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8364320: String encodeUTF8 latin1 with negatives #26597

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8364320: String encodeUTF8 latin1 with negatives #26597

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d19b904
use counted positive values when converting latin1 to utf-8
bokken Jul 26, 2025
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whitespace
bokken Jul 31, 2025
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coding conventions
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11 changes: 8 additions & 3 deletions src/java.base/share/classes/java/lang/String.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1284,13 +1284,18 @@ private static byte[] encodeUTF8(byte coder, byte[] val, boolean doReplace) {
return encodeUTF8_UTF16(val, doReplace);
}

if (!StringCoding.hasNegatives(val, 0, val.length)) {
int positives = StringCoding.countPositives(val, 0, val.length);
if (positives == val.length) {
return val.clone();
}

int dp = 0;
byte[] dst = StringUTF16.newBytesFor(val.length);
for (byte c : val) {
if (positives > 0) {
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I wonder if for very short strings, the overhead of the setup for arraycopy is worth it.
It might be interesting to raise the test here to 4 or 8 for the array copy and otherwise start the loop at 0 and see if the performance difference is detectable.

System.arraycopy(val, 0, dst, 0, positives);
}
int dp = positives;
for (int i = dp; i < val.length; i++) {
byte c = val[i];
if (c < 0) {
dst[dp++] = (byte) (0xc0 | ((c & 0xff) >> 6));
dst[dp++] = (byte) (0x80 | (c & 0x3f));
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