The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/inflate.c

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    1 /*
    2  * Most parts of this file are not covered by:
    3  * ----------------------------------------------------------------------------
    4  * "THE BEER-WARE LICENSE" (Revision 42):
    5  * <phk@FreeBSD.org> wrote this file.  As long as you retain this notice you
    6  * can do whatever you want with this stuff. If we meet some day, and you think
    7  * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
    8  * ----------------------------------------------------------------------------
    9  *
   10  * $FreeBSD: releng/5.0/sys/kern/inflate.c 93149 2002-03-25 13:52:45Z phk $
   11  *
   12  *
   13  */
   14 
   15 #include <sys/param.h>
   16 #include <sys/inflate.h>
   17 #ifdef _KERNEL
   18 #include <sys/systm.h>
   19 #include <sys/kernel.h>
   20 #endif
   21 #include <sys/malloc.h>
   22 
   23 #ifdef _KERNEL
   24 static MALLOC_DEFINE(M_GZIP, "Gzip trees", "Gzip trees");
   25 #endif
   26 
   27 /* needed to make inflate() work */
   28 #define uch u_char
   29 #define ush u_short
   30 #define ulg u_long
   31 
   32 /* Stuff to make inflate() work */
   33 #ifdef _KERNEL
   34 #define memzero(dest,len)      bzero(dest,len)
   35 #endif
   36 #define NOMEMCPY
   37 #ifdef _KERNEL
   38 #define FPRINTF printf
   39 #else
   40 extern void putstr (char *);
   41 #define FPRINTF putstr
   42 #endif
   43 
   44 #define FLUSH(x,y) {                                            \
   45         int foo = (*x->gz_output)(x->gz_private,x->gz_slide,y); \
   46         if (foo)                                                \
   47                 return foo;                                     \
   48         }
   49 
   50 static const int qflag = 0;
   51 
   52 #ifndef _KERNEL /* want to use this file in kzip also */
   53 extern unsigned char *kzipmalloc (int);
   54 extern void kzipfree (void*);
   55 #define malloc(x, y, z) kzipmalloc((x))
   56 #define free(x, y) kzipfree((x))
   57 #endif
   58 
   59 /*
   60  * This came from unzip-5.12.  I have changed it the flow to pass
   61  * a structure pointer around, thus hopefully making it re-entrant.
   62  * Poul-Henning
   63  */
   64 
   65 /* inflate.c -- put in the public domain by Mark Adler
   66    version c14o, 23 August 1994 */
   67 
   68 /* You can do whatever you like with this source file, though I would
   69    prefer that if you modify it and redistribute it that you include
   70    comments to that effect with your name and the date.  Thank you.
   71 
   72    History:
   73    vers    date          who           what
   74    ----  ---------  --------------  ------------------------------------
   75     a    ~~ Feb 92  M. Adler        used full (large, one-step) lookup table
   76     b1   21 Mar 92  M. Adler        first version with partial lookup tables
   77     b2   21 Mar 92  M. Adler        fixed bug in fixed-code blocks
   78     b3   22 Mar 92  M. Adler        sped up match copies, cleaned up some
   79     b4   25 Mar 92  M. Adler        added prototypes; removed window[] (now
   80                                     is the responsibility of unzip.h--also
   81                                     changed name to slide[]), so needs diffs
   82                                     for unzip.c and unzip.h (this allows
   83                                     compiling in the small model on MSDOS);
   84                                     fixed cast of q in huft_build();
   85     b5   26 Mar 92  M. Adler        got rid of unintended macro recursion.
   86     b6   27 Mar 92  M. Adler        got rid of nextbyte() routine.  fixed
   87                                     bug in inflate_fixed().
   88     c1   30 Mar 92  M. Adler        removed lbits, dbits environment variables.
   89                                     changed BMAX to 16 for explode.  Removed
   90                                     OUTB usage, and replaced it with flush()--
   91                                     this was a 20% speed improvement!  Added
   92                                     an explode.c (to replace unimplod.c) that
   93                                     uses the huft routines here.  Removed
   94                                     register union.
   95     c2    4 Apr 92  M. Adler        fixed bug for file sizes a multiple of 32k.
