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+// file : libbutl/sha1.hxx -*- C++ -*-
+// license : MIT; see accompanying LICENSE file
+
+#pragma once
+
+#include <iosfwd> // istream
+#include <string>
+#include <cstddef> // size_t
+#include <cstdint>
+#include <cstring> // strlen()
+
+#include <libbutl/export.hxx>
+
+namespace butl
+{
+ // SHA1 checksum calculator.
+ //
+ // For a single chunk of data a sum can be obtained in one line, for
+ // example:
+ //
+ // cerr << sha1 ("123").string () << endl;
+ //
+ class LIBBUTL_SYMEXPORT sha1
+ {
+ public:
+ sha1 () {reset ();}
+
+ // Append binary data.
+ //
+ void
+ append (const void*, std::size_t);
+
+ sha1 (const void* b, std::size_t n): sha1 () {append (b, n);}
+
+ // Append string.
+ //
+ // Note that the hash includes the '\0' terminator. Failed that, a call
+ // with an empty string will be indistinguishable from no call at all.
+ //
+ void
+ append (const std::string& s) {append (s.c_str (), s.size () + 1);}
+
+ void
+ append (const char* s) {append (s, std::strlen (s) + 1);}
+
+ explicit
+ sha1 (const std::string& s): sha1 () {append (s);}
+
+ explicit
+ sha1 (const char* s): sha1 () {append (s);}
+
+ // Append stream.
+ //
+ // Note that currently the stream is expected to be bufstreambuf-based
+ // (e.g., ifdstream).
+ //
+ void
+ append (std::istream&);
+
+ explicit
+ sha1 (std::istream& i): sha1 () {append (i);}
+
+ // Check if any data has been hashed.
+ //
+ bool
+ empty () const {return empty_;}
+
+ // Reset to the default-constructed state.
+ //
+ void
+ reset ();
+
+ // Extract result.
+ //
+ // It can be obtained as either a 20-byte binary digest or as a 40-
+ // character hex-encoded C-string.
+ //
+ using digest_type = std::uint8_t[20];
+
+ const digest_type&
+ binary () const;
+
+ const char*
+ string () const;
+
+ std::string
+ abbreviated_string (std::size_t n) const
+ {
+ return std::string (string (), n < 40 ? n : 40);
+ }
+
+ private:
+ struct context // Note: identical to SHA1_CTX.
+ {
+ union {
+ std::uint8_t b8[20];
+ std::uint32_t b32[5];
+ } h;
+ union {
+ std::uint8_t b8[8];
+ std::uint64_t b64[1];
+ } c;
+ union {
+ std::uint8_t b8[64];
+ std::uint32_t b32[16];
+ } m;
+ std::uint8_t count;
+ };
+
+ union
+ {
+ mutable context ctx_;
+ mutable char buf_[sizeof (context)]; // Also used to store string rep.
+ };
+
+ mutable digest_type bin_;
+ mutable bool done_;
+ bool empty_;
+ };
+}