1 files changed, 47 insertions, 22 deletions

diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index 460d479a3..c8fcdfed0 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -4,6 +4,7 @@
 #include <openssl/md5.h>
 #include <openssl/sha.h>
 
+#include "args.hh"
 #include "hash.hh"
 #include "archive.hh"
 #include "util.hh"
@@ -18,11 +19,13 @@ namespace nix {
 
 void Hash::init()
 {
-    if (type == htMD5) hashSize = md5HashSize;
-    else if (type == htSHA1) hashSize = sha1HashSize;
-    else if (type == htSHA256) hashSize = sha256HashSize;
-    else if (type == htSHA512) hashSize = sha512HashSize;
-    else abort();
+    if (!type) abort();
+    switch (*type) {
+    case htMD5: hashSize = md5HashSize; break;
+    case htSHA1: hashSize = sha1HashSize; break;
+    case htSHA256: hashSize = sha256HashSize; break;
+    case htSHA512: hashSize = sha512HashSize; break;
+    }
     assert(hashSize <= maxHashSize);
     memset(hash, 0, maxHashSize);
 }
@@ -102,11 +105,18 @@ string printHash16or32(const Hash & hash)
 }
 
 
+HashType assertInitHashType(const Hash & h) {
+    if (h.type)
+        return *h.type;
+    else
+        abort();
+}
+
 std::string Hash::to_string(Base base, bool includeType) const
 {
     std::string s;
     if (base == SRI || includeType) {
-        s += printHashType(type);
+        s += printHashType(assertInitHashType(*this));
         s += base == SRI ? '-' : ':';
     }
     switch (base) {
@@ -124,8 +134,10 @@ std::string Hash::to_string(Base base, bool includeType) const
     return s;
 }
 
+Hash::Hash(std::string_view s, HashType type) : Hash(s, std::optional { type }) { }
+Hash::Hash(std::string_view s) : Hash(s, std::optional<HashType>{}) { }
 
-Hash::Hash(std::string_view s, HashType type)
+Hash::Hash(std::string_view s, std::optional<HashType> type)
     : type(type)
 {
     size_t pos = 0;
@@ -136,17 +148,17 @@ Hash::Hash(std::string_view s, HashType type)
         sep = s.find('-');
         if (sep != string::npos) {
             isSRI = true;
-        } else if (type == htUnknown)
+        } else if (! type)
             throw BadHash("hash '%s' does not include a type", s);
     }
 
     if (sep != string::npos) {
         string hts = string(s, 0, sep);
         this->type = parseHashType(hts);
-        if (this->type == htUnknown)
+        if (!this->type)
             throw BadHash("unknown hash type '%s'", hts);
-        if (type != htUnknown && type != this->type)
-            throw BadHash("hash '%s' should have type '%s'", s, printHashType(type));
+        if (type && type != this->type)
+            throw BadHash("hash '%s' should have type '%s'", s, printHashType(*type));
         pos = sep + 1;
     }
 
@@ -202,13 +214,15 @@ Hash::Hash(std::string_view s, HashType type)
     }
 
     else
-        throw BadHash("hash '%s' has wrong length for hash type '%s'", s, printHashType(type));
+        throw BadHash("hash '%s' has wrong length for hash type '%s'", s, printHashType(*type));
 }
 
-Hash newHashAllowEmpty(std::string hashStr, HashType ht)
+Hash newHashAllowEmpty(std::string hashStr, std::optional<HashType> ht)
 {
     if (hashStr.empty()) {
-        Hash h(ht);
+        if (!ht)
+            throw BadHash("empty hash requires explicit hash type");
+        Hash h(*ht);
         warn("found empty hash, assuming '%s'", h.to_string(SRI, true));
         return h;
     } else
@@ -328,24 +342,35 @@ Hash compressHash(const Hash & hash, unsigned int newSize)
 }
 
 
-HashType parseHashType(const string & s)
+std::optional<HashType> parseHashTypeOpt(const string & s)
 {
     if (s == "md5") return htMD5;
     else if (s == "sha1") return htSHA1;
     else if (s == "sha256") return htSHA256;
     else if (s == "sha512") return htSHA512;
-    else return htUnknown;
+    else return std::optional<HashType> {};
 }
 
+HashType parseHashType(const string & s)
+{
+    auto opt_h = parseHashTypeOpt(s);
+    if (opt_h)
+        return *opt_h;
+    else
+        throw UsageError("unknown hash algorithm '%1%'", s);
+}
 
 string printHashType(HashType ht)
 {
-    if (ht == htMD5) return "md5";
-    else if (ht == htSHA1) return "sha1";
-    else if (ht == htSHA256) return "sha256";
-    else if (ht == htSHA512) return "sha512";
-    else abort();
+    switch (ht) {
+    case htMD5: return "md5"; break;
+    case htSHA1: return "sha1"; break;
+    case htSHA256: return "sha256"; break;
+    case htSHA512: return "sha512"; break;
+    }
+    // illegal hash type enum value internally, as opposed to external input
+    // which should be validated with nice error message.
+    abort();
 }
 
-
 }