Hand-apply bbfb370d7de28ec1e8f307865cc6253bb5d4366e from master; quicker digest calcu...

[dcpomatic.git] / src / lib / util.cc

diff --git a/src/lib/util.cc b/src/lib/util.cc
index c0e32b778669ce3b9f810d5d46ac4c188a3e067d..0a6f381db8adf23cd7c8028e3dd2cc624f49d575 100644 (file)
--- a/src/lib/util.cc
+++ b/src/lib/util.cc
@@ -417,45 +417,53 @@ dcpomatic_setup_gettext_i18n (string lang)
 #endif
 }
 
-/** @param job Optional job for which to report progress */
+/** Compute a digest of the first and last `size' bytes of a set of files. */
 string
-md5_digest (vector<boost::filesystem::path> files, shared_ptr<Job> job)
+md5_digest_head_tail (vector<boost::filesystem::path> files, boost::uintmax_t size)
 {
-       boost::uintmax_t const buffer_size = 64 * 1024;
-       char buffer[buffer_size];
-
+       boost::scoped_array<char> buffer (new char[size]);
        MD5Digester digester;
 
-       vector<int64_t> sizes;
-       for (size_t i = 0; i < files.size(); ++i) {
-               sizes.push_back (boost::filesystem::file_size (files[i]));
-       }
-
-       for (size_t i = 0; i < files.size(); ++i) {
+       /* Head */
+       boost::uintmax_t to_do = size;
+       char* p = buffer.get ();
+       int i = 0;
+       while (i < int64_t (files.size()) && to_do > 0) {
                FILE* f = fopen_boost (files[i], "rb");
                if (!f) {
                        throw OpenFileError (files[i].string());
                }
 
-               boost::uintmax_t const bytes = boost::filesystem::file_size (files[i]);
-               boost::uintmax_t remaining = bytes;
-
-               while (remaining > 0) {
-                       int const t = min (remaining, buffer_size);
-                       int const r = fread (buffer, 1, t, f);
-                       if (r != t) {
-                               throw ReadFileError (files[i], errno);
-                       }
-                       digester.add (buffer, t);
-                       remaining -= t;
-
-                       if (job) {
-                               job->set_progress ((float (i) + 1 - float(remaining) / bytes) / files.size ());
-                       }
+               boost::uintmax_t this_time = min (to_do, boost::filesystem::file_size (files[i]));
+               fread (p, 1, this_time, f);
+               p += this_time;
+               to_do -= this_time;
+               fclose (f);
+
+               ++i;
+       }
+       digester.add (buffer.get(), size - to_do);
+
+       /* Tail */
+       to_do = size;
+       p = buffer.get ();
+       i = files.size() - 1;
+       while (i >= 0 && to_do > 0) {
+               FILE* f = fopen_boost (files[i], "rb");
+               if (!f) {
+                       throw OpenFileError (files[i].string());
                }
 
+               boost::uintmax_t this_time = min (to_do, boost::filesystem::file_size (files[i]));
+               fseek (f, -this_time, SEEK_END);
+               fread (p, 1, this_time, f);
+               p += this_time;
+               to_do -= this_time;
                fclose (f);
-       }
+
+               --i;
+       }               
+       digester.add (buffer.get(), size - to_do);
 
        return digester.get ();
 }