From 76bff1a0003cc1b416dd6b1cc0e423a3a1ed6c74 Mon Sep 17 00:00:00 2001
From: wm4 <wm4@nowhere>
Date: Thu, 17 May 2018 15:51:47 +0200
Subject: json: format slightly nicer escape sequences

Make use the escape sequences allowed by JSON.

Also update the linked RFC to the newest one.
---
 misc/json.c | 23 ++++++++++++++++++-----
 test/json.c |  3 ++-
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/misc/json.c b/misc/json.c
index 4797fde4d0..9cc0730e4d 100644
--- a/misc/json.c
+++ b/misc/json.c
@@ -24,7 +24,7 @@
  *
  * Does not support extensions like unquoted string literals.
  *
- * Also see: http://tools.ietf.org/html/rfc4627
+ * Also see: http://tools.ietf.org/html/rfc8259
  *
  * JSON writer:
  *
@@ -34,9 +34,6 @@
  * to deal with somehow: either by using byte-strings for JSON, or by running
  * a "fixup" pass on the input data. The latter could for example change
  * invalid UTF-8 sequences to replacement characters.
- *
- * Currently, will insert \u literals for characters 0-31, '"', '\', and write
- * everything else literally.
  */
 
 #include <stdlib.h>
@@ -218,6 +215,14 @@ int json_parse(void *ta_parent, struct mpv_node *dst, char **src, int max_depth)
 
 #define APPEND(b, s) bstr_xappend(NULL, (b), bstr0(s))
 
+static const char special_escape[] = {
+    ['\b'] = 'b',
+    ['\f'] = 'f',
+    ['\n'] = 'n',
+    ['\r'] = 'r',
+    ['\t'] = 't',
+};
+
 static void write_json_str(bstr *b, unsigned char *str)
 {
     APPEND(b, "\"");
@@ -228,7 +233,15 @@ static void write_json_str(bstr *b, unsigned char *str)
         if (!cur[0])
             break;
         bstr_xappend(NULL, b, (bstr){str, cur - str});
-        bstr_xappend_asprintf(NULL, b, "\\u%04x", (unsigned char)cur[0]);
+        if (cur[0] == '\"') {
+            bstr_xappend(NULL, b, (bstr){"\\\"", 2});
+        } else if (cur[0] == '\\') {
+            bstr_xappend(NULL, b, (bstr){"\\\\", 2});
+        } else if (cur[0] < sizeof(special_escape) && special_escape[cur[0]]) {
+            bstr_xappend_asprintf(NULL, b, "\\%c", special_escape[cur[0]]);
+        } else {
+            bstr_xappend_asprintf(NULL, b, "\\u%04x", (unsigned char)cur[0]);
+        }
         str = cur + 1;
     }
     APPEND(b, str);
diff --git a/test/json.c b/test/json.c
index 74fd20d748..d624f61cca 100644
--- a/test/json.c
+++ b/test/json.c
@@ -40,7 +40,8 @@ static const struct entry entries[] = {
     { "abc", .expect_fail = true},
     { "  123  ", "123", NODE_INT64(123)},
     { "123.25", "123.250000", NODE_FLOAT(123.25)},
-    { TEXT("a\n\\"), TEXT("a\u000a\u005c"), NODE_STR("a\n\\")},
+    { TEXT("a\n\\\/\\\""), TEXT("a\n\\/\\\""), NODE_STR("a\n\\/\\\"")},
+    { TEXT("a\u2c29"), TEXT("aⰩ"), NODE_STR("a\342\260\251")},
     { "[1,2,3]", "[1,2,3]",
         NODE_ARRAY(NODE_INT64(1), NODE_INT64(2), NODE_INT64(3))},
     { "[ ]", "[]", NODE_ARRAY()},
-- 
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