backported support for loading uncompressed chd files

handle errors from both map_read as well as decompress_v5_map

src/chd.c

@@ -789,7 +789,6 @@ chd_error cdfl_codec_decompress(void *codec, const uint8_t *src, uint32_t comple
     CODEC INTERFACES
 ***************************************************************************/
 
-
 static const codec_interface codec_interfaces[] =
 {
 	/* "none" or no compression */
@@ -1081,18 +1080,28 @@ uint16_t crc16(const void *data, uint32_t length)
 	return crc;
 }
 
+/*-------------------------------------------------
+	compressed - test if CHD file is compressed
++-------------------------------------------------*/
+
+static inline int compressed(chd_header* header) {
+	return header->compression[0] != CHD_CODEC_NONE;
+}
+
 /*-------------------------------------------------
 	decompress_v5_map - decompress the v5 map
 -------------------------------------------------*/
 
 static chd_error decompress_v5_map(chd_file* chd, chd_header* header)
 {
-	if (header->mapoffset == 0)
+	int rawmapsize = map_size_v5(header);
+
+	if (!compressed(header))
 	{
-#if 0
-		memset(header->rawmap, 0xff,map_size_v5(header));
-#endif
-		return CHDERR_READ_ERROR;
+		header->rawmap = (uint8_t*)malloc(rawmapsize);
+		core_fseek(chd->file, header->mapoffset, SEEK_SET);
+		core_fread(chd->file, header->rawmap, rawmapsize);
+		return CHDERR_NONE;
 	}
 
 	/* read the reader */
@@ -1111,7 +1120,7 @@ static chd_error decompress_v5_map(chd_file* chd, chd_header* header)
 	core_fseek(chd->file, header->mapoffset + 16, SEEK_SET);
 	core_fread(chd->file, compressed, mapbytes);
 	struct bitstream* bitbuf = create_bitstream(compressed, sizeof(uint8_t) * mapbytes);
-	header->rawmap = (uint8_t*)malloc(sizeof(uint8_t) * map_size_v5(header));
+	header->rawmap = (uint8_t*)malloc(rawmapsize);
 
 	/* first decode the compression types */
 	struct huffman_decoder* decoder = create_huffman_decoder(16, 8);
@@ -1300,13 +1309,14 @@ chd_error chd_open_file(core_file *file, int mode, chd_file *parent, chd_file **
 	if (newchd->header.version < 5)
 	{
 		err = map_read(newchd);
-		if (err != CHDERR_NONE)
-			EARLY_EXIT(err);
 	}
 	else
 	{
 		err = decompress_v5_map(newchd, &(newchd->header));
 	}
+	if (err != CHDERR_NONE)
+		EARLY_EXIT(err);
+
 
 	/* allocate and init the hunk cache */
 	newchd->cache = (UINT8 *)malloc(newchd->header.hunkbytes);
@@ -1910,7 +1920,7 @@ static chd_error header_read(chd_file *chd, chd_header *header)
 		memcpy(header->rawsha1, &rawheader[64], CHD_SHA1_BYTES);
 
 		/* determine properties of map entries */
-		header->mapentrybytes = 12; /* TODO compressed() ? 12 : 4; */
+		header->mapentrybytes = compressed(header) ? 12 : 4;
 
 		/* hack */
 		header->totalhunks 		= header->hunkcount;
@@ -2039,22 +2049,24 @@ static chd_error hunk_read_into_memory(chd_file *chd, UINT32 hunknum, UINT8 *des
 		uint16_t blockcrc;
 		uint8_t *rawmap = &chd->header.rawmap[chd->header.mapentrybytes * hunknum];
 
-#if 0
-		/* uncompressed case - TODO */
-		if (!compressed())
+		/* uncompressed case */
+		if (!compressed(&chd->header))
 		{
-			blockoffs = uint64_t(be_read(rawmap, 4)) * uint64_t(m_hunkbytes);
-			if (blockoffs != 0)
-				file_read(blockoffs, dest, m_hunkbytes);
+			blockoffs = (uint64_t)get_bigendian_uint32(rawmap) * (uint64_t)chd->header.hunkbytes;
+			if (blockoffs != 0) {
+				core_fseek(chd->file, blockoffs, SEEK_SET);
+				core_fread(chd->file, dest, chd->header.hunkbytes);
+			/* TODO
 			else if (m_parent_missing)
-				throw CHDERR_REQUIRES_PARENT;
-			else if (m_parent != nullptr)
-				m_parent->read_hunk(hunknum, dest);
-			else
-				memset(dest, 0, m_hunkbytes);
-			return CHDERR_NONE;
+				throw CHDERR_REQUIRES_PARENT; */
+			} else if (chd->parent) {
+				err = hunk_read_into_memory(chd->parent, hunknum, dest);
+				if (err != CHDERR_NONE)
+					return err;
+			} else {
+				memset(dest, 0, chd->header.hunkbytes);
+			}
 		}
-#endif
 
 		/* compressed case */
 		blocklen = get_bigendian_uint24(&rawmap[1]);

src/chd.h

@@ -202,6 +202,7 @@ extern "C" {
 #define CHDCOMPRESSION_ZLIB_PLUS	2
 #define CHDCOMPRESSION_AV			3
 
+#define CHD_CODEC_NONE 0
 #define CHD_CODEC_ZLIB				CHD_MAKE_TAG('z','l','i','b')
 /* general codecs with CD frontend */
 #define CHD_CODEC_CD_ZLIB			CHD_MAKE_TAG('c','d','z','l')