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Make random_string() thread-safe (#2110)

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By making the random engine thread_local, each thread now has its own
independent random sequence, ensuring safe concurrent access.
Additionally, using an immediately invoked lambda expression to
initialize the engine eliminates the need for separate static seed
variables.
This commit is contained in:
Florian Albrechtskirchinger 2025-03-13 17:44:43 +01:00 committed by GitHub
parent 94a4028821
commit 2eaa2ea64f
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1 changed files with 9 additions and 10 deletions
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httplib.h
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@ -5100,16 +5100,15 @@ inline std::string random_string(size_t length) {
constexpr const char data[] =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
// std::random_device might actually be deterministic on some
// platforms, but due to lack of support in the c++ standard library,
// doing better requires either some ugly hacks or breaking portability.
static std::random_device seed_gen;
// Request 128 bits of entropy for initialization
static std::seed_seq seed_sequence{seed_gen(), seed_gen(), seed_gen(),
seed_gen()};
static std::mt19937 engine(seed_sequence);
static thread_local std::mt19937 engine([]() {
// std::random_device might actually be deterministic on some
// platforms, but due to lack of support in the c++ standard library,
// doing better requires either some ugly hacks or breaking portability.
std::random_device seed_gen;
// Request 128 bits of entropy for initialization
std::seed_seq seed_sequence{seed_gen(), seed_gen(), seed_gen(), seed_gen()};
return std::mt19937(seed_sequence);
}());
std::string result;
for (size_t i = 0; i < length; i++) {