2 files changed, 31 insertions, 1 deletions

diff --git a/src/eyetil.cc b/src/eyetil.cc
index 2fbd687..fe816a6 100644
--- a/src/eyetil.cc
+++ b/src/eyetil.cc
@@ -1,35 +1,36 @@
 #include <stdlib.h>
 #include <sys/stat.h>
 #include <syslog.h>
 #include <iostream>
 #include <cassert>
 #include <stdexcept>
+#include <algorithm>
+#include <numeric>
 #include <openssl/md5.h>
 #include "eyetil.h"
 
 binary_t& binary_t::from_hex(const std::string& h) {
-    /* TODO: algorithmize */
     std::string::size_type hs = h.length();
     if(hs&1)
         throw std::runtime_error("odd number of characters in hexadecimal number");
     int rvs = hs>>1;
     resize(rvs);
     const unsigned char *hp = (const unsigned char*)h.data();
     iterator oi=begin();
     char t[3] = { 0,0,0 };
     for(int i=0;i<rvs;++i) {
         t[0]=*(hp++); t[1]=*(hp++);
         *(oi++) = strtol(t,0,16);
     }
     return *this;
 }
 
 binary_t& binary_t::from_data(const void *d,size_t s) {
     resize(s);
     std::copy((const unsigned char*)d,(const unsigned char *)d+s,
             begin() );
     return *this;
 }
 
 std::string binary_t::hex() const {
     std::string rv;
@@ -96,24 +97,50 @@ tarchive_t::tarchive_t(void *p,size_t s) : a(archive_read_new()), e(0) {
     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();
+}
diff --git a/src/eyetil.h b/src/eyetil.h
index 195d24f..378f703 100644
--- a/src/eyetil.h
+++ b/src/eyetil.h
@@ -24,25 +24,28 @@ class tmpdir_t {
     public:
         std::string dir;
 
         tmpdir_t(const std::string& dt);
         ~tmpdir_t();
 
         std::string get_file(const std::string& f);
 };
 
 class tarchive_t {
     public:
         struct archive *a;
         struct archive_entry *e;
 
         tarchive_t(void *p,size_t s);
         ~tarchive_t();
 
         bool read_next_header();
 
         std::string entry_pathname();
 
         bool read_data_into_fd(int fd);
 };
 
+binary_t integrity_digest(const void *ptr,size_t size,
+        const std::string& ukey);
+
 #endif /* __EYETIL_H */