optimize integrity digest calculation memory use

Signed-off-by: Michael Krelin <hacker@klever.net>

1 files changed, 5 insertions, 9 deletions

diff --git a/src/eyetil.cc b/src/eyetil.cc
index 57ae607..2e6ab7e 100644
--- a/src/eyetil.cc
+++ b/src/eyetil.cc
@@ -120,58 +120,54 @@ std::string tmpdir_t::get_file(const std::string& f) {
 }
 
 tarchive_t::tarchive_t(void *p,size_t s) : a(archive_read_new()), e(0) {
     if(!a) throw std::runtime_error("failed to archive_read_new()");
     if(archive_read_support_format_tar(a)) {
 	archive_read_finish(a);
 	throw std::runtime_error("failed to archive_read_support_format_tar()");
     }
     if(archive_read_open_memory(a,p,s)) {
 	archive_read_finish(a);
 	throw std::runtime_error("failed to archive_read_open_memory()");
     }
 }
 tarchive_t::~tarchive_t() {
     assert(a);
     archive_read_finish(a);
 }
 
 bool tarchive_t::read_next_header() {
     assert(a);
     return archive_read_next_header(a,&e)==ARCHIVE_OK;
 }
 
 std::string tarchive_t::entry_pathname() {
     assert(a); assert(e);
     return archive_entry_pathname(e);
 }
 
 bool tarchive_t::read_data_into_fd(int fd) {
     assert(a);
     return archive_read_data_into_fd(a,fd)==ARCHIVE_OK;
 }
 
 #pragma pack(1)
 struct block512_t {
     enum { words = 512 / sizeof(uint16_t) };
     uint16_t data[words];
 
     static uint16_t tcpcksum(block512_t& data) {
 	uint32_t sum = std::accumulate(data.data,data.data+words,0);
 	while(uint32_t hw = sum>>16) sum = (sum&0xffff)+hw;
 	return ~sum;
     }
 
 };
 #pragma pack()
 
 binary_t integrity_digest(const void *ptr,size_t size,const std::string& ukey) {
-    binary_t key; key.from_hex(ukey);
-    std::vector<uint16_t> blksums; blksums.reserve(size/sizeof(block512_t));
-    block512_t *db = (block512_t*)ptr,
-	       *de = db + size/sizeof(block512_t);
-    std::transform( db, de, std::back_inserter(blksums), block512_t::tcpcksum );
-    binary_t subject;
-    subject.from_data((void*)&(blksums.front()),blksums.size()*sizeof(uint16_t));
-    std::copy( key.begin(), key.end(), std::back_inserter(subject) );
-    return subject.md5();
+    md5_digester rv;
+    std::transform( (block512_t*)ptr, ((block512_t*)ptr)+size/sizeof(block512_t),
+	    rv.updater<uint16_t>(), block512_t::tcpcksum );
+    rv.update( binary_t(ukey) );
+    return rv.final();
 }