Re: [Qemu-devel] [PATCH v5 2/9] Add rle_encode and rle_decode functions Implement Run Length Encoding compression

[Orit Wasserman <owasserm@redhat.com>]

On 01/03/2012 09:57 PM, Anthony Liguori wrote:
> On 01/03/2012 09:34 AM, Orit Wasserman wrote:
>> Signed-off-by: Orit Wasserman<owasserm@redhat.com>
>> ---
>>   arch_init.c |   58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   1 files changed, 58 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch_init.c b/arch_init.c
>> index fdda277..426b34d 100644
>> --- a/arch_init.c
>> +++ b/arch_init.c
>> @@ -139,6 +139,9 @@ typedef struct XBRLEHeader {
>>       uint32_t xh_cksum;
>>   } XBRLEHeader;
>>
>> +static int rle_encode(uint8_t *src, int slen, uint8_t *dst, int dlen);
>> +static int rle_decode(uint8_t *src, int slen, uint8_t *dst, int dlen);
>> +
>>   /***********************************************************/
>>   /* XBRLE page cache implementation */
>>   static CacheItem *cache_item_get(unsigned long pos, int item)
>> @@ -277,6 +280,61 @@ static void cache_insert(unsigned long addr, uint8_t *pdata)
>>       it->it_addr = addr;
>>   }
>>
>> +/* XBRLE (Xor Based Run-Length Encoding) */
>> +static int rle_encode(uint8_t *src, int slen, uint8_t *dst, int dlen)
>> +{
>> +    int d = 0, ch_run = 0, i;
>> +    uint8_t prev = 0, ch = 0;
>> +
>> +    for (i = 0; i<= slen; i++) {
>> +        if (i != slen) {
>> +            ch = src[i];
>> +        }
>> +
>> +        if (!i || (i != slen&&  ch == prev&&  ch_run<  255)) {
>> +            ch_run++;
>> +        } else {
>> +            if (d+2>  dlen) {
>> +                return -1;
>> +            }
>> +            *dst++ = ch_run;
>> +            *dst++ = prev;
>> +            d += 2;
>> +            ch_run = 1;
>> +        }
>> +
>> +        prev = ch;
>> +    }
>> +    return d;
>> +}
>> +
>> +static int rle_decode(uint8_t *src, int slen, uint8_t *dst, int dlen)
>> +{
>> +    int d = 0, s;
>> +
>> +    for (s = 0; s<  slen-1; s += 2) {
>> +        uint8_t ch_run = src[s];
>> +        uint8_t ch = src[s+1];
>> +        while (ch_run--) {
>> +            if (d == dlen) {
>> +                return -1;
>> +            }
>> +            dst[d] = ch;
>> +            d++;
>> +        }
>> +    }
>> +    return d;
>> +}
>> +
>> +static void xor_encode(uint8_t *dst, uint8_t *src1, uint8_t *src2)
>> +{
>> +    int i;
>> +
>> +    for (i = 0; i<  TARGET_PAGE_SIZE; i++) {
>> +        dst[i] = src1[i] ^ src2[i];
>> +    }
>> +}
>> +
> 
> I don't think any of these need to be in arch_init.c.  It would be nicer to make a xbzrle.c file for this stuff.
> 

I will fix it.

> Regards,
> 
> Anthony Liguori
> 
>>   static int is_dup_page(uint8_t *page, uint8_t ch)
>>   {
>>       uint32_t val = ch<<  24 | ch<<  16 | ch<<  8 | ch;
> 
>