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(* @needs Value *)
type blob = bytes
let blob_of_bytes (b : bytes) = b
let bytes_of_blob (b : blob) = b
(* A blob is a one-byte constructor tag followed by its payload. The
tag makes the encoding self-describing so [value_of_blob] can
recover the constructor:
- String ['\000'] ++ raw utf-8 bytes
- Integer ['\001'] ++ 8-byte big-endian int64 *)
let tag_string = '\000'
let tag_integer = '\001'
let blob_of_value = function
| Value.String s ->
let b = Bytes.create (1 + String.length s) in
Bytes.set b 0 tag_string;
Bytes.blit_string s 0 b 1 (String.length s);
b
| Value.Integer n ->
let b = Bytes.create 9 in
Bytes.set b 0 tag_integer;
Bytes.set_int64_be b 1 (Int64.of_int n);
b
let value_of_blob (b : blob) =
let n = Bytes.length b in
if n = 0 then invalid_arg "value_of_blob: empty blob";
match Bytes.get b 0 with
| c when c = tag_string -> Value.String (Bytes.sub_string b 1 (n - 1))
| c when c = tag_integer ->
if n <> 9 then invalid_arg "value_of_blob: malformed integer payload";
Value.Integer (Int64.to_int (Bytes.get_int64_be b 1))
| c -> invalid_arg (Printf.sprintf "value_of_blob: unknown tag %C" c)
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