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Use integer division trick to get exact base64 length #50549

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Merged
merged 2 commits into from
May 3, 2021
+4 −4
Merged

Use integer division trick to get exact base64 length #50549

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f4d5c9a
Use integer division trick to get exact base64 length and avoid modul…
gfoidl Mar 31, 2021
d6ea2d9
Update src/libraries/System.Private.CoreLib/src/System/Convert.cs
stephentoub Apr 1, 2021
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8 changes: 4 additions & 4 deletions src/libraries/System.Private.CoreLib/src/System/Convert.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2527,16 +2527,16 @@ private static unsafe int ConvertToBase64Array(char* outChars, byte* inData, int

private static int ToBase64_CalculateAndValidateOutputLength(int inputLength, bool insertLineBreaks)
{
long outlen = ((long)inputLength) / 3 * 4; // the base length - we want integer division here.
outlen += ((inputLength % 3) != 0) ? 4 : 0; // at most 4 more chars for the remainder
// the base length - we want integer division here, at most 4 more chars for the remainder
long outlen = ((long)inputLength + 2) / 3 * 4;

if (outlen == 0)
return 0;

if (insertLineBreaks)
{
long newLines = outlen / base64LineBreakPosition;
if ((outlen % base64LineBreakPosition) == 0)
(long newLines, long remainder) = Math.DivRem(outlen, base64LineBreakPosition);
if (remainder == 0)
{
--newLines;
}
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