2c2fd4946f
This was a problem when writing a fetcher that uses e.g. sha256 hashes for revisions. This doesn't actually do anything new, but allows for creating such fetchers in the future (perhaps when support for Git's SHA256 object format gains more popularity).
164 lines
4.3 KiB
C++
164 lines
4.3 KiB
C++
#pragma once
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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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enum Base : int { Base64, Base32, Base16, SRI };
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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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/* Create a zero-filled hash object. */
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Hash(HashType type);
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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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static Hash parseAny(std::string_view s, std::optional<HashType> type);
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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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static Hash parseAnyPrefixed(std::string_view s);
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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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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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/* 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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Hash(std::string_view s, HashType type, bool isSRI);
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public:
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/* Check whether two hash are equal. */
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bool operator == (const Hash & h2) const;
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/* Check whether two hash are not equal. */
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bool operator != (const Hash & h2) const;
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/* For sorting. */
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bool operator < (const Hash & h) const;
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/* Returns the length of a base-16 representation of this hash. */
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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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/* Returns the length of a base-32 representation of this hash. */
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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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/* Returns the length of a base-64 representation of this hash. */
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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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/* 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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std::string to_string(Base base, bool includeType) const;
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std::string gitRev() const
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{
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return to_string(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(Base16, false), 0, 7);
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}
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static Hash dummy;
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};
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/* Helper that defaults empty hashes to the 0 hash. */
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Hash newHashAllowEmpty(std::string_view hashStr, std::optional<HashType> ht);
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/* Print a hash in base-16 if it's MD5, or base-32 otherwise. */
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std::string printHash16or32(const Hash & hash);
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/* Compute the hash of the given string. */
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Hash hashString(HashType ht, std::string_view s);
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/* Compute the hash of the given file. */
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Hash hashFile(HashType ht, const Path & path);
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/* Compute the hash of the given path. The hash is defined as
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(essentially) hashString(ht, dumpPath(path)). */
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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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/* Compress a hash to the specified number of bytes by cyclically
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XORing bytes together. */
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Hash compressHash(const Hash & hash, unsigned int newSize);
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/* Parse a string representing a hash type. */
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HashType parseHashType(std::string_view s);
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/* Will return nothing on parse error */
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std::optional<HashType> parseHashTypeOpt(std::string_view s);
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/* And the reverse. */
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std::string 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 write(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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