Improve readChar

src/rars/riscv/syscalls/SyscallReadChar.java

@@ -36,7 +36,7 @@ a copy of this software and associated documentation files (the
 
 public class SyscallReadChar extends AbstractSyscall {
     public SyscallReadChar() {
-        super("ReadChar", "Reads a character from input console", "N/A", "a0 = the character");
+        super("ReadChar", "Reads a character from input console", "N/A", "a0 = the character or -1 if end of input.");
     }
 
     public void simulate(ProgramStatement statement) throws ExitingException {

src/rars/riscv/syscalls/SyscallReadString.java

@@ -50,7 +50,7 @@ a copy of this software and associated documentation files (the
 public class SyscallReadString extends AbstractSyscall {
     public SyscallReadString() {
         super("ReadString", "Reads a string from the console",
-                "a0 = address of input buffer<br>a1 = maximum number of characters to read", "N/A");
+                "a0 = address of input buffer<br>a1 = size of the buffer", "N/A");
     }
 
     public void simulate(ProgramStatement statement) throws ExitingException {

src/rars/util/SystemIO.java

@@ -177,24 +177,29 @@ public static String readString(int serviceNumber, int maxLength) {
      * Implements syscall having 12 in $v0, to read a char value.
      *
      * @param serviceNumber the number assigned to Read Char syscall (default 12)
-     * @return int value with lowest byte corresponding to user input
+     * @return int value with lowest byte corresponding to user input or -1 on EOF
      */
     public static int readChar(int serviceNumber) {
-        int returnValue = 0;
-
-        String input = readStringInternal("0", "Enter a character value (syscall " + serviceNumber + ")", 1);
-        // The whole try-catch is not really necessary in this case since I'm
-        // just propagating the runtime exception (the default behavior), but
-        // I want to make it explicit.  The client needs to catch it.
-        try {
-            returnValue = (int) (input.charAt(0)); // first character input
-        } catch (IndexOutOfBoundsException e) // no chars present
-        {
-            throw e;  // was: returnValue = 0;
+        int returnValue;
+
+        // Need a popup?
+        if (Globals.getGui() != null && Globals.getSettings().getBooleanSetting(Settings.Bool.POPUP_SYSCALL_INPUT)) {
+            String input = readStringInternal("0", "Enter a character value (syscall " + serviceNumber + ")", 1);
+            if (input.length()>0)
+                returnValue = input.charAt(0); // truncate
+            else
+                returnValue = -1; // assume EOF on empty string
+        } else {
+            // Otherwise delegate to the Read syscall
+            byte[] input = new byte[1];
+            int len = readFromFile(0, input, 1);
+            if (len>0)
+                returnValue = input[0];
+            else
+                returnValue = -1;
         }
 
         return returnValue;
-
     }
 
 

test/Test.java

@@ -89,7 +89,7 @@ public static String run(String path, Program p){
                     for(int i = 0; i < linenumbers.length; i++){
                         errorlines[i] = Integer.parseInt(linenumbers[i].trim());
                     }
-                } else if (line.startsWith("stdin:")) {
+                } else if (line.startsWith("#stdin:")) {
                     stdin = line.replaceFirst("#stdin:", "").replaceAll("\\\\n","\n");
                 } else if (line.startsWith("#stdout:")) {
                     stdout = line.replaceFirst("#stdout:", "").replaceAll("\\\\n","\n");

test/read.s

@@ -0,0 +1,73 @@
+#stdin:hello\nworldXremain
+#stdout:11hello\nworld....\n1Xello\nworld....\n0Xello\nworld....\n6remainworld....\n0remainworld....\n
+
+.eqv PrintInt, 1
+.eqv Read, 63
+.eqv PrintString, 4
+
+# Expect to read one and half line "hello\nworld"
+li a0, 0
+la a1, buf
+li a2, 11
+li a7, Read
+ecall
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read only a character
+li a0, 0
+la a1, buf
+li a2, 1
+li a7, Read
+ecall
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read nothing
+li a0, 0
+la a1, buf
+li a2, 0 # nothing
+li a7, Read
+ecall
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read what remains
+li a0, 0
+la a1, buf
+li a2, 12
+li a7, Read
+ecall
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read nothing, it's EOF
+li a0, 0
+la a1, buf
+li a2, 12
+li a7, Read
+ecall
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+li a0, 42 
+li a7, 93	# Exit2
+ecall
+
+.data
+buf: .string "...............\n"

test/readchar.s

@@ -0,0 +1,24 @@
+#stdin:a b\n\n!
+#stdout:97a32 98b10\n10\n33!-1ÿ-1ÿ
+
+.eqv PrintInt, 1
+.eqv ReadChar, 12
+.eqv PrintChar, 11
+
+li s0, 8
+loop:
+beqz s0, end
+addi s0, s0, -1
+li a7, ReadChar
+ecall
+li a7, PrintInt
+ecall
+# Note: lowest byte of -1 is ff, and U+FF is ÿ
+li a7, PrintChar
+ecall
+j loop
+
+end:
+li a0, 42 
+li a7, 93	# Exit2
+ecall

test/readstring.s

@@ -0,0 +1,100 @@
+#stdin:hello\n\nworldNOTWORLD\nXXXX\nYYYY\nremain
+#stdout:0hello\n1\n2world34A5remain\n6\n
+
+.eqv PrintInt, 1
+.eqv ReadString, 8
+.eqv PrintString, 4
+
+# Expect to read one line "hello\n"
+la a0, buf
+li a1, 256
+li a7, ReadString
+ecall
+li a0, 0
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read an empty line
+la a0, buf
+li a1, 256
+li a7, ReadString
+ecall
+li a0, 1
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read "world" only
+la a0, buf
+li a1, 6 # include space for '\0'
+li a7, ReadString
+ecall
+li a0, 2
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read nothing
+la a0, buf
+li a1, 1 # only space for a nullbyte
+li a7, ReadString
+ecall
+li a0, 3
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read nothing
+la a0, buf
+li a1, 'A'
+sb a1, 0(a0)
+sb zero, 1(a0) # Initialize buffer with "A\0"
+li a1, 0 # no space for a nullbyte
+li a7, ReadString
+ecall
+li a0, 4
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read the last line, a "\n" is added
+la a0, buf
+li a1, 256
+li a7, ReadString
+ecall
+li a0, 5
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+# Expect to read only an added "\n". ReadString has no concept of EOF
+la a0, buf
+li a1, 256
+li a7, ReadString
+ecall
+li a0, 6
+li a7, PrintInt
+ecall
+la a0, buf
+li a7, PrintString
+ecall
+
+li a0, 42 
+li a7, 93	# Exit2
+ecall
+
+.data
+buf: .space 256