deflate.h

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#ifndef _IPXE_DEFLATE_H
#define _IPXE_DEFLATE_H

/** @file
 *
 * DEFLATE decompression algorithm
 *
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <string.h>

/** Compression formats */
enum deflate_format {
        /** Raw DEFLATE data (no header or footer) */
        DEFLATE_RAW,
        /** ZLIB header and footer */
        DEFLATE_ZLIB,
};

/** Block header length (in bits) */
#define DEFLATE_HEADER_BITS 3

/** Block header final block flags bit */
#define DEFLATE_HEADER_BFINAL_BIT 0

/** Block header type LSB */
#define DEFLATE_HEADER_BTYPE_LSB 1

/** Block header type mask */
#define DEFLATE_HEADER_BTYPE_MASK 0x03

/** Block header type: literal data */
#define DEFLATE_HEADER_BTYPE_LITERAL 0

/** Block header type: static Huffman alphabet */
#define DEFLATE_HEADER_BTYPE_STATIC 1

/** Block header type: dynamic Huffman alphabet */
#define DEFLATE_HEADER_BTYPE_DYNAMIC 2

/** Literal header LEN/NLEN field length (in bits) */
#define DEFLATE_LITERAL_LEN_BITS 16

/** Dynamic header length (in bits) */
#define DEFLATE_DYNAMIC_BITS 14

/** Dynamic header HLIT field LSB */
#define DEFLATE_DYNAMIC_HLIT_LSB 0

/** Dynamic header HLIT field mask */
#define DEFLATE_DYNAMIC_HLIT_MASK 0x1f

/** Dynamic header HDIST field LSB */
#define DEFLATE_DYNAMIC_HDIST_LSB 5

/** Dynamic header HDIST field mask */
#define DEFLATE_DYNAMIC_HDIST_MASK 0x1f

/** Dynamic header HCLEN field LSB */
#define DEFLATE_DYNAMIC_HCLEN_LSB 10

/** Dynamic header HCLEN field mask */
#define DEFLATE_DYNAMIC_HCLEN_MASK 0x0f

/** Dynamic header code length length (in bits) */
#define DEFLATE_CODELEN_BITS 3

/** Maximum length of a Huffman symbol (in bits) */
#define DEFLATE_HUFFMAN_BITS 15

/** Quick lookup length for a Huffman symbol (in bits)
 *
 * This is a policy decision.
 */
#define DEFLATE_HUFFMAN_QL_BITS 7

/** Quick lookup shift */
#define DEFLATE_HUFFMAN_QL_SHIFT ( 16 - DEFLATE_HUFFMAN_QL_BITS )

/** Literal/length end of block code */
#define DEFLATE_LITLEN_END 256

/** Maximum value of a literal/length code */
#define DEFLATE_LITLEN_MAX_CODE 287

/** Maximum value of a distance code */
#define DEFLATE_DISTANCE_MAX_CODE 31

/** Maximum value of a code length code */
#define DEFLATE_CODELEN_MAX_CODE 18

/** ZLIB header length (in bits) */
#define ZLIB_HEADER_BITS 16

/** ZLIB header compression method LSB */
#define ZLIB_HEADER_CM_LSB 0

/** ZLIB header compression method mask */
#define ZLIB_HEADER_CM_MASK 0x0f

/** ZLIB header compression method: DEFLATE */
#define ZLIB_HEADER_CM_DEFLATE 8

/** ZLIB header preset dictionary flag bit */
#define ZLIB_HEADER_FDICT_BIT 13

/** ZLIB ADLER32 length (in bits) */
#define ZLIB_ADLER32_BITS 32

/** A Huffman-coded set of symbols of a given length */
struct deflate_huf_symbols {
        /** Length of Huffman-coded symbols */
        uint8_t bits;
        /** Shift to normalise symbols of this length to 16 bits */
        uint8_t shift;
        /** Number of Huffman-coded symbols having this length */
        uint16_t freq;
        /** First symbol of this length (normalised to 16 bits)
         *
         * Stored as a 32-bit value to allow the value 0x10000 to be
         * used for empty sets of symbols longer than the maximum
         * utilised length.
         */
        uint32_t start;
        /** Raw symbols having this length */
        uint16_t *raw;
};

/** A Huffman-coded alphabet */
struct deflate_alphabet {
        /** Huffman-coded symbol set for each length */
        struct deflate_huf_symbols huf[DEFLATE_HUFFMAN_BITS];
        /** Quick lookup table */
        uint8_t lookup[ 1 << DEFLATE_HUFFMAN_QL_BITS ];
        /** Raw symbols
         *
         * Ordered by Huffman-coded symbol length, then by symbol
         * value.  This field has a variable length.
         */
        uint16_t raw[0];
};

