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feat: implement window mechanism to eliminate memmove operations #17

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1 change: 1 addition & 0 deletions include/packet.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ typedef struct {
int size; /* the size for all valid characters in data buffer */
int cap; /* the capacity (1 << cap) of the data buffer */
int end_pos; /* the end position of the first packet in data buffer */
int start;
uint8_t *data;
} pktbuf_t;

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21 changes: 12 additions & 9 deletions src/packet.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7,13 +7,15 @@ static void pktbuf_clear(pktbuf_t *pktbuf)
{
pktbuf->end_pos = -1;
pktbuf->size = 0;
pktbuf->start = 0;
}

#define DEFAULT_CAP (10)
bool pktbuf_init(pktbuf_t *pktbuf)
{
pktbuf->cap = DEFAULT_CAP;
pktbuf->data = calloc(1, (1 << pktbuf->cap) * sizeof(uint8_t));
pktbuf->start = 0;
pktbuf_clear(pktbuf);

return true;
Expand Down Expand Up @@ -46,7 +48,7 @@ bool pktbuf_is_complete(pktbuf_t *pktbuf)

/* skip to the head of next packet */
for (int i = 0; i < pktbuf->size; i++) {
if (pktbuf->data[i] == '$') {
if (pktbuf->data[pktbuf->start + i] == '$') {
head = i;
break;
}
Expand All @@ -59,21 +61,23 @@ bool pktbuf_is_complete(pktbuf_t *pktbuf)

if (head > 0) {
/* moving memory for a valid packet */
memmove(pktbuf->data, pktbuf->data + head, pktbuf->size - head);
// memmove(pktbuf->data, pktbuf->data + head, pktbuf->size - head);
// pktbuf->size -= head;
pktbuf->start += head;
pktbuf->size -= head;
}

/* check the end of the buffer */
uint8_t *end_pos_ptr = memchr(pktbuf->data, '#', pktbuf->size);
uint8_t *end_pos_ptr =
memchr(pktbuf->data + pktbuf->start, '#', pktbuf->size);
if (end_pos_ptr == NULL)
return false;

int end_pos = (end_pos_ptr - pktbuf->data) + CSUM_SIZE;
if (end_pos > pktbuf->size)
int end_pos = (end_pos_ptr - (pktbuf->data + pktbuf->start)) + CSUM_SIZE;
if (end_pos >= pktbuf->size)
return false;

pktbuf->end_pos = end_pos;

return true;
}

Expand All @@ -85,12 +89,11 @@ packet_t *pktbuf_pop_packet(pktbuf_t *pktbuf)

int old_pkt_size = pktbuf->end_pos + 1;
packet_t *pkt = calloc(1, sizeof(packet_t) + old_pkt_size + 1);
memcpy(pkt->data, pktbuf->data, old_pkt_size);
memcpy(pkt->data, pktbuf->data + pktbuf->start, old_pkt_size);
pkt->end_pos = pktbuf->end_pos;
pkt->data[old_pkt_size] = 0;

memmove(pktbuf->data, pktbuf->data + old_pkt_size + 1,
pktbuf->size - old_pkt_size);
pktbuf->start += old_pkt_size + 1;
pktbuf->size -= old_pkt_size;
pktbuf->end_pos = -1;
return pkt;
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