From 0fef7fbd10b4efa704ffd78c6b4d3f936da060e3 Mon Sep 17 00:00:00 2001
From: swrup <swrup@protonmail.com>
Date: Tue, 7 Oct 2025 12:02:16 +0200
Subject: [PATCH] wip purpose sizeof

---
 src/binary_formats.ml | 44 +++++++++++++++++++++++++++++++------------
 test/test.ml          | 11 +++++++++++
 2 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/src/binary_formats.ml b/src/binary_formats.ml
index fd9cafe2..d833311f 100644
--- a/src/binary_formats.ml
+++ b/src/binary_formats.ml
@@ -2,6 +2,8 @@
 
    - numeric values are in network byte order (big endian) *)
 
+open Include
+
 (* TODO
    less boilerplate?
      - type t abstract
@@ -55,27 +57,38 @@ module Hash_code = struct
   (* usually SHA-512 *)
   type t = { hash: string (* = uint8_t hash[64] *) }
 
+  let size = 64
+
   let bin =
     let open Bin in
-    record (fun hash -> { hash }) |+ field (bytes 64) (fun t -> t.hash) |> sealr
+    record (fun hash -> { hash })
+    |+ field (bytes size) (fun t -> t.hash)
+    |> sealr
 end
 
 module Short_hash_code = struct
   type t = { hash: string }
 
+  let size = 32
+
   let bin =
     let open Bin in
-    record (fun hash -> { hash }) |+ field (bytes 32) (fun t -> t.hash) |> sealr
+    record (fun hash -> { hash })
+    |+ field (bytes size) (fun t -> t.hash)
+    |> sealr
 end
 
 module MAKE_H (H : sig
-  type t
+  type t = { hash: string }
 
+  val size : int
   val bin : t Bin.t
 end) =
 struct
   type t = { hash: H.t }
 
+  let size = H.size
+
   let bin =
     let open Bin in
     record (fun hash -> { hash }) |+ field H.bin (fun t -> t.hash) |> sealr
@@ -261,7 +274,8 @@ module Token_public_key_p = MAKE_EDDSA_PUB ()
 
 (* -- Signatures -- *)
 
-module Ecc_signature_purpose = struct
+(* EccSignaturePurpose *)
+module Purpose = struct
   type t = {
     (* This field equals the number of bytes being signed,
        namely 'sizeof (struct Data)'. *)
@@ -273,12 +287,16 @@ module Ecc_signature_purpose = struct
     purpose: int32;
   }
 
+  let size = 4 + 4
+
   let bin =
     let open Bin in
     record (fun size purpose -> { size; purpose })
     |+ field beint32 (fun t -> t.size)
     |+ field beint32 (fun t -> t.purpose)
     |> sealr
+
+  let make size purpose = { size= Int32.of_int size; purpose }
 end
 
 (* This is the running SHA512-hash over all
@@ -405,7 +423,7 @@ module Withdraw_request_ps = struct
   type t = {
     (* TODO set it in encode/decode *)
     (* Purpose is #TALER_SIGNATURE_WALLET_RESERVE_WITHDRAW *)
-    purpose: Ecc_signature_purpose.t;
+    purpose: Purpose.t;
     (* Amount to withdraw, excluding fees, i.e.
        the total sum of the denominations of the coins.
        Note that the reserve must have a value of at least amount+fee. *)
@@ -459,7 +477,7 @@ module Withdraw_request_ps = struct
           max_age_group;
           mask;
         })
-    |+ field Ecc_signature_purpose.bin (fun t -> t.purpose)
+    |+ field Purpose.bin (fun t -> t.purpose)
     |+ field Amount.bin (fun t -> t.amount)
     |+ field Amount.bin (fun t -> t.fee)
     |+ field Hash_planchets_p.bin (fun t -> t.h_planchets)
@@ -470,10 +488,9 @@ module Withdraw_request_ps = struct
 end
 
 module Withdraw_confirmation_ps = struct
+  (* Purpose is #TALER_SIGNATURE_EXCHANGE_CONFIRM_WITHDRAW.
+     Signed by a `struct TALER_ExchangePrivateKeyP` using EdDSA. *)
   type t = {
-    (* Purpose is #TALER_SIGNATURE_EXCHANGE_CONFIRM_WITHDRAW.
-       Signed by a `struct TALER_ExchangePrivateKeyP` using EdDSA. *)
-    purpose: Ecc_signature_purpose.t;
     (* Commitment made in the /withdraw request.
        Also needed for the /reveal-withdraw endpoint (in case
        of required proof of age restriction) and for /recoup *)
@@ -489,11 +506,14 @@ module Withdraw_confirmation_ps = struct
     noreveal_index: int32;
   }
 
+  let size = Purpose.size + Hash_planchets_p.size + 4
+  let purpose = Purpose.make size Taler_signatures.exchange_confirm_withdraw
+
   let bin =
     let open Bin in
-    record (fun purpose h_planchets noreveal_index ->
-        { purpose; h_planchets; noreveal_index })
-    |+ field Ecc_signature_purpose.bin (fun t -> t.purpose)
+    record (fun _purpose h_planchets noreveal_index ->
+        { h_planchets; noreveal_index })
+    |+ field Purpose.bin (Fun.const purpose)
     |+ field Hash_planchets_p.bin (fun t -> t.h_planchets)
     |+ field beint32 (fun t -> t.noreveal_index)
     |> sealr
diff --git a/test/test.ml b/test/test.ml
index dac934bc..bc491f9b 100644
--- a/test/test.ml
+++ b/test/test.ml
@@ -71,3 +71,14 @@ let () =
   check_bad "\"foo\" ,";
   check_bad ", \"foo\"";
   ()
+
+let () =
+  let open Binary_formats.Withdraw_confirmation_ps in
+  let str64 = String.make 64 '0' in
+  let dummy_t =
+    { h_planchets= { hash= { hash= str64 } }; noreveal_index= 0_l }
+  in
+  let size' = Bin.size_of_value bin dummy_t |> Option.get in
+  assert (size = size');
+  assert (size = 76);
+  ()