nix-hash: support base-64 and SRI format

doc/manual/src/command-ref/nix-hash.md

@@ -6,9 +6,7 @@
 
 `nix-hash` [`--flat`] [`--base32`] [`--truncate`] [`--type` *hashAlgo*] *path…*
 
-`nix-hash` `--to-base16` *hash…*
-
-`nix-hash` `--to-base32` *hash…*
+`nix-hash` [`--to-base16`|`--to-base32`|`--to-base64`|`--to-sri`] [`--type` *hashAlgo*] *hash…*
 
 # Description
 
@@ -40,6 +38,15 @@ md5sum`.
     This base-32 representation is more compact and can be used in Nix
     expressions (such as in calls to `fetchurl`).
 
+  - `--base64`\
+    Similar to --base32, but print the hash in a base-64 representation,
+    which is more compact than the base-32 one.
+
+  - `--sri`\
+    Print the hash in SRI format with base-64 encoding.
+    The type of hash algorithm will be prepended to the hash string,
+    followed by a hyphen (-) and the base-64 hash body.
+
   - `--truncate`\
     Truncate hashes longer than 160 bits (such as SHA-256) to 160 bits.
 
@@ -55,6 +62,14 @@ md5sum`.
     Don’t hash anything, but convert the hexadecimal hash representation
     *hash* to base-32.
 
+  - `--to-base64`\
+    Don’t hash anything, but convert the hexadecimal hash representation
+    *hash* to base-64.
+
+  - `--to-sri`\
+    Don’t hash anything, but convert the hexadecimal hash representation
+    *hash* to SRI.
+
 # Examples
 
 Computing the same hash as `nix-prefetch-url`:
@@ -91,12 +106,21 @@ $ nix-hash --type sha256 --flat test/world
 5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03
 ```
 
-Converting between hexadecimal and base-32:
+Converting between hexadecimal, base-32, base-64, and SRI:
 
 ```console
 $ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
 
 $ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
+
+$ nix-hash --type sha1 --to-base64 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
+5P2Lpfe76upazon+ECVVNs1g2rY=
+
+$ nix-hash --type sha1 --to-sri nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
+sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
+
+$ nix-hash --to-base16 sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
+e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
 ```

src/nix/hash.cc

@@ -161,11 +161,11 @@ static auto rCmdHash = registerCommand<CmdHash>("hash");
 /* Legacy nix-hash command. */
 static int compatNixHash(int argc, char * * argv)
 {
-    HashType ht = htMD5;
+    std::optional<HashType> ht;
     bool flat = false;
-    bool base32 = false;
+    Base base = Base16;
     bool truncate = false;
-    enum { opHash, opTo32, opTo16 } op = opHash;
+    enum { opHash, opTo } op = opHash;
     std::vector<std::string> ss;
 
     parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
@@ -174,14 +174,30 @@ static int compatNixHash(int argc, char * * argv)
         else if (*arg == "--version")
             printVersion("nix-hash");
         else if (*arg == "--flat") flat = true;
-        else if (*arg == "--base32") base32 = true;
+        else if (*arg == "--base32") base = Base32;
+        else if (*arg == "--base64") base = Base64;
+        else if (*arg == "--sri") base = SRI;
         else if (*arg == "--truncate") truncate = true;
         else if (*arg == "--type") {
             std::string s = getArg(*arg, arg, end);
             ht = parseHashType(s);
         }
-        else if (*arg == "--to-base16") op = opTo16;
-        else if (*arg == "--to-base32") op = opTo32;
+        else if (*arg == "--to-base16") {
+            op = opTo;
+            base = Base16;
+        }
+        else if (*arg == "--to-base32") {
+            op = opTo;
+            base = Base32;
+        }
+        else if (*arg == "--to-base64") {
+            op = opTo;
+            base = Base64;
+        }
+        else if (*arg == "--to-sri") {
+            op = opTo;
+            base = SRI;
+        }
         else if (*arg != "" && arg->at(0) == '-')
             return false;
         else
@@ -191,17 +207,18 @@ static int compatNixHash(int argc, char * * argv)
 
     if (op == opHash) {
         CmdHashBase cmd(flat ? FileIngestionMethod::Flat : FileIngestionMethod::Recursive);
-        cmd.ht = ht;
-        cmd.base = base32 ? Base32 : Base16;
+        if (!ht.has_value()) ht = htMD5;
+        cmd.ht = ht.value();
+        cmd.base = base;
         cmd.truncate = truncate;
         cmd.paths = ss;
         cmd.run();
     }
 
     else {
-        CmdToBase cmd(op == opTo32 ? Base32 : Base16);
+        CmdToBase cmd(base);
         cmd.args = ss;
-        cmd.ht = ht;
+        if (ht.has_value()) cmd.ht = ht;
         cmd.run();
     }