rewrite listdir and stdin builtins in zern

examples/euler8.zr

@@ -7,7 +7,7 @@ func main[] : I64
         let s: I64 = 1
         let j: I64 = 0
         while j < 13
-            s = s * U8.parse_i64(String.nth(n, i + j))
+            s = s * (String.nth(n, i + j) - '0')
             j = j + 1
         if s > out
             out = s

src/codegen_x86_64.rs

@@ -114,7 +114,7 @@ extern strcat
 extern strcpy
 extern strdup
 extern strncpy
-extern fgets
+extern syscall
 extern fopen
 extern fseek
 extern ftell
@@ -160,11 +160,6 @@ _builtin_set64:
     mov [rdi], rsi
     ret
 
-section .text._builtin_stdin
-_builtin_stdin:
-    mov rax, [rel stdin]
-    ret
-
 section .text._builtin_lshift
 _builtin_lshift:
     mov rcx, rsi
@@ -178,50 +173,6 @@ _builtin_rshift:
     mov rax, rdi
     sar rax, cl
     ret
-
-section .text._builtin_listdir
-_builtin_listdir:
-    push r14
-    push rbx
-    push rax
-    mov r14, rdi
-    call Array.new
-    mov rbx, rax
-    mov rdi, r14
-    call opendir
-    mov r14, rax
-._builtin_listdir.1:
-    mov rdi, r14
-    call readdir
-    test rax, rax
-    je ._builtin_listdir.3
-    cmp byte [rax+19], 46
-    jne ._builtin_listdir.2
-    movzx ecx, byte [rax+20]
-    test ecx, ecx
-    je ._builtin_listdir.1
-    cmp ecx, 46
-    jne ._builtin_listdir.2
-    cmp byte [rax+21], 0
-    je ._builtin_listdir.1
-._builtin_listdir.2:
-    add rax, 19
-    mov rdi, rax
-    call strdup
-    mov rsi, rax
-    mov rdi, rbx
-    mov [rsp], rbx
-    call Array.push
-    mov rbx, [rsp]
-    jmp ._builtin_listdir.1
-._builtin_listdir.3:
-    mov rdi, r14
-    call closedir
-    mov rax, rbx
-    add rsp, 8
-    pop rbx
-    pop r14
-    ret
 "
         );
         Ok(())

src/std.zr

@@ -60,12 +60,11 @@ func String.rev[s: String] : String
     String.set(out, len, 0)
     return out
 
-func IO.stdin[]: Ptr
-    return _builtin_stdin()
-
 func IO.read_line[]: String
     let buffer: String = malloc(1024)
-    fgets(buffer, 1024, IO.stdin())
+    let sys_read: I64 = 0
+    let stdin: I64 = 0
+    syscall(sys_read, stdin, buffer, 1024)
     return buffer
 
 func IO.read_file[path: String]: String
@@ -92,9 +91,6 @@ func IO.write_file[path: String, content: String] : Void
     fwrite(content, 1, strlen(content), file)
     fclose(file)
 
-func U8.parse_i64[c: U8]: I64
-    return c - '0'
-
 func I64.to_string[n: I64] : String
     let x: String = malloc(21)
     sprintf(x, "%ld", n)
@@ -213,7 +209,26 @@ func OS.time[] : I64
     return seconds * 1000 + microseconds / 1000
 
 func OS.listdir[path: String] : Array
-    return _builtin_listdir(path)
+    let dir: Ptr = opendir(path)
+    let files: Array = []
+
+    while true
+        let entry: Ptr = readdir(dir)
+        if entry == 0
+            break
+
+        let skip: Bool = false
+        if String.nth(entry, 19) == '.'
+            if String.nth(entry, 20) == 0
+                skip = true
+            else if String.nth(entry, 20) == '.'
+                if String.nth(entry, 21) == 0
+                    skip = true
+
+        if !skip
+            Array.push(files, strdup(entry + 19))
+    closedir(dir)
+    return files
 
 func Bit.lshift[a: I64, b: I64] : I64
     return _builtin_lshift(a, b)
@@ -242,7 +257,7 @@ func Crypto.from_hex_digit[d: U8] : I64
         return d - 'a' + 10
     if d >= 'A' && d <= 'F'
         return d - 'A' + 10
-    return U8.parse_i64(d)
+    return d - '0'
 
 func Crypto.hex_decode[s: String] : String
     let s_len: I64 = strlen(s)