From dc7272391191a76b4315d1b7849ff2e570fd69fe Mon Sep 17 00:00:00 2001
From: Vojtech Bubnik <bubnikv@gmail.com>
Date: Fri, 3 Sep 2021 16:19:16 +0200
Subject: [PATCH] Optimization of GCodeReader: 1) Use std::from_chars() instead
 of strtod() 2) Own implementation of buffered readline()

---
 src/libslic3r/GCodeReader.cpp | 40 +++++++++++++++++++++++++++++------
 src/libslic3r/GCodeReader.hpp | 13 ++++++------
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/src/libslic3r/GCodeReader.cpp b/src/libslic3r/GCodeReader.cpp
index 7dc3c9a8ac..54e6802e62 100644
--- a/src/libslic3r/GCodeReader.cpp
+++ b/src/libslic3r/GCodeReader.cpp
@@ -2,6 +2,7 @@
 #include <boost/algorithm/string/classification.hpp>
 #include <boost/algorithm/string/split.hpp>
 #include <boost/nowide/fstream.hpp>
+#include <charconv>
 #include <fstream>
 #include <iostream>
 #include <iomanip>
@@ -32,7 +33,7 @@ void GCodeReader::apply_config(const DynamicPrintConfig &config)
     m_extrusion_axis = get_extrusion_axis_char(m_config);
 }
 
-const char* GCodeReader::parse_line_internal(const char *ptr, GCodeLine &gline, std::pair<const char*, const char*> &command)
+const char* GCodeReader::parse_line_internal(const char *ptr, const char *end, GCodeLine &gline, std::pair<const char*, const char*> &command)
 {
     PROFILE_FUNC();
 
@@ -70,9 +71,9 @@ const char* GCodeReader::parse_line_internal(const char *ptr, GCodeLine &gline,
             }
             if (axis != NUM_AXES_WITH_UNKNOWN) {
                 // Try to parse the numeric value.
-                char   *pend = nullptr;
-                double  v = strtod(++ c, &pend);
-                if (pend != nullptr && is_end_of_word(*pend)) {
+                double v;
+                auto [pend, ec] = std::from_chars(++ c, end, v);
+                if (pend != c && is_end_of_word(*pend)) {
                     // The axis value has been parsed correctly.
                     if (axis != UNKNOWN_AXIS)
 	                    gline.m_axis[int(axis)] = float(v);
@@ -128,10 +129,37 @@ void GCodeReader::update_coordinates(GCodeLine &gline, std::pair<const char*, co
 void GCodeReader::parse_file(const std::string &file, callback_t callback)
 {
     boost::nowide::ifstream f(file);
+    f.sync_with_stdio(false);
+    std::vector<char> buffer(65536 * 10, 0);
     std::string line;
     m_parsing = true;
-    while (m_parsing && std::getline(f, line))
-        this->parse_line(line, callback);
+    GCodeLine gline;
+    bool eof = false;
+    while (m_parsing && ! eof) {
+        f.read(buffer.data(), buffer.size());
+        auto it        = buffer.begin();
+        auto it_bufend = buffer.begin() + f.gcount();
+        eof = ! f.good();
+        while (it != it_bufend) {
+            bool eol = false;
+            auto it_end = it;
+            for (; it_end != it_bufend && ! (eol = *it_end == '\r' || *it_end == '\n'); ++ it_end) ;
+            eol |= eof && it_end == it_bufend;
+            if (eol) {
+                gline.reset();
+                if (line.empty())
+                    this->parse_line(&(*it), &(*it_end), gline, callback);
+                else {
+                    line.insert(line.end(), it, it_end);
+                    this->parse_line(line.c_str(), line.c_str() + line.size(), gline, callback);
+                    line.clear();
+                }
+            } else
+                line.insert(line.end(), it, it_end);
+            // Skip all the empty lines.
+            for (it = it_end; it != it_bufend && (*it == '\r' || *it == '\n'); ++ it) ;
+        }
+    }
 }
 
 bool GCodeReader::GCodeLine::has(char axis) const
diff --git a/src/libslic3r/GCodeReader.hpp b/src/libslic3r/GCodeReader.hpp
index 6b58608e61..88c9df2841 100644
--- a/src/libslic3r/GCodeReader.hpp
+++ b/src/libslic3r/GCodeReader.hpp
@@ -83,11 +83,12 @@ public:
     void parse_buffer(const std::string &buffer, Callback callback)
     {
         const char *ptr = buffer.c_str();
+        const char *end = ptr + buffer.size();
         GCodeLine gline;
         m_parsing = true;
         while (m_parsing && *ptr != 0) {
             gline.reset();
-            ptr = this->parse_line(ptr, gline, callback);
+            ptr = this->parse_line(ptr, end, gline, callback);
         }
     }
 
@@ -95,18 +96,18 @@ public:
         { this->parse_buffer(buffer, [](GCodeReader&, const GCodeReader::GCodeLine&){}); }
 
     template<typename Callback>
-    const char* parse_line(const char *ptr, GCodeLine &gline, Callback &callback)
+    const char* parse_line(const char *ptr, const char *end, GCodeLine &gline, Callback &callback)
     {
         std::pair<const char*, const char*> cmd;
-        const char *end = parse_line_internal(ptr, gline, cmd);
+        const char *line_end = parse_line_internal(ptr, end, gline, cmd);
         callback(*this, gline);
         update_coordinates(gline, cmd);
-        return end;
+        return line_end;
     }
 
     template<typename Callback>
     void parse_line(const std::string &line, Callback callback)
-        { GCodeLine gline; this->parse_line(line.c_str(), gline, callback); }
+        { GCodeLine gline; this->parse_line(line.c_str(), line.c_str() + line.size(), gline, callback); }
 
     void parse_file(const std::string &file, callback_t callback);
     void quit_parsing() { m_parsing = false; }
@@ -127,7 +128,7 @@ public:
 //  void   set_extrusion_axis(char axis) { m_extrusion_axis = axis; }
 
 private:
-    const char* parse_line_internal(const char *ptr, GCodeLine &gline, std::pair<const char*, const char*> &command);
+    const char* parse_line_internal(const char *ptr, const char *end, GCodeLine &gline, std::pair<const char*, const char*> &command);
     void        update_coordinates(GCodeLine &gline, std::pair<const char*, const char*> &command);
 
     static bool         is_whitespace(char c)           { return c == ' ' || c == '\t'; }