/* Mostly based on code from http://balau82.wordpress.com */

#include <sys/stat.h>

enum {
 UART_FR_RXFE = 0x10,
 UART_FR_TXFF = 0x20,
 UART0_ADDR = 0x16000000,
};

#define UART_DR(baseaddr) (*(unsigned int *)(baseaddr))
#define UART_FR(baseaddr) (*(((unsigned int *)(baseaddr))+6))

/** 
 * Define all functions as weak in case the compiler toolchain provides them
 */
extern int _close(int file) __attribute__((weak));
extern int _fstat(int file, struct stat *st) __attribute__((weak));
extern int _isatty(int file) __attribute__((weak));
extern int _lseek(int file, int ptr, int dir) __attribute__((weak));
extern int _open(const char *name, int flags, int mode) __attribute__((weak));
extern int _read(int file, char *ptr, int len) __attribute__((weak));
extern caddr_t _sbrk(int incr) __attribute__((weak));
extern int _write(int file, char *ptr, int len) __attribute__((weak));


int _close(int file) { return -1; }

int _fstat(int file, struct stat *st) {
 st->st_mode = S_IFCHR;
 return 0;
}

int _isatty(int file) { return 1; }

int _lseek(int file, int ptr, int dir) { return 0; }

int _open(const char *name, int flags, int mode) { return -1; }

int _read(int file, char *ptr, int len) {
 int todo;
 if(len == 0)
  return 0;
 while(UART_FR(UART0_ADDR) & UART_FR_RXFE)
  ;
 *ptr++ = UART_DR(UART0_ADDR);
 for(todo = 1; todo < len; todo++) {
  if(UART_FR(UART0_ADDR) & UART_FR_RXFE) {
   break;
 }
 *ptr++ = UART_DR(UART0_ADDR);
 }
 return todo;
}

char *heap_end = 0;
caddr_t _sbrk(int incr) {
 extern char end; /* Defined by the linker */
 extern char heap_top; /* Defined by the linker */
 static char *heap_end;
 char *prev_heap_end;

 if (heap_end == 0) {
  heap_end = &end;
 }
 prev_heap_end = heap_end;

 if (heap_end + incr > &heap_top) {
  /* Heap and stack collision */
  return (caddr_t)0;
 }

 heap_end += incr;
 return (caddr_t) prev_heap_end;
 }

int _write(int file, char *ptr, int len) {
 int todo;

 for (todo = 0; todo < len; todo++) {
  while(UART_FR(UART0_ADDR) & UART_FR_TXFF)
   ;
  UART_DR(UART0_ADDR) = *ptr++;
 }
 return len;
 }