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libc/symtab: optimize the find speed by bisection 

Signed-off-by: chao.an <anchao@xiaomi.com>
This commit is contained in:
chao.an 2021-12-22 00:04:41 +08:00 committed by Xiang Xiao
parent 1d26d75e66
commit e0f7bab13c
2 changed files with 53 additions and 0 deletions
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47
libs/libc/symtab/symtab_findbyvalue.c
View File

@ -54,9 +54,55 @@ FAR const struct symtab_s *
symtab_findbyvalue(FAR const struct symtab_s *symtab,
FAR void *value, int nsyms)
{
#ifndef CONFIG_SYMTAB_ORDEREDBYVALUE
FAR const struct symtab_s *retval = NULL;
#else
int high = nsyms - 1;
int mid = high >> 1;
int low = 0;
#endif
DEBUGASSERT(symtab != NULL);
#ifdef CONFIG_SYMTAB_ORDEREDBYVALUE
while (high >= low)
{
mid = (low + high) >> 1;
if (symtab[mid].sym_value == value)
{
break;
}
else if (symtab[mid].sym_value > value)
{
if (symtab[mid - 1].sym_value <= value)
{
mid -= 1;
break;
}
else
{
high = mid - 1;
}
}
else if (symtab[mid].sym_value < value)
{
if (symtab[mid + 1].sym_value >= value)
{
break;
}
else
{
low = mid + 1;
}
}
}
return &symtab[mid];
#else /* CONFIG_SYMTAB_ORDEREDBYVALUE */
for (; nsyms > 0; symtab++, nsyms--)
{
/* Look for symbols of lesser or equal value (probably address) to
@ -89,4 +135,5 @@ symtab_findbyvalue(FAR const struct symtab_s *symtab,
}
return retval;
#endif /* CONFIG_SYMTAB_ORDEREDBYVALUE */
}

6
libs/libc/unistd/Kconfig
View File

@ -103,6 +103,12 @@ config SYMTAB_ORDEREDBYNAME
Otherwise, the symbol table is assumed to be un-ordered and only
slow, linear searches are supported.
config SYMTAB_ORDEREDBYVALUE
bool "Symbol Tables Ordered by Value"
default n
---help---
Select if the symbol table is ordered by symbol value.
config SYMTAB_DECORATED
bool "Symbols are decorated with leading underscores"
default n