x300: improve lvbitx bitstream md5 read time

- Reading line by line avoids loading the entire 25 MB bitstream into memory
  since the MD5 hash usually occurs within the first 1% of the file stream

1 files changed, 20 insertions, 10 deletions

diff --git a/host/lib/transport/nirio/nifpga_lvbitx.cpp b/host/lib/transport/nirio/nifpga_lvbitx.cpp
index 2d8b63293..ef4a02aff 100644
--- a/host/lib/transport/nirio/nifpga_lvbitx.cpp
+++ b/host/lib/transport/nirio/nifpga_lvbitx.cpp
@@ -17,21 +17,31 @@ namespace uhd { namespace niusrprio {
 
 std::string nifpga_lvbitx::_get_bitstream_checksum(const std::string& file_path)
 {
-    std::string checksum;
+    const boost::regex md5_regex(
+        "<BitstreamMD5>([a-fA-F0-9]{32})<\\/BitstreamMD5>",
+        boost::regex::icase);
+
     std::ifstream lvbitx_stream(file_path.c_str());
-    if (lvbitx_stream.is_open()) {
-        std::string lvbitx_contents;
-        lvbitx_stream.seekg(0, std::ios::end);
-        lvbitx_contents.reserve(static_cast<size_t>(lvbitx_stream.tellg()));
-        lvbitx_stream.seekg(0, std::ios::beg);
-        lvbitx_contents.assign((std::istreambuf_iterator<char>(lvbitx_stream)), std::istreambuf_iterator<char>());
+    if (!lvbitx_stream.is_open()) {
+        return std::string();
+    }
+
+    std::string checksum, line;
+    while (std::getline(lvbitx_stream, line))
+    {
         try {
+            // short-circuiting the regex search with a simple find is faster
+            // for cases where the tag doesn't exist
             boost::smatch md5_match;
-            if (boost::regex_search(lvbitx_contents, md5_match, boost::regex("<BitstreamMD5>([a-zA-Z0-9]{32})<\\/BitstreamMD5>", boost::regex::icase))) {
+            if (line.find("<BitstreamMD5>") != std::string::npos &&
+                boost::regex_search(line, md5_match, md5_regex))
+            {
                 checksum = std::string(md5_match[1].first, md5_match[1].second);
+                break;
             }
-        } catch (boost::exception&) {
-            checksum = "";
+        }
+        catch (boost::exception&) {
+
         }
     }
     boost::to_upper(checksum);