/* Implement a cached obstack.
Written by Fred Fish <fnf@cygnus.com>
Rewritten by Jim Blandy <jimb@cygnus.com>
- Copyright 1999, 2000 Free Software Foundation, Inc.
+
+ Copyright (C) 1999-2020 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2 of the License, or
+ the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
-
-#include <stddef.h>
-#include <stdlib.h>
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
-#include "obstack.h"
+#include "gdb_obstack.h"
#include "bcache.h"
-#include "gdb_string.h" /* For memcpy declaration */
-/* The old hash function was stolen from SDBM. This is what DB 3.0 uses now,
- * and is better than the old one.
- */
-\f
-unsigned long
-hash(void *addr, int length)
+#include <algorithm>
+
+namespace gdb {
+
+/* The type used to hold a single bcache string. The user data is
+ stored in d.data. Since it can be any type, it needs to have the
+ same alignment as the most strict alignment of any type on the host
+ machine. I don't know of any really correct way to do this in
+ stock ANSI C, so just do it the same way obstack.h does. */
+
+struct bstring
{
- const unsigned char *k, *e;
- unsigned long h;
-
- k = (const unsigned char *)addr;
- e = k+length;
- for (h=0; k< e;++k)
- {
- h *=16777619;
- h ^= *k;
- }
- return (h);
-}
+ /* Hash chain. */
+ struct bstring *next;
+ /* Assume the data length is no more than 64k. */
+ unsigned short length;
+ /* The half hash hack. This contains the upper 16 bits of the hash
+ value and is used as a pre-check when comparing two strings and
+ avoids the need to do length or memcmp calls. It proves to be
+ roughly 100% effective. */
+ unsigned short half_hash;
+
+ union
+ {
+ char data[1];
+ double dummy;
+ }
+ d;
+};
+
\f
/* Growing the bcache's hash table. */
resize our hash table. */
#define CHAIN_LENGTH_THRESHOLD (5)
-static void
-expand_hash_table (struct bcache *bcache)
+void
+bcache::expand_hash_table ()
{
/* A table of good hash table sizes. Whenever we grow, we pick the
next larger size from this table. sizes[i] is close to 1 << (i+10),
struct bstring **new_buckets;
unsigned int i;
+ /* Count the stats. Every unique item needs to be re-hashed and
+ re-entered. */
+ m_expand_count++;
+ m_expand_hash_count += m_unique_count;
+
/* Find the next size. */
- new_num_buckets = bcache->num_buckets * 2;
+ new_num_buckets = m_num_buckets * 2;
for (i = 0; i < (sizeof (sizes) / sizeof (sizes[0])); i++)
- if (sizes[i] > bcache->num_buckets)
+ if (sizes[i] > m_num_buckets)
{
new_num_buckets = sizes[i];
break;
/* Allocate the new table. */
{
size_t new_size = new_num_buckets * sizeof (new_buckets[0]);
+
new_buckets = (struct bstring **) xmalloc (new_size);
memset (new_buckets, 0, new_size);
- bcache->structure_size -= (bcache->num_buckets
- * sizeof (bcache->bucket[0]));
- bcache->structure_size += new_size;
+ m_structure_size -= m_num_buckets * sizeof (m_bucket[0]);
+ m_structure_size += new_size;
}
/* Rehash all existing strings. */
- for (i = 0; i < bcache->num_buckets; i++)
+ for (i = 0; i < m_num_buckets; i++)
{
struct bstring *s, *next;
- for (s = bcache->bucket[i]; s; s = next)
+ for (s = m_bucket[i]; s; s = next)
{
struct bstring **new_bucket;
next = s->next;
- new_bucket = &new_buckets[(hash (&s->d.data, s->length)
+ new_bucket = &new_buckets[(m_hash_function (&s->d.data, s->length)
% new_num_buckets)];
s->next = *new_bucket;
*new_bucket = s;
}
/* Plug in the new table. */
- if (bcache->bucket)
