From 95c1b4b6e8677a65168c20aab34ac8c49727466f Mon Sep 17 00:00:00 2001
From: Martin Michelsen <fuzziqersoftware+g@gmail.com>
Date: Fri, 10 Feb 2023 10:51:13 -0800
Subject: [PATCH] add support for decoding download QST files

---
 README.md    |  3 ++-
 src/Quest.cc | 39 ++++++++++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/README.md b/README.md
index 49aa69b3..fbcecbcb 100644
--- a/README.md
+++ b/README.md
@@ -149,7 +149,8 @@ There are multiple PSO quest formats out there; newserv supports most of them. I
 | Ep3 GCI                   | .bin.gci or .mnm.gci  | Download only     | decode-gci       |
 | Encrypted DLQ             | .bin.dlq and .dat.dlq | Yes               | decode-dlq       |
 | Ep3 DLQ                   | .bin.dlq or .mnm.dlq  | Download only     | decode-dlq       |
-| QST                       | .qst                  | Yes               | decode-qst       |
+| Online QST                | .qst                  | Yes               | decode-qst       |
+| Download QST              | .qst                  | Yes               | decode-qst       |
 
 *Notes:*
 1. *This is the default format. You can convert these to uncompressed format by running `newserv decompress-prs FILENAME.bin FILENAME.bind` (and similarly for .dat -> .datd)*
diff --git a/src/Quest.cc b/src/Quest.cc
index 5919c532..b101e6d3 100644
--- a/src/Quest.cc
+++ b/src/Quest.cc
@@ -859,6 +859,7 @@ static pair<string, string> decode_qst_t(FILE* f) {
   string internal_dat_filename;
   uint32_t bin_file_size = 0;
   uint32_t dat_file_size = 0;
+  Quest::FileFormat subformat = Quest::FileFormat::QST; // Stand-in for unknown
   while (!r.eof()) {
     // Handle BB's implicit 8-byte command alignment
     static constexpr size_t alignment = sizeof(HeaderT);
@@ -869,7 +870,22 @@ static pair<string, string> decode_qst_t(FILE* f) {
     }
 
     const auto& header = r.get<HeaderT>();
-    if (header.command == 0x44) {
+
+    if (header.command == 0x44 || header.command == 0x13) {
+      if (subformat == Quest::FileFormat::QST) {
+        subformat = Quest::FileFormat::BIN_DAT;
+      } else if (subformat != Quest::FileFormat::BIN_DAT) {
+        throw runtime_error("QST file contains mixed download and non-download commands");
+      }
+    } else if (header.command == 0xA6 || header.command == 0xA7) {
+      if (subformat == Quest::FileFormat::QST) {
+        subformat = Quest::FileFormat::BIN_DAT_DLQ;
+      } else if (subformat != Quest::FileFormat::BIN_DAT_DLQ) {
+        throw runtime_error("QST file contains mixed download and non-download commands");
+      }
+    }
+
+    if (header.command == 0x44 || header.command == 0xA6) {
       if (header.size != sizeof(HeaderT) + sizeof(OpenFileT)) {
         throw runtime_error("qst open file command has incorrect size");
       }
@@ -896,7 +912,7 @@ static pair<string, string> decode_qst_t(FILE* f) {
         throw runtime_error("qst contains non-bin, non-dat file");
       }
 
-    } else if (header.command == 0x13) {
+    } else if (header.command == 0x13 || header.command == 0xA7) {
       if (header.size != sizeof(HeaderT) + sizeof(S_WriteFile_13_A7)) {
         throw runtime_error("qst write file command has incorrect size");
       }
@@ -935,25 +951,30 @@ static pair<string, string> decode_qst_t(FILE* f) {
     throw runtime_error("dat file does not match expected size");
   }
 
+  if (subformat == Quest::FileFormat::BIN_DAT_DLQ) {
+    bin_contents = Quest::decode_dlq(bin_contents);
+    dat_contents = Quest::decode_dlq(dat_contents);
+  }
+
   return make_pair(bin_contents, dat_contents);
 }
 
 pair<string, string> Quest::decode_qst(const string& filename) {
   auto f = fopen_unique(filename, "rb");
 
-  // qst files start with an open file command, but the format differs depending
+  // QST files start with an open file command, but the format differs depending
   // on the PSO version that the qst file is for. We can detect the format from
   // the first 4 bytes in the file:
-  // - BB: 58 00 44 00
-  // - PC: 3C ?? 44 00
-  // - DC/V3: 44 ?? 3C 00
+  // - BB:    58 00 44 00 or 58 00 A6 00
+  // - PC:    3C 00 44 ?? or 3C 00 A6 ??
+  // - DC/V3: 44 ?? 3C 00 or A6 ?? 3C 00
   uint32_t signature = freadx<be_uint32_t>(f.get());
   fseek(f.get(), 0, SEEK_SET);
-  if (signature == 0x58004400) {
+  if (signature == 0x58004400 || signature == 0x5800A600) {
     return decode_qst_t<PSOCommandHeaderBB, S_OpenFile_BB_44_A6>(f.get());
-  } else if ((signature & 0xFF00FFFF) == 0x3C004400) {
+  } else if ((signature & 0xFFFFFF00) == 0x3C004400 || (signature & 0xFFFFFF00) == 0x3C00A600) {
     return decode_qst_t<PSOCommandHeaderPC, S_OpenFile_PC_V3_44_A6>(f.get());
-  } else if ((signature & 0xFF00FFFF) == 0x44003C00) {
+  } else if ((signature & 0xFF00FFFF) == 0x44003C00 || (signature & 0xFF00FFFF) == 0xA6003C00) {
     return decode_qst_t<PSOCommandHeaderDCV3, S_OpenFile_PC_V3_44_A6>(f.get());
   } else {
     throw runtime_error("invalid qst file format");