALUES = new String[100];
/** TENS[i] contains the tens digit of the number i, 0 <= i <= 99. */
private static final char[] TENS = {
'0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
'1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
'2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
'3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
'4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
'5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
'6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
'7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
'8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
'9', '9', '9', '9', '9', '9', '9', '9', '9', '9'
};
/** Ones [i] contains the tens digit of the number i, 0 <= i <= 99. */
private static final char[] ONES = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
};
/**
* Table for MOD / DIV 10 computation described in Section 10-21
* of Hank Warren's "Hacker's Delight" online addendum.
* http://www.hackersdelight.org/divcMore.pdf
*/
private static final char[] MOD_10_TABLE = {
0, 1, 2, 2, 3, 3, 4, 5, 5, 6, 7, 7, 8, 8, 9, 0
};
/**
* The digits for every supported radix.
*/
private static final char[] DIGITS = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y', 'z'
};
private static final char[] UPPER_CASE_DIGITS = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
'U', 'V', 'W', 'X', 'Y', 'Z'
};
private IntegralToString() {
}
/**
* Equivalent to Integer.toString(i, radix).
*/
public static String intToString(int i, int radix) {
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
radix = 10;
}
if (radix == 10) {
return intToString(i);
}
/*
* If i is positive, negate it. This is the opposite of what one might
* expect. It is necessary because the range of the negative values is
* strictly larger than that of the positive values: there is no
* positive value corresponding to Integer.MIN_VALUE.
*/
boolean negative = false;
if (i < 0) {
negative = true;
} else {
i = -i;
}
int bufLen = radix < 8 ? 33 : 12; // Max chars in result (conservative)
char[] buf = new char[bufLen];
int cursor = bufLen;
do {
int q = i / radix;
buf[--cursor] = DIGITS[radix * q - i];
i = q;
} while (i != 0);
if (negative) {
buf[--cursor] = '-';
}
return new String(cursor, bufLen - cursor, buf);
}
/**
* Equivalent to Integer.toString(i).
*/
public static String intToString(int i) {
return convertInt(null, i);
}
/**
* Equivalent to sb.append(Integer.toString(i)).
*/
public static void appendInt(AbstractStringBuilder sb, int i) {
convertInt(sb, i);
}
/**
* Returns the string representation of i and leaves sb alone if sb is null.
* Returns null and appends the string representation of i to sb if sb is non-null.
*/
private static String convertInt(AbstractStringBuilder sb, int i) {
boolean negative = false;
String quickResult = null;
if (i < 0) {
negative = true;
i = -i;
if (i < 100) {
if (i < 0) {
// If -n is still negative, n is Integer.MIN_VALUE
quickResult = "-2147483648";
} else {
quickResult = SMALL_NEGATIVE_VALUES[i];
if (quickResult == null) {
SMALL_NEGATIVE_VALUES[i] = quickResult =
i < 10 ? stringOf('-', ONES[i]) : stringOf('-', TENS[i], ONES[i]);
}
}
}
} else {
if (i < 100) {
quickResult = SMALL_NONNEGATIVE_VALUES[i];
if (quickResult == null) {
SMALL_NONNEGATIVE_VALUES[i] = quickResult =
i < 10 ? stringOf(ONES[i]) : stringOf(TENS[i], ONES[i]);
}
}
}
if (quickResult != null) {
if (sb != null) {
sb.append0(quickResult);
return null;
}
return quickResult;
}
int bufLen = 11; // Max number of chars in result
char[] buf = (sb != null) ? BUFFER.get() : new char[bufLen];
int cursor = bufLen;
// Calculate digits two-at-a-time till remaining digits fit in 16 bits
while (i >= (1 << 16)) {
// Compute q = n/100 and r = n % 100 as per "Hacker's Delight" 10-8
int q = (int) ((0x51EB851FL * i) >>> 37);
int r = i - 100*q;
buf[--cursor] = ONES[r];
buf[--cursor] = TENS[r];
i = q;
}
// Calculate remaining digits one-at-a-time for performance
while (i != 0) {
// Compute q = n/10 and r = n % 10 as per "Hacker's Delight" 10-8
int q = (0xCCCD * i) >>> 19;
int r = i - 10*q;
buf[--cursor] = DIGITS[r];
i = q;
}
if (negative) {
buf[--cursor] = '-';
}
if (sb != null) {
sb.append0(buf, cursor, bufLen - cursor);
return null;
} else {
return new String(cursor, bufLen - cursor, buf);
}
}
/**
* Equivalent to Long.toString(v, radix).
