OXYGENHUB
◆ main openmsx / src / utils / sha1.hh
3.8 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
e8555c89 Andy McCall 1 
#ifndef SHA1_HH
2 
#define SHA1_HH
3
4 
#include "serialize.hh"
5 
#include "strCat.hh"
6
7 
#include <array>
8 
#include <cstdint>
9 
#include <ostream>
10 
#include <span>
11 
#include <string>
12 
#include <string_view>
13
14 
namespace openmsx {
15
16 
/** This class represents the result of a sha1 calculation (a 160-bit value).
17 
  * Objects of this class can be constructed from/converted to 40-digit hex
18 
  * string.
19 
  * We treat the value '000...00' (all zeros) special. This value can be used
20 
  * to indicate a null-sha1sum value (e.g. sha1 not yet calculated, or not
21 
  * meaningful). In theory it's possible this special value is the result of an
22 
  * actual sha1 calculation, but this has an _extremely_ low probability.
23 
  */
24 
class Sha1Sum
25 
{
26 
public:
27 
	struct UninitializedTag {};
28 
	explicit Sha1Sum(UninitializedTag) {}
29
30 
	// note: default copy and assign are ok
31 
	Sha1Sum();
32 
	/** Construct from string, throws when string is malformed. */
33 
	explicit Sha1Sum(std::string_view hex);
34 
	void parse(std::string_view hex);
35
36 
	/** Parse from a 40-character long buffer.
37 
	 * @pre 'str' points to a buffer of at least 40 characters
38 
	 * @throws MSXException if chars are not 0-9, a-f, A-F
39 
	 */
40 
	void parse40(std::span<const char, 40> str);
41
42 
	void toBuffer(std::span<char, 40> buf) const;
43 
	[[nodiscard]] std::string_view toString(std::span<char, 40> buf) const {
44 
		toBuffer(buf);
45 
		return {buf.data(), 40};
46 
	}
47
48 
	// Test or set 'null' value.
49 
	[[nodiscard]] bool empty() const;
50 
	void clear();
51
52 
	[[nodiscard]] constexpr bool operator==(const Sha1Sum&) const = default;
53 
	[[nodiscard]] constexpr auto operator<=>(const Sha1Sum&) const = default;
54
55 
	friend std::ostream& operator<<(std::ostream& os, const Sha1Sum& sum) {
56 
		std::array<char, 40> buf;
57 
		sum.toBuffer(buf);
58 
		os.write(buf.data(), 40);
59 
		return os;
60 
	}
61
62 
	// We used to serialize sha1 as a string.
63 
	// * For on-disk formats we want to continue to do that.
64 
	// * Fos in-memory formats we can skip that formatting/parsing step
65 
	void serialize(MemInputArchive& ar, unsigned /*version*/) {
66 
		ar.serialize("a", a);
67 
	}
68 
	void serialize(MemOutputArchive& ar, unsigned /*version*/) const {
69 
		ar.serialize("a", a);
70 
	}
71 
	void serialize(XmlInputArchive& ar, unsigned /*version*/) {
72 
		std::string s;
73 
		ar.load(s); // no label
74 
		if (s.empty()) {
75 
			clear();
76 
		} else {
77 
			parse(s);
78 
		}
79 
	}
80 
	void serialize(XmlOutputArchive& ar, unsigned /*version*/) const {
81 
		if (empty()) return;
82 
		std::array<char, 40> buf;
83 
		toBuffer(buf);
84 
		std::string_view s(buf.data(), 40);
85 
		ar.save(s);
86 
	}
87
88 
private:
89 
	std::array<uint32_t, 5> a;
90 
	friend class SHA1;
91 
};
92
93
94 
/** Helper class to perform a sha1 calculation.
95 
  * Basic usage:
96 
  *  - construct a SHA1 object
97 
  *  - repeatedly call update()
98 
  *  - call digest() to get the result
99 
  * Alternatively, use calc() if all data can be passed at once (IOW when there
100 
  * would be exactly one call to update() in the recipe above).
101 
  */
102 
class SHA1
103 
{
104 
public:
105 
	SHA1();
106
107 
	/** Incrementally calculate the hash value. */
108 
	void update(std::span<const uint8_t> data);
109
110 
	/** Get the final hash. After this method is called, calls to update()
111 
	  * are invalid. */
112 
	[[nodiscard]] Sha1Sum digest();
113
114 
	/** Easier to use interface, if you can pass all data in one go. */
115 
	[[nodiscard]] static Sha1Sum calc(std::span<const uint8_t> data);
116
117 
private:
118 
	void transform(std::span<const uint8_t, 64> buffer);
119 
	void finalize();
120
121 
private:
122 
	uint64_t m_count = 0; // in bytes (sha1 reference implementation counts in bits)
123 
	Sha1Sum m_state;
124 
	std::array<uint8_t, 64> m_buffer;
125 
	bool m_finalized = false;
126 
};
127
128 
} // namespace openmsx
129
130 
// For efficient strCat() (without Sha1Sum::toString())
131 
template<> struct strCatImpl::ConcatUnit<openmsx::Sha1Sum>
132 
{
133 
	explicit ConcatUnit(openmsx::Sha1Sum sum_)
134 
		: sum(sum_) {}
135
136 
	[[nodiscard]] size_t size() const { return 40; }
137
138 
	[[nodiscard]] char* copy(char* dst) const {
139 
		sum.toBuffer(std::span<char, 40>(dst, 40));
140 
		return dst + 40;
141 
	}
142
143 
private:
144 
	openmsx::Sha1Sum sum;
145 
};
146
147 
#endif