From 0a1c5c69244b1199cb877aed029a3c9aca68f60a Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Fri, 12 May 2017 21:11:57 +0200
Subject: added a itoa

---
 src/kernel.c      | 34 ++++++++++++++++------------------
 src/stddef.h      |  6 ++++++
 src/stdlib.c      | 43 ++++++++++++++++++++++++++++++++++++++++++-
 tests/Makefile    | 16 ++++++++++++----
 tests/test_itoa.c | 13 +++++++++++++
 5 files changed, 89 insertions(+), 23 deletions(-)
 create mode 100644 src/stddef.h
 create mode 100644 tests/test_itoa.c

diff --git a/src/kernel.c b/src/kernel.c
index 8232a12..91ed26b 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -12,8 +12,6 @@ void entry( void )
 	
 	vga_put_string( &vga, "ABAOS 0.0.1 STARTING" );
 	
-	// clang 4.0.0 needs volatile otherwise it takes a random value
-	// from the register in the second vga_put_char_at below??!
 	const char bar[] = "\\|/-";
 	int y_pos = vga_get_cursor_y( &vga );
 	int x_pos = vga_get_cursor_x( &vga );
@@ -33,21 +31,21 @@ void entry( void )
 	vga_put_hex( &vga, 4711 );
 	vga_put_newline( &vga );
 
-	vga_set_color( &vga, VGA_COLOR_WHITE );
-	vga_set_background_color( &vga, VGA_COLOR_RED );
-	vga_clear_screen( &vga );
+	//~ vga_set_color( &vga, VGA_COLOR_WHITE );
+	//~ vga_set_background_color( &vga, VGA_COLOR_RED );
+	//~ vga_clear_screen( &vga );
 
-	for( int i = 0; i < 50; i++ ) {
-		for( int j = 0; j < i; j++ ) {
-			vga_put_char( &vga, '-' );
-		}
-		vga_put_char( &vga, '>' );
-		vga_put_string( &vga, (const char *)"TEST TEST TEST" );
-		vga_put_newline( &vga );
-	}
-	for( int j = 0; j < 50; j++ ) {
-		vga_put_char( &vga, '-' );
-	}
-	vga_put_char( &vga, '>' );
-	vga_put_string( &vga, (const char *)"TEST TEST TEST" );
+	//~ for( int i = 0; i < 50; i++ ) {
+		//~ for( int j = 0; j < i; j++ ) {
+			//~ vga_put_char( &vga, '-' );
+		//~ }
+		//~ vga_put_char( &vga, '>' );
+		//~ vga_put_string( &vga, (const char *)"TEST TEST TEST" );
+		//~ vga_put_newline( &vga );
+	//~ }
+	//~ for( int j = 0; j < 50; j++ ) {
+		//~ vga_put_char( &vga, '-' );
+	//~ }
+	//~ vga_put_char( &vga, '>' );
+	//~ vga_put_string( &vga, (const char *)"TEST TEST TEST" );
 }
diff --git a/src/stddef.h b/src/stddef.h
new file mode 100644
index 0000000..962e1aa
--- /dev/null
+++ b/src/stddef.h
@@ -0,0 +1,6 @@
+#ifndef STDDEF_H
+#define STDDEF_H
+
+#define NULL ( (void *)0 )
+
+#endif /* STDDEF_H */
diff --git a/src/stdlib.c b/src/stdlib.c
index 9a9425f..46bdce8 100644
--- a/src/stdlib.c
+++ b/src/stdlib.c
@@ -1,7 +1,48 @@
+#include <stdbool.h>
+#include "string.h"
 #include "stdlib.h"
+#include "stddef.h"
 
+static void strreverse( char *s )
+{
+	char *end = s + strlen( s ) - 1;
+	
+	while( s < end ) {
+		// XOR swap;
+		*s ^= *end;
+		*end ^= *s;
+		*s ^= *end;
+		s++;
+		end--;
+	}
+}
+    
 char *itoa( int v, char *s, int base )
 {
-	//~ *s = '\0';
+	static char digit[] = "0123456789ABCDEF";
+	bool sign = false;
+	char *p = s;
+	
+	if( base < 2 || base > 16 ) {
+		return NULL;
+	}
+	
+	if( v < 0 ) {
+		v = -v;
+		sign = true;
+	} 
+	
+	do {
+		*p++ = digit[v % base];
+	} while( ( v /= base ) > 0 );
+
+	if( sign ) {
+		*p++ = '-';
+	}
+	*p = '\0';
+	
+	strreverse( s );
+	
 	return s;
 }
+  
diff --git a/tests/Makefile b/tests/Makefile
index af20182..6b91c9b 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -5,19 +5,27 @@ LD := ld
 
 all: test
 
-test_strlcpy: test_strlcpy.o
-
 test_strlcpy: test_strlcpy.o ../src/string.o
 	$(CC) -o test_strlcpy test_strlcpy.o ../src/string.o
 
 test_strlcpy.o: test_strlcpy.c
 	$(CC) $(CFLAGS) $(INCLUDES) -c -o test_strlcpy.o test_strlcpy.c
 
+test_itoa: test_itoa.o ../src/stdlib.o ../src/string.o
+	$(CC) -o test_itoa test_itoa.o ../src/stdlib.o ../src/string.o
+
+test_itoa.o: test_itoa.c ../src/stdlib.o
+	$(CC) $(CFLAGS) $(INCLUDES) -c -o test_itoa.o test_itoa.c
+
 ../src/string.o: ../src/string.c
 	$(CC) $(CFLAGS) -c -o ../src/string.o ../src/string.c
 
-test: test_strlcpy
+../src/stdlib.o: ../src/stdlib.c
+	$(CC) $(CFLAGS) -c -o ../src/stdlib.o ../src/stdlib.c
+
+test: test_strlcpy test_itoa
 	./test_strlcpy
+	./test_itoa
 	
 clean:
-	-rm -f test_strlcpy *.o
+	-rm -f test_strlcpy test_itoa *.o
diff --git a/tests/test_itoa.c b/tests/test_itoa.c
new file mode 100644
index 0000000..76df145
--- /dev/null
+++ b/tests/test_itoa.c
@@ -0,0 +1,13 @@
+#include "stdlib.h"
+#include "string.h"
+
+int main( void )
+{
+	char *res;
+	char buf[11];
+	
+	res = itoa( 568876, buf, 10 );
+	if( strcmp( res, buf ) ) return 1;
+	
+	return 0;
+}
-- 
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