Syndicate, test and fix base64 implementation
llvm/Support/Base64, fix its implementation and provide a decent test suite.
Previous implementation code was using + operator instead of | to combine
results, which is a problem when shifting signed values. (0xFF << 16) is
implicitly converted to a (signed) int, and thus results in 0xffff0000,
h is
negative. Combining negative numbers with a + in that context is not what we
want to do.
This is a recommit of 5a1958f2673f8c771e406a7e309e160b432c9a79 with UB removved.
This fixes https://github.com/llvm/llvm-project/issues/149.
Differential Revision: https://reviews.llvm.org/D75057
GitOrigin-RevId: 1454c27b60447d969d0c1ecaf20b2186fe9d85ec
diff --git a/FuzzerUtil.cpp b/FuzzerUtil.cpp
index 7aa84a1..87180d1 100644
--- a/FuzzerUtil.cpp
+++ b/FuzzerUtil.cpp
@@ -151,32 +151,36 @@
return true;
}
+// Code duplicated (and tested) in llvm/include/llvm/Support/Base64.h
std::string Base64(const Unit &U) {
static const char Table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";
- std::string Res;
- size_t i;
- for (i = 0; i + 2 < U.size(); i += 3) {
- uint32_t x = (U[i] << 16) + (U[i + 1] << 8) + U[i + 2];
- Res += Table[(x >> 18) & 63];
- Res += Table[(x >> 12) & 63];
- Res += Table[(x >> 6) & 63];
- Res += Table[x & 63];
+ std::string Buffer;
+ Buffer.resize(((U.size() + 2) / 3) * 4);
+
+ size_t i = 0, j = 0;
+ for (size_t n = U.size() / 3 * 3; i < n; i += 3, j += 4) {
+ uint32_t x = (U[i] << 16) | (U[i + 1] << 8) | U[i + 2];
+ Buffer[j + 0] = Table[(x >> 18) & 63];
+ Buffer[j + 1] = Table[(x >> 12) & 63];
+ Buffer[j + 2] = Table[(x >> 6) & 63];
+ Buffer[j + 3] = Table[x & 63];
}
if (i + 1 == U.size()) {
uint32_t x = (U[i] << 16);
- Res += Table[(x >> 18) & 63];
- Res += Table[(x >> 12) & 63];
- Res += "==";
+ Buffer[j + 0] = Table[(x >> 18) & 63];
+ Buffer[j + 1] = Table[(x >> 12) & 63];
+ Buffer[j + 2] = '=';
+ Buffer[j + 3] = '=';
} else if (i + 2 == U.size()) {
- uint32_t x = (U[i] << 16) + (U[i + 1] << 8);
- Res += Table[(x >> 18) & 63];
- Res += Table[(x >> 12) & 63];
- Res += Table[(x >> 6) & 63];
- Res += "=";
+ uint32_t x = (U[i] << 16) | (U[i + 1] << 8);
+ Buffer[j + 0] = Table[(x >> 18) & 63];
+ Buffer[j + 1] = Table[(x >> 12) & 63];
+ Buffer[j + 2] = Table[(x >> 6) & 63];
+ Buffer[j + 3] = '=';
}
- return Res;
+ return Buffer;
}
static std::mutex SymbolizeMutex;
