nix-hash: support base-64 and SRI format

Add the --base64 and --sri flags for the Base64 and SRI format output.

Add the --base16 flag to explicitly specify the hexadecimal format.

Add the --to-base64 and --to-sri flag to convert a hash to the above
mentioned 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
 
@@ -35,11 +33,23 @@ md5sum`.
     The result is identical to that produced by the GNU commands
     `md5sum` and `sha1sum`.
 
+  - `--base16`\
+    Print the hash in a hexadecimal representation (default).
+
   - `--base32`\
     Print the hash in a base-32 representation rather than hexadecimal.
     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 +65,14 @@ 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`:
@@ -81,22 +99,40 @@ $ nix-store --dump test/ | md5sum (for comparison)
 $ nix-hash --type sha1 test/
 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
 
+$ nix-hash --type sha1 --base16 test/
+e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
+
 $ nix-hash --type sha1 --base32 test/
 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
 
+$ nix-hash --type sha1 --base64 test/
+5P2Lpfe76upazon+ECVVNs1g2rY=
+
+$ nix-hash --type sha1 --sri test/
+sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
+
 $ nix-hash --type sha256 --flat test/
 error: reading file `test/': Is a directory
 
 $ 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
 ```

doc/manual/src/release-notes/rl-next.md

@@ -4,6 +4,19 @@
   passed the `--stdin` flag. This is primarily useful when you have a large amount of paths which
   exceed the OS arg limit.
 
+* The `builtins.readDir` function has been optimized when encountering not-yet-known
+  file types from POSIX's `readdir`. In such cases the type of each file is/was
+  discovered by making multiple syscalls. This change makes these operations
+  lazy such that these lookups will only be performed if the attribute is used.
+  This optimization affects a minority of filesystems and operating systems.
+
+* The `nix-hash` command now supports Base64 and SRI. Use the flags `--base64`
+  or `--sri` to specify the format of output hash as Base64 or SRI, and `--to-base64`
+  or `--to-sri` to convert a hash to Base64 or SRI format, respectively.
+
+  As the choice of hash formats is no longer binary, the `--base16` flag is also added
+  to explicitly specify the Base16 format, which is still the default.
+
 * The special handling of an [installable](../command-ref/new-cli/nix.md#installables) with `.drv` suffix being interpreted as all of the given [store derivation](../glossary.md#gloss-store-derivation)'s output paths is removed, and instead taken as the literal store path that it represents.
 
   The new `^` syntax for store paths introduced in Nix 2.13 allows explicitly referencing output paths of a derivation.

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 +174,31 @@ 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 == "--base16") base = Base16;
+        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 +208,18 @@ 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();
     }
 

tests/hash.sh

@@ -2,9 +2,14 @@ source common.sh
 
 try () {
     printf "%s" "$2" > $TEST_ROOT/vector
+    hash="$(nix-hash --flat ${FORMAT_FLAG-} --type "$1" "$TEST_ROOT/vector")"
+    if ! (( "${NO_TEST_CLASSIC-}" )) && test "$hash" != "$3"; then
+        echo "try nix-hash: hash $1, expected $3, got $hash"
+        exit 1
+    fi
     hash="$(nix hash file ${FORMAT_FLAG-} --type "$1" "$TEST_ROOT/vector")"
-    if test "$hash" != "$3"; then
-        echo "hash $1, expected $3, got $hash"
+    if ! (( "${NO_TEST_NIX_COMMAND-}" )) && test "$hash" != "$3"; then
+        echo "try nix hash: hash $1, expected $3, got $hash"
         exit 1
     fi
 }
@@ -42,7 +47,13 @@ try sha512 "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq" "sha512-IE
 try sha256 "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq" "sha256-JI1qYdIGOLjlwCaTDD5gOaM85Flk/yFn9uzt1BnbBsE="
 unset FORMAT_FLAG
 
+NO_TEST_NIX_COMMAND=1 # nix-hash [--flat] defaults to the Base16 format
+try sha512 "abc" "ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f"
+unset NO_TEST_NIX_COMMAND
+
+NO_TEST_CLASSIC=1 # nix hash [file|path] defaults to the SRI format
 try sha512 "abc" "sha512-3a81oZNherrMQXNJriBBMRLm+k6JqX6iCp7u5ktV05ohkpkqJ0/BqDa6PCOj/uu9RU1EI2Q86A4qmslPpUyknw=="
+unset NO_TEST_CLASSIC
 
 try2 () {
     hash=$(nix-hash --type "$1" $TEST_ROOT/hash-path)
@@ -74,8 +85,12 @@ try2 md5 "f78b733a68f5edbdf9413899339eaa4a"
 
 # Conversion.
 try3() {
+    h64=$(nix-hash --type "$1" --to-base64 "$2")
+    [ "$h64" = "$4" ]
     h64=$(nix hash to-base64 --type "$1" "$2")
     [ "$h64" = "$4" ]
+    sri=$(nix-hash --type "$1" --to-sri "$2")
+    [ "$sri" = "$1-$4" ]
     sri=$(nix hash to-sri --type "$1" "$2")
     [ "$sri" = "$1-$4" ]
     h32=$(nix-hash --type "$1" --to-base32 "$2")