Restructuring of code

code/external/libsmacker/smk_bitstream.c

@@ -0,0 +1,125 @@
+/*
+	libsmacker - A C library for decoding .smk Smacker Video files
+	Copyright (C) 2012-2013 Greg Kennedy
+
+	See smacker.h for more information.
+
+	smk_bitstream.c
+		Implements a bitstream structure, which can extract and
+		return a bit at a time from a raw block of bytes.
+*/
+
+#include "smk_bitstream.h"
+
+/* malloc and friends */
+#include "smk_malloc.h"
+
+/* BITSTREAM Functions */
+struct smk_bit_t *smk_bs_init(unsigned char *b, const unsigned long size)
+{
+	struct smk_bit_t *ret = NULL;
+
+	smk_null_check(b);
+
+	/* allocate a bitstream struct */
+	smk_malloc(ret,sizeof(struct smk_bit_t));
+
+	/* set up the pointer to bitstream, and the size counter */
+	ret->bitstream = b;
+	ret->size = size;
+
+	/* point to initial byte */
+	ret->byte_num = -1;
+	ret->bit_num = 7;
+
+	/* either way NULL is returned : ) */
+error:
+	return ret;
+}
+
+/* returns "enough bits left for a byte?" */
+static char smk_bs_query_8(struct smk_bit_t *bs)
+{
+	/* sanity check */
+	smk_null_check(bs);
+	return (bs->byte_num + 1 < bs->size);
+
+error:
+	return -1;
+}
+
+/* returns "any bits left?" */
+static char smk_bs_query_1(struct smk_bit_t *bs)
+{
+	/* sanity check */
+	smk_null_check(bs)
+	return (bs->bit_num < 7 || smk_bs_query_8(bs));
+
+error:
+	return -1;
+}
+
+/* Reads a bit
+	Returns -1 if error encountered */
+char smk_bs_read_1(struct smk_bit_t *bs)
+{
+	/* sanity check */
+	smk_null_check(bs);
+
+	/* don't die when running out of bits, but signal */
+	if (!smk_bs_query_1(bs))
+	{
+		fputs("libsmacker::smk_bs_read_1(bs) - ERROR: bitstream exhausted.\n",stderr);
+		goto error;
+	}
+
+	/* advance to next bit */
+	bs->bit_num ++;
+
+	/* Out of bits in this byte: next! */
+	if (bs->bit_num > 7)
+	{
+		bs->byte_num ++;
+		bs->bit_num = 0;
+	}
+
+	return (((bs->bitstream[bs->byte_num]) & (0x01 << bs->bit_num)) != 0);
+
+error:
+	return -1;
+}
+
+/* Reads a byte
+	Returns -1 if error. */
+short smk_bs_read_8(struct smk_bit_t *bs)
+{
+	unsigned char ret = 0, i;
+
+	/* sanity check */
+	smk_null_check(bs);
+
+	/* don't die when running out of bits, but signal */
+	if (!smk_bs_query_8(bs))
+	{
+		fputs("libsmacker::smk_bs_read_8(bs) - ERROR: bitstream exhausted.\n",stderr);
+		goto error;
+	}
+
+	for (i = 0; i < 8; i ++)
+	{
+		ret = ret >> 1;
+		ret |= (smk_bs_read_1(bs) << 7);
+	}
+	return ret;
+
+error:
+	return -1;
+}
+
+/* aligns struct to start of next byte */
+/*
+void smk_bs_align(struct smk_bit_t *bs)
+{
+	bs->bit_num = 7;
+}
+*/