Add support for brotli compression

Build logs on cache.nixos.org are compressed using Brotli (since this
allows them to be decompressed automatically by Chrome and Firefox),
so it's handy if "nix log" can decompress them.

3 files changed, 28 insertions, 2 deletions

diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index 6567a4dc4754..d9b8fbc08080 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -5,6 +5,8 @@
 #include "store-api.hh"
 #include "archive.hh"
 #include "s3.hh"
+#include "compression.hh"
+
 #ifdef ENABLE_S3
 #include <aws/core/client/ClientConfiguration.h>
 #endif
@@ -70,6 +72,8 @@ struct CurlDownloader : public Downloader
 
         struct curl_slist * requestHeaders = 0;
 
+        std::string encoding;
+
         DownloadItem(CurlDownloader & downloader, const DownloadRequest & request)
             : downloader(downloader), request(request)
         {
@@ -127,6 +131,7 @@ struct CurlDownloader : public Downloader
                 auto ss = tokenizeString<vector<string>>(line, " ");
                 status = ss.size() >= 2 ? ss[1] : "";
                 result.data = std::make_shared<std::string>();
+                encoding = "";
             } else {
                 auto i = line.find(':');
                 if (i != string::npos) {
@@ -142,7 +147,8 @@ struct CurlDownloader : public Downloader
                             debug(format("shutting down on 200 HTTP response with expected ETag"));
                             return 0;
                         }
-                    }
+                    } else if (name == "content-encoding")
+                        encoding = trim(string(line, i + 1));;
                 }
             }
             return realSize;
@@ -268,7 +274,18 @@ struct CurlDownloader : public Downloader
             {
                 result.cached = httpStatus == 304;
                 done = true;
-                callSuccess(success, failure, const_cast<const DownloadResult &>(result));
+
+                /* Ad hoc support for brotli, since curl doesn't do
+                   this yet. */
+                try {
+                    if (encoding == "br")
+                        result.data = decompress("br", *result.data);
+
+                    callSuccess(success, failure, const_cast<const DownloadResult &>(result));
+                } catch (...) {
+                    done = true;
+                    callFailure(failure, std::current_exception());
+                }
             } else {
                 Error err =
                     (httpStatus == 404 || code == CURLE_FILE_COULDNT_READ_FILE) ? NotFound :
diff --git a/src/libutil/compression.cc b/src/libutil/compression.cc
index a3bbb5170d9f..723b072af968 100644
--- a/src/libutil/compression.cc
+++ b/src/libutil/compression.cc
@@ -89,6 +89,11 @@ static ref<std::string> decompressBzip2(const std::string & in)
     }
 }
 
+static ref<std::string> decompressBrotli(const std::string & in)
+{
+    return make_ref<std::string>(runProgram(BRO, true, {"-d"}, in));
+}
+
 ref<std::string> compress(const std::string & method, const std::string & in)
 {
     StringSink ssink;
@@ -106,6 +111,8 @@ ref<std::string> decompress(const std::string & method, const std::string & in)
         return decompressXZ(in);
     else if (method == "bzip2")
         return decompressBzip2(in);
+    else if (method == "br")
+        return decompressBrotli(in);
     else
         throw UnknownCompressionMethod(format("unknown compression method ‘%s’") % method);
 }
diff --git a/src/libutil/local.mk b/src/libutil/local.mk
index cac5c8795db7..0721b21c2089 100644
--- a/src/libutil/local.mk
+++ b/src/libutil/local.mk
@@ -9,3 +9,5 @@ libutil_SOURCES := $(wildcard $(d)/*.cc)
 libutil_LDFLAGS = $(LIBLZMA_LIBS) -lbz2 -pthread $(OPENSSL_LIBS)
 
 libutil_LIBS = libformat
+
+libutil_CXXFLAGS = -DBRO=\"$(bro)\"