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Simplify parseHash32

This commit is contained in:
Eelco Dolstra 2015-02-03 18:56:47 +01:00 committed by Ludovic Courtès
parent 70c3d2f176
commit 8ab23f2924
1 changed files with 11 additions and 38 deletions
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49
nix/libutil/hash.cc
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@ -141,51 +141,24 @@ string printHash16or32(const Hash & hash)
}
static bool mul(unsigned char * bytes, unsigned char y, int maxSize)
{
unsigned char carry = 0;
for (int pos = 0; pos < maxSize; ++pos) {
unsigned int m = bytes[pos] * y + carry;
bytes[pos] = m & 0xff;
carry = m >> 8;
}
return carry;
}
static bool add(unsigned char * bytes, unsigned char y, int maxSize)
{
unsigned char carry = y;
for (int pos = 0; pos < maxSize; ++pos) {
unsigned int m = bytes[pos] + carry;
bytes[pos] = m & 0xff;
carry = m >> 8;
if (carry == 0) break;
}
return carry;
}
Hash parseHash32(HashType ht, const string & s)
{
Hash hash(ht);
unsigned int len = hashLength32(ht);
assert(s.size() == len);
const char * chars = base32Chars.data();
for (unsigned int i = 0; i < s.length(); ++i) {
char c = s[i];
for (unsigned int n = 0; n < len; ++n) {
char c = s[len - n - 1];
unsigned char digit;
for (digit = 0; digit < base32Chars.size(); ++digit) /* !!! slow */
if (chars[digit] == c) break;
if (base32Chars[digit] == c) break;
if (digit >= 32)
throw Error(format("invalid base-32 hash `%1%'") % s);
if (mul(hash.hash, 32, hash.hashSize) ||
add(hash.hash, digit, hash.hashSize))
throw Error(format("base-32 hash `%1%' is too large") % s);
throw Error(format("invalid base-32 hash '%1%'") % s);
unsigned int b = n * 5;
unsigned int i = b / 8;
unsigned int j = b % 8;
hash.hash[i] |= digit << j;
if (i < hash.hashSize - 1) hash.hash[i + 1] |= digit >> (8 - j);
}
return hash;