chore(3p/nix/hash): eliminate exposed global variable

Change-Id: I3b34e3e17a751e225831ae599c6c6bb782a25679
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1486
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
This commit is contained in:
Kane York 2020-07-27 17:07:51 -07:00 committed by kanepyork
parent d9262bd6c6
commit 976a36c2e4
3 changed files with 61 additions and 38 deletions

View file

@ -13,38 +13,21 @@ namespace nix {
static unsigned int refLength = 32; /* characters */
static void search(const unsigned char* s, size_t len, StringSet& hashes,
static void search(const char* s, size_t len, StringSet& hashes,
StringSet& seen) {
static bool initialised = false;
static bool isBase32[256];
if (!initialised) {
for (bool& i : isBase32) {
i = false;
}
for (char base32Char : base32Chars) {
isBase32[static_cast<unsigned char>(base32Char)] = true;
}
initialised = true;
}
for (size_t i = 0; i + refLength <= len;) {
int j = 0;
bool match = true;
for (j = refLength - 1; j >= 0; --j) {
if (!isBase32[s[i + j]]) {
i += j + 1;
match = false;
break;
}
}
absl::string_view ref(s + i, refLength);
bool match = Hash::IsValidBase32(ref);
if (!match) {
continue;
}
std::string ref(reinterpret_cast<const char*>(s) + i, refLength);
if (hashes.find(ref) != hashes.end()) {
// TODO(kanepyork): convert StringSet to flat_hash_set, delay owned string
// conversion into the 'if'
std::string sref(ref);
if (hashes.find(sref) != hashes.end()) {
DLOG(INFO) << "found reference to '" << ref << "' at offset " << i;
seen.insert(ref);
hashes.erase(ref);
seen.insert(sref);
hashes.erase(sref);
}
++i;
}
@ -65,22 +48,21 @@ struct RefScanSink : Sink {
void RefScanSink::operator()(const unsigned char* data, size_t len) {
hashSink(data, len);
const char* data_ = reinterpret_cast<const char*>(data);
/* It's possible that a reference spans the previous and current
fragment, so search in the concatenation of the tail of the
previous fragment and the start of the current fragment. */
std::string s = tail + std::string(reinterpret_cast<const char*>(data),
len > refLength ? refLength : len);
search(reinterpret_cast<const unsigned char*>(s.data()), s.size(), hashes,
seen);
std::string s = tail + std::string(data_, len > refLength ? refLength : len);
search(s.data(), s.size(), hashes, seen);
search(data, len, hashes, seen);
search(data_, len, hashes, seen);
size_t tailLen = len <= refLength ? len : refLength;
tail =
std::string(tail, tail.size() < refLength - tailLen
? 0
: tail.size() - (refLength - tailLen)) +
std::string(reinterpret_cast<const char*>(data) + len - tailLen, tailLen);
tail = std::string(tail, tail.size() < refLength - tailLen
? 0
: tail.size() - (refLength - tailLen)) +
std::string(data_ + len - tailLen, tailLen);
}
PathSet scanForReferences(const std::string& path, const PathSet& refs,

View file

@ -78,6 +78,45 @@ static std::string printHash16(const Hash& hash) {
// omitted: E O U T
const std::string base32Chars = "0123456789abcdfghijklmnpqrsvwxyz";
constexpr signed char kUnBase32[] = {
-1, -1, -1, -1, -1, -1, -1, -1, /* unprintables */
-1, -1, -1, -1, -1, -1, -1, -1, /* unprintables */
-1, -1, -1, -1, -1, -1, -1, -1, /* unprintables */
-1, -1, -1, -1, -1, -1, -1, -1, /* unprintables */
-1, -1, -1, -1, -1, -1, -1, -1, /* SP..' */
-1, -1, -1, -1, -1, -1, -1, -1, /* (../ */
0, 1, 2, 3, 4, 5, 6, 7, /* 0..7 */
8, 9, -1, -1, -1, -1, -1, -1, /* 8..? */
-1, -1, -1, -1, -1, -1, -1, -1, /* @..G */
-1, -1, -1, -1, -1, -1, -1, -1, /* H..O */
-1, -1, -1, -1, -1, -1, -1, -1, /* P..W */
-1, -1, -1, -1, -1, -1, -1, -1, /* X.._ */
-1, 10, 11, 12, 13, -1, 14, 15, /* `..g */
16, 17, 18, 19, 20, 21, 22, -1, /* h..o */
23, 24, 25, 26, -1, -1, 27, 28, /* p..w */
29, 30, 31, -1, -1, -1, -1, -1, /* x..DEL */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* high */
};
bool Hash::IsValidBase32(absl::string_view s) {
static_assert(sizeof(kUnBase32) == 256);
for (char c : s) {
if (kUnBase32[static_cast<unsigned char>(c)] == -1) {
return false;
}
}
return true;
}
static std::string printHash32(const Hash& hash) {
assert(hash.hashSize);
size_t len = hash.base32Len();

View file

@ -14,8 +14,6 @@ const int sha1HashSize = 20;
const int sha256HashSize = 32;
const int sha512HashSize = 64;
extern const std::string base32Chars;
enum Base : int { Base64, Base32, Base16, SRI };
struct Hash {
@ -65,6 +63,10 @@ struct Hash {
or base-64. By default, this is prefixed by the hash type
(e.g. "sha256:"). */
std::string to_string(Base base = Base32, bool includeType = true) const;
/* Returns whether the passed string contains entirely valid base32
characters. */
static bool IsValidBase32(absl::string_view s);
};
/* Print a hash in base-16 if it's MD5, or base-32 otherwise. */