233/376: Support control characters in JSON output

[Ludovic Courtès]

civodul pushed a commit to tag 1.8
in repository guix.

commit d61853430a3df8914995ae35ac7a0795827d7a87
Author: Eelco Dolstra <address@hidden>
Date:   Tue Sep 30 00:41:18 2014 +0200

    Support control characters in JSON output
---
 src/libexpr/value-to-json.cc |    3 +++
 src/libexpr/value-to-json.hh |    5 +++++
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc
index a2004df..d1ec9b5 100644
--- a/src/libexpr/value-to-json.cc
+++ b/src/libexpr/value-to-json.cc
@@ -3,6 +3,7 @@
 #include "util.hh"
 
 #include <cstdlib>
+#include <iomanip>
 
 
 namespace nix {
@@ -16,6 +17,8 @@ void escapeJSON(std::ostream & str, const string & s)
         else if (*i == '\n') str << "\\n";
         else if (*i == '\r') str << "\\r";
         else if (*i == '\t') str << "\\t";
+        else if (*i >= 0 && *i < 32)
+            str << "\\u" << std::setfill('0') << std::setw(4) << std::hex << 
(uint16_t) *i << std::dec;
         else str << *i;
     str << "\"";
 }
diff --git a/src/libexpr/value-to-json.hh b/src/libexpr/value-to-json.hh
index e3a97ef..f6796f2 100644
--- a/src/libexpr/value-to-json.hh
+++ b/src/libexpr/value-to-json.hh
@@ -36,6 +36,11 @@ struct JSONObject
         attr(s);
         escapeJSON(str, t);
     }
+    void attr(const string & s, int n)
+    {
+        attr(s);
+        str << n;
+    }
 };
 
 struct JSONList