From 38d49136ce15d3506f4885663a5e77464ad79e7e Mon Sep 17 00:00:00 2001
From: Brad Parker <cbparker@gmail.com>
Date: Thu, 4 Jul 2019 18:20:05 -0400
Subject: [PATCH] cdrom: add function for reading via LBA numbers

---
 libretro-common/cdrom/cdrom.c                 | 53 +++++++++++++++++++
 libretro-common/include/cdrom/cdrom.h         |  2 +
 .../vfs/vfs_implementation_cdrom.c            |  1 +
 3 files changed, 56 insertions(+)

diff --git a/libretro-common/cdrom/cdrom.c b/libretro-common/cdrom/cdrom.c
index bd6bb81204..e263ca146a 100644
--- a/libretro-common/cdrom/cdrom.c
+++ b/libretro-common/cdrom/cdrom.c
@@ -1058,6 +1058,59 @@ int cdrom_read(libretro_vfs_implementation_file *stream, unsigned char min, unsi
 
    rv = cdrom_send_command(stream, DIRECTION_IN, s, len, cdb, sizeof(cdb), skip);
 
+#ifdef CDROM_DEBUG
+   printf("read msf status code %d\n", rv);
+   fflush(stdout);
+#endif
+
+   if (rv)
+      return 1;
+
+   return 0;
+}
+
+int cdrom_read_lba(libretro_vfs_implementation_file *stream, unsigned lba, void *s, size_t len, size_t skip)
+{
+   /* MMC Command: READ CD */
+   unsigned char cdb[] = {0xBE, 0, 0, 0, 0, 0, 0, 0, 0, 0xF8, 0, 0};
+   unsigned lba_orig = lba;
+   int rv;
+
+   lba = swap_if_big32(lba);
+
+   cdb[2] = (lba >> 24) & 0xFF;
+   cdb[3] = (lba >> 16) & 0xFF;
+   cdb[4] = (lba >> 8) & 0xFF;
+   cdb[5] = (lba >> 0) & 0xFF;
+
+   if (len + skip <= 2352)
+   {
+      cdb[8] = 1;
+
+#ifdef CDROM_DEBUG
+      printf("single-frame read: from %d count %d skip %" PRId64 "\n", lba_orig, 1, skip);
+      fflush(stdout);
+#endif
+   }
+   else
+   {
+      unsigned frames = lba_orig + ceil((len + skip) / 2352.0);
+      unsigned lba_count = frames - lba_orig;
+
+      lba_count = swap_if_big32(lba_count);
+
+      cdb[6] = (lba_count >> 16) & 0xFF;
+      cdb[7] = (lba_count >> 8) & 0xFF;
+      cdb[8] = (lba_count >> 0) & 0xFF;
+
+#ifdef CDROM_DEBUG
+      printf("multi-frame read: from %d to %d len %d skip %" PRId64 "\n", lba_orig, frames, frames - lba_orig, skip);
+      fflush(stdout);
+#endif
+   }
+
+   rv = cdrom_send_command(stream, DIRECTION_IN, s, len, cdb, sizeof(cdb), skip);
+
 #ifdef CDROM_DEBUG
    printf("read status code %d\n", rv);
    fflush(stdout);
diff --git a/libretro-common/include/cdrom/cdrom.h b/libretro-common/include/cdrom/cdrom.h
index 372c8e8f4a..3c73847240 100644
--- a/libretro-common/include/cdrom/cdrom.h
+++ b/libretro-common/include/cdrom/cdrom.h
@@ -79,6 +79,8 @@ int cdrom_get_inquiry(const libretro_vfs_implementation_file *stream, char *mode
 
 int cdrom_read(libretro_vfs_implementation_file *stream, unsigned char min, unsigned char sec, unsigned char frame, void *s, size_t len, size_t skip);
 
+int cdrom_read_lba(libretro_vfs_implementation_file *stream, unsigned lba, void *s, size_t len, size_t skip);
+
 int cdrom_set_read_speed(libretro_vfs_implementation_file *stream, unsigned speed);
 
 int cdrom_stop(const libretro_vfs_implementation_file *stream);
diff --git a/libretro-common/vfs/vfs_implementation_cdrom.c b/libretro-common/vfs/vfs_implementation_cdrom.c
index 0e9f578b2b..8b90322177 100644
--- a/libretro-common/vfs/vfs_implementation_cdrom.c
+++ b/libretro-common/vfs/vfs_implementation_cdrom.c
@@ -372,6 +372,7 @@ int64_t retro_vfs_file_read_cdrom(libretro_vfs_implementation_file *stream,
 #endif
 
       rv = cdrom_read(stream, min, sec, frame, s, (size_t)len, skip);
+      /*rv = cdrom_read_lba(stream, stream->cdrom.cur_lba, s, (size_t)len, skip);*/
 
       if (rv)
       {