File content as of revision 0:ccdea31d8eba:

#include <stm32f4xx.h>
#include <sys/stat.h>
#include <unistd.h>

#include "drivers/uart.h"

#define STACK_POINTER (__get_MSP())
#define UART_AUTO_ECHO


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


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


int _isatty(int file)
{
    switch(file) {
    case 1: // stdio
    case 2: // stderr
    return 1;

    default: return 0;
    }
}


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


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


int _read(int file, char *ptr, int len)
{
    UNUSED(file);
    int i;
    for (i = 0; i < len; i++) {
        ptr[i] = _uart_getc();
        #ifdef UART_AUTO_ECHO
        _uart_putc(ptr[i]);
        #endif
        /* Return partial buffer if we get EOL */
        if ('\r' == ptr[i]) {
            ++i;
            ptr[i] = '\n';
            return i;
        }
    }

    ptr[i-1] = '\r';
    ptr[i] = '\n';
    return  i;
}


caddr_t _sbrk(int incr)
{
    extern char _end;		/* 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 ((unsigned)(heap_end + incr) > STACK_POINTER) {
        /* 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)
{
    if (!isatty(file)) {
        return BSP_UARTx_transmit((uint8_t*)ptr, len) == 0 ? len : 0;
    }

    int todo;
    for (todo = 0; todo < len; todo++) {
        const char c = *ptr++;
        if (c == '\n') BSP_UARTx_transmit((uint8_t*)&(char){'\r'}, 1);
        if (BSP_UARTx_transmit((uint8_t*)&c, 1) != 0) break;
    }

    return todo;
}


void _init(void) {}