diff options
| -rw-r--r-- | libpipe/pq.h | 71 |
1 files changed, 49 insertions, 22 deletions
diff --git a/libpipe/pq.h b/libpipe/pq.h index 963c9e90..abd193f8 100644 --- a/libpipe/pq.h +++ b/libpipe/pq.h @@ -23,6 +23,7 @@ #include <errno.h> #include <stddef.h> /* for size_t */ +#include <string.h> #include <mach/mach.h> struct packet @@ -119,22 +120,51 @@ int packet_extend (struct packet *packet, size_t new_len); returned. */ error_t packet_realloc (struct packet *packet, size_t new_len); +/* Try to make space in PACKET for AMOUNT more bytes without growing the + buffer, returning true if we could do it. */ +extern inline int +packet_fit (struct packet *packet, size_t amount) +{ + char *buf = packet->buf, *end = packet->buf_end; + size_t buf_len = packet->buf_len; + size_t left = buf + buf_len - end; /* Free space at the end of the buffer. */ + + if (amount > left) + { + char *start = packet->buf_start; + size_t cur_len = end - start; /* Amount of data currently in the buf. */ + + if (buf_len - cur_len >= amount + && cur_len < PACKET_SIZE_LARGE && cur_len < (buf_len >> 2)) + /* If we could fit the data in by moving what's already in the + buffer, and there's not too much there, and it represents less + than 25% of the buffer size, then move the data instead of growing + the buffer. */ + { + bcopy (start, buf, cur_len); + packet->buf_start = buf; + packet->buf_end = buf + cur_len; + } + else + return 0; /* We failed... */ + } + + return 1; +} + /* Make sure that PACKET has room for at least AMOUNT more bytes, or return the reason why not. */ extern inline error_t packet_ensure (struct packet *packet, size_t amount) { - size_t new_len; - size_t left = packet->buf + packet->buf_len - packet->buf_end; - - if (amount < left) - return 0; - - new_len = packet_new_size (packet, amount); - if (packet_extend (packet, new_len)) - return 0; - else - return packet_realloc (packet, new_len); + if (! packet_fit (packet, amount)) + /* We must make the buffer bigger. */ + { + size_t new_len = packet_new_size (packet, amount); + if (! packet_extend (packet, new_len)) + return packet_realloc (packet, new_len); + } + return 0; } /* Make sure that PACKET has room for at least AMOUNT more bytes, *only* if @@ -144,17 +174,14 @@ packet_ensure (struct packet *packet, size_t amount) extern inline int packet_ensure_efficiently (struct packet *packet, size_t amount) { - size_t new_len; - size_t left = packet->buf + packet->buf_len - packet->buf_end; - - if (amount < left) - return 1; - - new_len = packet_new_size (packet, amount); - if (packet_extend (packet, new_len)) - return 1; - if ((packet->buf_end - packet->buf_start) < PACKET_SIZE_LARGE) - return packet_realloc (packet, new_len) == 0; + if (! packet_fit (packet, amount)) + { + size_t new_len = packet_new_size (packet, amount); + if (packet_extend (packet, new_len)) + return 1; + if ((packet->buf_end - packet->buf_start) < PACKET_SIZE_LARGE) + return packet_realloc (packet, new_len) == 0; + } return 0; } |