Add the parse of access in mode of the open function, to close #465.

doc/specs/stdlib_io.md

@@ -49,7 +49,7 @@ Experimental
 
 ### Description
 
-Returns the unit number of a file opened to read, to write, or to read and write. The file might be a text file or a binary file. All files are opened using a streamed access.
+Returns the unit number of a file opened to read, to write, or to read and write. The file might be a text file or a binary file. All files are opened using a streamed access by default.
 
 ### Syntax
 
@@ -71,9 +71,12 @@ Returns the unit number of a file opened to read, to write, or to read and write
 | `'+'` | open for updating (reading and writing) |
 | `'b'` | binary mode |
 | `'t'` | text mode (default) |
+| `'u'` | sequential access |
+| `'d'` | direct access |
+| `'s'` | stream access (default) |
 
 
-The default `mode` is `'rt'` (i.e. open for reading a text file). The `mode` may include one of the four different methods for opening a file (i.e., `'r'`, `'w'`, `'x'`, and `'a'`). These four methods can be associated with the character `'+'` to open the file for updating. In addition, it can be specified if the file should be handled as a binary file (`'b'`) or a text file (`'t'`).
+The default `mode` is `'rts'` (i.e. open for reading a text file). The `mode` may include one of the four different methods for opening a file (i.e., `'r'`, `'w'`, `'x'`, and `'a'`). These four methods can be associated with the character `'+'` to open the file for updating. In addition, it can be specified if the file should be handled as a binary file (`'b'`) or a text file (`'t'`).
 
 `iostat` (optional): Shall be a scalar of type `integer` that receives the error status of `open`, if provided. If no error exists, `iostat` is zero.
 

src/stdlib_io.fypp

@@ -211,7 +211,7 @@ contains
     character(*), intent(in), optional :: mode
     integer, intent(out), optional :: iostat
 
-    character(3) :: mode_
+    character(4) :: mode_
     character(:),allocatable :: action_, position_, status_, access_, form_
 
 
@@ -263,7 +263,11 @@ contains
       call error_stop("Unsupported mode: "//mode_(3:3))
     end select
 
-    access_ = 'stream'
+    select case (mode_(4:4))
+        case('u'); access_ = 'sequential'
+        case('d'); access_ = 'direct'
+        case('s'); access_ = 'stream'
+    end select
 
     if (present(iostat)) then
       open(newunit=u, file=filename, &
@@ -278,14 +282,14 @@ contains
 
   end function open
 
-  character(3) function parse_mode(mode) result(mode_)
+  character(4) function parse_mode(mode) result(mode_)
     character(*), intent(in) :: mode
 
     integer :: i
     character(:),allocatable :: a
-    logical :: lfirst(3)
+    logical :: lfirst(4)
 
-    mode_ = 'r t'
+    mode_ = 'r ts'
 
     if (len_trim(mode) == 0) return
     a=trim(adjustl(mode))
@@ -303,6 +307,9 @@ contains
       else if (lfirst(3) .and. (a(i:i) == 't' .or. a(i:i) == 'b')) then
         mode_(3:3) = a(i:i)
         lfirst(3)=.false.
+      else if (lfirst(4) .and. (a(i:i) == 'u' .or. a(i:i) == 'd' .or. a(i:i) == 's')) then
+        mode_(4:4) = a(i:i)
+        lfirst(4)=.false.
       else if (a(i:i) == ' ') then
         cycle
       else if(any(.not.lfirst)) then

src/tests/io/test_open.f90

@@ -80,6 +80,20 @@ program test_open
 u = open(filename, "r", io)
 call check(io /= 0)
 
+! Sequential file
+filename = get_outpath() // "/io_open.sequential"
+
+! Test mode "w"
+u = open(filename, "wu")
+write(u, *) 1, 2, 3
+close(u)
+
+! Test mode "r"
+u = open(filename, "ru")
+read(u, *) a
+call check(all(a == [1, 2, 3]))
+close(u)
+
 
 contains
 

src/tests/io/test_parse_mode.f90

@@ -183,5 +183,18 @@ subroutine test_parse_mode_always_fail()
 
     end subroutine
 
+    subroutine test_parse_mode_access()
+        character(1) :: m
+
+        m = parse_mode("s")
+        call check(m == "r ts")
+
+        m = parse_mode("u")
+        call check(m == "r tu")
+
+        m = parse_mode("d")
+        call check(m == "r td")
+
+    end subroutine test_parse_mode_access
 
 end program