nix-channel: implement in c++

.gitignore

@@ -38,7 +38,6 @@ Makefile.config
 /scripts/nix-switch
 /scripts/nix-collect-garbage
 /scripts/nix-prefetch-url
-/scripts/nix-channel
 /scripts/nix-build
 /scripts/nix-copy-closure
 /scripts/NixConfig.pm
@@ -73,6 +72,9 @@ Makefile.config
 # /src/nix-daemon/
 /src/nix-daemon/nix-daemon
 
+# /src/nix-channel/
+/src/nix-channel/nix-channel
+
 # /src/download-via-ssh/
 /src/download-via-ssh/download-via-ssh
 

Makefile

@@ -12,6 +12,7 @@ makefiles = \
   src/nix-daemon/local.mk \
   src/nix-collect-garbage/local.mk \
   src/nix-prefetch-url/local.mk \
+  src/nix-channel/local.mk \
   perl/local.mk \
   scripts/local.mk \
   corepkgs/local.mk \

scripts/local.mk

@@ -1,6 +1,5 @@
 nix_bin_scripts := \
   $(d)/nix-build \
-  $(d)/nix-channel \
   $(d)/nix-copy-closure \
   $(d)/nix-push
 

src/libstore/download.cc

@@ -31,7 +31,7 @@ struct CurlDownloader : public Downloader
 {
     CURL * curl;
     ref<std::string> data;
-    string etag, status, expectedETag;
+    string etag, status, expectedETag, effectiveUrl;
 
     struct curl_slist * requestHeaders;
 
@@ -199,6 +199,11 @@ struct CurlDownloader : public Downloader
                 % url % curl_easy_strerror(res) % res);
         }
 
+        char *effectiveUrlCStr;
+        curl_easy_getinfo(curl, CURLINFO_EFFECTIVE_URL, &effectiveUrlCStr);
+        if (effectiveUrlCStr)
+            effectiveUrl = effectiveUrlCStr;
+
         if (httpStatus == 304) return false;
 
         return true;
@@ -212,6 +217,7 @@ struct CurlDownloader : public Downloader
             res.data = data;
         } else
             res.cached = true;
+        res.effectiveUrl = effectiveUrl;
         res.etag = etag;
         return res;
     }
@@ -223,6 +229,12 @@ ref<Downloader> makeDownloader()
 }
 
 Path Downloader::downloadCached(ref<Store> store, const string & url_, bool unpack, const Hash & expectedHash)
+{
+    string ignored;
+    return downloadCached(store, url_, unpack, ignored, expectedHash);
+}
+
+Path Downloader::downloadCached(ref<Store> store, const string & url_, bool unpack, string & effectiveUrl, const Hash & expectedHash)
 {
     auto url = resolveUri(url_);
 
@@ -259,9 +271,10 @@ Path Downloader::downloadCached(ref<Store> store, const string & url_, bool unpa
             auto ss = tokenizeString<vector<string>>(readFile(dataFile), "\n");
             if (ss.size() >= 3 && ss[0] == url) {
                 time_t lastChecked;
-                if (string2Int(ss[2], lastChecked) && lastChecked + ttl >= time(0))
+                if (string2Int(ss[2], lastChecked) && lastChecked + ttl >= time(0)) {
                     skip = true;
-                else if (!ss[1].empty()) {
+                    effectiveUrl = url_;
+                } else if (!ss[1].empty()) {
                     printMsg(lvlDebug, format("verifying previous ETag ‘%1%’") % ss[1]);
                     expectedETag = ss[1];
                 }
@@ -276,6 +289,7 @@ Path Downloader::downloadCached(ref<Store> store, const string & url_, bool unpa
             DownloadOptions options;
             options.expectedETag = expectedETag;
             auto res = download(url, options);
+            effectiveUrl = res.effectiveUrl;
 
             if (!res.cached) {
                 ValidPathInfo info;

src/libstore/download.hh

@@ -19,6 +19,7 @@ struct DownloadResult
 {
     bool cached;
     string etag;
+    string effectiveUrl;
     std::shared_ptr<std::string> data;
 };
 
@@ -31,6 +32,11 @@ struct Downloader
     Path downloadCached(ref<Store> store, const string & url, bool unpack,
         const Hash & expectedHash = Hash());
 
+    /* Need to overload because can't have an rvalue default value for non-const reference */
+
+    Path downloadCached(ref<Store> store, const string & url, bool unpack,
+        string & effectiveUrl, const Hash & expectedHash = Hash());
+
     enum Error { NotFound, Forbidden, Misc };
 };
 

src/nix-channel/local.mk

@@ -0,0 +1,7 @@
+programs += nix-channel
+
+nix-channel_DIR := $(d)
+
+nix-channel_LIBS = libmain libutil libformat libstore
+
+nix-channel_SOURCES := $(d)/nix-channel.cc