/* * Copyright 2018-2019 Raffaello Giulietti * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ package jdk.internal.math; import java.io.IOException; import java.io.StringReader; import java.math.BigDecimal; import java.math.BigInteger; /* A checker for the Javadoc specification. It just relies on straightforward use of (expensive) BigDecimal arithmetic, not optimized at all. */ abstract class ToDecimalChecker extends BasicChecker { // The string to check private final String s; // The decimal parsed from s is c 10^q private long c; private int q; // The number of digits parsed from s: 10^(len10-1) <= c < 10^len10 private int len10; ToDecimalChecker(String s) { this.s = s; } /* Returns e be such that 10^(e-1) <= c 2^q < 10^e. */ static int e(double v) { // log10(v) + 1 is a first good approximation of e int e = (int) Math.floor(Math.log10(v)) + 1; // Full precision search for e such that 10^(e-1) <= c 2^q < 10^e. BigDecimal bv = new BigDecimal(v); BigDecimal low = new BigDecimal(BigInteger.ONE, -(e - 1)); while (low.compareTo(bv) > 0) { e -= 1; low = new BigDecimal(BigInteger.ONE, -(e - 1)); } BigDecimal high = new BigDecimal(BigInteger.ONE, -e); while (bv.compareTo(high) >= 0) { e += 1; high = new BigDecimal(BigInteger.ONE, -e); } return e; } void assertTrue() { if (isOK()) { return; } String msg = "toString applied to the bits " + hexBits() + " returns " + "\"" + s + "\"" + ", which is not correct according to the specification."; if (FAILURE_THROWS_EXCEPTION) { throw new RuntimeException(msg); } System.err.println(msg); } /* Returns whether s syntactically meets the expected output of toString. It is restricted to finite positive outputs. It is an unusually long method but rather straightforward, too. Many conditionals could be merged, but KISS here. */ private boolean parse(String t) { try { // first determine interesting boundaries in the string StringReader r = new StringReader(t); int ch = r.read(); int i = 0; while (ch == '0') { ++i; ch = r.read(); } // i is just after zeroes starting the integer int p = i; while ('0' <= ch && ch <= '9') { c = 10 * c + (ch - '0'); if (c < 0) { return false; } ++len10; ++p; ch = r.read(); } // p is just after digits ending the integer int fz = p; if (ch == '.') { ++fz; ch = r.read(); } // fz is just after a decimal '.' int f = fz; while (ch == '0') { c = 10 * c + (ch - '0'); if (c < 0) { return false; } ++len10; ++f; ch = r.read(); } // f is just after zeroes starting the fraction if (c == 0) { len10 = 0; } int x = f; while ('0' <= ch && ch <= '9') { c = 10 * c + (ch - '0'); if (c < 0) { return false; } ++len10; ++x; ch = r.read(); } // x is just after digits ending the fraction int g = x; if (ch == 'E') { ++g; ch = r.read(); } // g is just after an exponent indicator 'E' int ez = g; if (ch == '-') { ++ez; ch = r.read(); } // ez is just after a '-' sign in the exponent int e = ez; while (ch == '0') { ++e; ch = r.read(); } // e is just after zeroes starting the exponent int z = e; while ('0' <= ch && ch <= '9') { q = 10 * q + (ch - '0'); if (q < 0) { return false; } ++z; ch = r.read(); } // z is just after digits ending the exponent // No other char after the number if (z != t.length()) { return false; } // The integer must be present if (p == 0) { return false; } // The decimal '.' must be present if (fz == p) { return false; } // The fraction must be present if (x == fz) { return false; } // The fraction is not 0 or it consists of exactly one 0 if (f == x && f - fz > 1) { return false; } // Plain notation, no exponent if (x == z) { // At most one 0 starting the integer if (i > 1) { return false; } // If the integer is 0, at most 2 zeroes start the fraction if (i == 1 && f - fz > 2) { return false; } // The integer cannot have more than 7 digits if (p > 7) { return false; } q = fz - x; // OK for plain notation return true; } // Computerized scientific notation // The integer has exactly one nonzero digit if (i != 0 || p != 1) { return false; } // // There must be an exponent indicator if (x == g) { return false; } // There must be an exponent if (ez == z) { return false; } // The exponent must not start with zeroes if (ez != e) { return false; } if (g != ez) { q = -q; } // The exponent must not lie in [-3, 7) if (-3 <= q && q < 7) { return false; } q += fz - x; // OK for computerized scientific notation return true; } catch (IOException ex) { // An IOException on a StringReader??? Please... return false; } } private boolean isOK() { if (isNaN()) { return s.equals("NaN"); } String t = s; if (isNegative()) { if (s.isEmpty() || s.charAt(0) != '-') { return false; } negate(); t = s.substring(1); } if (isInfinity()) { return t.equals("Infinity"); } if (isZero()) { return t.equals("0.0"); } if (!parse(t)) { return false; } if (len10 < 2) { c *= 10; q -= 1; len10 += 1; } if (2 > len10 || len10 > maxLen10()) { return false; } // The exponent is bounded if (minExp() > q + len10 || q + len10 > maxExp()) { return false; } // s must recover v try { if (!recovers(t)) { return false; } } catch (NumberFormatException e) { return false; } // Get rid of trailing zeroes, still ensuring at least 2 digits while (len10 > 2 && c % 10 == 0) { c /= 10; q += 1; len10 -= 1; } if (len10 > 2) { // Try with a shorter number less than v... if (recovers(BigDecimal.valueOf(c / 10, -q - 1))) { return false; } // ... and with a shorter number greater than v if (recovers(BigDecimal.valueOf(c / 10 + 1, -q - 1))) { return false; } } // Try with the decimal predecessor... BigDecimal dp = c == 10 ? BigDecimal.valueOf(99, -q + 1) : BigDecimal.valueOf(c - 1, -q); if (recovers(dp)) { BigDecimal bv = toBigDecimal(); BigDecimal deltav = bv.subtract(BigDecimal.valueOf(c, -q)); if (deltav.signum() >= 0) { return true; } BigDecimal delta = dp.subtract(bv); if (delta.signum() >= 0) { return false; } int cmp = deltav.compareTo(delta); return cmp > 0 || cmp == 0 && (c & 0x1) == 0; } // ... and with the decimal successor BigDecimal ds = BigDecimal.valueOf(c + 1, -q); if (recovers(ds)) { BigDecimal bv = toBigDecimal(); BigDecimal deltav = bv.subtract(BigDecimal.valueOf(c, -q)); if (deltav.signum() <= 0) { return true; } BigDecimal delta = ds.subtract(bv); if (delta.signum() <= 0) { return false; } int cmp = deltav.compareTo(delta); return cmp < 0 || cmp == 0 && (c & 0x1) == 0; } return true; } abstract BigDecimal toBigDecimal(); abstract boolean recovers(BigDecimal b); abstract boolean recovers(String s); abstract String hexBits(); abstract int minExp(); abstract int maxExp(); abstract int maxLen10(); abstract boolean isZero(); abstract boolean isInfinity(); abstract void negate(); abstract boolean isNegative(); abstract boolean isNaN(); }