added diskio.f_tell() and f_tell32() on the cx16 target

compiler/res/prog8lib/cx16/diskio.p8

@@ -688,7 +688,7 @@ io_error:
     }
 
     sub send_command(uword commandptr) {
-        ; -- send a dos command to the drive
+        ; -- send a dos command to the drive (don't read any response)
         cbm.SETNAM(string.length(commandptr), commandptr)
         cbm.SETLFS(15, drivenumber, 15)
         void cbm.OPEN()
@@ -869,7 +869,6 @@ io_error:
         command[3] = msb(pos_loword)
         command[4] = lsb(pos_hiword)
         command[5] = msb(pos_hiword)
-    send_command:
         cbm.SETNAM(sizeof(command), &command)
         cbm.SETLFS(15, drivenumber, 15)
         void cbm.OPEN()
@@ -892,4 +891,64 @@ io_error:
         reset_write_channel()    ; back to the write io channel
     }
 
+    asmsub f_tell32() -> uword @R0, uword @R1, uword @R2, uword @R3 {
+        ; -- Returns the current read position in R0 and R1 (low + high words)
+        ;    and the file size in R1 and R2 (low + high words).
+        ;    Returns 0 as size if the command is not supported by the DOS implementation/version.
+        %asm {{
+            jmp  internal_f_tell
+        }}
+    }
+
+    asmsub f_tell() -> uword @R0, uword @R2 {
+        ; -- 16 bits version of f_tell32() because most file sizes will be <64Kb.
+        ;    Returns the current read position in R0 and the file size in R2 (R1 is not used in this case). Both in bytes.
+        ;    Returns 0 as size if the command is not supported by the DOS implementation/version.
+        %asm {{
+            jmp  internal_f_tell
+        }}
+    }
+
+    sub internal_f_tell(ubyte channel) {
+        ; gets the (32 bits) position + file size of the given open channel
+        ubyte[2] command = ['t',0]
+        command[1] = READ_IO_CHANNEL       ; f_open uses this secondary address
+        cbm.SETNAM(sizeof(command), &command)
+        cbm.SETLFS(15, drivenumber, 15)
+        void cbm.OPEN()
+        void cbm.CHKIN(15)        ; use #15 as input channel
+        bool success=false
+        ; valid response starts with "07," followed by hex notations of the position and filesize
+        if cbm.CHRIN()=='0' and cbm.CHRIN()=='7' and cbm.CHRIN()==',' {
+            cx16.r1 = read4hex()
+            cx16.r0 = read4hex()        ; position in R1:R0
+            void cbm.CHRIN()            ; separator space
+            cx16.r3 = read4hex()
+            cx16.r2 = read4hex()        ; filesize in R3:R2
+            success = true
+        }
+
+        while cbm.READST()==0 {
+            cx16.r5L = cbm.CHRIN()
+            if cx16.r5L=='\r' or cx16.r5L=='\n'
+                break
+        }
+
+        cbm.CLOSE(15)
+        reset_read_channel()       ; back to the read io channel
+        if success
+            return
+
+        cx16.r0 = cx16.r1 = cx16.r2 = cx16.r3 = 0
+
+        sub read4hex() -> uword {
+            str hex = "0000"
+            hex[0] = cbm.CHRIN()
+            hex[1] = cbm.CHRIN()
+            hex[2] = cbm.CHRIN()
+            hex[3] = cbm.CHRIN()
+            return conv.hex2uword(hex)
+        }
+    }
+
 }

examples/test.p8

@@ -1,15 +1,40 @@
+%import diskio
+%import textio
 %zeropage basicsafe
 
 main {
     sub start() {
-        ubyte @requirezp b1
-        ubyte @zp b2
-        ubyte b3
-        ubyte @nozp b4
+        if diskio.f_open("tehtriz.asm") {
+            repeat 10 {
+                void diskio.f_read($6000, 9999)
+            }
+            uword pl, ph, sl, sh
+            pl, ph, sl, sh = diskio.f_tell32()
 
-        b1++
-        b2++
-        b3++
-        b4++
+            txt.print("\npos: ")
+            txt.print_uwhex(ph, true)
+            txt.print_uwhex(pl, false)
+            txt.print("\nsize: ")
+            txt.print_uwhex(sh, true)
+            txt.print_uwhex(sl, false)
+            txt.nl()
+
+            diskio.f_close()
+        }
+
+        if diskio.f_open("test.p8ir") {
+            repeat 5 {
+                void diskio.f_read($6000, 999)
+            }
+
+            pl, sl = diskio.f_tell()
+            txt.print("\npos16: ")
+            txt.print_uwhex(pl, true)
+            txt.print("\nsize16: ")
+            txt.print_uwhex(sl, true)
+            txt.nl()
+
+            diskio.f_close()
+        }
     }
 }