*/
public static String longToString(long v, int radix) {
int i = (int) v;
if (i == v) {
return intToString(i, radix);
}
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
radix = 10;
}
if (radix == 10) {
return longToString(v);
}
/*
* If v is positive, negate it. This is the opposite of what one might
* expect. It is necessary because the range of the negative values is
* strictly larger than that of the positive values: there is no
* positive value corresponding to Integer.MIN_VALUE.
*/
boolean negative = false;
if (v < 0) {
negative = true;
} else {
v = -v;
}
int bufLen = radix < 8 ? 65 : 23; // Max chars in result (conservative)
char[] buf = new char[bufLen];
int cursor = bufLen;
do {
long q = v / radix;
buf[--cursor] = DIGITS[(int) (radix * q - v)];
v = q;
} while (v != 0);
if (negative) {
buf[--cursor] = '-';
}
return new String(cursor, bufLen - cursor, buf);
}
/**
* Equivalent to Long.toString(l).
*/
public static String longToString(long l) {
return convertLong(null, l);
}
/**
* Equivalent to sb.append(Long.toString(l)).
*/
public static void appendLong(AbstractStringBuilder sb, long l) {
convertLong(sb, l);
}
/**
* Returns the string representation of n and leaves sb alone if sb is null.
* Returns null and appends the string representation of n to sb if sb is non-null.
*/
private static String convertLong(AbstractStringBuilder sb, long n) {
int i = (int) n;
if (i == n) {
return convertInt(sb, i);
}
boolean negative = (n < 0);
if (negative) {
n = -n;
if (n < 0) {
// If -n is still negative, n is Long.MIN_VALUE
String quickResult = "-9223372036854775808";
if (sb != null) {
sb.append0(quickResult);
return null;
}
return quickResult;
}
}
int bufLen = 20; // Maximum number of chars in result
char[] buf = (sb != null) ? BUFFER.get() : new char[bufLen];
int low = (int) (n % 1000000000); // Extract low-order 9 digits
int cursor = intIntoCharArray(buf, bufLen, low);
// Zero-pad Low order part to 9 digits
while (cursor != (bufLen - 9)) {
buf[--cursor] = '0';
}
/*
* The remaining digits are (n - low) / 1,000,000,000. This
* "exact division" is done as per the online addendum to Hank Warren's
* "Hacker's Delight" 10-20, http://www.hackersdelight.org/divcMore.pdf
*/
n = ((n - low) >>> 9) * 0x8E47CE423A2E9C6DL;
/*
* If the remaining digits fit in an int, emit them using a
* single call to intIntoCharArray. Otherwise, strip off the
* low-order digit, put it in buf, and then call intIntoCharArray
* on the remaining digits (which now fit in an int).
*/
if ((n & (-1L << 32)) == 0) {
cursor = intIntoCharArray(buf, cursor, (int) n);
} else {
/*
* Set midDigit to n % 10
*/
int lo32 = (int) n;
int hi32 = (int) (n >>> 32);
// midDigit = ((unsigned) low32) % 10, per "Hacker's Delight" 10-21
int midDigit = MOD_10_TABLE[(0x19999999 * lo32 + (lo32 >>> 1) + (lo32 >>> 3)) >>> 28];
// Adjust midDigit for hi32. (assert hi32 == 1 || hi32 == 2)
midDigit -= hi32 << 2; // 1L << 32 == -4 MOD 10
if (midDigit < 0) {
midDigit += 10;
}
buf[--cursor] = DIGITS[midDigit];
// Exact division as per Warren 10-20
int rest = ((int) ((n - midDigit) >>> 1)) * 0xCCCCCCCD;
cursor = intIntoCharArray(buf, cursor, rest);
}
if (negative) {
buf[--cursor] = '-';
}
if (sb != null) {
sb.append0(buf, cursor, bufLen - cursor);
return null;
} else {
return new String(cursor, bufLen - cursor, buf);
}
}
/**
* Inserts the unsigned decimal integer represented by n into the specified
* character array starting at position cursor. Returns the index after
* the last character inserted (i.e., the value to pass in as cursor the
* next time this method is called). Note that n is interpreted as a large
* positive integer (not a negative integer) if its sign bit is set.
*/
private static int intIntoCharArray(char[] buf, int cursor, int n) {
// Calculate digits two-at-a-time till remaining digits fit in 16 bits
while ((n & 0xffff0000) != 0) {
/*
* Compute q = n/100 and r = n % 100 as per "Hacker's Delight" 10-8.
