From d576127429a7be7d8e393d06f1bdd004fa37096c Mon Sep 17 00:00:00 2001 From: Tom Gundersen Date: Wed, 2 Apr 2014 10:00:31 +0200 Subject: libsystemd-network: Speed up checksum computation using 64 bit integers Improve the checksum computation by using 64 bit integers instead of the 16 bit integers in the existing implementation. This change speeds up the computation with approximately 78% both on 64 bit and 32 bit systems. Please see RFC 1071 for details. --- src/libsystemd-network/dhcp-packet.c | 51 +++++++++++++++++++++++++++--------- 1 file changed, 39 insertions(+), 12 deletions(-) (limited to 'src/libsystemd-network/dhcp-packet.c') diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c index 102ed096af..fba9c46ef2 100644 --- a/src/libsystemd-network/dhcp-packet.c +++ b/src/libsystemd-network/dhcp-packet.c @@ -59,21 +59,48 @@ int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, return 0; } -uint16_t dhcp_packet_checksum(void *buf, int len) { - uint32_t sum; - uint16_t *check; - int i; - uint8_t *odd; +uint16_t dhcp_packet_checksum(void *buf, size_t len) { + uint64_t *buf_64 = buf; + uint64_t *end_64 = (uint64_t*)buf + (len / sizeof(uint64_t)); + uint32_t *buf_32; + uint16_t *buf_16; + uint8_t *buf_8; + uint64_t sum = 0; + + while (buf_64 < end_64) { + sum += *buf_64; + if (sum < *buf_64) + sum++; + + buf_64 ++; + } + + buf_32 = (uint32_t*)buf_64; + + if (len & sizeof(uint32_t)) { + sum += *buf_32; + if (sum < *buf_32) + sum++; + + buf_32 ++; + } + + buf_16 = (uint16_t*)buf_32; - sum = 0; - check = buf; + if (len & sizeof(uint16_t)) { + sum += *buf_16; + if (sum < *buf_16) + sum ++; + + buf_16 ++; + } - for (i = 0; i < len / 2 ; i++) - sum += check[i]; + buf_8 = (uint8_t*)buf_16; - if (len & 0x01) { - odd = buf; - sum += odd[len - 1]; + if (len & sizeof(uint8_t)) { + sum += *buf_8; + if (sum < *buf_8) + sum++; } while (sum >> 16) -- cgit v1.2.3-54-g00ecf