ENH: allow '_' prefix when reading/writing SHA1Digest

- the resulting SHA1 can be written and parsed directly
  without any ambiguities when it starts with a digit
  eg, SHA1: _024ea2fa570968069f52f55aa47ee82ac417f5f6

- provide same optional prefix functionality in conversion to string
  and in comparison with strings

- add SHA1Digest::null

src/OpenFOAM/primitives/hashes/SHA1/SHA1.C

@@ -241,10 +241,10 @@ Foam::SHA1::processBlock(const void *data, size_t len)
     while (words < endp)
     {
         uint32_t tm;
-        for (int t = 0; t < 16; t++)
+        for (int t = 0; t < 16; ++t)
         {
             x[t] = swapBytes(*words);
-            words++;
+            ++words;
         }
 
         R( a, b, c, d, e, F1, K1, x[ 0] );

src/OpenFOAM/primitives/hashes/SHA1/SHA1Digest.C

@@ -30,6 +30,8 @@ License
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
+const Foam::SHA1Digest Foam::SHA1Digest::null;
+
 //! \cond fileScope
 static const char hexChars[] = "0123456789abcdef";
 //! \endcond
@@ -40,12 +42,18 @@ static const char hexChars[] = "0123456789abcdef";
 unsigned char Foam::SHA1Digest::readHexDigit(Istream& is)
 {
     // Takes into account that 'a' (or 'A') is 10
-    static const label alphaOffset = toupper('A') - 10;
+    static const int alphaOffset = toupper('A') - 10;
     // Takes into account that '0' is 0
-    static const label zeroOffset = int('0');
+    static const int zeroOffset = int('0');
 
+
+    // silently ignore leading or intermediate '_'
     char c = 0;
+    do
+    {
         is.read(c);
+    }
+    while (c == '_');
 
     if (!isxdigit(c))
     {
@@ -101,12 +109,21 @@ bool Foam::SHA1Digest::empty() const
 }
 
 
-std::string Foam::SHA1Digest::str() const
+std::string Foam::SHA1Digest::str(const bool prefixed) const
 {
     std::string buf;
-    buf.resize(length*2);
-
     unsigned nChar = 0;
+
+    if (prefixed)
+    {
+        buf.resize(1 + length*2);
+        buf[nChar++] = '_';
+    }
+    else
+    {
+        buf.resize(length*2);
+    }
+
     for (unsigned i = 0; i < length; ++i)
     {
         buf[nChar++] = hexChars[((v_[i] >> 4) & 0xF)];
@@ -117,6 +134,24 @@ std::string Foam::SHA1Digest::str() const
 }
 
 
+Foam::Ostream& Foam::SHA1Digest::write(Ostream& os, const bool prefixed) const
+{
+    if (prefixed)
+    {
+        os.write('_');
+    }
+
+    for (unsigned i = 0; i < length; ++i)
+    {
+        os.write(hexChars[((v_[i] >> 4) & 0xF)]);
+        os.write(hexChars[(v_[i] & 0xF)]);
+    }
+
+    os.check("SHA1Digest::write(Ostream&, const bool)");
+    return os;
+}
+
+
 // * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * * //
 
 bool Foam::SHA1Digest::operator==(const SHA1Digest& rhs) const
@@ -141,21 +176,26 @@ bool Foam::SHA1Digest::operator==(const std::string& hexdigits) const
         return empty();
     }
 
+    // skip possible '_' prefix
+    unsigned charI = 0;
+    if (hexdigits[0] == '_')
+    {
+        ++charI;
+    }
+
     // incorrect length - can never match
-    if (hexdigits.size() != length*2)
+    if (hexdigits.size() != charI + length*2)
     {
         return false;
     }
 
-    for (unsigned i = 0, charI = 0; i < length; ++i, charI += 2)
+    for (unsigned i = 0; i < length; ++i)
     {
         const char c1 = hexChars[((v_[i] >> 4) & 0xF)];
         const char c2 = hexChars[(v_[i] & 0xF)];
 
-        if (c1 != hexdigits[charI] || c2 != hexdigits[charI+1])
+        if (c1 != hexdigits[charI++]) return false;
-        {
+        if (c2 != hexdigits[charI++]) return false;
-            return false;
-        }
     }
 
     return true;
@@ -170,21 +210,26 @@ bool Foam::SHA1Digest::operator==(const char* hexdigits) const
         return empty();
     }
 