* This computation is slightly different from the corresponding
* computation in intToString: the shifts before and after
* multiply can't be combined, as that would yield the wrong result
* if n's sign bit were set.
*/
int q = (int) ((0x51EB851FL * (n >>> 2)) >>> 35);
int r = n - 100*q;
buf[--cursor] = ONES[r];
buf[--cursor] = TENS[r];
n = q;
}
// Calculate remaining digits one-at-a-time for performance
while (n != 0) {
// Compute q = n / 10 and r = n % 10 as per "Hacker's Delight" 10-8
int q = (0xCCCD * n) >>> 19;
int r = n - 10*q;
buf[--cursor] = DIGITS[r];
n = q;
}
return cursor;
}
public static String intToBinaryString(int i) {
int bufLen = 32; // Max number of binary digits in an int
char[] buf = new char[bufLen];
int cursor = bufLen;
do {
buf[--cursor] = DIGITS[i & 1];
} while ((i >>>= 1) != 0);
return new String(cursor, bufLen - cursor, buf);
}
public static String longToBinaryString(long v) {
int i = (int) v;
if (v >= 0 && i == v) {
return intToBinaryString(i);
}
int bufLen = 64; // Max number of binary digits in a long
char[] buf = new char[bufLen];
int cursor = bufLen;
do {
buf[--cursor] = DIGITS[((int) v) & 1];
} while ((v >>>= 1) != 0);
return new String(cursor, bufLen - cursor, buf);
}
public static StringBuilder appendByteAsHex(StringBuilder sb, byte b, boolean upperCase) {
char[] digits = upperCase ? UPPER_CASE_DIGITS : DIGITS;
sb.append(digits[(b >> 4) & 0xf]);
sb.append(digits[b & 0xf]);
return sb;
}
public static String byteToHexString(byte b, boolean upperCase) {
char[] digits = upperCase ? UPPER_CASE_DIGITS : DIGITS;
char[] buf = new char[2]; // We always want two digits.
buf[0] = digits[(b >> 4) & 0xf];
buf[1] = digits[b & 0xf];
return new String(0, 2, buf);
}
public static String bytesToHexString(byte[] bytes, boolean upperCase) {
char[] digits = upperCase ? UPPER_CASE_DIGITS : DIGITS;
char[] buf = new char[bytes.length * 2];
int c = 0;
for (byte b : bytes) {
buf[c++] = digits[(b >> 4) & 0xf];
buf[c++] = digits[b & 0xf];
}
return new String(buf);
}
public static String intToHexString(int i, boolean upperCase, int minWidth) {
int bufLen = 8; // Max number of hex digits in an int
char[] buf = new char[bufLen];
int cursor = bufLen;
char[] digits = upperCase ? UPPER_CASE_DIGITS : DIGITS;
do {
buf[--cursor] = digits[i & 0xf];
} while ((i >>>= 4) != 0 || (bufLen - cursor < minWidth));
return new String(cursor, bufLen - cursor, buf);
}
public static String longToHexString(long v) {
int i = (int) v;
if (v >= 0 && i == v) {
return intToHexString(i, false, 0);
}
int bufLen = 16; // Max number of hex digits in a long
char[] buf = new char[bufLen];
int cursor = bufLen;
do {
buf[--cursor] = DIGITS[((int) v) & 0xF];
} while ((v >>>= 4) != 0);
return new String(cursor, bufLen - cursor, buf);
}
public static String intToOctalString(int i) {
int bufLen = 11; // Max number of octal digits in an int
char[] buf = new char[bufLen];
int cursor = bufLen;
do {
buf[--cursor] = DIGITS[i & 7];
} while ((i >>>= 3) != 0);
return new String(cursor, bufLen - cursor, buf);
}
public static String longToOctalString(long v) {
int i = (int) v;
if (v >= 0 && i == v) {
return intToOctalString(i);
}
int bufLen = 22; // Max number of octal digits in a long
char[] buf = new char[bufLen];
int cursor = bufLen;
do {
buf[--cursor] = DIGITS[((int) v) & 7];
} while ((v >>>= 3) != 0);
return new String(cursor, bufLen - cursor, buf);
}
/**
* Returns a string composed of the specified characters. Note that the
* autoboxing does *not* result in an extra copy of the char array: we are
* using a package-private string constructor that incorporates the
* "autoboxing array" into the new string.
*/
private static String stringOf(char... args) {
return new String(0, args.length, args);
}
}
