From d0c4fb0b420cbd21bb9330a475f7dce52602cf7e Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Sat, 6 Sep 2025 17:46:16 -0500
Subject: [PATCH] IT import: comments, channel names and pat names

the latter two are MPT extensions

this may not work on songs with MIDI macro setup info
---
 src/engine/fileOps/it.cpp | 97 +++++++++++++++++++++++++++++++++++++++
 src/engine/safeReader.cpp | 26 +++++++++++
 src/engine/safeReader.h   |  3 ++
 3 files changed, 126 insertions(+)

diff --git a/src/engine/fileOps/it.cpp b/src/engine/fileOps/it.cpp
index ba6b6d743..0975ed698 100644
--- a/src/engine/fileOps/it.cpp
+++ b/src/engine/fileOps/it.cpp
@@ -363,6 +363,103 @@ bool DivEngine::loadIT(unsigned char* file, size_t len) {
       patPtr[i]=reader.readI();
     }
 
+    // skip edit history if present
+    if (special&2) {
+      logD("skipping edit history...");
+      unsigned short editHistSize=reader.readS();
+      if (editHistSize>0) {
+        if (!reader.seek(editHistSize*8,SEEK_CUR)) {
+          logV("what? I wasn't expecting that from you.");
+        }
+      }
+    }
+
+    // read extension blocks, if any
+    logD("looking for extensions...");
+    bool hasExtensions=true;
+    while (hasExtensions) {
+      char extType[4];
+      unsigned int extSize=0;
+      memset(extType,0,4);
+
+      reader.read(extType,4);
+      extSize=reader.readI();
+
+      if (memcmp(extType,"PNAM",4)==0) {
+        logV("found MPT extension: pattern names");
+        // check whether this block is valid
+        if (extSize>patCount*32) {
+          logV("block may not be valid");
+          break;
+        }
+        // read pattern names
+        logV("reading pattern names...");
+        for (unsigned int i=0; i<(extSize>>5); i++) {
+          DivPattern* p=ds.subsong[0]->pat[0].getPattern(i,true);
+          p->name=reader.readStringLatin1(32);
+        }
+      } else if (memcmp(extType,"CNAM",4)==0) {
+        logV("found MPT extension: channel names");
+        // check whether this block is valid
+        if (extSize>DIV_MAX_CHANS*20) {
+          logV("block may not be valid");
+          break;
+        }
+        // read channel names
+        logV("reading channel names...");
+        for (unsigned int i=0; i<(extSize>>5); i++) {
+          String chanName=reader.readStringLatin1(20);
+          for (DivSubSong* j: ds.subsong) {
+            j->chanName[i]=chanName;
+          }
+        }
+      } else if (memcmp(extType,"CHFX",4)==0) {
+        logV("found MPT extension: channel effects");
+        // skip (stop if we cannot seek)
+        if (!reader.seek(extSize,SEEK_CUR)) {
+          break;
+        }
+      } else if (
+        extType[0]=='F' &&
+        (extType[1]=='X' || (extType[1]>='0' && extType[1]<='9')) &&
+        (extType[2]>='0' && extType[2]<='9') &&
+        (extType[3]>='0' && extType[3]<='9')
+      ) { // effect slot
+        logV("found MPT extension: effect slot");
+        // skip (stop if we cannot seek)
+        if (!reader.seek(extSize,SEEK_CUR)) {
+          break;
+        }
+      } else {
+        logV("no further extensions found... %.2x%.2x%.2x%.2x",extType[0],extType[1],extType[2],extType[3]);
+        hasExtensions=false;
+      }
+    }
+
+    // read song comment
+    logD("reading song comment...");
+    if (reader.seek(commentPtr,SEEK_SET)) {
+      try {
+        String comment=reader.readStringLatin1Special(commentLen);
+
+        ds.notes="";
+        ds.notes.reserve(comment.size());
+
+        for (char& i: comment) {
+          if (i=='\r') {
+            ds.notes+='\n';
+          } else {
+            ds.notes+=i;
+          }
+        }
+      } catch (EndOfFileException& e) {
+        logW("couldn't read song comment due to premature end of file.");
+      }
+    } else {
+      logW("couldn't seek to comment!");
+    }
+    
+
     // read instruments
     for (int i=0; i<ds.insLen; i++) {
       DivInstrument* ins=new DivInstrument;
diff --git a/src/engine/safeReader.cpp b/src/engine/safeReader.cpp
index e8db7175f..29ba2a0b8 100644
--- a/src/engine/safeReader.cpp
+++ b/src/engine/safeReader.cpp
@@ -271,6 +271,15 @@ String SafeReader::readStringWithEncoding(DivStringEncoding encoding, size_t stl
             ret.push_back(c);
           }
         }
+      } else if (encoding==DIV_ENCODING_LATIN1_SPECIAL) {
+        if (c&0x80) {
+          if (c>=0xa0) {
+            ret.push_back(0xc0|(c>>6));
+            ret.push_back(0x80|(c&63));
+          }
+        } else {
+          ret.push_back(c);
+        }
       } else {
         ret.push_back(c);
       }
@@ -297,6 +306,15 @@ String SafeReader::readStringWithEncoding(DivStringEncoding encoding) {
           ret.push_back(c);
         }
       }
+    } else if (encoding==DIV_ENCODING_LATIN1_SPECIAL) {
+      if (c&0x80) {
+        if (c>=0xa0) {
+          ret.push_back(0xc0|(c>>6));
+          ret.push_back(0x80|(c&63));
+        }
+      } else {
+        ret.push_back(c);
+      }
     } else {
       ret.push_back(c);
     }
@@ -320,6 +338,14 @@ String SafeReader::readStringLatin1(size_t stlen) {
   return readStringWithEncoding(DIV_ENCODING_LATIN1,stlen);
 }
 
+String SafeReader::readStringLatin1Special() {
+  return readStringWithEncoding(DIV_ENCODING_LATIN1_SPECIAL);
+}
+
+String SafeReader::readStringLatin1Special(size_t stlen) {
+  return readStringWithEncoding(DIV_ENCODING_LATIN1_SPECIAL,stlen);
+}
+
 String SafeReader::readStringLine() {
   String ret;
   unsigned char c;
diff --git a/src/engine/safeReader.h b/src/engine/safeReader.h
index 04385c3b6..a3b0579d8 100644
--- a/src/engine/safeReader.h
+++ b/src/engine/safeReader.h
@@ -33,6 +33,7 @@ enum DivStringEncoding {
   DIV_ENCODING_NONE=0,
   DIV_ENCODING_UTF8,
   DIV_ENCODING_LATIN1,
+  DIV_ENCODING_LATIN1_SPECIAL,
   DIV_ENCODING_SHIFT_JIS
 };
 
@@ -77,6 +78,8 @@ class SafeReader {
     String readString(size_t len);
     String readStringLatin1();
     String readStringLatin1(size_t len);
+    String readStringLatin1Special();
+    String readStringLatin1Special(size_t len);
     String readStringLine();
     String readStringToken(unsigned char delim, bool stripContiguous);
     String readStringToken();