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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xcalloc (size_t m, size_t n)
{
void *p = calloc (m, n);
if (!p)
exit_fatal ("calloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->len = 0;
self->str = xcalloc (1, (self->alloc = 16));
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->str[self->len += n] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Main --------------------------------------------------------------------
struct str program; ///< Raw program
struct str data; ///< Data tape
enum command { RIGHT, LEFT, INC, DEC, SET, IN, OUT, BEGIN, END };
bool grouped[] = { 1, 1, 1, 1, 1, 0, 0, 0, 0 };
struct instruction { enum command cmd; size_t arg; };
int
main (int argc, char *argv[])
{
(void) argc; str_init (&program);
(void) argv; str_init (&data);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
FILE *input = fopen ("/dev/tty", "rb");
if (!input)
exit_fatal ("can't open terminal for reading\n");
// - - Decode and group - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct instruction *parsed = xcalloc (sizeof *parsed, program.len);
size_t parsed_len = 0;
for (size_t i = 0; i < program.len; i++)
{
enum command cmd;
switch (program.str[i])
{
case '>': cmd = RIGHT; break;
case '<': cmd = LEFT; break;
case '+': cmd = INC; break;
case '-': cmd = DEC; break;
case '.': cmd = OUT; break;
case ',': cmd = IN; break;
case '[': cmd = BEGIN; break;
case ']': cmd = END; break;
default: continue;
}
if (!parsed_len || !grouped[cmd] || parsed[parsed_len - 1].cmd != cmd)
parsed_len++;
parsed[parsed_len - 1].cmd = cmd;
parsed[parsed_len - 1].arg++;
}
// - - Simple optimization pass - - - - - - - - - - - - - - - - - - - - - - - -
size_t in = 0, out = 0;
for (; in < parsed_len; in++, out++)
{
if (in + 2 < parsed_len
&& parsed[in ].cmd == BEGIN
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == END)
{
parsed[out].cmd = SET;
parsed[out].arg = 0;
in += 2;
}
else if (out && parsed[out - 1].cmd == SET && parsed[in].cmd == INC)
parsed[--out].arg += parsed[in].arg;
else if (out != in)
parsed[out] = parsed[in];
}
parsed_len = out;
// - - Loop pairing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t nesting = 0;
size_t *stack = xcalloc (sizeof *stack, parsed_len);
for (size_t i = 0; i < parsed_len; i++)
{
switch (parsed[i].cmd)
{
case BEGIN:
stack[nesting++] = i;
break;
case END:
assert (nesting > 0);
--nesting;
parsed[stack[nesting]].arg = i;
parsed[i].arg = stack[nesting];
default:
break;
}
}
assert (nesting == 0);
// - - Runtime - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t dataptr = 0;
str_append_c (&data, 0);
for (size_t i = 0; i < parsed_len; i++)
{
size_t arg = parsed[i].arg;
switch (parsed[i].cmd)
{
case RIGHT:
assert (SIZE_MAX - dataptr > arg);
dataptr += arg;
while (dataptr >= data.len)
str_append_c (&data, 0);
break;
case LEFT:
assert (dataptr >= arg);
dataptr -= arg;
break;
case INC: data.str[dataptr] += arg; break;
case DEC: data.str[dataptr] -= arg; break;
case SET: data.str[dataptr] = arg; break;
case OUT:
fputc (data.str[dataptr], stdout);
break;
case IN:
data.str[dataptr] = c = fgetc (input);
assert (c != EOF);
break;
case BEGIN: if (!data.str[dataptr]) i = arg; break;
case END: if ( data.str[dataptr]) i = arg; break;
}
}
return 0;
}
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