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type json =
[ `Null
| `Bool of bool
| `Float of float
| `String of string
| `Array of json list
| `Object of (string * json) list ]
let rec buffer_add_json b = function
| `Null -> Buffer.add_string b "null"
| `Bool bool -> Buffer.add_string b (if bool then "true" else "false")
| `Float f -> Buffer.add_string b (Printf.sprintf "%.16g" f)
| `String s -> buffer_add_json_string b s
| `Array els -> (
match els with
| [] -> Buffer.add_string b "[]"
| el :: els ->
let add_sep_el b e =
Buffer.add_char b ',';
buffer_add_json b e
in
Buffer.add_char b '[';
buffer_add_json b el;
List.iter (add_sep_el b) els;
Buffer.add_char b ']')
| `Object mems -> (
match mems with
| [] -> Buffer.add_string b "{}"
| mem :: mems ->
let add_mem b (k, v) =
buffer_add_json_string b k;
Buffer.add_char b ':';
buffer_add_json b v
in
let add_sep_mem b mem =
Buffer.add_char b ',';
add_mem b mem
in
Buffer.add_char b '{';
add_mem b mem;
List.iter (add_sep_mem b) mems;
Buffer.add_char b '}')
and buffer_add_json_string b s =
let is_control = function '\x00' .. '\x1F' | '\x7F' -> true | _ -> false in
let len = String.length s in
let max_idx = len - 1 in
let flush b start i =
if start < len then Buffer.add_substring b s start (i - start)
in
let rec loop start i =
match i > max_idx with
| true -> flush b start i
| false -> (
let next = i + 1 in
match String.get s i with
| '"' ->
flush b start i;
Buffer.add_string b "\\\"";
loop next next
| '\\' ->
flush b start i;
Buffer.add_string b "\\\\";
loop next next
| c when is_control c ->
flush b start i;
Buffer.add_string b (Printf.sprintf "\\u%04X" (Char.code c));
loop next next
| _c -> loop start next)
in
Buffer.add_char b '"';
loop 0 0;
Buffer.add_char b '"'
let to_string json =
let b = Buffer.create 1024 in
buffer_add_json b json;
Buffer.contents b