adds newlib-nano settings

newlib-nano/syscalls.c

@@ -0,0 +1,79 @@
+#include <unistd.h>
+#include <sys/stat.h>
+
+extern int _end;
+void* _sbrk(int incr);
+int _close(int file);
+int _fstat(int file, struct stat *st);
+int _isatty(int fd);
+int _lseek(int file, int ptr, int dir);
+
+void _kill(int pid, int sig);
+int _getpid(void);
+void write_hex(int fd, unsigned long int hex);
+
+void *_sbrk(int incr) {
+  static unsigned char *heap = NULL;
+  unsigned char *prev_heap;
+  if (heap == NULL) {
+    heap = (unsigned char *)&_end;
+  }
+  prev_heap = heap;
+  heap += incr;
+  return prev_heap;
+}
+
+int _close(int file) {
+  (void)file;
+  return -1;
+}
+
+int _fstat(int file, struct stat *st) {
+  (void)file;
+  st->st_mode = S_IFCHR;
+  return 0;
+}
+
+int _isatty(int fd) {
+  if (fd == STDOUT_FILENO || fd == STDERR_FILENO)
+    return 1;
+  return 0;
+}
+
+int _lseek(int file, int ptr, int dir) {
+  (void)file;
+  (void)ptr;
+  (void)dir;
+  return 0;
+}
+
+void _exit(int status) {
+  const char message[] = "\nProgam has exited with code:";
+  write(STDERR_FILENO, message, sizeof(message) - 1);
+  write_hex(STDERR_FILENO, status);
+  write(STDERR_FILENO, "\n", 1);
+  for (;;);
+}
+
+void _kill(int pid, int sig) {
+  (void)pid;
+  (void)sig;
+  return;
+}
+
+int _getpid(void) {
+  return -1;
+}
+
+void write_hex(int fd, unsigned long int hex){
+  uint8_t ii;
+  uint8_t jj;
+  char towrite;
+  write(fd , "0x", 2);
+  for (ii = sizeof(unsigned long int) * 2 ; ii > 0; ii--) {
+    jj = ii - 1;
+    uint8_t digit = ((hex & (0xF << (jj*4))) >> (jj*4));
+    towrite = digit < 0xA ? ('0' + digit) : ('A' +  (digit - 0xA));
+    write(fd, &towrite, 1);
+  }
+}