Add Bytes.{starts,ends}_with

stdlib/bytes.ml

@@ -236,6 +236,27 @@ let apply1 f s =
 let capitalize_ascii s = apply1 Char.uppercase_ascii s
 let uncapitalize_ascii s = apply1 Char.lowercase_ascii s
 
+(* duplicated in string.ml *)
+let starts_with ~prefix s =
+  let len_s = length s
+  and len_pre = length prefix in
+  let rec aux i =
+    if i = len_pre then true
+    else if unsafe_get s i <> unsafe_get prefix i then false
+    else aux (i + 1)
+  in len_s >= len_pre && aux 0
+
+(* duplicated in string.ml *)
+let ends_with ~suffix s =
+  let len_s = length s
+  and len_suf = length suffix in
+  let diff = len_s - len_suf in
+  let rec aux i =
+    if i = len_suf then true
+    else if unsafe_get s (diff + i) <> unsafe_get suffix i then false
+    else aux (i + 1)
+  in diff >= 0 && aux 0
+
 (* duplicated in string.ml *)
 let rec index_rec s lim i c =
   if i >= lim then raise Not_found else

stdlib/bytes.mli

@@ -323,6 +323,19 @@ val equal: t -> t -> bool
 (** The equality function for byte sequences.
     @since 4.03.0 (4.05.0 in BytesLabels) *)
 
+val starts_with :
+  prefix (* comment thwarts tools/sync_stdlib_docs *) :bytes -> bytes -> bool
+(** [starts_with ][~][prefix s] is [true] if and only if [s] starts with
+    [prefix].
+
+    @since 4.13.0 *)
+
+val ends_with :
+  suffix (* comment thwarts tools/sync_stdlib_docs *) :bytes -> bytes -> bool
+(** [ends_with suffix s] is [true] if and only if [s] ends with [suffix].
+
+    @since 4.13.0 *)
+
 (** {1:unsafe Unsafe conversions (for advanced users)}
 
     This section describes unsafe, low-level conversion functions

stdlib/bytesLabels.mli

@@ -323,6 +323,19 @@ val equal: t -> t -> bool
 (** The equality function for byte sequences.
     @since 4.03.0 (4.05.0 in BytesLabels) *)
 
+val starts_with :
+  prefix (* comment thwarts tools/sync_stdlib_docs *) :bytes -> bytes -> bool
+(** [starts_with ][~][prefix s] is [true] if and only if [s] starts with
+    [prefix].
+
+    @since 4.13.0 *)
+
+val ends_with :
+  suffix (* comment thwarts tools/sync_stdlib_docs *) :bytes -> bytes -> bool
+(** [ends_with suffix s] is [true] if and only if [s] ends with [suffix].
+
+    @since 4.13.0 *)
+
 (** {1:unsafe Unsafe conversions (for advanced users)}
 
     This section describes unsafe, low-level conversion functions

stdlib/string.ml

@@ -202,6 +202,7 @@ let capitalize_ascii s =
 let uncapitalize_ascii s =
   B.uncapitalize_ascii (bos s) |> bts
 
+(* duplicated in bytes.ml *)
 let starts_with ~prefix s =
   let len_s = length s
   and len_pre = length prefix in
@@ -211,6 +212,7 @@ let starts_with ~prefix s =
     else aux (i + 1)
   in len_s >= len_pre && aux 0
 
+(* duplicated in bytes.ml *)
 let ends_with ~suffix s =
   let len_s = length s
   and len_suf = length suffix in