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/* FIXME */
#include <assert.h>
/* FIXME: this is small for testing */
#define BUFFER_SIZE (8)
#define LEN(X, I) ((X)->p[(I)].one_past_end - (X)->p[(I)].start)
#define EMPTY(X) ((X)->n_bufs == 1 && LEN (X, 0) == 0)
#define ONE_PAST_END(X, I) ((X)->p[(I)].one_past_end)
struct Line_ptr
{
size_t i;
char *ptr;
};
typedef struct Line_ptr Line_ptr;
struct B_pair
{
char *start;
char *one_past_end;
};
struct Buf
{
size_t n_bufs;
struct obstack obs;
struct B_pair *p;
};
typedef struct Buf Buf;
static int
buf_init_from_stdin (Buf *x, int eol_byte)
{
int last_byte_is_eol_byte = 1;
int fail = 0;
#define OBS (&(x->obs))
obstack_init (OBS);
while (1)
{
char *buf = (char *) malloc (BUFFER_SIZE);
int bytes_read;
if (buf == NULL)
{
/* Fall back on the code that relies on a temporary file.
Write all buffers to that file and free them. */
/* FIXME */
fail = 1;
break;
}
bytes_read = full_read (STDIN_FILENO, buf, BUFFER_SIZE);
if (bytes_read < 0)
error (EXIT_FAILURE, errno, _("read error"));
{
struct B_pair bp;
bp.start = buf;
bp.one_past_end = buf + bytes_read;
obstack_grow (OBS, &bp, sizeof (bp));
}
if (bytes_read > 0)
last_byte_is_eol_byte = (buf[bytes_read - 1] == eol_byte);
if (bytes_read < BUFFER_SIZE)
break;
}
if (!fail)
{
/* If the file was non-empty and lacked an EOL_BYTE at its end,
then add a buffer containing just that one byte. */
if (!last_byte_is_eol_byte)
{
char *buf = malloc (1);
if (buf == NULL)
{
/* FIXME: just like above */
fail = 1;
}
else
{
struct B_pair bp;
*buf = eol_byte;
bp.start = buf;
bp.one_past_end = buf + 1;
obstack_grow (OBS, &bp, sizeof (bp));
}
}
}
x->n_bufs = obstack_object_size (OBS) / sizeof (x->p[0]);
x->p = (struct B_pair *) obstack_finish (OBS);
/* If there are two or more buffers and the last buffer is empty,
then free the last one and decrement the buffer count. */
if (x->n_bufs >= 2
&& x->p[x->n_bufs - 1].start == x->p[x->n_bufs - 1].one_past_end)
free (x->p[--(x->n_bufs)].start);
return fail;
}
static void
buf_free (Buf *x)
{
int i;
for (i = 0; i < x->n_bufs; i++)
free (x->p[i].start);
obstack_free (OBS, NULL);
}
Line_ptr
line_ptr_decrement (const Buf *x, const Line_ptr *lp)
{
Line_ptr lp_new;
if (lp->ptr > x->p[lp->i].start)
{
lp_new.i = lp->i;
lp_new.ptr = lp->ptr - 1;
}
else
{
assert (lp->i > 0);
lp_new.i = lp->i - 1;
lp_new.ptr = ONE_PAST_END (x, lp->i - 1) - 1;
}
return lp_new;
}
Line_ptr
line_ptr_increment (const Buf *x, const Line_ptr *lp)
{
Line_ptr lp_new;
assert (lp->ptr <= ONE_PAST_END (x, lp->i) - 1);
if (lp->ptr < ONE_PAST_END (x, lp->i) - 1)
{
lp_new.i = lp->i;
lp_new.ptr = lp->ptr + 1;
}
else
{
assert (lp->i < x->n_bufs - 1);
lp_new.i = lp->i + 1;
lp_new.ptr = x->p[lp->i + 1].start;
}
return lp_new;
}
static int
find_bol (const Buf *x,
const Line_ptr *last_bol, Line_ptr *new_bol, char eol_byte)
{
int i;
Line_ptr tmp;
char *last_bol_ptr;
if (last_bol->ptr == x->p[0].start)
return 0;
tmp = line_ptr_decrement (x, last_bol);
last_bol_ptr = tmp.ptr;
i = tmp.i;
while (1)
{
char *nl = memrchr (x->p[i].start, last_bol_ptr, eol_byte);
if (nl)
{
Line_ptr nl_pos;
nl_pos.i = i;
nl_pos.ptr = nl;
*new_bol = line_ptr_increment (x, &nl_pos);
return 1;
}
if (i <= 0)
break;
--i;
last_bol_ptr = ONE_PAST_END (x, i);
}
/* If last_bol->ptr didn't point at the first byte of X, then reaching
this point means that we're about to return the line that is at the
beginning of X. */
if (last_bol->ptr != x->p[0].start)
{
new_bol->i = 0;
new_bol->ptr = x->p[0].start;
return 1;
}
return 0;
}
static void
print_line (FILE *out_stream, const Buf *x,
const Line_ptr *bol, const Line_ptr *bol_next)
{
int i;
for (i = bol->i; i <= bol_next->i; i++)
{
char *a = (i == bol->i ? bol->ptr : x->p[i].start);
char *b = (i == bol_next->i ? bol_next->ptr : ONE_PAST_END (x, i));
fwrite (a, 1, b - a, out_stream);
}
}
static int
tac_mem ()
{
Buf x;
Line_ptr bol;
char eol_byte = '\n';
int fail;
fail = buf_init_from_stdin (&x, eol_byte);
if (fail)
{
buf_free (&x);
return 1;
}
/* Special case the empty file. */
if (EMPTY (&x))
return 0;
/* Initially, point at one past the last byte of the file. */
bol.i = x.n_bufs - 1;
bol.ptr = ONE_PAST_END (&x, bol.i);
while (1)
{
Line_ptr new_bol;
int found = find_bol (&x, &bol, &new_bol, eol_byte);
if (!found)
break;
print_line (stdout, &x, &new_bol, &bol);
bol = new_bol;
}
return 0;
}
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