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This commit is contained in:
Jeff Parsons 2017-02-17 12:15:48 -08:00 • committed by Jeff Parsons
commit 689adca2a7
1 changed files with 15 additions and 13 deletions
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28
modules/shared/lib/int36.js
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@ -232,8 +232,11 @@ class Int36 {
* *
* This can be confirmed independently by examining the sign bits (BIT35) of the original value * This can be confirmed independently by examining the sign bits (BIT35) of the original value
* (V), the operand (O), the result (R), as well as two intermediate calculations, VR = (V ^ R) * (V), the operand (O), the result (R), as well as two intermediate calculations, VR = (V ^ R)
* and OR = (O ^ R), and a final calculation: E = (VR & OR). In the case of subtraction (fSub), * and OR = (O ^ R), and a final calculation, E = (VR & OR). If E is set, then overflow (V == 0)
* OV replaces OR. * or underflow (V == 1) occurred.
*
* In the case of subtraction (when fSub is true), consult the second table, which replaces OR
* with OV (O ^ V).
* *
* V O R VR OR E * V O R VR OR E
* - - - -- -- - * - - - -- -- -
@ -309,7 +312,7 @@ class Int36 {
if (DEBUG && (delta > 0) != !(e & v)) e = 0; if (DEBUG && (delta > 0) != !(e & v)) e = 0;
} }
} }
if (DEBUG && (!this.error) != (!e)) console.log("overflow mismatch"); if (DEBUG && (!this.error) != (!e)) console.log("overflow inconsistency");
} }
return result; return result;
} }
@ -386,9 +389,9 @@ class Int36 {
* mulExtended(value) * mulExtended(value)
* *
* To support 72-bit results, we perform the multiplication process as you would "by hand", * To support 72-bit results, we perform the multiplication process as you would "by hand",
* treating each of the operands to be multiplied as two 2-digit numbers, where each digit is * treating the operands to be multiplied as two 2-digit numbers, where each digit is an 18-bit
* an 18-bit number (base 2^18). Each individual multiplication of these 18-bit "digits" * number (base 2^18). Each individual multiplication of these 18-bit "digits" will produce
* will produce a result within 2^36, well within JavaScript integer accuracy. * a result within 2^36, well within JavaScript integer accuracy.
* *
* @this {Int36} * @this {Int36}
* @param {number} value * @param {number} value
@ -457,13 +460,13 @@ class Int36 {
/** /**
* divExtended(divisor) * divExtended(divisor)
* *
* We disallow a divisor of zero; however, we no longer disallow a divisor smaller than the than * We disallow a divisor of zero; however, we no longer disallow a divisor smaller than the
* the extended portion of the dividend, even though such a divisor would produce a quotient larger * extended portion of the dividend, even though such a divisor would produce a quotient larger
* than 36 bits. Instead, we support extended quotients, because some of our internal functions * than 36 bits. Instead, we support extended quotients, because some of our internal functions
* (eg, toDecimal()) require it. * (eg, toDecimal()) require it.
* *
* For callers that can only handle 36-bit quotients, they can either perform their own preliminary * For callers that can only handle 36-bit quotients, they can either perform their own preliminary
* check of the divisor against any dividend extension, or they can simply allow all divisions to * check of the divisor against any extended dividend, or they can simply allow all divisions to
* proceed, check for an extended quotient afterward, and report the appropriate error. * proceed, check for an extended quotient afterward, and report the appropriate error.
* *
* @this {Int36} * @this {Int36}
@ -528,12 +531,11 @@ class Int36 {
/** /**
* extend() * extend()
*
* Set the extended field to match the sign of the value (if not already set).
*/ */
extend() extend()
{ {
/*
* Set extended to match the sign of value (if not already set).
*/
if (this.extended == null) { if (this.extended == null) {
this.extended = (this.value > Int36.MAXPOS? Int36.MAXVAL : 0); this.extended = (this.value > Int36.MAXPOS? Int36.MAXVAL : 0);
} }
@ -696,7 +698,7 @@ class Int36 {
/* /*
* Although it's expected that most callers will supply unsigned 36-bit values, we're nice about * Although it's expected that most callers will supply unsigned 36-bit values, we're nice about
* converting any signed values to their unsigned (two's complement) counterpart, provided they are * converting any signed values to their unsigned (two's complement) counterpart, provided they are
* within the acceptable range. Any signed values outside that range will be dealt with afterward. * within the acceptable range. Any values outside that range will be dealt with afterward.
*/ */
if (num < 0 && num >= Int36.MINNEG) { if (num < 0 && num >= Int36.MINNEG) {
num += Int36.BIT36; num += Int36.BIT36;