feat: url_decode function

src/builtin.jq

@@ -197,6 +197,43 @@ def ascii_downcase:
 def ascii_upcase:
   explode | map( if 97 <= . and . <= 122 then . - 32  else . end) | implode;
 
+# inverse of @uri in jq
+def url_decode:
+  def unhex:
+    if 48 <= . and . <= 57 then . - 48 elif 65 <= . and . <= 70 then . - 55 else . - 87 end;
+
+  def bytes:
+    def loop($i):
+      if $i >= length then empty else 16 * (.[$i+1] | unhex) + (.[$i+2] | unhex), loop($i+3) end;
+    [loop(0)];
+
+  def codepoints:
+    def loop($i):
+      if $i >= length then empty
+      elif .[$i] >= 240 then (.[$i+3]-128) + 64*(.[$i+2]-128) + 4096*(.[$i+1]-128) + 262144*(.[$i]-240), loop($i+4)
+      elif .[$i] >= 224 then (.[$i+2]-128) + 64*(.[$i+1]-128) + 4096*(.[$i]-224), loop($i+3)
+      elif .[$i] >= 192 then (.[$i+1]-128) + 64*(.[$i]-192), loop($i+2)
+      else .[$i], loop($i+1)
+      end;
+    [loop(0)];
+
+  # Note that URL-encoding implies percent-encoded UTF-8 octets, so we have to
+  # manually reassemble these into codepoints for implode
+  gsub("(?<m>(?:%[0-9a-fA-F]{2})+)"; .m | explode | bytes | codepoints | implode);
+
+# reimplementation of @uri in jq to maintain a similar name to url_decode
+def url_encode:
+   # The helper function checks whether the input corresponds to one of the characters: !'()*
+   def recode: . as $c | [33,39,40,41,42] | index($c);
+   def hex:   if . < 10 then 48 + . else  55 + . end;
+   @uri
+   | explode
+   # 37 ==> "%", 50 ==> "2"
+   | map( if recode then (37, 50, ((. - 32) | hex)) else . end )
+   | implode;
+
+
+
 # Streaming utilities
 def truncate_stream(stream):
   . as $n | null | stream | . as $input | if (.[0]|length) > $n then setpath([0];$input[0][$n:]) else empty end;

tests/jq.test

@@ -2091,3 +2091,27 @@ try ("foobar" | .[1.5]) catch .
 null
 "Cannot index string with number"
 
+# url_encode/url_decode
+url_encode
+"="
+"%3D"
+
+url_encode
+"á"
+"%C3%A1"
+
+url_encode | url_decode
+"á"
+"á"
+
+url_decode
+"http%3A%2F%2Ffoo%20bar%2F"
+"http://foo bar/"
+
+(@uri | url_decode) == (url_encode | url_decode)
+"http://foo bar/"
+true
+
+@uri | url_decode | url_encode
+"è"
+"%C3%A8"