/** A static Huffman alphabet length pattern */
struct deflate_static_length_pattern {
        /** Length pair */
        uint8_t fill;
        /** Repetition count */
        uint8_t count;
} __attribute__ (( packed ));

/** Decompressor */
struct deflate {
        /** Resume point
         *
         * Used as the target of a computed goto to jump to the
         * appropriate point within the state machine.
         */
        void *resume;
        /** Format */
        enum deflate_format format;

        /** Current input data pointer */
        const uint8_t *in;
        /** End of input data pointer */
        const uint8_t *end;

        /** Accumulator */
        uint32_t accumulator;
        /** Bit-reversed accumulator
         *
         * Don't ask.
         */
        uint32_t rotalumucca;
        /** Number of bits within the accumulator */
        unsigned int bits;

        /** Current block header */
        unsigned int header;
        /** Remaining length of data (e.g. within a literal block) */
        size_t remaining;
        /** Current length index within a set of code lengths */
        unsigned int length_index;
        /** Target length index within a set of code lengths */
        unsigned int length_target;
        /** Current length within a set of code lengths */
        unsigned int length;
        /** Number of extra bits required */
        unsigned int extra_bits;
        /** Length of a duplicated string */
        size_t dup_len;
        /** Distance of a duplicated string */
        size_t dup_distance;

        /** Literal/length Huffman alphabet */
        struct deflate_alphabet litlen;
        /** Literal/length raw symbols
         *
         * Must immediately follow the literal/length Huffman alphabet.
         */
        uint16_t litlen_raw[ DEFLATE_LITLEN_MAX_CODE + 1 ];
        /** Number of symbols in the literal/length Huffman alphabet */
        unsigned int litlen_count;

        /** Distance and code length Huffman alphabet
         *
         * The code length Huffman alphabet has a maximum Huffman
         * symbol length of 7 and a maximum code value of 18, and is
         * thus strictly smaller than the distance Huffman alphabet.
         * Since we never need both alphabets simultaneously, we can
         * reuse the storage space for the distance alphabet to
         * temporarily hold the code length alphabet.
         */
        struct deflate_alphabet distance_codelen;
        /** Distance and code length raw symbols
         *
         * Must immediately follow the distance and code length
         * Huffman alphabet.
         */
        uint16_t distance_codelen_raw[ DEFLATE_DISTANCE_MAX_CODE + 1 ];
        /** Number of symbols in the distance Huffman alphabet */
        unsigned int distance_count;

        /** Huffman code lengths
         *
         * The literal/length and distance code lengths are
         * constructed as a single set of lengths.
         *
         * The code length Huffman alphabet has a maximum code value
         * of 18 and the set of lengths is thus strictly smaller than
         * the combined literal/length and distance set of lengths.
         * Since we never need both alphabets simultaneously, we can
         * reuse the storage space for the literal/length and distance
         * code lengths to temporarily hold the code length code
         * lengths.
         */
        uint8_t lengths[ ( ( DEFLATE_LITLEN_MAX_CODE + 1 ) +
                           ( DEFLATE_DISTANCE_MAX_CODE + 1 ) +
                           1 /* round up */ ) / 2 ];
};

/** A chunk of data */
struct deflate_chunk {
        /** Data */
        void *data;
        /** Current offset */
        size_t offset;
        /** Length of data */
        size_t len;
};

/**
 * Initialise chunk of data
 *
 * @v chunk             Chunk of data to initialise
 * @v data              Data
 * @v offset            Starting offset
 * @v len               Length
 */
static inline __attribute__ (( always_inline )) void
deflate_chunk_init ( struct deflate_chunk *chunk, void *data,
                     size_t offset, size_t len ) {

        chunk->data = data;
        chunk->offset = offset;
        chunk->len = len;
}

/**
 * Check if decompression has finished
 *
 * @v deflate           Decompressor
 * @ret finished        Decompression has finished
 */
static inline int deflate_finished ( struct deflate *deflate ) {
        return ( deflate->resume == NULL );
}

extern void deflate_init ( struct deflate *deflate,
                           enum deflate_format format );
extern int deflate_inflate ( struct deflate *deflate,
                             const void *data, size_t len,
                             struct deflate_chunk *out );

#endif /* _IPXE_DEFLATE_H */