   96     c3   10 Apr 92  M. Adler        reduced memory of code tables made by
   97                                     huft_build significantly (factor of two to
   98                                     three).
   99     c4   15 Apr 92  M. Adler        added NOMEMCPY do kill use of memcpy().
  100                                     worked around a Turbo C optimization bug.
  101     c5   21 Apr 92  M. Adler        added the GZ_WSIZE #define to allow reducing
  102                                     the 32K window size for specialized
  103                                     applications.
  104     c6   31 May 92  M. Adler        added some typecasts to eliminate warnings
  105     c7   27 Jun 92  G. Roelofs      added some more typecasts (444:  MSC bug).
  106     c8    5 Oct 92  J-l. Gailly     added ifdef'd code to deal with PKZIP bug.
  107     c9    9 Oct 92  M. Adler        removed a memory error message (~line 416).
  108     c10  17 Oct 92  G. Roelofs      changed ULONG/UWORD/byte to ulg/ush/uch,
  109                                     removed old inflate, renamed inflate_entry
  110                                     to inflate, added Mark's fix to a comment.
  111    c10.5 14 Dec 92  M. Adler        fix up error messages for incomplete trees.
  112     c11   2 Jan 93  M. Adler        fixed bug in detection of incomplete
  113                                     tables, and removed assumption that EOB is
  114                                     the longest code (bad assumption).
  115     c12   3 Jan 93  M. Adler        make tables for fixed blocks only once.
  116     c13   5 Jan 93  M. Adler        allow all zero length codes (pkzip 2.04c
  117                                     outputs one zero length code for an empty
  118                                     distance tree).
  119     c14  12 Mar 93  M. Adler        made inflate.c standalone with the
  120                                     introduction of inflate.h.
  121    c14b  16 Jul 93  G. Roelofs      added (unsigned) typecast to w at 470.
  122    c14c  19 Jul 93  J. Bush         changed v[N_MAX], l[288], ll[28x+3x] arrays
  123                                     to static for Amiga.
  124    c14d  13 Aug 93  J-l. Gailly     de-complicatified Mark's c[*p++]++ thing.
  125    c14e   8 Oct 93  G. Roelofs      changed memset() to memzero().
  126    c14f  22 Oct 93  G. Roelofs      renamed quietflg to qflag; made Trace()
  127                                     conditional; added inflate_free().
  128    c14g  28 Oct 93  G. Roelofs      changed l/(lx+1) macro to pointer (Cray bug)
  129    c14h   7 Dec 93  C. Ghisler      huft_build() optimizations.
  130    c14i   9 Jan 94  A. Verheijen    set fixed_t{d,l} to NULL after freeing;
  131                     G. Roelofs      check NEXTBYTE macro for GZ_EOF.
  132    c14j  23 Jan 94  G. Roelofs      removed Ghisler "optimizations"; ifdef'd
  133                                     GZ_EOF check.
  134    c14k  27 Feb 94  G. Roelofs      added some typecasts to avoid warnings.
  135    c14l   9 Apr 94  G. Roelofs      fixed split comments on preprocessor lines
  136                                     to avoid bug in Encore compiler.
  137    c14m   7 Jul 94  P. Kienitz      modified to allow assembler version of
  138                                     inflate_codes() (define ASM_INFLATECODES)
  139    c14n  22 Jul 94  G. Roelofs      changed fprintf to FPRINTF for DLL versions
  140    c14o  23 Aug 94  C. Spieler      added a newline to a debug statement;
  141                     G. Roelofs      added another typecast to avoid MSC warning
  142  */
  143 
  144 
  145 /*
  146    Inflate deflated (PKZIP's method 8 compressed) data.  The compression
  147    method searches for as much of the current string of bytes (up to a
  148    length of 258) in the previous 32K bytes.  If it doesn't find any
  149    matches (of at least length 3), it codes the next byte.  Otherwise, it
  150    codes the length of the matched string and its distance backwards from
  151    the current position.  There is a single Huffman code that codes both
  152    single bytes (called "literals") and match lengths.  A second Huffman
  153    code codes the distance information, which follows a length code.  Each
  154    length or distance code actually represents a base value and a number
  155    of "extra" (sometimes zero) bits to get to add to the base value.  At
  156    the end of each deflated block is a special end-of-block (EOB) literal/
  157    length code.  The decoding process is basically: get a literal/length
  158    code; if EOB then done; if a literal, emit the decoded byte; if a
  159    length then get the distance and emit the referred-to bytes from the
  160    sliding window of previously emitted data.
