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c-multihash
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some cursory review

whys-review
Jeromy 2016-08-11 12:09:42 -07:00
parent e0781d0536
commit be3ec97ef9
2 changed files with 37 additions and 29 deletions
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7
src/hashes.c
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@ -24,6 +24,10 @@ static const struct hash_info {
{ MH_H_BLAKE2S, "blake2s", 32 }
};
// REVIEW NOTE:
// This could just be a table where the index into the array is the hash
// function. This would make the lookups much simpler.
mh_assert_static(sizeof(hash_infos) / sizeof(hash_infos[0]) == MH_H_COUNT);
// Searches for given hash in hash info table
@ -40,7 +44,8 @@ static const struct hash_info *find_hash(int hash) {
const char *mh_hash_name(int hash) {
const struct hash_info *info = find_hash(hash);
return info ? info->name : NULL;
return (info != NULL) ? info->name : NULL;
// I prefer explicit checks against null pointers
}

59
src/multihash.c
View File

@ -10,66 +10,69 @@
#define VARINT_MASK (1 << 7)
static int check_len(size_t len) {
if (len < 1) {
if (len < 1)
return MH_E_TOO_SHORT;
} else if (len >= 128) {
else if (len >= 128)
return MH_E_TOO_LONG;
}
return MH_E_NO_ERROR;
return 0;
}
static int check_multihash(const unsigned char mh[], size_t len) {
int error;
int err;
if (len < 3)
return MH_E_TOO_SHORT;
if (mh[0] & VARINT_MASK) {
// In near future multihash format will be
// extended with varints, this is how we are protecting
// against it.
// This value is a varint, but there are currently no supported values
// that require more than a single byte to represent.
return MH_E_VARINT_NOT_SUPPORTED;
} else if (mh[1] & VARINT_MASK) {
return MH_E_VARINT_NOT_SUPPORTED;
}
error = check_len(mh[1]);
if (error)
return error;
err = check_len(mh[1]);
if (err)
return err;
return MH_E_NO_ERROR;
return 0;
}
// returns hash code or error (which is < 0)
int mh_multihash_hash(const unsigned char *mh, size_t len) {
if (check_multihash(mh, len))
return check_multihash(mh, len);
int err;
err = check_multihash(mh, len);
return err;
return (int) mh[0];
}
// returns length of multihash or error (which is < 0)
int mh_multihash_length(const unsigned char *mh, size_t len) {
if (check_multihash(mh, len))
return check_multihash(mh, len);
int err;
err = check_multihash(mh, len);
if (err)
return err;
return (int) mh[1];
}
// gives access to raw digset inside multihash buffer
// gives access to raw digest inside multihash buffer
// returns 0 or negative error
int mh_multihash_digset(unsigned char *multihash, size_t len, unsigned char **digset,
size_t *digset_len) {
int mh_multihash_digest(unsigned char *multihash, size_t len, unsigned char **digest,
size_t *digest_len) {
int error = check_multihash(multihash, len);
if (error)
return error;
(*digset_len) = (size_t) mh_multihash_length(multihash, len);
(*digset) = multihash + 2; // Always true without varint
(*digest_len) = (size_t) mh_multihash_length(multihash, len);
(*digest) = multihash + 2; // Always true without varint
return MH_E_NO_ERROR;
return 0;
}
int mh_new_length(int code, size_t hash_len) {
@ -79,17 +82,17 @@ int mh_new_length(int code, size_t hash_len) {
return 2 + hash_len;
}
int mh_new(unsigned char *buffer, int code, const unsigned char *digset,
size_t digset_len) {
int mh_new(unsigned char *buffer, int code, const unsigned char *digest,
size_t digest_len) {
if (code & VARINT_MASK)
return MH_E_VARINT_NOT_SUPPORTED;
if (digset_len > 127)
if (digest_len > 127)
return MH_E_DIGSET_TOO_LONG;
buffer[0] = (unsigned char) ((unsigned int) code) & 255;
buffer[1] = (unsigned char) digset_len;
memcpy(buffer + 2, digset, digset_len);
buffer[1] = (unsigned char) digest_len;
memcpy(buffer + 2, digest, digest_len);
return MH_E_NO_ERROR;
return 0;
}