refactor(3p/nix): Remove custom base64 implementation r/1462

Replace the custom, rather questionable base64 implementation with
absl::Base64{Une,E}scape. To make sure that the custom implementation
was doing the same thing I've also added a test covering
nix::Hash::to_string, which was one function that used it - the test
passed prior to the replacement, and continued to pass afterwards.

The previous base64Decode function threw an exception on failure - to
avoid going too far down the rabbit hole I've replicated that
functionality at all call sites, but this should be replaced with more
sensible error handling such as StatusOr eventually.

Also, before this change:

    ❯ nix eval -f . users.tazjin.emacs.outPath
    "/nix/store/g6ri2q8nra96ix20bcsc734r1yyaylb1-tazjins-emacs"

And after:

    ❯ ./result/bin/nix eval -f . users.tazjin.emacs.outPath
    "/nix/store/g6ri2q8nra96ix20bcsc734r1yyaylb1-tazjins-emacs"

Change-Id: Id292ffbb82fe808f3f1b34670afbe7b8c13ad615
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1385
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

1 files changed, 9 insertions, 2 deletions

diff --git a/third_party/nix/src/libutil/hash.cc b/third_party/nix/src/libutil/hash.cc
index 5c2ddc4bda8e..0d80972cceda 100644
--- a/third_party/nix/src/libutil/hash.cc
+++ b/third_party/nix/src/libutil/hash.cc
@@ -3,6 +3,7 @@
 #include <cstring>
 #include <iostream>
 
+#include <absl/strings/escaping.h>
 #include <fcntl.h>
 #include <openssl/md5.h>
 #include <openssl/sha.h>
@@ -117,7 +118,9 @@ std::string Hash::to_string(Base base, bool includeType) const {
       break;
     case Base64:
     case SRI:
-      s += base64Encode(std::string((const char*)hash, hashSize));
+      std::string b64;
+      absl::Base64Escape(std::string((const char*)hash, hashSize), &b64);
+      s += b64;
       break;
   }
   return s;
@@ -201,7 +204,11 @@ Hash::Hash(const std::string& s, HashType type) : type(type) {
   }
 
   else if (isSRI || size == base64Len()) {
-    auto d = base64Decode(std::string(s, pos));
+    std::string d;
+    if (!absl::Base64Unescape(std::string(s, pos), &d)) {
+      // TODO(grfn): replace this with StatusOr
+      throw Error("Invalid Base64");
+    }
     if (d.size() != hashSize) {
       throw BadHash("invalid %s hash '%s'", isSRI ? "SRI" : "base-64", s);
     }