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Fix empty attribute crash in DataChannelRereader2 #775

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Merged
jabrena merged 1 commit into from
Jan 3, 2021
Merged

Fix empty attribute crash in DataChannelRereader2 #775

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11 changes: 6 additions & 5 deletions src/main/java/ev3dev/utils/DataChannelRereader2.java
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Original file line number Diff line number Diff line change
Expand Up @@ -90,17 +90,18 @@ public String readString() {
// try to do the read
// only one try, as:
// - value >0 indicates success
// - value =0 does not tell us much, as there's a possibility of reading an empty attribute
// - value <0 indicates failure
// - value =0 indicates empty attribute (???)
// - value <0 indicates empty attribute
int n = channel.read(buffer, 0);
if (n == -1) {
throw new IOException("Premature end of file " + path);
// minus one reliably occurs on empty file, zero should be similar
if (n <= 0) {
return "";
}

// strip trailing newline & return data as a string
// rationale: ev3dev sysfs often appends \n, but this breaks parseFloat/parseInt/...
byte[] bytes = buffer.array();
if (n > 0 && bytes[n - 1] == '\n') {
if (bytes[n - 1] == '\n') {
return new String(bytes, 0, n - 1, StandardCharsets.UTF_8);
} else {
return new String(bytes, 0, n, StandardCharsets.UTF_8);
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