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Encoding, hashes and IDs

The functions to encode and decode Base64, hex and percent-encoding; hash and checksum data; generate UUIDs, grouped by what you want to do. The From column says what a program needs before it can call one:

• std/<Name>: #import "std/<Name>", then using <Name> to call it by its bare name.

Jump to: Encode and decode base64 · Encode and decode hex · Percent-encode text for URLs · Encode and decode base32 · Find out why decoding failed · Hash or checksum data in one call · Pick a checksum or hash · Hash data in pieces · Sign and check a message with HMAC · Make a UUID · Turn a UUID into text or bytes and back · Inspect a UUID · Read numbers from a byte buffer · Write numbers into a byte buffer

Encode and decode base64

Function	What it does	From
Base64Encode	Returns bytes or a string as base64 text, in the standard or URL-safe alphabet.	std/codec
Base64Decode	Decodes base64 text into a byte array and returns the byte count, or an error.	std/codec
Base64DecodeText	Decodes base64 text straight to a string; the decoded bytes must be UTF-8.	std/codec

Encode and decode hex

Function	What it does	From
HexEncode	Returns bytes or a string as hexadecimal text, two digits a byte, lower or upper case.	std/codec
HexDecode	Decodes hexadecimal text into a byte array and returns the byte count, or an error.	std/codec
HexDecodeText	Decodes hexadecimal text straight to a string; the decoded bytes must be UTF-8.	std/codec

Percent-encode text for URLs

Function	What it does	From
PercentEncode	Returns text with the characters a URL cannot hold written as %XX escapes.	std/codec
PercentDecode	Turns %XX escapes, and + in query mode, back into text, or returns an error.	std/codec

Encode and decode base32

Function	What it does	From
Base32Encode	Returns bytes or a string as base32 text, in the standard or sortable hex alphabet.	std/codec
Base32Decode	Decodes base32 text into a byte array and returns the byte count, or an error.	std/codec
Base32DecodeText	Decodes base32 text straight to a string; the decoded bytes must be UTF-8.	std/codec

Find out why decoding failed

Function	What it does	From
EncodingError	Holds why decoding failed: a code, the position of the first bad character, a message.	std/codec

Hash or checksum data in one call

Function	What it does	From
Digest	Returns the digest of text or a byte array as bytes, for the algorithm named.	std/hash
DigestHex	Returns the digest of text or a byte array as lower-case hex.	std/hash
DigestFile	Returns the digest of a whole file, read in 64 KB pieces, or why it could not be read.	std/hash
HashStream	Feeds a stream from where it is to its end into a hasher; returns the bytes read.	std/hash
HashAlgorithm	Names the algorithms the one-call functions take, from HASH_CRC32 to HASH_SHA512.	std/hash
NewHasher	Returns a new hasher for an algorithm, which the caller deletes, or nullptr.	std/hash

Pick a checksum or hash

Function	What it does	From
Crc32	Holds a CRC-32 checksum, the 4-byte one zip, gzip and PNG use.	std/hash
Crc32C	Holds a CRC-32C checksum, the 4-byte one iSCSI and ext4 use.	std/hash
Adler32	Holds an Adler-32 checksum, the 4-byte one zlib streams use.	std/hash
Fnv1a32	Holds a 32-bit FNV-1a hash, quick for short keys; not for security.	std/hash
Fnv1a64	Holds a 64-bit FNV-1a hash, quick for short keys; not for security.	std/hash
XxHash64	Holds a 64-bit xxHash with an optional seed, fast on large data; not for security.	std/hash
Md5	Holds a 16-byte MD5 hash, only for matching formats that already use it.	std/hash
Sha1	Holds a 20-byte SHA-1 hash, only for matching formats that already use it.	std/hash
Sha224	Holds a 28-byte SHA-224 hash, for data someone could tamper with.	std/hash
Sha256	Holds a 32-byte SHA-256 hash, for data someone could tamper with.	std/hash
Sha384	Holds a 48-byte SHA-384 hash, faster than SHA-256 on long messages on 64-bit machines.	std/hash
Sha512	Holds a 64-byte SHA-512 hash, faster than SHA-256 on long messages on 64-bit machines.	std/hash