  161 
  162    There are (currently) three kinds of inflate blocks: stored, fixed, and
  163    dynamic.  The compressor outputs a chunk of data at a time and decides
  164    which method to use on a chunk-by-chunk basis.  A chunk might typically
  165    be 32K to 64K, uncompressed.  If the chunk is uncompressible, then the
  166    "stored" method is used.  In this case, the bytes are simply stored as
  167    is, eight bits per byte, with none of the above coding.  The bytes are
  168    preceded by a count, since there is no longer an EOB code.
  169 
  170    If the data is compressible, then either the fixed or dynamic methods
  171    are used.  In the dynamic method, the compressed data is preceded by
  172    an encoding of the literal/length and distance Huffman codes that are
  173    to be used to decode this block.  The representation is itself Huffman
  174    coded, and so is preceded by a description of that code.  These code
  175    descriptions take up a little space, and so for small blocks, there is
  176    a predefined set of codes, called the fixed codes.  The fixed method is
  177    used if the block ends up smaller that way (usually for quite small
  178    chunks); otherwise the dynamic method is used.  In the latter case, the
  179    codes are customized to the probabilities in the current block and so
  180    can code it much better than the pre-determined fixed codes can.
  181 
  182    The Huffman codes themselves are decoded using a mutli-level table
  183    lookup, in order to maximize the speed of decoding plus the speed of
  184    building the decoding tables.  See the comments below that precede the
  185    lbits and dbits tuning parameters.
  186  */
  187 
  188 
  189 /*
  190    Notes beyond the 1.93a appnote.txt:
  191 
  192    1. Distance pointers never point before the beginning of the output
  193       stream.
  194    2. Distance pointers can point back across blocks, up to 32k away.
  195    3. There is an implied maximum of 7 bits for the bit length table and
  196       15 bits for the actual data.
  197    4. If only one code exists, then it is encoded using one bit.  (Zero
  198       would be more efficient, but perhaps a little confusing.)  If two
  199       codes exist, they are coded using one bit each (0 and 1).
  200    5. There is no way of sending zero distance codes--a dummy must be
  201       sent if there are none.  (History: a pre 2.0 version of PKZIP would
  202       store blocks with no distance codes, but this was discovered to be
  203       too harsh a criterion.)  Valid only for 1.93a.  2.04c does allow
  204       zero distance codes, which is sent as one code of zero bits in
  205       length.
  206    6. There are up to 286 literal/length codes.  Code 256 represents the
  207       end-of-block.  Note however that the static length tree defines
  208       288 codes just to fill out the Huffman codes.  Codes 286 and 287
  209       cannot be used though, since there is no length base or extra bits
  210       defined for them.  Similarily, there are up to 30 distance codes.
  211       However, static trees define 32 codes (all 5 bits) to fill out the
  212       Huffman codes, but the last two had better not show up in the data.
  213    7. Unzip can check dynamic Huffman blocks for complete code sets.
  214       The exception is that a single code would not be complete (see #4).
  215    8. The five bits following the block type is really the number of
  216       literal codes sent minus 257.
  217    9. Length codes 8,16,16 are interpreted as 13 length codes of 8 bits
  218       (1+6+6).  Therefore, to output three times the length, you output
  219       three codes (1+1+1), whereas to output four times the same length,
  220       you only need two codes (1+3).  Hmm.
  221   10. In the tree reconstruction algorithm, Code = Code + Increment
  222       only if BitLength(i) is not zero.  (Pretty obvious.)
  223   11. Correction: 4 Bits: # of Bit Length codes - 4     (4 - 19)
  224   12. Note: length code 284 can represent 227-258, but length code 285
  225       really is 258.  The last length deserves its own, short code
  226       since it gets used a lot in very redundant files.  The length
  227       258 is special since 258 - 3 (the min match length) is 255.
  228   13. The literal/length and distance code bit lengths are read as a
  229       single stream of lengths.  It is possible (and advantageous) for
  230       a repeat code (16, 17, or 18) to go across the boundary between
  231       the two sets of lengths.
