From e8186085e07104d4b844208613c2d704b5b57dec Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 13 Mar 2017 14:40:15 +0100
Subject: [PATCH] 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.
---
 Makefile.config.in         |  1 +
 configure.ac               |  1 +
 release.nix                |  8 ++++++--
 shell.nix                  |  3 ++-
 src/libstore/download.cc   | 21 +++++++++++++++++++--
 src/libutil/compression.cc |  7 +++++++
 src/libutil/local.mk       |  2 ++
 7 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/Makefile.config.in b/Makefile.config.in
index d4953b521..fccf63b36 100644
--- a/Makefile.config.in
+++ b/Makefile.config.in
@@ -14,6 +14,7 @@ LIBLZMA_LIBS = @LIBLZMA_LIBS@
 SQLITE3_LIBS = @SQLITE3_LIBS@
 bash = @bash@
 bindir = @bindir@
+bro = @bro@
 datadir = @datadir@
 datarootdir = @datarootdir@
 docdir = @docdir@
diff --git a/configure.ac b/configure.ac
index 34dcd6b2a..21ca78af0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -128,6 +128,7 @@ NEED_PROG(gzip, gzip)
 NEED_PROG(xz, xz)
 AC_PATH_PROG(dot, dot)
 AC_PATH_PROG(pv, pv, pv)
+NEED_PROG(bro, bro)
 
 
 # Test that Perl has the open/fork feature (Perl 5.8.0 and beyond).
diff --git a/release.nix b/release.nix
index e61e81bdf..a266af7c2 100644
--- a/release.nix
+++ b/release.nix
@@ -24,7 +24,8 @@ let
         inherit officialRelease;
 
         buildInputs =
-          [ curl bison flex perl libxml2 libxslt bzip2 xz
+          [ curl bison flex perl libxml2 libxslt
+            bzip2 xz brotli
             pkgconfig sqlite libsodium boehmgc
             docbook5 docbook5_xsl
             autoconf-archive
@@ -73,7 +74,10 @@ let
         src = tarball;
 
         buildInputs =
-          [ curl perl bzip2 xz openssl pkgconfig sqlite boehmgc ]
+          [ curl perl
+            bzip2 xz brotli
+            openssl pkgconfig sqlite boehmgc
+          ]
           ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium
           ++ lib.optional (stdenv.isLinux || stdenv.isDarwin)
             (aws-sdk-cpp.override {
diff --git a/shell.nix b/shell.nix
index 4c1608230..df0ad01df 100644
--- a/shell.nix
+++ b/shell.nix
@@ -6,7 +6,8 @@ with import <nixpkgs> {};
   name = "nix";
 
   buildInputs =
-    [ curl bison flex perl libxml2 libxslt bzip2 xz
+    [ curl bison flex perl libxml2 libxslt
+      bzip2 xz brotli
       pkgconfig sqlite libsodium boehmgc
       docbook5 docbook5_xsl
       autoconf-archive
diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index 6567a4dc4..d9b8fbc08 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 a3bbb5170..723b072af 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 cac5c8795..0721b21c2 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)\"