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Eliminate pthread_once in tag table preparation
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Move the tag table initialization to static object constructor so
it runs before there are threads to worry about. This will slightly
increase our startup time for the arbitrary 'rpm --eval "%foo"' type
use but unlikely to matter in practise.

To do this, minimally objectify our tag entry table. The resulting
code division doesn't make too much sense but that can be cleaned
up later.
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@pmatilai
pmatilai committed Sep 24, 2024
1 parent 5487968 commit d5236d7
Showing 1 changed file with 53 additions and 49 deletions.
102 changes: 53 additions & 49 deletions lib/tagname.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,6 @@
*/

#include "system.h"

#include <pthread.h>

#include <rpm/header.h>
#include <rpm/rpmstring.h>
#include "debug.h"
Expand All @@ -28,9 +25,6 @@ struct headerTagTableEntry_s {
#define TABLESIZE (sizeof(rpmTagTable) / sizeof(rpmTagTable[0]) - 1)
static const int rpmTagTableSize = TABLESIZE;

static headerTagTableEntry tagsByName[TABLESIZE]; /*!< tags sorted by name. */
static headerTagTableEntry tagsByValue[TABLESIZE]; /*!< tags sorted by value. */

/**
* Compare tag table entries by name.
* @param *avp tag table entry a
Expand Down Expand Up @@ -61,21 +55,32 @@ static int tagCmpValue(const void * avp, const void * bvp)
return ret;
}

static pthread_once_t tagsLoaded = PTHREAD_ONCE_INIT;
class tagTable {
public:
tagTable();
headerTagTableEntry getEntry(const char *tag);
headerTagTableEntry getEntry(rpmTagVal tag);
int getNames(rpmtd tagnames, int fullname);

private:
headerTagTableEntry byName[TABLESIZE]; /*!< tags sorted by name */
headerTagTableEntry byValue[TABLESIZE]; /*!< tags sorted by value */

};

/* Initialize tag by-value and by-name lookup tables */
static void loadTags(void)
tagTable::tagTable()
{
/* Initialize tag by-value and by-name lookup tables */
for (int i = 0; i < rpmTagTableSize; i++) {
tagsByValue[i] = &rpmTagTable[i];
tagsByName[i] = &rpmTagTable[i];
byValue[i] = &rpmTagTable[i];
byName[i] = &rpmTagTable[i];
}

qsort(tagsByValue, rpmTagTableSize, sizeof(*tagsByValue), tagCmpValue);
qsort(tagsByName, rpmTagTableSize, sizeof(*tagsByName), tagCmpName);
qsort(byValue, rpmTagTableSize, sizeof(*byValue), tagCmpValue);
qsort(byName, rpmTagTableSize, sizeof(*byName), tagCmpName);
}

static headerTagTableEntry entryByTag(rpmTagVal tag)
headerTagTableEntry tagTable::getEntry(rpmTagVal tag)
{
headerTagTableEntry entry = NULL;
int i, comparison;
Expand All @@ -84,25 +89,25 @@ static headerTagTableEntry entryByTag(rpmTagVal tag)

while (l < u) {
i = (l + u) / 2;
comparison = (tag - tagsByValue[i]->val);
comparison = (tag - byValue[i]->val);

if (comparison < 0) {
u = i;
} else if (comparison > 0) {
l = i + 1;
} else {
/* Make sure that the bsearch retrieve is stable. */
while (i > 0 && tag == tagsByValue[i-1]->val) {
while (i > 0 && tag == byValue[i-1]->val) {
i--;
}
entry = tagsByValue[i];
entry = byValue[i];
break;
}
}
return entry;
}

static headerTagTableEntry entryByName(const char *tag)
headerTagTableEntry tagTable::getEntry(const char *tag)
{
headerTagTableEntry entry = NULL;
int i, comparison;
Expand All @@ -111,27 +116,49 @@ static headerTagTableEntry entryByName(const char *tag)

while (l < u) {
i = (l + u) / 2;
comparison = rstrcasecmp(tag, tagsByName[i]->shortname);
comparison = rstrcasecmp(tag, byName[i]->shortname);

if (comparison < 0) {
u = i;
} else if (comparison > 0) {
l = i + 1;
} else {
entry = tagsByName[i];
entry = byName[i];
break;
}
}
return entry;
}

int tagTable::getNames(rpmtd tagnames, int fullname)
{
const char **names;
const char *name;

if (tagnames == NULL)
return 0;

rpmtdReset(tagnames);
tagnames->count = rpmTagTableSize;
tagnames->data = names = (const char **)xmalloc(tagnames->count * sizeof(*names));
tagnames->type = RPM_STRING_ARRAY_TYPE;
tagnames->flags = RPMTD_ALLOCED | RPMTD_IMMUTABLE;

for (int i = 0; i < tagnames->count; i++) {
name = fullname ? byName[i]->name :
byName[i]->shortname;
names[i] = name;
}
return tagnames->count;
}

static tagTable tags;

const char * rpmTagGetName(rpmTagVal tag)
{
const char *name = "(unknown)";
const struct headerTagTableEntry_s *t;

pthread_once(&tagsLoaded, loadTags);

switch (tag) {
case RPMDBI_PACKAGES:
name = "Packages";
Expand All @@ -145,7 +172,7 @@ const char * rpmTagGetName(rpmTagVal tag)
break;

default:
t = entryByTag(tag);
t = tags.getEntry(tag);
if (t && t->shortname)
name = t->shortname;
break;
Expand All @@ -158,9 +185,7 @@ rpmTagType rpmTagGetType(rpmTagVal tag)
const struct headerTagTableEntry_s *t;
rpmTagType tagtype = RPM_NULL_TYPE;

pthread_once(&tagsLoaded, loadTags);

t = entryByTag(tag);
t = tags.getEntry(tag);
if (t) {
/* XXX this is dumb */
tagtype = (rpmTagType)(t->type | t->retype);
Expand All @@ -173,12 +198,10 @@ rpmTagVal rpmTagGetValue(const char * tagstr)
const struct headerTagTableEntry_s *t;
rpmTagVal tagval = RPMTAG_NOT_FOUND;

pthread_once(&tagsLoaded, loadTags);

if (!rstrcasecmp(tagstr, "Packages"))
return RPMDBI_PACKAGES;

t = entryByName(tagstr);
t = tags.getEntry(tagstr);
if (t)
tagval = t->val;

Expand Down Expand Up @@ -229,24 +252,5 @@ rpmTagClass rpmTagGetClass(rpmTagVal tag)

int rpmTagGetNames(rpmtd tagnames, int fullname)
{
const char **names;
const char *name;

pthread_once(&tagsLoaded, loadTags);

if (tagnames == NULL)
return 0;

rpmtdReset(tagnames);
tagnames->count = rpmTagTableSize;
tagnames->data = names = (const char **)xmalloc(tagnames->count * sizeof(*names));
tagnames->type = RPM_STRING_ARRAY_TYPE;
tagnames->flags = RPMTD_ALLOCED | RPMTD_IMMUTABLE;

for (int i = 0; i < tagnames->count; i++) {
name = fullname ? tagsByName[i]->name :
tagsByName[i]->shortname;
names[i] = name;
}
return tagnames->count;
return tags.getNames(tagnames, fullname);
}

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