Implement stat, and primitives to use it.

PRIMITIVES.md

@@ -84,6 +84,9 @@ Note that functions have their names mangled a little bit ("-" is converted to "
     * Return the ASCII character corresponding to the given integer.
   * `cons`
     * Add the element to the start of the given (potentially empty) list.
+  * `entries`
+    * Return the names of all files in the given directory.
+    * See [test/entries.lisp](test/entries.lisp) for an example
   * `environment`
     * Return a list of all environmental variables.
   * `exit`
@@ -134,6 +137,8 @@ Note that functions have their names mangled a little bit ("-" is converted to "
   * `split-all`
     * Return a list of all parts of string, split by the character.
     * e.g. `(split-all (getenv "PATH") #\:)` to find all directories on the PATH.
+  * `stat`
+    * Returns file information as a list (TYPE SIZE MODE), or nil on failure.
   * `strcat`
     * Join two strings together and return them.
   * `strcmp`
@@ -158,8 +163,14 @@ The implementation of these primitives can be found in the file [stdlib.slisp](s
   * Test if every item in a list is true.
 * `append`
   * Append the given value to the specified list.  If the list is empty just return the specified item.
+* `dir?`
+  * Does the given path exist as a directory?
 * `even?`
   * Return 1 if the given number is even, nil otherwise.
+* `exists?`
+  * Does the given filename exist?
+* `file?`
+  * Does the given path exist as a file?
 * `filter`
   * Return a list consisting of all members of the input list for which the given predicate returns non-nil.
 * `find`

README.md

@@ -64,7 +64,7 @@ It should be noted that we prepend a standard library of functions to all user p
 * File I/O operations:
   * `fopen`, `fclose`, `fread`, and `fwrite`.
 * Filesystem primitive:
-  * `entries`.
+  * `entries`, `stat`, `dir?`, `exists?`, and `file?`.
 * Comparison operations:
   * `=`, `<`, `<=`, `>=`, `>`, and `!` to invert a result.
 * Special forms

compiler/template.tmpl

@@ -34,6 +34,7 @@ SYS_read        equ 0
 SYS_write       equ 1
 SYS_open        equ 2
 SYS_close       equ 3
+SYS_stat        equ 4
 SYS_lseek       equ 8
 SYS_exit        equ 60
 SYS_getdents64  equ 217
@@ -44,6 +45,16 @@ SYS_getrandom   equ 318
 O_RDONLY        equ 0
 O_DIRECTORY     equ 0200000o
 
+;; (stat)
+S_IFMT          equ 0170000o
+S_IFSOCK        equ 0140000o
+S_IFLNK         equ 0120000o
+S_IFREG         equ 0100000o
+S_IFBLK         equ 0060000o
+S_IFDIR         equ 0040000o
+S_IFCHR         equ 0020000o
+S_IFIFO         equ 0010000o
+
 
 
 
@@ -1683,6 +1694,104 @@ FUNC fn_split
     ret
 
 
+
+;;
+;; stat(path)
+;;
+;; Returns:
+;;
+;;    (type size mode)
+;;
+;; type:
+;;    0 = regular file
+;;    1 = directory
+;;    2 = symlink
+;;    3 = character device
+;;    4 = block device
+;;    5 = fifo
+;;    6 = socket
+;;
+;; Returns NIL on failure.
+;;
+
+FUNC fn_stat
+    mov rbx,rdi                      ; type-check arg1: string
+    GET_TAG_BITS rbx
+    cmp rbx,TAG_ID_STRING
+    jne type_error
+    UNTAG_REG rdi
+
+    sub rsp, 160                     ; Reserve space for struct stat.
+
+    mov eax,SYS_stat
+    mov rsi,rsp                      ; stack buffer
+    syscall
+    test rax,rax
+    js .failure
+
+    movzx eax,word [rsp+24]          ; Get the mode
+    mov ecx,eax                      ; save it
+
+    and eax,S_IFMT
+    xor edx,edx                      ; default = regular file
+
+    cmp eax,S_IFREG                  ; compare against other explicitly known types
+    je .type_done
+    mov edx,1
+    cmp eax,S_IFDIR
+    je .type_done
+    mov edx,2
+    cmp eax,S_IFLNK
+    je .type_done
+    mov edx,3
+    cmp eax,S_IFCHR
+    je .type_done
+    mov edx,4
+    cmp eax,S_IFBLK
+    je .type_done
+    mov edx,5
+    cmp eax,S_IFIFO
+    je .type_done
+    mov edx,6
+    cmp eax,S_IFSOCK
+    je .type_done
+
+    xor edx,edx                        ; unknown -> regular file
+
+.type_done:
+    xor r13,r13                ; create nil for end of list
+    TAG_NIL_REG r13
+
+    mov eax,ecx                ; add mode
+    and eax,0777o
+    TAG_INTEGER_REG rax
+    mov rdi,rax
+    mov rsi,r13
+    call fn_cons
+    mov r13,rax
+
+    mov rax,[rsp+48]           ; add size
+    TAG_INTEGER_REG rax
+    mov rdi,rax
+    mov rsi,r13
+    call fn_cons
+    mov r13,rax
+
+    mov eax,edx                ; add type
+    TAG_INTEGER_REG rax
+    mov rdi,rax
+    mov rsi,r13
+    call fn_cons
+    add rsp, 160               ; restore stack
+    ret
+
+.failure:
+    add rsp, 160               ; restore stack
+    xor rax,rax
+    TAG_NIL_REG rax
+    ret
+
+
 ;; join the two given strings and return a new one.
 FUNC fn_strcat
     mov rbx, rdi            ; type-check arg1: str

stdlib.slisp

@@ -61,6 +61,28 @@ do the right thing for each entry in the given list."
 
 
 
+;;; filesystem primitives
+
+(defun exists? (path)
+  "Does the named path exist?"
+  (cons? (stat path)))
+
+(defun file? (path)
+  "Is the given path a file?"
+  (let ((res (stat path)))
+    (if res
+        (if (= 0 (car res))
+            t))))
+
+(defun dir? (path)
+  "Is the given path a directory?"
+  (let ((res (stat path)))
+    (if res
+        (if (= 1 (car res))
+            t))))
+
+
+
 
 ;;; logical functions
 

test/stat.lisp

@@ -0,0 +1,22 @@
+(defun main ()
+
+  ;; basic tests
+  (println "/etc exists as directory:" (dir? "/etc"))
+  (println "/etc/fstab exists as directory:" (dir? "/etc/fstab"))
+  (println "/etc/fstab exists as file:" (file? "/etc/fstab"))
+
+  (let ((s (stat "stat.lisp")))
+
+    ;; If stat succeeds it returns a three-element list
+    (let ((type (nth s 0))
+          (size (nth s 1))
+          (mode (nth s 2)))
+
+      ;; Show what we got
+      (println "file type for stat.lisp: " type)
+      (println "file size for stat.lisp: " size)
+      (println "file mode for stat.lisp: " mode)))
+
+  ;; Returns nil on failure
+  (println "stat of a missing file:")
+  (println (stat "/the/file/does'nt/exist")))

test/stat.test.expected

@@ -0,0 +1,8 @@
+/etc exists as directory:1
+/etc/fstab exists as directory:<nil>
+/etc/fstab exists as file:1
+file type for stat.lisp: 0
+file size for stat.lisp: 676
+file mode for stat.lisp: 420
+stat of a missing file:
+<nil>