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Fix encoding bug in js_dtoa_radix (#399)

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- fix radix conversion rounding code: incrementing the digit
  does not work for '9'.  We can assume ASCII so it works for
  all other digits, especially all letters
- also avoid recomputing the string length
This commit is contained in:
Charlie Gordon 2024-05-07 19:35:34 +02:00 committed by GitHub
parent 6cb1301305
commit f9ecc1a598
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GPG key ID: B5690EEEBB952194
2 changed files with 34 additions and 20 deletions
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53
quickjs.c
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@ -11261,9 +11261,10 @@ static JSValue js_dtoa(JSContext *ctx,
return JS_NewStringLen(ctx, buf, len);
}
/* d is guaranteed to be finite */
static JSValue js_dtoa_radix(JSContext *ctx, double d, int radix)
{
char buf[2200], *ptr, *ptr2;
char buf[2200], *ptr, *ptr2, *ptr3;
/* d is finite */
int sign = d < 0;
int digit;
@ -11272,8 +11273,8 @@ static JSValue js_dtoa_radix(JSContext *ctx, double d, int radix)
d = fabs(d);
d0 = trunc(d);
frac = d - d0;
ptr = buf + 1100;
*ptr = '\0';
ptr2 = buf + 1100; /* ptr2 points to the end of the string */
ptr = ptr2; /* ptr points to the beginning of the string */
if (d0 <= MAX_SAFE_INTEGER) {
int64_t n = n0 = (int64_t)d0;
while (n >= radix) {
@ -11297,7 +11298,6 @@ static JSValue js_dtoa_radix(JSContext *ctx, double d, int radix)
if (frac != 0) {
double log2_radix = log2(radix);
double prec = 1023 + 51; // handle subnormals
ptr2 = buf + 1100;
*ptr2++ = '.';
while (frac != 0 && n0 <= MAX_SAFE_INTEGER/2 && prec > 0) {
frac *= radix;
@ -11307,32 +11307,45 @@ static JSValue js_dtoa_radix(JSContext *ctx, double d, int radix)
n0 = n0 * radix + digit;
prec -= log2_radix;
}
*ptr2 = '\0';
if (frac * radix >= radix / 2) {
/* round up the string representation manually */
char nine = digits36[radix - 1];
// round to closest
while (ptr2[-1] == nine)
*--ptr2 = '\0';
if (ptr2[-1] == '.') {
*--ptr2 = '\0';
while (ptr2[-1] == nine)
*--ptr2 = '0';
while (ptr2[-1] == nine) {
/* strip trailing '9' or equivalent digits */
ptr2--;
}
if (ptr2[-1] == '.') {
/* strip the 'decimal' point */
ptr2--;
/* increment the integral part */
for (ptr3 = ptr2;;) {
if (ptr3[-1] != nine) {
ptr3[-1] = (ptr3[-1] == '9') ? 'a' : ptr3[-1] + 1;
break;
}
*--ptr3 = '0';
if (ptr3 <= ptr) {
/* prepend a '1' if number was all nines */
*--ptr = '1';
break;
}
}
} else {
/* increment the last fractional digit */
ptr2[-1] = (ptr2[-1] == '9') ? 'a' : ptr2[-1] + 1;
}
if (ptr2 - 1 == ptr)
*--ptr = '1';
else
ptr2[-1] += 1;
} else {
/* strip trailing fractional zeroes */
while (ptr2[-1] == '0')
*--ptr2 = '\0';
if (ptr2[-1] == '.')
*--ptr2 = '\0';
ptr2--;
/* strip the 'decimal' point if last */
ptr2 -= (ptr2[-1] == '.');
}
}
done:
ptr[-1] = '-';
ptr -= sign;
return JS_NewString(ctx, ptr);
return js_new_string8(ctx, (uint8_t *)ptr, ptr2 - ptr);
}
JSValue JS_ToStringInternal(JSContext *ctx, JSValue val, BOOL is_ToPropertyKey)

1
tests/test_builtin.js
View file

@ -439,6 +439,7 @@ function test_number()
return;
}
assert((1-2**-53).toString(12), "0.bbbbbbbbbbbbbba");
assert((25).toExponential(0), "3e+1");
assert((-25).toExponential(0), "-3e+1");
assert((2.5).toPrecision(1), "3");