Hash data in pieces

Function	What it does	From
Hasher	Holds what every hash type shares, so one procedure can take any of them.	std/hash
Hasher.Update	Adds a number of bytes at a pointer to the hash.	std/hash
Hasher.UpdateBytes	Adds the bytes of an Array to the hash.	std/hash
Hasher.UpdateText	Adds text to the hash as its UTF-8 bytes.	std/hash
Hasher.UpdateRaw	Adds the bytes of a string to the hash as they are, with no conversion.	std/hash
Hasher.Finish	Returns the digest so far as bytes; more data can still be added after it.	std/hash
Hasher.FinishHex	Returns the digest so far as lower-case hex; more data can still be added after it.	std/hash
Hasher.Reset	Forgets everything added and starts the hash again.	std/hash
Hasher.DigestSize	Returns the size of the digest in bytes.	std/hash
Hasher.BlockSize	Returns the size of the block the algorithm works on, in bytes.	std/hash
Sum32 / Sum64	Returns a checksum or fast hash as a number instead of bytes.	std/hash

Sign and check a message with HMAC

Function	What it does	From
Hmac	Holds an HMAC: a cryptographic hash with a key, which is itself a Hasher.	std/hash
HmacHex	Returns the HMAC of a message under a key as lower-case hex, in one call.	std/hash
ConstantTimeEquals	Returns true if two byte arrays match, taking the same time whichever byte differs.	std/hash

Make a UUID

Function	What it does	From
Uuid	Holds a 128-bit identifier that can be compared, sorted and used as a Map key.	std/uuids
NewV4	Returns a new random UUID from the system's secure random generator.	std/uuids
NewV7	Returns a new UUID that starts with the time, so each one sorts after the one before.	std/uuids
NilUuid	Returns the nil UUID, with all 16 bytes zero.	std/uuids
MaxUuid	Returns the max UUID, with every bit set.	std/uuids

Turn a UUID into text or bytes and back

Function	What it does	From
Parse	Parses a UUID with or without hyphens, braces or a urn:uuid: prefix, or returns an error.	std/uuids
Uuid.ToString	Returns the UUID as 36 characters of lower-case text in the 8-4-4-4-12 form.	std/uuids
FromBytes	Returns a UUID from an array of exactly 16 bytes, or an error.	std/uuids
Uuid.ToBytes	Returns the UUID's 16 bytes as an Array.	std/uuids
UuidError	Holds why a UUID did not parse: a code and the position of the offending character.	std/uuids

Inspect a UUID

Function	What it does	From
Uuid.Version	Returns the UUID's version, such as 4 or 7, or 0 for the nil UUID.	std/uuids
Uuid.Variant	Returns the UUID's variant field, which is 1 for every standard UUID.	std/uuids
Uuid.IsNil	Returns true if all 16 bytes of the UUID are zero.	std/uuids
Uuid.UnixMillis	Returns when a version 7 UUID was made, in Unix milliseconds, or -1 for any other.	std/uuids
Uuid.HashOf	Returns a hash of the UUID, used when it is a Map or Set key.	std/uuids

Read numbers from a byte buffer

Function	What it does	From
GetU16LE … GetF64BE	Reads a fixed-width integer or float at a byte offset, little- or big-endian.	std/codec
ReadUVarint	Reads an unsigned variable-length integer at an offset and moves the offset past it.	std/codec
ReadVarint	Reads a signed variable-length integer at an offset and moves the offset past it.	std/codec

Write numbers into a byte buffer

Function	What it does	From
PutU16LE … PutF64BE	Writes a fixed-width number at a byte offset, growing the array if it is too short.	std/codec
AppendU16LE … AppendF64BE	Adds a fixed-width number to the end of a byte array, little- or big-endian.	std/codec
AppendUVarint	Adds an unsigned integer to a byte array in as few bytes as it needs.	std/codec
AppendVarint	Adds a signed integer to a byte array, keeping small negative numbers short.	std/codec

See Also

• Codec guide
• Hash guide
• UUID guide
• Array, which holds the bytes
• Result, which the decoders and Parse return

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