- xfree (bcache->bucket);
- bcache->bucket = new_buckets;
- bcache->num_buckets = new_num_buckets;
+ xfree (m_bucket);
+ m_bucket = new_buckets;
+ m_num_buckets = new_num_buckets;
}
\f
/* Find a copy of the LENGTH bytes at ADDR in BCACHE. If BCACHE has
never seen those bytes before, add a copy of them to BCACHE. In
- either case, return a pointer to BCACHE's copy of that string. */
-void *
-bcache (void *addr, int length, struct bcache *bcache)
+ either case, return a pointer to BCACHE's copy of that string. If
+ optional ADDED is not NULL, return 1 in case of new entry or 0 if
+ returning an old entry. */
+
+const void *
+bcache::insert (const void *addr, int length, int *added)
{
+ unsigned long full_hash;
+ unsigned short half_hash;
int hash_index;
struct bstring *s;
+ if (added)
+ *added = 0;
+
+ /* Lazily initialize the obstack. This can save quite a bit of
+ memory in some cases. */
+ if (m_total_count == 0)
+ {
+ /* We could use obstack_specify_allocation here instead, but
+ gdb_obstack.h specifies the allocation/deallocation
+ functions. */
+ obstack_init (&m_cache);
+ }
+
/* If our average chain length is too high, expand the hash table. */
- if (bcache->unique_count >= bcache->num_buckets * CHAIN_LENGTH_THRESHOLD)
- expand_hash_table (bcache);
+ if (m_unique_count >= m_num_buckets * CHAIN_LENGTH_THRESHOLD)
+ expand_hash_table ();
- bcache->total_count++;
- bcache->total_size += length;
+ m_total_count++;
+ m_total_size += length;
- hash_index = hash (addr, length) % bcache->num_buckets;
+ full_hash = m_hash_function (addr, length);
- /* Search the hash bucket for a string identical to the caller's. */
- for (s = bcache->bucket[hash_index]; s; s = s->next)
- if (s->length == length
- && ! memcmp (&s->d.data, addr, length))
- return &s->d.data;
+ half_hash = (full_hash >> 16);
+ hash_index = full_hash % m_num_buckets;
+
+ /* Search the hash m_bucket for a string identical to the caller's.
+ As a short-circuit first compare the upper part of each hash
+ values. */
+ for (s = m_bucket[hash_index]; s; s = s->next)
+ {
+ if (s->half_hash == half_hash)
+ {
+ if (s->length == length
+ && m_compare_function (&s->d.data, addr, length))
+ return &s->d.data;
+ else
+ m_half_hash_miss_count++;
+ }
+ }
/* The user's string isn't in the list. Insert it after *ps. */
{
- struct bstring *new
- = obstack_alloc (&bcache->cache, BSTRING_SIZE (length));
- memcpy (&new->d.data, addr, length);
- new->length = length;
- new->next = bcache->bucket[hash_index];
- bcache->bucket[hash_index] = new;
-
- bcache->unique_count++;
- bcache->unique_size += length;
- bcache->structure_size += BSTRING_SIZE (length);
-
- return &new->d.data;
+ struct bstring *newobj
+ = (struct bstring *) obstack_alloc (&m_cache,
+ BSTRING_SIZE (length));
+
+ memcpy (&newobj->d.data, addr, length);
+ newobj->length = length;
+ newobj->next = m_bucket[hash_index];
+ newobj->half_hash = half_hash;
+ m_bucket[hash_index] = newobj;
+
+ m_unique_count++;
+ m_unique_size += length;
+ m_structure_size += BSTRING_SIZE (length);
+
+ if (added)
+ *added = 1;
+
+ return &newobj->d.data;
}
}
-
\f
-/* Freeing bcaches. */
-/* Free all the storage associated with BCACHE. */
-void
-free_bcache (struct bcache *bcache)
+/* Compare the byte string at ADDR1 of lenght LENGHT to the
+ string at ADDR2. Return 1 if they are equal. */
+
+int
+bcache::compare (const void *addr1, const void *addr2, int length)
{
- obstack_free (&bcache->cache, 0);
- if (bcache->bucket)
