From 0ea100758d303fefae795624922b34e3f5d239ab Mon Sep 17 00:00:00 2001
From: Thulinma <jaron@vietors.com>
Date: Thu, 2 Mar 2017 17:26:39 +0100
Subject: [PATCH] Added FLV::seekToTagType function for fast FLV seeking, now
 used in MistInFLV

---
 lib/flv_tag.cpp         | 41 +++++++++++++++++++++++++++++++++++++++++
 lib/flv_tag.h           |  3 +++
 src/input/input_flv.cpp |  6 ++++++
 3 files changed, 50 insertions(+)

diff --git a/lib/flv_tag.cpp b/lib/flv_tag.cpp
index 70636616..e6683c35 100644
--- a/lib/flv_tag.cpp
+++ b/lib/flv_tag.cpp
@@ -1,9 +1,11 @@
 /// \file flv_tag.cpp
 /// Holds all code for the FLV namespace.
 
+#include "defines.h"
 #include "rtmpchunks.h"
 #include "flv_tag.h"
 #include "timing.h"
+#include "util.h"
 #include <stdio.h> //for Tag::FileLoader
 #include <unistd.h> //for Tag::FileLoader
 #include <fcntl.h> //for Tag::FileLoader
@@ -52,6 +54,45 @@ bool FLV::is_header(char * header) {
   return true;
 } //FLV::is_header
 
+
+/// Helper function that can quickly skip through a file looking for a particular tag type
+bool FLV::seekToTagType(FILE * f, uint8_t t){
+  long long startPos = Util::ftell(f);
+  DONTEVEN_MSG("Starting seek at %lld", startPos);
+  char buf[4];
+  if (fread(buf, 4, 1, f) != 1){return false;}
+  while (!feof(f) && !ferror(f)){
+    switch (buf[0]){
+      case 0x09:
+      case 0x08:
+      case 0x12:
+        {
+          if (t == buf[0]){
+            if (fseek(f, -4, SEEK_CUR)){
+              WARN_MSG("Could not seek back in FLV stream!");
+            }
+            INSANE_MSG("Found tag of type %u at %lld", t, Util::ftell(f));
+            return true;
+          }
+          long len = (buf[1] << 16) | (buf[2] << 8) | buf[3];
+          if (fseek(f, len+11, SEEK_CUR)){
+            WARN_MSG("Could not seek forward in FLV stream!");
+          }else{
+            DONTEVEN_MSG("Seeking %ld+4 bytes forward, now at %lld", len+11, Util::ftell(f));
+          }
+          if (fread(buf, 4, 1, f) != 1){return false;}
+        }
+        break;
+      default:
+        WARN_MSG("Invalid FLV tag detected! Aborting search.");
+        if (fseek(f, -4, SEEK_CUR)){
+          WARN_MSG("Could not seek back in FLV stream!");
+        }
+        return false;
+    }
+  }
+}
+
 /// True if this media type requires init data.
 /// Will always return false if the tag type is not 0x08 or 0x09.
 /// Returns true for H263, AVC (H264), AAC.
diff --git a/lib/flv_tag.h b/lib/flv_tag.h
index 4e430830..0dbc6fd3 100644
--- a/lib/flv_tag.h
+++ b/lib/flv_tag.h
@@ -24,6 +24,9 @@ namespace FLV {
   bool check_header(char * header); ///< Checks a FLV Header for validness.
   bool is_header(char * header); ///< Checks the first 3 bytes for the string "FLV".
 
+  /// Helper function that can quickly skip through a file looking for a particular tag type
+  bool seekToTagType(FILE * f, uint8_t type);
+
   /// This class is used to hold, work with and get information about a single FLV tag.
   class Tag {
     public:
diff --git a/src/input/input_flv.cpp b/src/input/input_flv.cpp
index 9d8f6557..66ffa930 100644
--- a/src/input/input_flv.cpp
+++ b/src/input/input_flv.cpp
@@ -103,6 +103,12 @@ namespace Mist {
   
   void inputFLV::getNext(bool smart) {
     long long int lastBytePos = Util::ftell(inFile);
+    if (selectedTracks.size() == 1){
+      uint8_t targetTag = 0x08;
+      if (selectedTracks.count(1)){targetTag = 0x09;}
+      if (selectedTracks.count(3)){targetTag = 0x12;}
+      FLV::seekToTagType(inFile, targetTag);
+    }
     while (!feof(inFile) && !FLV::Parse_Error){
       if (tmpTag.FileLoader(inFile)){
         if ( !selectedTracks.count(tmpTag.getTrackID())){