Demo Session Laboruebung 4

.gitignore

@@ -66,4 +66,4 @@ toupper/strtoupper?
 lettercount/lettercount64
 lettercount/genchartable
 lettercount/asciitable.inc
-
+asciitoint/asciitoint

asciitoint/Makefile

@@ -0,0 +1,43 @@
+#=============================================================================
+#
+# Makefile
+#
+#-----------------------------------------------------------------------------
+#
+# DHBW Ravensburg - Campus Friedrichshafen
+#
+# Vorlesung Systemnahe Programmierung / Verteilte Systeme
+#
+# Author: Ralf Reutemann
+#
+#=============================================================================
+
+CC          = gcc
+LD          = ld
+NASM        = nasm
+NASMOPT64   = -g -f elf64 -F dwarf
+CFLAGS      = -Wall -g -std=gnu11 -O2 -fno-inline-small-functions
+
+OS          := $(shell uname -s)
+ARCH        := $(shell uname -m)
+
+TARGETS     = asciitoint
+
+.SECONDARY: main.o
+
+.PHONY: all
+all: $(TARGETS)
+
+asciitoint : main.o asciitoint.o
+	$(CC) $(CFLAGS) -o $@ $^
+
+%.o : %.asm
+	$(NASM) $(NASMOPT64) -l $(basename $<).lst -o $@ $<
+
+%.o : %.c
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+.PHONY: clean
+clean:
+	rm -f *.o *.lst $(TARGETS)
+

asciitoint/asciitoint.asm

@@ -0,0 +1,69 @@
+
+SECTION .text
+
+;-------------------------------------------------------------------
+; FUNCTION:   dec_to_uint
+;
+; PURPOSE:    Convert ASCII string to unsigned integer 
+;
+; PARAMETERS: (via register)
+;             RDI - pointer to input ASCII string
+;             RSI - pointer to address of first invalid character
+;
+; RETURN:     RAX - result of conversion, or 0 in case of error
+;
+;-------------------------------------------------------------------
+        global dec_to_uint:function
+dec_to_uint:
+        push    rbx
+        push    r12
+
+        xor     ecx,ecx
+        xor     edx,edx
+        xor     eax,eax         ; holds converted result
+        mov     ebx,10          ; decimal multiplier per input digit
+
+        ; skip leading spaces
+.skipspace:
+        mov     cl,[rdi]
+        cmp     cl,' '
+        jne     .checksign
+        inc     rdi
+        jmp     .skipspace
+.checksign:
+        ; check +/- sign
+        xor     r12,r12         ; clear sign flag
+        mov     cl,[rdi]
+        cmp     cl,'+'
+        je      .skipsign
+        cmp     cl,'-'
+        jne     .loop
+        inc     r12
+.skipsign:
+        inc     rdi
+.loop:
+        mov     cl,[rdi]
+        test    cl,cl
+        jz      .loop_exit
+        sub     cl,'0'
+        cmp     cl,9
+        ja      .func_exit
+        mul     ebx
+        test    edx,edx
+        jnz     .func_exit
+        add     eax,ecx
+        jc      .func_exit
+        inc     rdi
+        jmp     .loop
+.loop_exit:
+        test    r12,r12            ; check sign flag
+        jz      .func_exit
+        neg     rax                ; negate result if set
+.func_exit:
+        test    rsi,rsi
+        jz      .nullptr
+        mov     [rsi],rdi
+.nullptr:
+        pop     r12
+        pop     rbx
+        ret

asciitoint/main.c

@@ -0,0 +1,32 @@
+/*===================================================================
+ * DHBW Ravensburg - Campus Friedrichshafen
+ *
+ * Vorlesung Systemnahe Programmierung (SNP)
+ *
+ * main.c - test skeleton for asciitoint
+ *
+ * Author:  Ralf Reutemann
+ * Created: 09.01.2022
+ *
+ *===================================================================*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+extern int dec_to_uint(char *s, char **errptr);
+
+int
+main(int argc, char *argv[])
+{
+    char *errptr;
+
+    for(int i = 1; i < argc; i++) {
+        int result = dec_to_uint(argv[i], &errptr);
+        printf("'%12s' -> %12d %12d '%c'\n",
+                argv[i], atoi(argv[i]),
+                result, *errptr);
+    }
+
+    exit(EXIT_SUCCESS);
+} /* end of main */