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//printf needs following syscalls: sbrk write close fstat isatty lseek read
//
#include <sys/stat.h>
#include <string.h>
static int preread;
static int alloc;
easywrite(char *c);
void syscalls_init()
{
preread=0;
alloc=0xff0000;
}
int close(int file)
{
// easywrite("syscall: close\n");
return -1;
}
int fstat(int file, struct stat *st)
{
// easywrite("syscall: fstat\n");
st->st_mode = S_IFCHR;
return 0;
}
int isatty(int file)
{
// easywrite("syscall: isatty\n");
return 1;
}
int lseek(int file, int ptr, int dir)
{
// printf("syscall: lseek %i %i %i",file,ptr,dir);
if(dir==0)preread=ptr;
else{ puts("other modes unsupported sorry"); while(1);}
return preread;
}
int read(int file, char *ptr, int len)
{
// easywrite("syscall: read\n");
int i;
char buf[]="++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.";
if(preread>=strlen(buf)){
// easywrite("syscall: read = EOF\n");
return 0; //EOF
}
for(i=0;i<len;i++)
{
if(preread>=strlen(buf))return i;
ptr[i]=buf[preread++];
}
return len;
}
int open(const char *name, int flags, int mode)
{
// easywrite("syscall: open\n");
return 99;
return -1;
}
int write(int file, char *ptr, int len)
{
int todo;
for (todo = 0; todo < len; todo++)
{
char byte=(*ptr++);
int byt=byte;
int ebx; // will hold return value;
// system call
asm("pusha");
asm("mov $61,%eax"); // select syscall)
asm("mov %0,%%edx"::"m"(byt));
//asm("mov $88,%edx");
asm("int $0x80"); // actual syscall ! interrupt
asm("mov %%ebx, %0": "=b" (ebx));
asm("popa");
//
}
return len;
}
caddr_t sbrk(int incr)
{
// easywrite("syscall: sbrk!!\n");
int oldalloc=alloc;
alloc+=incr;
return oldalloc;
/*
extern char end;
// char _end;
static char *heap_end;
char *prev_heap_end;
if (heap_end == 0) {
heap_end = &end;
}
prev_heap_end = heap_end;
if (heap_end + incr > stack_ptr) {
write (1, "Heap and stack collision\n", 25);
abort ();
}
heap_end += incr;
return (caddr_t) prev_heap_end;
*/
}
//
// helpers
easywrite(char *c)
{
write(1,c,strlen(c));
}
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