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manage tag string allocations in a pool
There are many duplicated strings in the tag database, e.g. many songs having the same artist. Don't allocate such strings twice, manage all strings in a pool.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,135 @@ | ||
| /* libmpdclient | ||
| (c) 2003-2008 The Music Player Daemon Project | ||
| This project's homepage is: http://www.musicpd.org | ||
| Redistribution and use in source and binary forms, with or without | ||
| modification, are permitted provided that the following conditions | ||
| are met: | ||
| - Redistributions of source code must retain the above copyright | ||
| notice, this list of conditions and the following disclaimer. | ||
| - Redistributions in binary form must reproduce the above copyright | ||
| notice, this list of conditions and the following disclaimer in the | ||
| documentation and/or other materials provided with the distribution. | ||
| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | ||
| ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | ||
| LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | ||
| A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR | ||
| CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | ||
| EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | ||
| PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | ||
| PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | ||
| LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | ||
| NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | ||
| SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| */ | ||
|
|
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| #include "str_pool.h" | ||
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| #include <assert.h> | ||
| #include <stddef.h> | ||
| #include <stdlib.h> | ||
| #include <string.h> | ||
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| #define NUM_SLOTS 4096 | ||
|
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| struct slot { | ||
| struct slot *next; | ||
| unsigned char ref; | ||
| char value[1]; | ||
| } __attribute__((packed)); | ||
|
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| static struct slot *slots[NUM_SLOTS]; | ||
|
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| static inline unsigned | ||
| calc_hash(const char *p) | ||
| { | ||
| unsigned hash = 5381; | ||
|
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| assert(p != NULL); | ||
|
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| while (*p != 0) | ||
| hash = (hash << 5) + hash + *p++; | ||
|
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| return hash; | ||
| } | ||
|
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| static inline struct slot * | ||
| value_to_slot(char *value) | ||
| { | ||
| return (struct slot*)(value - offsetof(struct slot, value)); | ||
| } | ||
|
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| static struct slot *slot_alloc(struct slot *next, const char *value) | ||
| { | ||
| size_t length = strlen(value); | ||
| struct slot *slot = malloc(sizeof(*slot) + length); | ||
| if (slot == NULL) | ||
| abort(); /* XXX */ | ||
|
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| slot->next = next; | ||
| slot->ref = 1; | ||
| memcpy(slot->value, value, length + 1); | ||
| return slot; | ||
| } | ||
|
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| char *str_pool_get(const char *value) | ||
| { | ||
| struct slot **slot_p, *slot; | ||
|
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| slot_p = &slots[calc_hash(value) % NUM_SLOTS]; | ||
| for (slot = *slot_p; slot != NULL; slot = slot->next) { | ||
| if (strcmp(value, slot->value) == 0 && slot->ref < 0xff) { | ||
| assert(slot->ref > 0); | ||
| ++slot->ref; | ||
| return slot->value; | ||
| } | ||
| } | ||
|
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| slot = slot_alloc(*slot_p, value); | ||
| *slot_p = slot; | ||
| return slot->value; | ||
| } | ||
|
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| char *str_pool_dup(char *value) | ||
| { | ||
| struct slot *slot = value_to_slot(value); | ||
|
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| assert(slot->ref > 0); | ||
|
|
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| if (slot->ref < 0xff) { | ||
| ++slot->ref; | ||
| return value; | ||
| } else { | ||
| /* the reference counter overflows above 0xff; | ||
| duplicate the value, and start with 1 */ | ||
| struct slot **slot_p = | ||
| &slots[calc_hash(slot->value) % NUM_SLOTS]; | ||
| slot = slot_alloc(*slot_p, slot->value); | ||
| *slot_p = slot; | ||
| return slot->value; | ||
| } | ||
| } | ||
|
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| void str_pool_put(char *value) | ||
| { | ||
| struct slot **slot_p, *slot; | ||
|
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| slot = value_to_slot(value); | ||
| assert(slot->ref > 0); | ||
| --slot->ref; | ||
|
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| if (slot->ref > 0) | ||
| return; | ||
|
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| for (slot_p = &slots[calc_hash(value) % NUM_SLOTS]; | ||
| *slot_p != slot; | ||
| slot_p = &(*slot_p)->next) { | ||
| assert(*slot_p != NULL); | ||
| } | ||
|
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| *slot_p = slot->next; | ||
| free(slot); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,38 @@ | ||
| /* libmpdclient | ||
| (c) 2003-2008 The Music Player Daemon Project | ||
| This project's homepage is: http://www.musicpd.org | ||
| Redistribution and use in source and binary forms, with or without | ||
| modification, are permitted provided that the following conditions | ||
| are met: | ||
| - Redistributions of source code must retain the above copyright | ||
| notice, this list of conditions and the following disclaimer. | ||
| - Redistributions in binary form must reproduce the above copyright | ||
| notice, this list of conditions and the following disclaimer in the | ||
| documentation and/or other materials provided with the distribution. | ||
| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | ||
| ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | ||
| LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | ||
| A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR | ||
| CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | ||
| EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | ||
| PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | ||
| PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | ||
| LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | ||
| NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | ||
| SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| */ | ||
|
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| #ifndef STR_POOL_H | ||
| #define STR_POOL_H | ||
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| char *str_pool_get(const char *value); | ||
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| char *str_pool_dup(char *value); | ||
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| void str_pool_put(char *value); | ||
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| #endif |