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Bug#49491: Much overhead for MD5() and SHA1() on short strings

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MySQL's hash functions MD5 and SHA relied on the somewhat slow 
sprintf function to convert the digests to hex representations.
This patch replaces the sprintf with a specific and inline hex
conversion function.

Patch contributed by Jan Steemann.
This commit is contained in:
Davi Arnaut 2010-01-26 15:05:19 -02:00
parent b9d94d2a09
commit 60fc7967df
1 changed files with 16 additions and 15 deletions
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31
sql/item_strfunc.cc
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@ -42,6 +42,20 @@ C_MODE_END
String my_empty_string("",default_charset_info);
/*
Convert an array of bytes to a hexadecimal representation.
Used to generate a hexadecimal representation of a message digest.
*/
static void array_to_hex(char *to, const char *str, uint len)
{
const char *str_end= str + len;
for (; str != str_end; ++str)
{
*to++= _dig_vec_lower[((uchar) *str) >> 4];
*to++= _dig_vec_lower[((uchar) *str) & 0x0F];
}
}
bool Item_str_func::fix_fields(THD *thd, Item **ref)
@ -114,12 +128,7 @@ String *Item_func_md5::val_str(String *str)
null_value=1;
return 0;
}
sprintf((char *) str->ptr(),
"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
digest[0], digest[1], digest[2], digest[3],
digest[4], digest[5], digest[6], digest[7],
digest[8], digest[9], digest[10], digest[11],
digest[12], digest[13], digest[14], digest[15]);
array_to_hex((char *) str->ptr(), (const char*) digest, 16);
str->length((uint) 32);
return str;
}
@ -160,15 +169,7 @@ String *Item_func_sha::val_str(String *str)
if (!( str->alloc(SHA1_HASH_SIZE*2) ||
(mysql_sha1_result(&context,digest))))
{
sprintf((char *) str->ptr(),
"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\
%02x%02x%02x%02x%02x%02x%02x%02x",
digest[0], digest[1], digest[2], digest[3],
digest[4], digest[5], digest[6], digest[7],
digest[8], digest[9], digest[10], digest[11],
digest[12], digest[13], digest[14], digest[15],
digest[16], digest[17], digest[18], digest[19]);
array_to_hex((char *) str->ptr(), (const char*) digest, SHA1_HASH_SIZE);
str->length((uint) SHA1_HASH_SIZE*2);
null_value=0;
return str;