lib/uzlib: Combine zlib/gzip header parsing to allow auto-detect.

This supports `wbits` values between +40 to +47.

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

1 files changed, 133 insertions, 0 deletions

diff --git a/lib/uzlib/header.c b/lib/uzlib/header.c
new file mode 100644
index 000000000..edd2b08ab
--- /dev/null
+++ b/lib/uzlib/header.c
@@ -0,0 +1,133 @@
+/*
+ * uzlib  -  tiny deflate/inflate library (deflate, gzip, zlib)
+ *
+ * Copyright (c) 2003 by Joergen Ibsen / Jibz
+ * All Rights Reserved
+ *
+ * http://www.ibsensoftware.com/
+ *
+ * Copyright (c) 2014-2018 by Paul Sokolovsky
+ *
+ * Optimised for MicroPython:
+ * Copyright (c) 2023 by Jim Mussared
+ *
+ * This software is provided 'as-is', without any express
+ * or implied warranty.  In no event will the authors be
+ * held liable for any damages arising from the use of
+ * this software.
+ *
+ * Permission is granted to anyone to use this software
+ * for any purpose, including commercial applications,
+ * and to alter it and redistribute it freely, subject to
+ * the following restrictions:
+ *
+ * 1. The origin of this software must not be
+ *    misrepresented; you must not claim that you
+ *    wrote the original software. If you use this
+ *    software in a product, an acknowledgment in
+ *    the product documentation would be appreciated
+ *    but is not required.
+ *
+ * 2. Altered source versions must be plainly marked
+ *    as such, and must not be misrepresented as
+ *    being the original software.
+ *
+ * 3. This notice may not be removed or altered from
+ *    any source distribution.
+ */
+
+#include "uzlib.h"
+
+#define FTEXT    1
+#define FHCRC    2
+#define FEXTRA   4
+#define FNAME    8
+#define FCOMMENT 16
+
+void tinf_skip_bytes(uzlib_uncomp_t *d, int num);
+uint16_t tinf_get_uint16(uzlib_uncomp_t *d);
+
+void tinf_skip_bytes(uzlib_uncomp_t *d, int num)
+{
+    while (num--) uzlib_get_byte(d);
+}
+
+uint16_t tinf_get_uint16(uzlib_uncomp_t *d)
+{
+    unsigned int v = uzlib_get_byte(d);
+    v = (uzlib_get_byte(d) << 8) | v;
+    return v;
+}
+
+int uzlib_parse_zlib_gzip_header(uzlib_uncomp_t *d, int *wbits)
+{
+    /* -- check format -- */
+    unsigned char cmf = uzlib_get_byte(d);
+    unsigned char flg = uzlib_get_byte(d);
+
+    /* check for gzip id bytes */
+    if (cmf == 0x1f && flg == 0x8b) {
+        /* check method is deflate */
+        if (uzlib_get_byte(d) != 8) return UZLIB_DATA_ERROR;
+
+        /* get flag byte */
+        flg = uzlib_get_byte(d);
+
+        /* check that reserved bits are zero */
+        if (flg & 0xe0) return UZLIB_DATA_ERROR;
+
+        /* -- find start of compressed data -- */
+
+        /* skip rest of base header of 10 bytes */
+        tinf_skip_bytes(d, 6);
+
+        /* skip extra data if present */
+        if (flg & FEXTRA)
+        {
+           unsigned int xlen = tinf_get_uint16(d);
+           tinf_skip_bytes(d, xlen);
+        }
+
+        /* skip file name if present */
+        if (flg & FNAME) { while (uzlib_get_byte(d)); }
+
+        /* skip file comment if present */
+        if (flg & FCOMMENT) { while (uzlib_get_byte(d)); }
+
+        /* check header crc if present */
+        if (flg & FHCRC)
+        {
+           /*unsigned int hcrc =*/ tinf_get_uint16(d);
+
+            // TODO: Check!
+    //       if (hcrc != (tinf_crc32(src, start - src) & 0x0000ffff))
+    //          return UZLIB_DATA_ERROR;
+        }
+
+        /* initialize for crc32 checksum */
+        d->checksum_type = UZLIB_CHKSUM_CRC;
+        d->checksum = ~0;
+
+        return UZLIB_HEADER_GZIP;
+    } else {
+       /* check checksum */
+       if ((256*cmf + flg) % 31) return UZLIB_DATA_ERROR;
+
+       /* check method is deflate */
+       if ((cmf & 0x0f) != 8) return UZLIB_DATA_ERROR;
+
+       /* check window size is valid */
+       if ((cmf >> 4) > 7) return UZLIB_DATA_ERROR;
+
+       /* check there is no preset dictionary */
+       if (flg & 0x20) return UZLIB_DATA_ERROR;
+
+       /* initialize for adler32 checksum */
+       d->checksum_type = UZLIB_CHKSUM_ADLER;
+       d->checksum = 1;
+
+       *wbits = (cmf >> 4) + 8;
+
+        return UZLIB_HEADER_ZLIB;
+    }
+}