com.oracle.truffle.js.runtime.doubleconv.DtoaBuffer Maven / Gradle / Ivy
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package com.oracle.truffle.js.runtime.doubleconv;
import java.nio.charset.StandardCharsets;
/**
* A buffer for generating string representations of doubles.
*/
public final class DtoaBuffer {
private static final char EXPONENT_CHARACTER = 'e';
// The character buffer
final byte[] chars;
// The number of characters in the buffer
int length = 0;
// The position of the decimal point
int decimalPoint = 0;
// Is this a negative number?
boolean isNegative = false;
/**
* Maximal length of numbers converted by FastDtoa
*/
public static final int kFastDtoaMaximalLength = FastDtoa.kFastDtoaMaximalLength;
/**
* Create a buffer with the given capacity.
*
* @param capacity the capacity of the buffer.
*/
public DtoaBuffer(final int capacity) {
chars = new byte[capacity];
}
/**
* Append a character to the buffer, increasing its length.
*
* @param c character
*/
void append(final int c) {
assert (c & 0xff) == c : c;
chars[length++] = (byte) c;
}
/**
* Clear the buffer contents and set its length to {@code 0}.
*/
public void reset() {
length = 0;
decimalPoint = 0;
}
/**
* Get the raw digits of this buffer as string.
*
* @return the raw buffer contents
*/
public String getRawDigits() {
return new String(chars, 0, length);
}
/**
* Get the position of the decimal point.
*
* @return the decimal point position
*/
public int getDecimalPoint() {
return decimalPoint;
}
/**
* Returns the number of characters in the buffer.
*
* @return buffer length
*/
public int getLength() {
return length;
}
/**
* Returns the formatted buffer content as string, using the specified conversion mode and
* padding.
*
* @param mode conversion mode
* @param digitsAfterPoint number of digits after point
* @return formatted string
*/
public String format(final DtoaMode mode, final int digitsAfterPoint) {
switch (mode) {
case SHORTEST:
if (decimalPoint < -5 || decimalPoint > 21) {
return toExponentialFormat(isNegative);
} else {
return toFixedFormat(digitsAfterPoint, isNegative);
}
case FIXED:
return toFixedFormat(digitsAfterPoint, isNegative);
case PRECISION:
default:
if (decimalPoint < -5 || decimalPoint > length) {
return toExponentialFormat(isNegative);
} else {
return toFixedFormat(digitsAfterPoint, isNegative);
}
}
}
private String toFixedFormat(final int digitsAfterPoint, boolean minus) {
final int formatLength = calculateFixedFormatLength(digitsAfterPoint, minus);
final StringBuilder buffer = new StringBuilder(formatLength);
if (minus) {
buffer.append('-');
}
if (decimalPoint <= 0) {
// < 1,
buffer.append('0');
if (length > 0) {
buffer.append('.');
final int padding = -decimalPoint;
for (int i = 0; i < padding; i++) {
buffer.append('0');
}
appendBytes(buffer, chars, 0, length);
} else {
decimalPoint = 1;
}
} else if (decimalPoint >= length) {
// large integer, add trailing zeroes
appendBytes(buffer, chars, 0, length);
for (int i = length; i < decimalPoint; i++) {
buffer.append('0');
}
} else {
assert decimalPoint < length;
// >= 1, split decimals and insert decimalPoint
appendBytes(buffer, chars, 0, decimalPoint);
buffer.append('.');
appendBytes(buffer, chars, decimalPoint, length - decimalPoint);
}
// Create trailing zeros if requested
if (digitsAfterPoint > 0) {
if (decimalPoint >= length) {
buffer.append('.');
}
for (int i = Math.max(0, length - decimalPoint); i < digitsAfterPoint; i++) {
buffer.append('0');
}
}
assert buffer.length() == formatLength : "expected length: " + formatLength + " actual length: " + buffer.length();
return buffer.toString();
}
private int calculateFixedFormatLength(final int digitsAfterPoint, boolean minus) {
int formatLength = minus ? 1 : 0; // '-'
if (decimalPoint <= 0) {
// < 1,
formatLength += 1; // '0'
if (length > 0) {
formatLength += 1; // '1'
final int padding = -decimalPoint;
formatLength += padding; // zero padding
formatLength += length; // digits
} else {
decimalPoint = 1;
}
} else if (decimalPoint >= length) {
// large integer, add trailing zeroes
formatLength += length; // digits
formatLength += decimalPoint - length; // trailing zeroes
} else {
assert decimalPoint < length;
// >= 1, split decimals and insert decimalPoint
formatLength += decimalPoint; // digits
formatLength += 1; // '.'
formatLength += length - decimalPoint; // digits
}
// Create trailing zeros if requested
if (digitsAfterPoint > 0) {
if (decimalPoint >= length) {
formatLength += 1; // '.'
}
formatLength += Math.max(0, digitsAfterPoint - Math.max(0, length - decimalPoint));
}
return formatLength;
}
String toExponentialFormat(boolean minus) {
final int formatLength = calculateExponentialFormatLength(minus);
final StringBuilder buffer = new StringBuilder(formatLength);
if (minus) {
buffer.append('-');
}
assert length != 0;
buffer.append((char) chars[0]);
if (length > 1) {
// insert decimal decimalPoint if more than one digit was produced
buffer.append('.');
appendBytes(buffer, chars, 1, length - 1);
}
buffer.append(EXPONENT_CHARACTER);
final int exponent = decimalPoint - 1;
assert Math.abs(exponent) < 10000;
if (exponent >= 0) {
buffer.append('+');
}
buffer.append(exponent);
assert buffer.length() == formatLength : "expected length: " + formatLength + " actual length: " + buffer.length();
return buffer.toString();
}
private int calculateExponentialFormatLength(boolean minus) {
assert length != 0;
int formatLength = minus ? 1 : 0; // '-'
formatLength += length;
if (length > 1) {
formatLength += 1; // '.'
}
formatLength += 2; // 'e+' or 'e-'
int exponent = decimalPoint - 1;
formatLength += numberOfDigits(Math.abs(exponent));
return formatLength;
}
private static int numberOfDigits(int x) {
assert x >= 0 : x;
for (int i = 1, p = 10; i < 10; i++, p *= 10) {
if (x < p) {
return i;
}
}
return 10;
}
private static void appendBytes(StringBuilder buffer, byte[] chars, int start, int len) {
for (int i = start; i < start + len; i++) {
buffer.append((char) chars[i]);
}
}
@Override
public String toString() {
return "[chars:" + new String(chars, 0, length, StandardCharsets.ISO_8859_1) + ", decimalPoint:" + decimalPoint + "]";
}
}
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