metal_newlib_syscalls.c

/**
 * @file   metal_syscalls.c
 * @date   19.07.2016
 * @author Klemens D. Morgenstern
 *



 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

typedef enum metal_func_t
{
    metal_func_chown = 0,
    metal_func_close,
    metal_func_fstat,
    metal_func_isatty,
    metal_func_link,
    metal_func_lseek,
    metal_func_open,
    metal_func_read,
    metal_func_stat,
    metal_func_sysmlink,
    metal_func_unlink,
    metal_func_write
} metal_func;

int metal_func_stub(metal_func func_type __attribute__((unused)),
                 const char* arg1  __attribute__((unused)),
                 const char* arg2  __attribute__((unused)),
                 int arg3          __attribute__((unused)),
                 int arg4          __attribute__((unused)),
                 int arg5          __attribute__((unused)),
                 char* arg6        __attribute__((unused)),
                 struct stat* arg7 __attribute__((unused)))
{
    return -1;
}

int _open (char* file, int flags, int mode);
int _read (int file, char* ptr, int len);
int _write(int file, char* ptr, int len);
int _lseek(int file, int ptr, int dir);
int _close(int);


int _fstat(int fildes, struct stat* st)
{
    return metal_func_stub(metal_func_fstat,
                0, // const char* arg1,
                0, // const char* arg2
                fildes, // int arg3
                0, // int arg4
                0, // int arg5
                0, // char* arg6
                st // struct stat* arg7
                );
}

int _isatty(int file)
{
    return metal_func_stub(metal_func_isatty,
                0, // const char* arg1,
                0, // const char* arg2
                file, // int arg3
                0, // int arg4
                0, // int arg5
                0, // char* arg6
                0 // struct stat* arg7
                );
}


int _link(char* existing, char* _new)
{
    return metal_func_stub(metal_func_link,
                existing, // const char* arg1,
                _new, // const char* arg2
                0, // int arg3
                0, // int arg4
                0, // int arg5
                0, // char* arg6
                0  // struct stat* arg7
                );
}


#ifndef METAL_NEWLIB_BUFFER_SIZE
#define METAL_NEWLIB_BUFFER_SIZE 0x400
#endif

//write buffer
static int write_fd  = -1;
static int write_pos = 0;
static char write_buf[METAL_NEWLIB_BUFFER_SIZE];

static void flush_write()
{
    if (write_pos > 0)
    {
        _write(write_fd, write_buf, write_pos);
        write_fd = -1;
        write_pos = 0;
    }
}

static int _buffered_write(int file, char* ptr, int len __attribute__((unused)))
{
    if ((file != write_fd) || (write_pos == METAL_NEWLIB_BUFFER_SIZE))
    {
        flush_write();
        write_fd = file;
    }

    write_buf[write_pos++] = *ptr;

    if ((*ptr == '\n')) //flush on newline, but put it into the buffer first.
    {
        flush_write();
        write_fd = file;
    }

    return 1;
}


//read buffer
static int read_fd = -1;
static int read_pos = 0;
static int read_end = 0;
static char read_buf[METAL_NEWLIB_BUFFER_SIZE];

void read_clear()
{
    read_pos = 0;
    read_end = 0;
    read_fd = -1;
}

void _read_init_buffer(int fd)
{
    read_fd = fd;
    read_pos = 0;
    read_end = metal_func_stub(metal_func_read,
            0,    // const char* arg1,
            0,    // const char* arg2
            read_fd, // int arg3
            METAL_NEWLIB_BUFFER_SIZE,  // int arg4
            0,    // int arg5
            read_buf,  // char* arg6
            0     // struct stat* arg7
            );
}

int _read_buffered(char* ptr, int len)
{
    if( (read_pos == read_end) && (read_end == METAL_NEWLIB_BUFFER_SIZE))
    {
        read_pos = 0;
        read_end = metal_func_stub(metal_func_read,
                0,    // const char* arg1,
                0,    // const char* arg2
                read_fd, // int arg3
                METAL_NEWLIB_BUFFER_SIZE,  // int arg4
                0,    // int arg5
                read_buf,  // char* arg6
                0     // struct stat* arg7
                );
    }

    //read what's available
    int i = 0;
    for (; ((read_pos + i) < read_end) && (i<len); i++) //read current buffer
        ptr[i] = read_buf[read_pos+i];

    read_pos += i;
    return i;
}



int _open(char* file, int flags, int mode)
{
    return metal_func_stub(metal_func_open,
                file, // const char* arg1
                0, // const char* arg2
                flags, // int arg3
                mode, // int arg4
                0, // int arg5
                0, // char* arg6
                0  // struct stat* arg7
                );
}


int _close(int fildes)
{
    flush_write();
    if (read_fd == fildes)
        read_clear();
    return metal_func_stub(metal_func_close,
                0, // const char* arg1,
                0, // const char* arg2
                fildes, // int arg3
                0, // int arg4
                0, // int arg5
                0, // char* arg6
                0 // struct stat* ar7B
                );
}

int _lseek(int file, int ptr, int dir)
{
    return metal_func_stub(metal_func_lseek,
            0, // const char* arg1,
            0, // const char* arg2
            file, // int arg3
            ptr, // int arg4
            dir, //int arg5
            0, // char * arg6
            0  // struct stat* arg7
            );
}


int _read(int file, char* ptr, int len)
{
    if ((read_fd != -1) && (file == read_fd))
        return _read_buffered(ptr, len);
    else if ((read_fd == -1) && (len>0))
    {
       _read_init_buffer(file);
      return  _read_buffered(ptr, len);
    }
    else
        return metal_func_stub(metal_func_read,
                0,    // const char* arg1,
                0,    // const char* arg2
                file, // int arg3
                len,  // int arg4
                0,    // int arg5
                ptr,  // char* arg6
                0     // struct stat* arg7
                );
}

int _write(int file, char* ptr, int len)
{
    if (len == 1)
        return _buffered_write(file, ptr, len);
    else
    {
        return metal_func_stub(metal_func_write,
                0,    // const char* arg1
                0,    // const char* arg2
                file, // int arg3
                len,  // int arg4
                0,    // int arg5
                ptr,  // char* arg6
                0     // struct stat* arg7
                );
    }
}

int _stat(const char* file, struct stat* st)
{
    return metal_func_stub(metal_func_stat,
                file, // const char* arg1
                0,    // const char* arg2
                0,    // int arg3
                0,    // int arg4
                0,    // int arg5
                0,    // char* arg6
                st    // struct stat* arg7
                );
}

int _symlink(const char* path1, const char* path2)
{
    return metal_func_stub(metal_func_sysmlink,
                path1, // const char* arg1,
                path2, // const char* arg2
                0,     // int arg3
                0,     // int arg4
                0,     // int arg5
                0,     // char* arg6
                0      // struct stat* arg7
                );
}

int _unlink(char* name)
{
    return metal_func_stub(metal_func_unlink,
                0,    // const char* arg1
                0,    // const char* arg2
                0,    // int arg3
                0,    // int arg4
                0,    // int arg5
                name, // char* arg6
                0     // struct stat* arg7
                );
}