Hash | Documents for Coost

#Hash

#hash32

uint32 hash32(const void* s, size_t n);
uint32 hash32(const char* s);
uint32 hash32(const fastring& s)
uint32 hash32(const std::string& s);

This function returns a 32-bit murmur hash value.
When s is a pointer, it is required to be sizeof(void*) byte aligned.

#hash64

uint64 hash64(const void* s, size_t n);
uint64 hash64(const char* s);
uint64 hash64(const fastring& s);
uint64 hash64(const std::string& s);

This function returns a 64-bit murmur hash value.
When s is a pointer, it is required to be 8-byte aligned.

#murmur_hash

size_t murmur_hash(const void* s, size_t n);

This function returns a hash value of size_t type. This value is 64-bit on 64-bit platform and 32-bit on 32-bit platform.
The parameter s is generally required to be sizeof(void*) byte-aligned.

#md5

#md5digest

void md5digest(const void* s, size_t n, char res[16]);
fastring md5digest(const void* s, size_t n);
fastring md5digest(const char* s);
fastring md5digest(const fastring& s);
fastring md5digest(const std::string& s);

This function calculates the md5 of a string and returns a 16-byte binary string.

#md5sum

void md5sum(const void* s, size_t n, char res[32]);
fastring md5sum(const void* s, size_t n);
fastring md5sum(const char* s);
fastring md5sum(const fastring& s);
fastring md5sum(const std::string& s);

This function calculates the md5 of a string and returns a 32-byte string containing only hexadecimal characters(0-9,a-f).

#Lower level APIs

void md5_init(md5_ctx_t* ctx);
void md5_update(md5_ctx_t* ctx, const void* s, size_t n);
void md5_final(md5_ctx_t* ctx, uint8 res[16]);

The above 3 APIs can be used to calculate md5 incrementally.
Example

char buf[4096];
uint8 res[16];
md5_ctx_t ctx;
md5_init(&ctx);

while (true) {
    int r = read(fd, buf, 4096);
    if (r > 0) {
        md5_update(&ctx, buf, r);
    } else {
        break;
    }
}

md5_final(&ctx, res);

#sha256

#sha256digest

void sha256digest(const void* s, size_t n, char res[32]);
fastring sha256digest(const void* s, size_t n);
fastring sha256digest(const char* s);
fastring sha256digest(const fastring& s);
fastring sha256digest(const std::string& s);

This function calculates the sha256 of a string and returns a 32-byte binary string.

#sha256sum

void sha256sum(const void* s, size_t n, char res[64]);
fastring sha256sum(const void* s, size_t n);
fastring sha256sum(const char* s);
fastring sha256sum(const fastring& s);
fastring sha256sum(const std::string& s);

This function calculates the sha256 of a string and returns a 64-byte string containing only hexadecimal characters(0-9,a-f).

#Lower level APIs

void sha256_init(sha256_ctx_t* ctx);
void sha256_update(sha256_ctx_t* ctx, const void* s, size_t n);
void sha256_final(sha256_ctx_t* ctx, uint8 res[32]);

The above 3 APIs can be used to calculate sha256 incrementally like that in md5.

#base64

#base64_encode

fastring base64_encode(const void* s, size_t n);
fastring base64_encode(const char* s);
fastring base64_encode(const fastring& s);
fastring base64_encode(const std::string& s);

base64 encoding, \r\n is not added in this implementation.

#base64_decode

fastring base64_decode(const void* s, size_t n);
fastring base64_decode(const char* s);
fastring base64_decode(const fastring& s);
fastring base64_decode(const std::string& s);

base64 decoding, if the input is not valid base64-encoded data, the decoding will fail and an empty string will be returned.

#url

#url_encode

fastring url_encode(const void* s, size_t n);
fastring url_encode(const char* s);
fastring url_encode(const fastring& s);
fastring url_encode(const std::string& s);

url encoding, reserved characters !()*#$&'+,/:;=?@[] and a-z A-Z 0-9 -_.~ will not be encoded, all other characters will be encoded.

#url_decode

fastring url_decode(const void* s, size_t n);
fastring url_decode(const char* s);
fastring url_decode(const fastring& s);
fastring url_decode(const std::string& s);

url decoding, if the input is not a reasonably encoded url, the decoding will fail and an empty string will be returned.

#crc16

uint16_t crc16(const void* s, size_t n);
uint16_t crc16(const char* s);
uint16_t crc16(const fastring& s);
uint16_t crc16(const std::string& s);

This function calculates the crc16 value of a string. The implementation is taken from redis and will be used when implementing the redis cluster client.