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INTERNAL: Refactor a memcached_fetch function #337

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INTERNAL: Refactor a memcached_fetch function #337

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62 changes: 9 additions & 53 deletions libmemcached/fetch.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -63,73 +63,29 @@ char *memcached_fetch(memcached_st *ptr, char *key, size_t *key_length,
if (not error)
error= &unused;


unlikely (ptr->flags.use_udp)
{
if (value_length)
*value_length= 0;

if (key_length)
*key_length= 0;

if (flags)
*flags= 0;

if (key)
*key= 0;

*error= MEMCACHED_NOT_SUPPORTED;
return NULL;
}

result_buffer= memcached_fetch_result(ptr, result_buffer, error);
if (result_buffer == NULL or memcached_failed(*error))
if (result_buffer == NULL || result_buffer->key_length > MEMCACHED_MAX_KEY)
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result_buffer != NULL์ด์ง€๋งŒ, *error ๊ฐ’์ด failture์ธ ๊ฒฝ์šฐ๋Š” ์—†๋‹ค๋Š” ๊ฒƒ์ด์ฃ ?

memcached_fetch_result() ํ•จ์ˆ˜์—์„œ
result_buffer != NULL์ด๋ฉด์„œ result_buffer->key_length > MEMCACHED_MAX_KEY ๊ฒฝ์šฐ
MEMCACHED_KEY_TOO_BIG ์—๋Ÿฌ ์„ค์ •ํ•˜์—ฌ ๋ฆฌํ„ดํ•˜๋ ค๋Š” ์˜๋„๊ฐ€ ์žˆ์—ˆ๋˜ ๊ฒƒ์ด ์•„๋‹Œ์ง€ ?

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์˜๋„๊นŒ์ง€๋Š” ๋ชจ๋ฅด๊ฒ ์œผ๋‚˜ memcached_fetch_result์—์„œ MEMCACHED_MAX_KEY๋ฅผ ๋ฐ˜ํ™˜ํ•˜๋Š” ํ˜•ํƒœ๊ฐ€ ๋” ์ž์—ฐ์Šค๋Ÿฌ์šด ๊ฒƒ ๊ฐ™์Šต๋‹ˆ๋‹ค.

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@ing-eoking
๋…ผ๋ฆฌ์ ์œผ๋กœ ๋ด์„œ,
result_buffer->key_length > MEMCACHED_MAX_KEY ์ธ ๊ฒฝ์šฐ ์˜ค๋ฅ˜๋ฅผ ๋ฆฌํ„ดํ•  ํ•„์š”๋Š” ์—†์–ด ๋ณด์ž…๋‹ˆ๋‹ค.

ํŠนํžˆ๋‚˜, memcached_fetch()์—์„œ๋Š” key์— ๋Œ€ํ•ด ๊ด€์‹ฌ์ด ์—†๊ณ  ๋‹จ์ง€ value๋งŒ ์กฐํšŒํ•˜๋Š” ๊ฒฝ์šฐ์ž…๋‹ˆ๋‹ค.
์ด๋Ÿฌํ•œ ์กฐ๊ฑด ๊ฒ€์‚ฌ๊ฐ€ ๋“ค์–ด๊ฐ„ ์ด์œ ๋ฅผ ๊ฐ„๋‹จํžˆ ํ™•์ธํ•ด ๋ณผ ์ˆ˜ ์žˆ์„๊นŒ์š”?

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@jhpark816

libmemcached ์ปค๋ฐ‹ ๋ฉ”์‹œ์ง€๋ฅผ ํ™•์ธํ•œ ๊ฒฐ๊ณผ, ๋”ฐ๋กœ ์ด์œ ๋ฅผ ์ ์–ด ๋†“์ง€๋Š” ์•Š์•˜์Šต๋‹ˆ๋‹ค.
awesomized/libmemcached#7e592f0

We now check return key size for memcached_fetch() to make sure it is not
too big (compared to original ascii server). result_st is now initialized 
differently. This should make it a bit faster.

ํ•˜์ง€๋งŒ result_buffer->key_length > MEMCACHED_MAX_KEY ๋น„๊ต๋ฅผ memcached_fetch๋‚˜ memcached_fetch_result์—์„œ ํ•˜๋Š” ๊ฒƒ์€ ๋‹ค์†Œ ๋ถ€์ž์—ฐ์Šค๋Ÿฌ์›Œ ๋ณด์ž…๋‹ˆ๋‹ค.

result_buffer ๊ตฌ์กฐ์ฒด ๋‚ด์˜ item_key ๋ณ€์ˆ˜๊ฐ€ ์ด๋ฏธ MEMCACHED_MAX_KEY ํฌ๊ธฐ๋กœ ๊ณ ์ •๋˜์–ด ์žˆ์Šต๋‹ˆ๋‹ค.
ํ‚ค๋ฅผ ์ €์žฅํ•  ๋•Œ ์˜ค๋ฒ„ํ”Œ๋กœ์šฐ๊ฐ€ ๋ฐœ์ƒํ•œ ๊ฒฝ์šฐ ์ด๋ฅผ ์ฒ˜๋ฆฌํ•˜๋Š” ๋ฐฉ์‹์ด ๋” ์ ํ•ฉํ•˜์ง€ ์•Š์„๊นŒ ์ƒ๊ฐ๋ฉ๋‹ˆ๋‹ค.

struct memcached_result_st {
  ...
  size_t key_length;
  ...
  char item_key[MEMCACHED_MAX_KEY];
  ...
};

{
WATCHPOINT_ASSERT(result_buffer == NULL);
if (value_length)
*value_length= 0;

if (key_length)
*key_length= 0;

if (flags)
*flags= 0;
*error= (result_buffer != NULL) ? MEMCACHED_KEY_TOO_BIG : *error;

if (key)
*key= 0;
if (key) *key= 0;
if (key_length) *key_length= 0;
if (value_length) *value_length= 0;
if (flags) *flags= 0;

return NULL;
}

if (value_length)
{
*value_length= memcached_string_length(&result_buffer->value);
}

if (key)
{
if (result_buffer->key_length > MEMCACHED_MAX_KEY)
{
*error= MEMCACHED_KEY_TOO_BIG;
if (value_length)
*value_length= 0;

if (key_length)
*key_length= 0;

if (flags)
*flags= 0;

if (key)
*key= 0;

return NULL;
}
strncpy(key, result_buffer->item_key, result_buffer->key_length); // For the binary protocol we will cut off the key :(
if (key_length)
*key_length= result_buffer->key_length;
}

if (value_length)
*value_length= memcached_string_length(&result_buffer->value);

if (flags)
*flags= result_buffer->item_flags;

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