- xfree (bcache->bucket);
+ return memcmp (addr1, addr2, length) == 0;
+}
- /* This isn't necessary, but at least the bcache is always in a
- consistent state. */
- memset (bcache, 0, sizeof (*bcache));
+/* Free all the storage associated with BCACHE. */
+bcache::~bcache ()
+{
+ /* Only free the obstack if we actually initialized it. */
+ if (m_total_count > 0)
+ obstack_free (&m_cache, 0);
+ xfree (m_bucket);
}
\f
/* Printing statistics. */
-static int
-compare_ints (const void *ap, const void *bp)
-{
- /* Because we know we're comparing two ints which are positive,
- there's no danger of overflow here. */
- return * (int *) ap - * (int *) bp;
-}
-
-
static void
print_percentage (int portion, int total)
{
if (total == 0)
- printf_filtered ("(not applicable)\n");
+ /* i18n: Like "Percentage of duplicates, by count: (not applicable)". */
+ printf_filtered (_("(not applicable)\n"));
else
- printf_filtered ("%3d%%\n", portion * 100 / total);
+ printf_filtered ("%3d%%\n", (int) (portion * 100.0 / total));
}
BCACHE holds. Statistics are printed using `printf_filtered' and
its ilk. */
void
-print_bcache_statistics (struct bcache *c, char *type)
+bcache::print_statistics (const char *type)
{
int occupied_buckets;
int max_chain_length;
int median_chain_length;
+ int max_entry_size;
+ int median_entry_size;
- /* Count the number of occupied buckets, and measure chain lengths. */
+ /* Count the number of occupied buckets, tally the various string
+ lengths, and measure chain lengths. */
{
unsigned int b;
- int *chain_length
- = (int *) alloca (c->num_buckets * sizeof (*chain_length));
+ int *chain_length = XCNEWVEC (int, m_num_buckets + 1);
+ int *entry_size = XCNEWVEC (int, m_unique_count + 1);
+ int stringi = 0;
occupied_buckets = 0;
- for (b = 0; b < c->num_buckets; b++)
+ for (b = 0; b < m_num_buckets; b++)
{
- struct bstring *s = c->bucket[b];
+ struct bstring *s = m_bucket[b];
chain_length[b] = 0;
while (s)
{
+ gdb_assert (b < m_num_buckets);
chain_length[b]++;
+ gdb_assert (stringi < m_unique_count);
+ entry_size[stringi++] = s->length;
s = s->next;
}
}
}
- /* To compute the median, we need the set of chain lengths sorted. */
- qsort (chain_length, c->num_buckets, sizeof (chain_length[0]),
- compare_ints);
+ /* To compute the median, we need the set of chain lengths
+ sorted. */
+ std::sort (chain_length, chain_length + m_num_buckets);
+ std::sort (entry_size, entry_size + m_unique_count);
- if (c->num_buckets > 0)
+ if (m_num_buckets > 0)
{
- max_chain_length = chain_length[c->num_buckets - 1];
- median_chain_length = chain_length[c->num_buckets / 2];
+ max_chain_length = chain_length[m_num_buckets - 1];
+ median_chain_length = chain_length[m_num_buckets / 2];
}
else
{
max_chain_length = 0;
median_chain_length = 0;
}
+ if (m_unique_count > 0)
+ {
+ max_entry_size = entry_size[m_unique_count - 1];
+ median_entry_size = entry_size[m_unique_count / 2];
+ }
+ else
+ {
+ max_entry_size = 0;
+ median_entry_size = 0;
+ }
+
+ xfree (chain_length);
+ xfree (entry_size);
}
- printf_filtered (" Cached '%s' statistics:\n", type);
- printf_filtered (" Total object count: %ld\n", c->total_count);
- printf_filtered (" Unique object count: %lu\n", c->unique_count);
- printf_filtered (" Percentage of duplicates, by count: ");
- print_percentage (c->total_count - c->unique_count, c->total_count);
+ printf_filtered (_(" M_Cached '%s' statistics:\n"), type);
+ printf_filtered (_(" Total object count: %ld\n"), m_total_count);
