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6b47635180
Add hash format analogy of parseHashTypeOpt, parseHashType, and printHashType. Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
240 lines
5.6 KiB
C++
240 lines
5.6 KiB
C++
#pragma once
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///@file
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#include "types.hh"
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#include "serialise.hh"
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namespace nix {
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MakeError(BadHash, Error);
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enum HashType : char { htMD5 = 42, htSHA1, htSHA256, htSHA512 };
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const int md5HashSize = 16;
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const int sha1HashSize = 20;
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const int sha256HashSize = 32;
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const int sha512HashSize = 64;
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extern std::set<std::string> hashTypes;
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extern const std::string base32Chars;
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/**
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* @brief Enumeration representing the hash formats.
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*/
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enum struct HashFormat : int {
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/// @brief Base 64 encoding.
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/// @see [IETF RFC 4648, section 4](https://datatracker.ietf.org/doc/html/rfc4648#section-4).
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Base64,
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/// @brief Nix-specific base-32 encoding. @see base32Chars
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Base32,
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/// @brief Lowercase hexadecimal encoding. @see base16Chars
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Base16,
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/// @brief "<hash algo>:<Base 64 hash>", format of the SRI integrity attribute.
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/// @see W3C recommendation [Subresource Intergrity](https://www.w3.org/TR/SRI/).
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SRI
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};
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struct Hash
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{
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constexpr static size_t maxHashSize = 64;
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size_t hashSize = 0;
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uint8_t hash[maxHashSize] = {};
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HashType type;
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/**
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* Create a zero-filled hash object.
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*/
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Hash(HashType type);
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/**
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* Parse the hash from a string representation in the format
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* "[<type>:]<base16|base32|base64>" or "<type>-<base64>" (a
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* Subresource Integrity hash expression). If the 'type' argument
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* is not present, then the hash type must be specified in the
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* string.
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*/
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static Hash parseAny(std::string_view s, std::optional<HashType> type);
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/**
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* Parse a hash from a string representation like the above, except the
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* type prefix is mandatory is there is no separate arguement.
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*/
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static Hash parseAnyPrefixed(std::string_view s);
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/**
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* Parse a plain hash that musst not have any prefix indicating the type.
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* The type is passed in to disambiguate.
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*/
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static Hash parseNonSRIUnprefixed(std::string_view s, HashType type);
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static Hash parseSRI(std::string_view original);
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private:
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/**
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* The type must be provided, the string view must not include <type>
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* prefix. `isSRI` helps disambigate the various base-* encodings.
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*/
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Hash(std::string_view s, HashType type, bool isSRI);
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public:
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/**
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* Check whether two hash are equal.
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*/
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bool operator == (const Hash & h2) const;
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/**
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* Check whether two hash are not equal.
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*/
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bool operator != (const Hash & h2) const;
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/**
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* For sorting.
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*/
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bool operator < (const Hash & h) const;
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/**
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* Returns the length of a base-16 representation of this hash.
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*/
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size_t base16Len() const
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{
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return hashSize * 2;
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}
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/**
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* Returns the length of a base-32 representation of this hash.
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*/
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size_t base32Len() const
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{
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return (hashSize * 8 - 1) / 5 + 1;
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}
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/**
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* Returns the length of a base-64 representation of this hash.
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*/
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size_t base64Len() const
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{
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return ((4 * hashSize / 3) + 3) & ~3;
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}
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/**
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* Return a string representation of the hash, in base-16, base-32
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* or base-64. By default, this is prefixed by the hash type
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* (e.g. "sha256:").
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*/
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std::string to_string(HashFormat hashFormat, bool includeType) const;
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std::string gitRev() const
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{
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return to_string(HashFormat::Base16, false);
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}
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std::string gitShortRev() const
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{
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return std::string(to_string(HashFormat::Base16, false), 0, 7);
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}
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static Hash dummy;
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};
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/**
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* Helper that defaults empty hashes to the 0 hash.
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*/
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Hash newHashAllowEmpty(std::string_view hashStr, std::optional<HashType> ht);
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/**
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* Print a hash in base-16 if it's MD5, or base-32 otherwise.
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*/
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std::string printHash16or32(const Hash & hash);
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/**
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* Compute the hash of the given string.
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*/
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Hash hashString(HashType ht, std::string_view s);
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/**
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* Compute the hash of the given file, hashing its contents directly.
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*
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* (Metadata, such as the executable permission bit, is ignored.)
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*/
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Hash hashFile(HashType ht, const Path & path);
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/**
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* Compute the hash of the given path, serializing as a Nix Archive and
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* then hashing that.
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*
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* The hash is defined as (essentially) hashString(ht, dumpPath(path)).
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*/
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typedef std::pair<Hash, uint64_t> HashResult;
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HashResult hashPath(HashType ht, const Path & path,
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PathFilter & filter = defaultPathFilter);
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/**
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* Compress a hash to the specified number of bytes by cyclically
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* XORing bytes together.
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*/
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Hash compressHash(const Hash & hash, unsigned int newSize);
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/**
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* Parse a string representing a hash format.
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*/
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HashFormat parseHashFormat(std::string_view hashFormatName);
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/**
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* std::optional version of parseHashFormat that doesn't throw error.
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*/
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std::optional<HashFormat> parseHashFormatOpt(std::string_view hashFormatName);
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/**
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* The reverse of parseHashFormat.
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*/
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std::string_view printHashFormat(HashFormat hashFormat);
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/**
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* Parse a string representing a hash type.
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*/
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HashType parseHashType(std::string_view s);
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/**
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* Will return nothing on parse error
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*/
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std::optional<HashType> parseHashTypeOpt(std::string_view s);
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/**
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* And the reverse.
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*/
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std::string_view printHashType(HashType ht);
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union Ctx;
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struct AbstractHashSink : virtual Sink
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{
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virtual HashResult finish() = 0;
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};
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class HashSink : public BufferedSink, public AbstractHashSink
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{
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private:
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HashType ht;
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Ctx * ctx;
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uint64_t bytes;
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public:
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HashSink(HashType ht);
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HashSink(const HashSink & h);
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~HashSink();
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void writeUnbuffered(std::string_view data) override;
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HashResult finish() override;
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HashResult currentHash();
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};
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}
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