+++ /dev/null
-/*
- * decomp.h
- *
- * Functions useful for decompression, mainly bitstreams.
- */
-
-#ifndef _WIMLIB_DECOMP_H
-#define _WIMLIB_DECOMP_H
-
-#include "util.h"
-#include "endianness.h"
-
-/* Must be at least 32 bits. */
-typedef unsigned long input_bitbuf_t;
-
-/* Structure to provide a bitstream. */
-struct input_bitstream {
-
- /* A variable of length at least 32 bits that is used to hold bits that
- * have been read from the stream. The bits are ordered from high-order
- * to low-order; the next bit is always the high-order bit. */
- input_bitbuf_t bitbuf;
-
- /* Pointer to the next byte to be retrieved from the input. */
- const u8 *data;
-
- /* Number of bits in @bitbuf that are valid. */
- unsigned bitsleft;
-
- /* Number of words of data that are left. */
- unsigned data_bytes_left;
-};
-
-/* Initializes a bitstream to receive its input from @data. */
-static inline void init_input_bitstream(struct input_bitstream *istream,
- const void *data, unsigned num_data_bytes)
-{
- istream->bitbuf = 0;
- istream->bitsleft = 0;
- istream->data = data;
- istream->data_bytes_left = num_data_bytes;
-}
-
-/* Ensures that the bit buffer contains @num_bits bits. */
-static inline int bitstream_ensure_bits(struct input_bitstream *istream,
- unsigned num_bits)
-{
- wimlib_assert(num_bits <= 16);
-
- /* Unfortunately this needs to be different for the different
- * compression types. LZX requires reading no more than the number of
- * bits needed, otherwise the end of the compressed data may be overrun.
- * XPRESS, on the other hand, requires that we always return with at
- * least 16 bits in the buffer, even if fewer are requested. This is
- * important because this may change the location of a literal byte
- * read with bitstream_read_byte(). */
-#ifdef XPRESS_DECOMP
- while (istream->bitsleft < 16) {
-#else
- while (istream->bitsleft < num_bits) {
-#endif
- if (istream->data_bytes_left < 2)
- return 1;
-
- unsigned shift = sizeof(input_bitbuf_t) * 8 - 16 -
- istream->bitsleft;
- istream->bitbuf |= (input_bitbuf_t)le16_to_cpu(
- *(u16*)istream->data) << shift;
- istream->data += 2;
- istream->bitsleft += 16;
- istream->data_bytes_left -= 2;
- }
- return 0;
-}
-
-/* Returns the next @num_bits bits in the bit buffer. It must contain at least
- * @num_bits bits to call this function. */
-static inline unsigned
-bitstream_peek_bits(const struct input_bitstream *istream, unsigned num_bits)
-{
- if (num_bits == 0)
- return 0;
- return istream->bitbuf >> (sizeof(input_bitbuf_t) * 8 - num_bits);
-}
-
-/* Removes @num_bits bits from the bit buffer. It must contain at least
- * @num_bits bits to call this function. */
-static inline void bitstream_remove_bits(struct input_bitstream *istream,
- unsigned num_bits)
-{
- istream->bitbuf <<= num_bits;
- istream->bitsleft -= num_bits;
-}
-
-/* Reads and returns @num_bits bits from the input bitstream. */
-static inline int bitstream_read_bits(struct input_bitstream *istream,
- unsigned num_bits, unsigned *n)
-{
- int ret;
- ret = bitstream_ensure_bits(istream, num_bits);
- if (ret != 0) {
- ERROR("bitstream_read_bits(): Input buffer exhausted");
- return ret;
- }
- *n = bitstream_peek_bits(istream, num_bits);
- bitstream_remove_bits(istream, num_bits);
- return 0;
-}
-
-/* In the XPRESS format there can be literal length bytes embedded in the
- * compressed bitstream. These bytes are basically separate from the bitstream,
- * as they come AFTER the bits that are currently in the buffer variable (based
- * on reading 16 bits at a time), even though the buffer variable may not be
- * empty.
- *
- * This function returns the next such literal length byte in the input
- * bitstream. Returns -1 if we are at the end of the bitstream. */
-static inline int bitstream_read_byte(struct input_bitstream *istream)
-{
- wimlib_assert(istream->bitsleft < 32);
-
- if (istream->data_bytes_left == 0) {
- ERROR("bitstream_read_byte(): Input buffer exhausted");
- return -1;
- }
- istream->data_bytes_left--;
- return *istream->data++;
-}
-
-/* Reads @num_bits bits from the bit buffer without checking to see if that many
- * bits are in the buffer or not. */
-static inline unsigned
-bitstream_read_bits_nocheck(struct input_bitstream *istream, unsigned num_bits)
-{
- unsigned n = bitstream_peek_bits(istream, num_bits);
- bitstream_remove_bits(istream, num_bits);
- return n;
-}
-
-/* Removes the bits that have been read into the bit buffer variable. */
-static inline void flush_input_bitstream(struct input_bitstream *istream)
-{
- bitstream_remove_bits(istream, istream->bitsleft);
- istream->bitsleft = 0;
- istream->bitbuf = 0;
-}
-
-extern int bitstream_read_bytes(struct input_bitstream *istream, size_t n,
- void *dest);
-
-extern int align_input_bitstream(struct input_bitstream *istream,
- bool skip_word_if_aligned);
-
-extern int read_huffsym(struct input_bitstream *stream,
- const u16 decode_table[],
- const u8 lengths[],
- unsigned num_symbols,
- unsigned table_bits,
- unsigned *n,
- unsigned max_codeword_len);
-
-extern int make_huffman_decode_table(u16 decode_table[], unsigned num_syms,
- unsigned num_bits, const u8 lengths[],
- unsigned max_codeword_len);
-
-#endif /* _WIMLIB_DECOMP_H */
git://wimlib.net / wimlib / blobdiff