+ printf_filtered (_(" Unique object count: %lu\n"), m_unique_count);
+ printf_filtered (_(" Percentage of duplicates, by count: "));
+ print_percentage (m_total_count - m_unique_count, m_total_count);
printf_filtered ("\n");
- printf_filtered (" Total object size: %ld\n", c->total_size);
- printf_filtered (" Unique object size: %ld\n", c->unique_size);
- printf_filtered (" Percentage of duplicates, by size: ");
- print_percentage (c->total_size - c->unique_size, c->total_size);
+ printf_filtered (_(" Total object size: %ld\n"), m_total_size);
+ printf_filtered (_(" Unique object size: %ld\n"), m_unique_size);
+ printf_filtered (_(" Percentage of duplicates, by size: "));
+ print_percentage (m_total_size - m_unique_size, m_total_size);
printf_filtered ("\n");
- printf_filtered (" Total memory used by bcache, including overhead: %ld\n",
- c->structure_size);
- printf_filtered (" Percentage memory overhead: ");
- print_percentage (c->structure_size - c->unique_size, c->unique_size);
- printf_filtered (" Net memory savings: ");
- print_percentage (c->total_size - c->structure_size, c->total_size);
+ printf_filtered (_(" Max entry size: %d\n"), max_entry_size);
+ printf_filtered (_(" Average entry size: "));
+ if (m_unique_count > 0)
+ printf_filtered ("%ld\n", m_unique_size / m_unique_count);
+ else
+ /* i18n: "Average entry size: (not applicable)". */
+ printf_filtered (_("(not applicable)\n"));
+ printf_filtered (_(" Median entry size: %d\n"), median_entry_size);
printf_filtered ("\n");
- printf_filtered (" Hash table size: %3d\n", c->num_buckets);
- printf_filtered (" Hash table population: ");
- print_percentage (occupied_buckets, c->num_buckets);
- printf_filtered (" Median hash chain length: %3d\n",
+ printf_filtered (_(" \
+Total memory used by bcache, including overhead: %ld\n"),
+ m_structure_size);
+ printf_filtered (_(" Percentage memory overhead: "));
+ print_percentage (m_structure_size - m_unique_size, m_unique_size);
+ printf_filtered (_(" Net memory savings: "));
+ print_percentage (m_total_size - m_structure_size, m_total_size);
+ printf_filtered ("\n");
+
+ printf_filtered (_(" Hash table size: %3d\n"),
+ m_num_buckets);
+ printf_filtered (_(" Hash table expands: %lu\n"),
+ m_expand_count);
+ printf_filtered (_(" Hash table hashes: %lu\n"),
+ m_total_count + m_expand_hash_count);
+ printf_filtered (_(" Half hash misses: %lu\n"),
+ m_half_hash_miss_count);
+ printf_filtered (_(" Hash table population: "));
+ print_percentage (occupied_buckets, m_num_buckets);
+ printf_filtered (_(" Median hash chain length: %3d\n"),
median_chain_length);
- printf_filtered (" Average hash chain length: ");
- if (c->num_buckets > 0)
- printf_filtered ("%3lu\n", c->unique_count / c->num_buckets);
+ printf_filtered (_(" Average hash chain length: "));
+ if (m_num_buckets > 0)
+ printf_filtered ("%3lu\n", m_unique_count / m_num_buckets);
else
- printf_filtered ("(not applicable)\n");
- printf_filtered (" Maximum hash chain length: %3d\n", max_chain_length);
+ /* i18n: "Average hash chain length: (not applicable)". */
+ printf_filtered (_("(not applicable)\n"));
+ printf_filtered (_(" Maximum hash chain length: %3d\n"),
+ max_chain_length);
printf_filtered ("\n");
}
+
+int
+bcache::memory_used ()
+{
+ if (m_total_count == 0)
+ return 0;
+ return obstack_memory_used (&m_cache);
+}
+
+} /* namespace gdb */
projects / deliverable / binutils-gdb.git / blobdiff