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Fix random alpha-numeric string affixed to binary path uprobe keys that are too long. #4

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etep wants to merge 4 commits into from
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Fix random alpha-numeric string affixed to binary path uprobe keys that are too long. #4

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7832054
Fix random_alnum_string in BPF.cc.
Dec 1, 2022
52aa2c2
Fix distribution range.
Dec 1, 2022
2fa33ab
Tidy.
Dec 3, 2022
d00b129
Tidy random_alnum_string.
Dec 5, 2022
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6 changes: 3 additions & 3 deletions src/cc/api/BPF.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -858,12 +858,12 @@ namespace {

std::string random_alnum_string(int len) {
static constexpr char kDict[] = "0123456789abcdefghijklmnopqrstuvwxyz";
static std::random_device rd;
std::uniform_int_distribution<size_t> dist(0, sizeof(kDict)-1);
static std::mt19937 gen;
static std::uniform_int_distribution<size_t> dist(0, sizeof(kDict)-2);

@oazizi000 oazizi000 Dec 5, 2022

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Offline discussion: Why -2? Turns out it is for the null character.

Instead we should consider using:

static constexpr std::string_view kDict = "0123456789abcdefghijklmnopqrstuvwxyz"

And then we can do kDict.size() - 1

@etep etep Dec 5, 2022

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Done in d00b129.

std::string res;
res.reserve(len);
for (int i = 0; i < len; ++i) {
res.push_back(kDict[dist(rd)]);
res.push_back(kDict[dist(gen)]);
}
return res;
}
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