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Loop on Win32 to satisfy large random byte requests (as is done on Linux) #62364

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Merged
merged 2 commits into from
Dec 5, 2022
Merged

Loop on Win32 to satisfy large random byte requests (as is done on Linux) #62364

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Loop on Win32 to satisfy large random byte requests (as is done on Li…
grynspan Dec 2, 2022
9de9205
Add NOMINMAX so std::min is usable.
grynspan Dec 5, 2022
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21 changes: 12 additions & 9 deletions stdlib/public/stubs/Random.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@

#if defined(_WIN32) && !defined(__CYGWIN__)
#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <Windows.h>
#include <Bcrypt.h>
#pragma comment(lib, "bcrypt.lib")
Expand Down Expand Up @@ -65,16 +66,18 @@ void swift_stdlib_random(void *buf, __swift_size_t nbytes) {

SWIFT_RUNTIME_STDLIB_API
void swift_stdlib_random(void *buf, __swift_size_t nbytes) {
if (nbytes > ULONG_MAX) {
fatalError(0, "Fatal error: %zd exceeds ULONG_MAX\n", nbytes);
}
while (nbytes > 0) {
auto actual_nbytes = std::min(nbytes, (__swift_size_t)ULONG_MAX);
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It would be nice to use static_cast as this is C++.

Suggested change
auto actual_nbytes = std::min(nbytes, (__swift_size_t)ULONG_MAX);
auto actual_nbytes = std::min(nbytes, static_cast<__swift_size_t>(ULONG_MAX));

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@compnerd Can the #warning on line 64 be removed?

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Good question. AFAIK the unit tests for random number generation are not conditionalized by platform, are they?

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swift_stdlib_random is used in validation-test/stdlib/Random.swift, on all platforms AFAIK.

The #warning was originally an #error, because swift_stdlib_random was written without access to a compiler for Windows.

NTSTATUS status = BCryptGenRandom(nullptr,
static_cast<PUCHAR>(buf),
static_cast<ULONG>(actual_nbytes),
BCRYPT_USE_SYSTEM_PREFERRED_RNG);
if (!BCRYPT_SUCCESS(status)) {
fatalError(0, "Fatal error: 0x%lX in '%s'\n", status, __func__);
}

NTSTATUS status = BCryptGenRandom(nullptr,
static_cast<PUCHAR>(buf),
static_cast<ULONG>(nbytes),
BCRYPT_USE_SYSTEM_PREFERRED_RNG);
if (!BCRYPT_SUCCESS(status)) {
fatalError(0, "Fatal error: 0x%lX in '%s'\n", status, __func__);
buf = static_cast<uint8_t *>(buf) + actual_nbytes;
nbytes -= actual_nbytes;
}
}

Expand Down