+    // skip possible '_' prefix
+    unsigned charI = 0;
+    if (hexdigits[0] == '_')
+    {
+        ++charI;
+    }
+
     // incorrect length - can never match
-    if (strlen(hexdigits) != length*2)
+    if (strlen(hexdigits) != charI + length*2)
     {
         return false;
     }
 
-    for (unsigned i = 0, charI = 0; i < length; ++i, charI += 2)
+    for (unsigned i = 0; i < length; ++i)
     {
         const char c1 = hexChars[((v_[i] >> 4) & 0xF)];
         const char c2 = hexChars[(v_[i] & 0xF)];
 
-        if (c1 != hexdigits[charI] || c2 != hexdigits[charI+1])
+        if (c1 != hexdigits[charI++]) return false;
-        {
+        if (c2 != hexdigits[charI++]) return false;
-            return false;
-        }
     }
 
     return true;
@@ -230,16 +275,7 @@ Foam::Istream& Foam::operator>>(Istream& is, SHA1Digest& dig)
 
 Foam::Ostream& Foam::operator<<(Ostream& os, const SHA1Digest& dig)
 {
-    const unsigned char *v = dig.v_;
+    return dig.write(os);
-
-    for (unsigned i = 0; i < dig.length; ++i)
-    {
-        os.write(hexChars[((v[i] >> 4) & 0xF)]);
-        os.write(hexChars[(v[i] & 0xF)]);
-    }
-
-    os.check("Ostream& operator<<(Ostream&, const SHA1Digest&)");
-    return os;
 }
 
 

src/OpenFOAM/primitives/hashes/SHA1/SHA1Digest.H

@@ -46,8 +46,8 @@ namespace Foam
 {
 
 // Forward declaration of classes
-class Ostream;
 class Istream;
+class Ostream;
 
 // Forward declaration of friend functions and operators
 class SHA1;
@@ -65,23 +65,40 @@ class SHA1Digest
 public:
     friend class SHA1;
 
-    //- The length of the digest contents
+    // Static data members
+
+        //- The length of the (uncoded) digest contents
         static const unsigned length = 20;
 
+        //- A null digest (ie, all zero)
+        static const SHA1Digest null;
+
+
+    // Constructors
+
         //- Construct a zero digest
         SHA1Digest();
 
         //- Construct read a digest
         SHA1Digest(Istream&);
 
+
+    // Member Functions
+
         //- Reset the digest to zero
         void clear();
 
         //- Return true if the digest is empty (ie, all zero).
         bool empty() const;
 
-    //- Return string representation
+        //- Return (40-byte) text representation, optionally with '_' prefix
-    std::string str() const;
+        std::string str(const bool prefixed=false) const;
+
+        //- Write (40-byte) text representation, optionally with '_' prefix
+        Ostream& write(Ostream&, const bool prefixed=false) const;
+
+
+    // Member Operators
 
         //- Equality operator
         bool operator==(const SHA1Digest&) const;
@@ -89,11 +106,13 @@ public:
         //- Compare to (40-byte) text representation (eg, from sha1sum)
         //  An %empty string is equivalent to
         //  "0000000000000000000000000000000000000000"
+        //  The hexdigits may optionally start with a '_' prefix
         bool operator==(const std::string& hexdigits) const;
 
         //- Compare to (40-byte) text representation (eg, from sha1sum)
         //  A %null or %empty string is equivalent to
         //  "0000000000000000000000000000000000000000"
+        //  The hexdigits may optionally start with a '_' prefix
         bool operator==(const char* hexdigits) const;
 
 
@@ -107,14 +126,27 @@ public:
         bool operator!=(const char* hexdigits) const;
 
 
-    friend Ostream& operator<<(Ostream&, const SHA1Digest&);
+
+
+    // IOstream Operators
+
+        //- Read (40-byte) text representation
+        //  Since leading and intermediate underscores are skipped, a '_' can
+        //  be prefixed to the text representation to use an unquoted
+        //  SHA1Digest without parsing ambiguities as a number.
         friend Istream& operator>>(Istream&, SHA1Digest&);
 
+        //- Write (40-byte) text representation, unquoted and without prefix
+        friend Ostream& operator<<(Ostream&, const SHA1Digest&);
+
+
 private:
+    // Private data
 
         //- The digest contents
         unsigned char v_[length];
 
+        //- Read hexadecimal value, ignoring leading or intermediate '_'
         static unsigned char readHexDigit(Istream&);
 };