Merge pull request #1538 from aviks/json

Improve JSON parsing performance

extras/json.jl

@@ -3,17 +3,25 @@
 #Original BSD Licence, (c) 2011, François Glineur
 
 
-module Json
+module JSON
 
 using Base
 
-export parse_json
+export parse
 
 
-function parse_json(strng::String)
+function parse(strng::String)
+
+    pos::Int = 1
+    len::Int = length(strng)
+
+    # String delimiters and escape characters are identified beforehand to improve speed
+    len_esc::Int = 0
+    index_esc::Int = 1
+
+    esc_locations::Array{Int64,1}  = map(x->x.offset, [each_match(r"[\"\\\\]", strng)...])
+    len_esc=length(esc_locations)  
 
-    pos = 1
-    len = length(strng)
 
     function parse_object()
         parse_char('{')
@@ -87,6 +95,17 @@ function parse_json(strng::String)
         end
         str = ""
         while pos <= len
+            while index_esc <= len_esc && esc_locations[index_esc] < pos 
+                 index_esc = index_esc + 1;
+            end
+            if index_esc > len_esc
+                str = strcat(str, strng[pos:end]);
+                pos = len + 1;
+                break;
+            else
+                str = strcat(str, strng[pos:esc_locations[index_esc]-1]);
+                pos = esc_locations[index_esc];
+            end
             nc = strng[pos]
             if nc == '"' 
                     pos = nextind(strng, pos)

test/json.jl

@@ -1,15 +1,14 @@
 load("json")
-using Json
 
 load("test/json_samples")
 
 
-@assert parse_json(a) != nothing
-@assert parse_json(b) != nothing
-@assert parse_json(c) != nothing
-@assert parse_json(d) != nothing
+@assert JSON.parse(a) != nothing
+@assert JSON.parse(b) != nothing
+@assert JSON.parse(c) != nothing
+@assert JSON.parse(d) != nothing
 
-j=parse_json(e) 
+j=JSON.parse(e) 
 @assert  j!= nothing
 typeof(j) == Dict{String, Any}
 @assert length(j) == 1
@@ -24,27 +23,27 @@ typeof(j["menu"]) == Dict{String, Any}
 
 
 
-@assert parse_json(gmaps) != nothing
-@assert parse_json(colors1) != nothing
-@assert parse_json(colors2) != nothing
-@assert parse_json(colors3) != nothing
-@assert parse_json(twitter) != nothing
-@assert parse_json(facebook) != nothing
+@assert JSON.parse(gmaps) != nothing
+@assert JSON.parse(colors1) != nothing
+@assert JSON.parse(colors2) != nothing
+@assert JSON.parse(colors3) != nothing
+@assert JSON.parse(twitter) != nothing
+@assert JSON.parse(facebook) != nothing
 
-k=parse_json(flickr)
+k=JSON.parse(flickr)
 @assert k!= nothing
 @assert k["totalItems"] == 222
 @assert k["items"][1]["description"][12] == '\"'
-@assert parse_json(youtube) != nothing
-@assert parse_json(iphone) != nothing
-@assert parse_json(customer) != nothing
-@assert parse_json(product) != nothing
-@assert parse_json(interop) != nothing
+@assert JSON.parse(youtube) != nothing
+@assert JSON.parse(iphone) != nothing
+@assert JSON.parse(customer) != nothing
+@assert JSON.parse(product) != nothing
+@assert JSON.parse(interop) != nothing
 
-u=parse_json(unicode) 
+u=JSON.parse(unicode) 
 @assert u!=nothing
 @assert u["অলিম্পিকস"]["রেকর্ড"][2]["Marathon"] == "জনি হেইস"
 
 #Uncomment while doing timing tests
-@time for i=1:100 ; parse_json(d) ; end
+#@time for i=1:100 ; JSON.parse(d) ; end