Fix S3BinaryCacheStore

It failed with

   AWS error uploading ‘6gaxphsyhg66mz0a00qghf9nqf7majs2.ls.xz’: Unable to parse ExceptionName: MissingContentLength Message: You must provide the Content-Length HTTP header.

possibly because the istringstream_nocopy introduced in
0d2ebb4373e509521f27a6e8f16bfd39d05b2188 doesn't supply the seek
method that the AWS library expects. So bring back the old version,
but only for S3BinaryCacheStore.

2 files changed, 10 insertions, 1 deletions

diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 5562d4689..d934bda38 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -155,7 +155,7 @@ static StringSet parseStrings(std::istream & str, bool arePaths)
 static Derivation parseDerivation(const string & s)
 {
     Derivation drv;
-    istringstream_nocopy str(s);
+    std::istringstream str(s);
     expect(str, "Derive([");
 
     /* Parse the list of outputs. */
diff --git a/src/libstore/s3-binary-cache-store.cc b/src/libstore/s3-binary-cache-store.cc
index 1bc8576a8..3c5101f00 100644
--- a/src/libstore/s3-binary-cache-store.cc
+++ b/src/libstore/s3-binary-cache-store.cc
@@ -18,6 +18,15 @@
 
 namespace nix {
 
+struct istringstream_nocopy : public std::stringstream
+{
+    istringstream_nocopy(const std::string & s)
+    {
+        rdbuf()->pubsetbuf(
+            (char *) s.data(), s.size());
+    }
+};
+
 struct S3Error : public Error
 {
     Aws::S3::S3Errors err;