diff options
| -rw-r--r-- | libpipe/pq.c | 72 |
1 files changed, 33 insertions, 39 deletions
diff --git a/libpipe/pq.c b/libpipe/pq.c index 8177dfe2..504182e9 100644 --- a/libpipe/pq.c +++ b/libpipe/pq.c @@ -19,9 +19,8 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include <malloc.h> -#include <string.h> /* for bcopy */ +#include <string.h> #include <stddef.h> -#include <assert.h> #include "pq.h" @@ -147,17 +146,18 @@ pq_queue (struct pq *pq, unsigned type, void *source) /* ---------------------------------------------------------------- */ -/* Returns a size to which a packet can be set, which will be at least GOAL, - but perhaps more. */ +/* Returns a legal size to which PACKET can be set allowing enough room for + EXTRA bytes more than what's already in it, and perhaps more. */ size_t -packet_size_adjust (size_t goal) +packet_new_size (struct packet *packet, size_t extra) { - if (goal > PACKET_SIZE_LARGE) - /* Round GOAL up to a page boundary (OLD_LEN should already be). */ - return round_page (goal); + size_t new_len = (packet->buf_end - packet->buf) + extra; + if (packet->buf_vm_alloced || new_len >= PACKET_SIZE_LARGE) + /* Round NEW_LEN up to a page boundary (OLD_LEN should already be). */ + return round_page (new_len); else /* Otherwise, just round up to a multiple of 512 bytes. */ - return (goal + 511) & ~511; + return (new_len + 511) & ~511; } /* Try to extend PACKET to be NEW_LEN bytes long, which should be greater @@ -178,7 +178,6 @@ packet_extend (struct packet *packet, size_t new_len) /* A vm_alloc'd packet. */ { char *extension = packet->buf + old_len; - /* Try to allocate memory at the end of our current buffer. */ if (vm_allocate (mach_task_self (), (vm_address_t *)&extension, new_len - old_len, 0) != 0) @@ -348,57 +347,52 @@ packet_read (struct packet *packet, char **data, size_t *data_len, size_t amount) { char *start = packet->buf_start; + char *end = packet->buf_end; - if (amount > packet->buf_end - start) - amount = packet->buf_end - start; + if (amount > end - start) + amount = end - start; if (amount > 0) { - if (packet->buf_vm_alloced && amount > vm_page_size) + if (packet->buf_vm_alloced && amount >= vm_page_size) /* We can return memory from BUF directly without copying. */ { char *buf = packet->buf; - char *end = packet->buf_end; - - /* Return the buffer directly. */ - *data = start; - if (buf > start) + if (buf + vm_page_size <= start) /* BUF_START has been advanced past the start of the buffer (perhaps by a series of small reads); as we're going to assume everything before START is gone, make sure we deallocate any memory on pages before those we return to the user. */ - { - char *first_page = (char *)trunc_page (start); - if (first_page > buf) - vm_deallocate (mach_task_self (), - (vm_address_t)buf, first_page - buf); - } + vm_deallocate (mach_task_self (), + (vm_address_t)buf, + trunc_page (start) - (vm_address_t)buf); + + *data = start; /* Return the buffer directly. */ + start += amount; /* Advance the read point. */ - if (start + amount < end) + if (start < end) /* Since returning a partial page actually means returning the whole page, we have to be careful not to grab past the page - boundary before the end of the data we want, unless the rest - of the page is unimportant. */ - amount = (char *)trunc_page (start + amount) - start; - - /* Advance the read point. */ - start = (char *)round_page (start + amount); - - if (start > end) - /* Make sure BUF_START is never beyond BUF_END (page-aligning the - new BUF_START may have move it past). */ + boundary before the end of the data we want. */ { - packet->buf_end = start; - packet->buf_len = 0; /* Pin at 0, despite moving past the end. */ + char *non_aligned_start = start; + start = (char *)trunc_page (start); + amount -= non_aligned_start - start; } else - /* Adjust BUF_LEN to reflect what the read has consumed. */ - packet->buf_len -= start - buf; + /* This read will be up to the end of the buffer, so we can just + consume any space on the page following BUF_END (vm_alloced + buffers are always allocated in whole pages). */ + { + start = (char *)round_page (start); + packet->buf_end = start; /* Ensure BUF_START <= BUF_END. */ + } /* We've actually consumed the memory at the start of BUF. */ packet->buf = start; packet->buf_start = start; + packet->buf_len -= start - buf; } else /* Just copy the data the old fashioned way.... */ |