From 571507743c7ae3d61063e9ed1fbb9edb52092226 Mon Sep 17 00:00:00 2001
From: Jean-Philip Desjardins <jean-philip.desjardins@polymtl.ca>
Date: Thu, 29 Dec 2022 21:53:49 -0500
Subject: [PATCH] Add support for 'huff' codec.

---
 include/libchdr/chd.h |  1 +
 src/libchdr_chd.c     | 80 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/include/libchdr/chd.h b/include/libchdr/chd.h
index 9ff2f12..160fcb7 100644
--- a/include/libchdr/chd.h
+++ b/include/libchdr/chd.h
@@ -205,6 +205,7 @@ extern "C" {
 #define CHD_CODEC_NONE 0
 #define CHD_CODEC_ZLIB				CHD_MAKE_TAG('z','l','i','b')
 #define CHD_CODEC_LZMA				CHD_MAKE_TAG('l','z','m','a')
+#define CHD_CODEC_HUFFMAN 			CHD_MAKE_TAG('h','u','f','f')
 #define CHD_CODEC_FLAC				CHD_MAKE_TAG('f','l','a','c')
 /* general codecs with CD frontend */
 #define CHD_CODEC_CD_ZLIB			CHD_MAKE_TAG('c','d','z','l')
diff --git a/src/libchdr_chd.c b/src/libchdr_chd.c
index 1330d61..734ae7a 100644
--- a/src/libchdr_chd.c
+++ b/src/libchdr_chd.c
@@ -227,6 +227,12 @@ struct _lzma_codec_data
 	lzma_allocator	allocator;
 };
 
+typedef struct _huff_codec_data huff_codec_data;
+struct _huff_codec_data
+{
+	struct huffman_decoder* decoder;
+};
+
 /* codec-private data for the CDZL codec */
 typedef struct _cdzl_codec_data cdzl_codec_data;
 struct _cdzl_codec_data {
@@ -293,8 +299,9 @@ struct _chd_file
 	const codec_interface *	codecintf[4];	/* interface to the codec */
 
 	zlib_codec_data			zlib_codec_data;		/* zlib codec data */
-	lzma_codec_data			lzma_codec_data;		/* zlib codec data */
-	flac_codec_data			flac_codec_data;		/* zlib codec data */
+	lzma_codec_data			lzma_codec_data;		/* lzma codec data */
+	huff_codec_data			huff_codec_data;		/* huff codec data */
+	flac_codec_data			flac_codec_data;		/* flac codec data */
 	cdzl_codec_data			cdzl_codec_data;		/* cdzl codec data */
 	cdlz_codec_data			cdlz_codec_data;		/* cdlz codec data */
 	cdfl_codec_data			cdfl_codec_data;		/* cdfl codec data */
@@ -355,6 +362,11 @@ static chd_error lzma_codec_init(void *codec, uint32_t hunkbytes);
 static void lzma_codec_free(void *codec);
 static chd_error lzma_codec_decompress(void *codec, const uint8_t *src, uint32_t complen, uint8_t *dest, uint32_t destlen);
 
+/* huff compression codec */
+static chd_error huff_codec_init(void *codec, uint32_t hunkbytes);
+static void huff_codec_free(void *codec);
+static chd_error huff_codec_decompress(void *codec, const uint8_t *src, uint32_t complen, uint8_t *dest, uint32_t destlen);
+
 /* flac compression codec */
 static chd_error flac_codec_init(void *codec, uint32_t hunkbytes);
 static void flac_codec_free(void *codec);
@@ -771,6 +783,47 @@ static chd_error cdzl_codec_decompress(void *codec, const uint8_t *src, uint32_t
 	return CHDERR_NONE;
 }
 
+/***************************************************************************
+ *  HUFFMAN DECOMPRESSOR
+ ***************************************************************************
+ */
+
+static chd_error huff_codec_init(void* codec, uint32_t hunkbytes)
+{
+	huff_codec_data* huff_codec = (huff_codec_data*) codec;
+	huff_codec->decoder = create_huffman_decoder(256, 16);
+	return CHDERR_NONE;
+}
+
+static void huff_codec_free(void *codec)
+{
+	huff_codec_data* huff_codec = (huff_codec_data*) codec;
+	delete_huffman_decoder(huff_codec->decoder);
+}
+
+static chd_error huff_codec_decompress(void *codec, const uint8_t *src, uint32_t complen, uint8_t *dest, uint32_t destlen)
+{
+	huff_codec_data* huff_codec = (huff_codec_data*) codec;
+	struct bitstream* bitbuf = create_bitstream(src, complen);
+
+	// first import the tree
+	enum huffman_error err = huffman_import_tree_huffman(huff_codec->decoder, bitbuf);
+	if (err != HUFFERR_NONE)
+	{
+		free(bitbuf);
+		return err;
+	}
+
+	// then decode the data
+	for (uint32_t cur = 0; cur < destlen; cur++)
+		dest[cur] = huffman_decode_one(huff_codec->decoder, bitbuf);
+	bitstream_flush(bitbuf);
+	chd_error result = bitstream_overflow(bitbuf) ? CHDERR_DECOMPRESSION_ERROR : CHDERR_NONE;
+
+	free(bitbuf);
+	return result;
+}
+ 
 /***************************************************************************
  *  CD FLAC DECOMPRESSOR
  ***************************************************************************
@@ -993,6 +1046,17 @@ static const codec_interface codec_interfaces[] =
 		NULL
 	},
 
+	/* V5 huffman compression */
+	{
+		CHD_CODEC_HUFFMAN,
+		"Huffman",
+		FALSE,
+		huff_codec_init,
+		huff_codec_free,
+		huff_codec_decompress,
+		NULL
+	},
+
 	/* V5 flac compression */
 	{
 		CHD_CODEC_FLAC,
@@ -1613,6 +1677,10 @@ CHD_EXPORT chd_error chd_open_core_file(core_file *file, int mode, chd_file *par
 						codec = &newchd->lzma_codec_data;
 						break;
 
+					case CHD_CODEC_HUFFMAN:
+						codec = &newchd->huff_codec_data;
+						break;
+
 					case CHD_CODEC_FLAC:
 						codec = &newchd->flac_codec_data;
 						break;
@@ -1762,6 +1830,10 @@ CHD_EXPORT void chd_close(chd_file *chd)
 					codec = &chd->lzma_codec_data;
 					break;
 
+				case CHD_CODEC_HUFFMAN:
+					codec = &chd->huff_codec_data;
+					break;
+
 				case CHD_CODEC_FLAC:
 					codec = &chd->flac_codec_data;
 					break;
@@ -2488,6 +2560,10 @@ static chd_error hunk_read_into_memory(chd_file *chd, UINT32 hunknum, UINT8 *des
 						codec = &chd->lzma_codec_data;
 						break;
 
+					case CHD_CODEC_HUFFMAN:
+						codec = &chd->huff_codec_data;
+						break;
+
 					case CHD_CODEC_FLAC:
 						codec = &chd->flac_codec_data;
 						break;