Get rid of cstruct

And update opam file

lib/dune

@@ -1,4 +1,4 @@
 (library
  (public_name solo5-elftool)
  (name solo5_elftool)
- (libraries owee cstruct cachet fmt))
+ (libraries owee cachet fmt))

lib/solo5_elftool.ml

@@ -70,43 +70,41 @@ let guard m b = if not b then Error (`Msg m) else Ok ()
 let sizeof_mft_entry = 104
 let mft_max_entries = 64l
 
-let parse_mft_entry buf =
+let parse_mft_entry s =
   (* invariant: Cstruct.length buf = sizeof_mft_entry *)
-  let name_raw = Cstruct.sub buf 0 68 in
-  let typ = Cstruct.LE.get_uint32 buf 68 in
-  let u = Cstruct.sub buf 72 16 in
-  let b = Cstruct.sub buf 88 8 in
-  let attached = Cstruct.get_uint8 buf 96 <> 0 in
+  let name_raw = String.sub s 0 68 in
+  let typ = String.get_int32_le s 68 in
+  let u = String.sub s 72 16 in
+  let b = String.sub s 88 8 in
+  let attached = String.get_uint8 s 96 <> 0 in
   let* name =
-    Cstruct.cut ~sep:(Cstruct.create 1) name_raw
-    |> Option.map (fun (name, _) -> Cstruct.to_string name)
+    String.index_opt name_raw '\000'
+    |> Option.map (fun idx -> String.sub name_raw 0 idx)
     |> Option.to_result ~none:(`Msg "unterminated device name")
   in
-  let* () = guard "non-zero mft_entry.u" (Cstruct.for_all ((=) '\000') u) in
-  let* () = guard "non-zero mft_entry.b" (Cstruct.for_all ((=) '\000') b) in
+  let* () = guard "non-zero mft_entry.u" (String.for_all ((=) '\000') u) in
+  let* () = guard "non-zero mft_entry.b" (String.for_all ((=) '\000') b) in
   let* () = guard "non-zero mft_entry.attached" (not attached) in
   let* typ = mft_type_of_int typ in
   match typ with
   | Reserved_first ->
-    let* () = guard "non-zero RESERVED_FIRST" (Cstruct.for_all ((=) '\000') name_raw) in
+    let* () = guard "non-zero RESERVED_FIRST" (String.for_all ((=) '\000') name_raw) in
     Ok `Reserved_first
   | Dev_block_basic ->
     Ok (`Dev_block_basic name)
   | Dev_net_basic ->
     Ok (`Dev_net_basic name)
 
-let parse_mft buf =
-  let buf = Cstruct.of_string buf in
+let parse_mft s =
   let* () = guard "manifest too small"
-      (Cstruct.length buf >= 4 + 8 + sizeof_mft_entry)
+      (String.length s >= 4 + 8 + sizeof_mft_entry)
   in
   (* Solo5 defines a struct mft1_note consisting of the ELF note header
    * followed by a struct mft for reading and writing the ELF note. The note
    * header is 20 bytes long, so to get 8-byte alignment the note header is
    * padded with 4 bytes. See {[solo5/mft_abi.h]}. *)
-  let buf = Cstruct.shift buf 4 in
-  let version = Cstruct.LE.get_uint32 buf 0
-  and entries = Cstruct.LE.get_uint32 buf 4
+  let version = String.get_int32_le s 4
+  and entries = String.get_int32_le s 8
   in
   let* () = guard "unsupported manifest version" (version = 1l) in
   let* () = guard "zero manifest entries" (Int32.unsigned_compare entries 0l > 0) in
@@ -118,25 +116,25 @@ let parse_mft buf =
    * mft_max_entries, so this is safely equivalent to:
    *   (Option.get (Int32.unsigned_to_int entries) *)
   let entries = Int32.to_int entries in
-  let buf = Cstruct.shift buf 8 in
+  let off = 12 in
   let* () = guard "unexpected note size"
-      (Cstruct.length buf = entries * sizeof_mft_entry)
+      (String.length s = entries * sizeof_mft_entry + 12)
   in
   let* () =
-    match parse_mft_entry (Cstruct.sub buf 0 sizeof_mft_entry) with
+    match parse_mft_entry (String.sub s off sizeof_mft_entry) with
     | Ok `Reserved_first -> Ok ()
     | _ -> Error (`Msg "expected RESERVED_FIRST")
   in
-  let buf = Cstruct.shift buf sizeof_mft_entry in
+  let off = off + sizeof_mft_entry in
   let entries =
     Array.init (entries - 1)
-      (fun i -> Cstruct.sub buf (i * sizeof_mft_entry) sizeof_mft_entry)
+      (fun i -> String.sub s (off + i * sizeof_mft_entry) sizeof_mft_entry)
   in
   let* entries =
     Array.fold_left
-      (fun r buf ->
+      (fun r s ->
          let* acc = r in
-         let* mft_entry = parse_mft_entry buf in
+         let* mft_entry = parse_mft_entry s in
          match mft_entry with
          | `Dev_block_basic name -> Ok (Dev_block_basic name :: acc)
          | `Dev_net_basic name -> Ok (Dev_net_basic name :: acc)
@@ -147,13 +145,12 @@ let parse_mft buf =
   in
   Ok { version = Int32.to_int version; entries }
 
-let parse_abi buf =
-  let buf = Cstruct.of_string buf in
-  let* () = guard "abi manifest size mismatch" (Cstruct.length buf = 4 * 4) in
-  let target = Cstruct.LE.get_uint32 buf 0 in
-  let version = Cstruct.LE.get_uint32 buf 4 in
-  let reserved0 = Cstruct.LE.get_uint32 buf 8 in
-  let reserved1 = Cstruct.LE.get_uint32 buf 12 in
+let parse_abi s =
+  let* () = guard "abi manifest size mismatch" (String.length s = 4 * 4) in
+  let target = String.get_int32_le s 0 in
+  let version = String.get_int32_le s 4 in
+  let reserved0 = String.get_int32_le s 8 in
+  let reserved1 = String.get_int32_le s 12 in
   let* target = abi_target_of_int target in
   let* () = guard "non-zero reserved0" (reserved0 = 0l) in
   let* () = guard "non-zero reserved1" (reserved1 = 0l) in

solo5-elftool.opam

@@ -15,8 +15,7 @@ build: [
 depends: [
   "ocaml" {>= "4.08.0"}
   "dune" {>= "2.9"}
-  "owee" {>= "0.4"}
-  "cstruct" {>= "6.0.0"}
+  "cachet"
   "fmt" {>= "0.8.7"}
   "cmdliner" {>= "1.1.0"}
 ]