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Use only one bit per field/offset in array, not one `int'.

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(printable_field): Change type to `unsigned char'.
(mark_printable_field, is_printable_field): New functions.
Use them in place of all direct accesses of `printable_field'.
This commit is contained in:
Jim Meyering
2003-07-26 09:40:14 +00:00
parent 421680e11c
commit df1bfa25aa
1 changed files with 34 additions and 14 deletions
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48
src/cut.c
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@@ -95,14 +95,15 @@ static unsigned int max_range_endpoint;
to end of line. */
static unsigned int eol_range_start;
/* In byte mode, which bytes to output.
/* This is a bit vector.
In byte mode, which bytes to output.
In field mode, which DELIM-separated fields to output.
Both bytes and fields are numbered starting with 1,
so the zeroth element of this array is unused.
so the zeroth bit of this array is unused.
A field or byte K has been selected if
(K <= MAX_RANGE_ENDPOINT and PRINTABLE_FIELD[K])
(K <= MAX_RANGE_ENDPOINT and is_printable_field(K))
|| (EOL_RANGE_START > 0 && K >= EOL_RANGE_START). */
static int *printable_field;
static unsigned char *printable_field;
enum operating_mode
{
@@ -224,6 +225,20 @@ With no FILE, or when FILE is -, read standard input.\n\
exit (status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
}
static inline void
mark_printable_field (unsigned int i)
{
size_t n = i / CHAR_BIT;
printable_field[n] |= (1 << (i % CHAR_BIT));
}
static inline bool
is_printable_field (unsigned int i)
{
size_t n = i / CHAR_BIT;
return (printable_field[n] & (1 << (i % CHAR_BIT))) ? true : false;
}
unsigned int
hash_int (const void *x, unsigned int tablesize)
{
@@ -258,7 +273,7 @@ print_kth (unsigned int k, int *range_start)
return 1;
}
if (k <= max_range_endpoint && printable_field[k])
if (k <= max_range_endpoint && is_printable_field (k))
{
if (range_start)
*range_start = is_range_start_index (k);
@@ -277,12 +292,15 @@ print_kth (unsigned int k, int *range_start)
through end of line. Return nonzero if FIELDSTR contains at least
one field specification, zero otherwise. */
/* FIXME-someday: What if the user wants to cut out the 1,000,000-th field
of some huge input file? This function shouldn't have to allocate a table
of a million ints just so we can test every field < 10^6 with an array
dereference. Instead, consider using a dynamic hash table. It would be
simpler and nearly as good a solution to use a 32K x 4-byte table with
one bit per field index instead of a whole `int' per index. */
/* FIXME-someday: What if the user wants to cut out the 1,000,000-th
field of some huge input file? This function shouldn't have to
allocate a table of a million bits just so we can test every
field < 10^6 with an array dereference. Instead, consider using
an adaptive approach: if the range of selected fields is too large,
but only a few fields/byte-offsets are actually selected, use a
hash table. If the range of selected fields is too large, and
too many are selected, then resort to using the range-pairs (the
`rp' array) directly. */
static int
set_fields (const char *fieldstr)
@@ -445,7 +463,8 @@ set_fields (const char *fieldstr)
the field numbers corresponding to all finite ranges
(i.e. `2-6' or `-4', but not `5-') in FIELDSTR. */
printable_field = xcalloc ((max_range_endpoint + 1) * sizeof (int), 1);
printable_field = xcalloc (((max_range_endpoint / CHAR_BIT + 1)
* sizeof (*printable_field)), 1);
/* Set the array entries corresponding to integers in the ranges of RP. */
for (i = 0; i < n_rp; i++)
@@ -453,7 +472,7 @@ set_fields (const char *fieldstr)
unsigned int j;
for (j = rp[i].lo; j <= rp[i].hi; j++)
{
printable_field[j] = 1;
mark_printable_field (j);
}
}
@@ -465,7 +484,8 @@ set_fields (const char *fieldstr)
unsigned int j = rp[i].lo;
for (j = rp[i].lo; j <= rp[i].hi; j++)
{
if (0 < j && printable_field[j] && !printable_field[j - 1])
if (0 < j && is_printable_field (j)
&& !is_printable_field (j - 1))
{
/* Record the fact that `j' is a range-start index. */
void *ent_from_table = hash_insert (range_start_ht,