  232  */
  233 
  234 
  235 #define PKZIP_BUG_WORKAROUND    /* PKZIP 1.93a problem--live with it */
  236 
  237 /*
  238     inflate.h must supply the uch slide[GZ_WSIZE] array and the NEXTBYTE,
  239     FLUSH() and memzero macros.  If the window size is not 32K, it
  240     should also define GZ_WSIZE.  If INFMOD is defined, it can include
  241     compiled functions to support the NEXTBYTE and/or FLUSH() macros.
  242     There are defaults for NEXTBYTE and FLUSH() below for use as
  243     examples of what those functions need to do.  Normally, you would
  244     also want FLUSH() to compute a crc on the data.  inflate.h also
  245     needs to provide these typedefs:
  246 
  247         typedef unsigned char uch;
  248         typedef unsigned short ush;
  249         typedef unsigned long ulg;
  250 
  251     This module uses the external functions malloc() and free() (and
  252     probably memset() or bzero() in the memzero() macro).  Their
  253     prototypes are normally found in <string.h> and <stdlib.h>.
  254  */
  255 #define INFMOD                  /* tell inflate.h to include code to be
  256                                  * compiled */
  257 
  258 /* Huffman code lookup table entry--this entry is four bytes for machines
  259    that have 16-bit pointers (e.g. PC's in the small or medium model).
  260    Valid extra bits are 0..13.  e == 15 is EOB (end of block), e == 16
  261    means that v is a literal, 16 < e < 32 means that v is a pointer to
  262    the next table, which codes e - 16 bits, and lastly e == 99 indicates
  263    an unused code.  If a code with e == 99 is looked up, this implies an
  264    error in the data. */
  265 struct huft {
  266         uch             e;      /* number of extra bits or operation */
  267         uch             b;      /* number of bits in this code or subcode */
  268         union {
  269                 ush             n;      /* literal, length base, or distance
  270                                          * base */
  271                 struct huft    *t;      /* pointer to next level of table */
  272         }               v;
  273 };
  274 
  275 
  276 /* Function prototypes */
  277 static int huft_build(struct inflate *, unsigned *, unsigned, unsigned, const ush *, const ush *, struct huft **, int *);
  278 static int huft_free(struct inflate *, struct huft *);
  279 static int inflate_codes(struct inflate *, struct huft *, struct huft *, int, int);
  280 static int inflate_stored(struct inflate *);
  281 static int xinflate(struct inflate *);
  282 static int inflate_fixed(struct inflate *);
  283 static int inflate_dynamic(struct inflate *);
  284 static int inflate_block(struct inflate *, int *);
  285 
  286 /* The inflate algorithm uses a sliding 32K byte window on the uncompressed
  287    stream to find repeated byte strings.  This is implemented here as a
  288    circular buffer.  The index is updated simply by incrementing and then
  289    and'ing with 0x7fff (32K-1). */
  290 /* It is left to other modules to supply the 32K area.  It is assumed
  291    to be usable as if it were declared "uch slide[32768];" or as just
  292    "uch *slide;" and then malloc'ed in the latter case.  The definition
  293    must be in unzip.h, included above. */
  294 
  295 
  296 /* Tables for deflate from PKZIP's appnote.txt. */
  297 
  298 /* Order of the bit length code lengths */
  299 static const unsigned border[] = {
  300         16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
  301 
  302 static const ush cplens[] = {   /* Copy lengths for literal codes 257..285 */
  303         3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
  304         35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
  305  /* note: see note #13 above about the 258 in this list. */
  306 
  307 static const ush cplext[] = {   /* Extra bits for literal codes 257..285 */
  308         0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
  309         3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 99, 99}; /* 99==invalid */
  310 
  311 static const ush cpdist[] = {   /* Copy offsets for distance codes 0..29 */
  312         1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
  313         257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
  314         8193, 12289, 16385, 24577};
  315 
  316 static const ush cpdext[] = {   /* Extra bits for distance codes */
  317         0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
  318         7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
  319         12, 12, 13, 13};
  320 
  321 /* And'ing with mask[n] masks the lower n bits */
  322 static const ush mask[] = {
  323         0x0000,
  324         0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
  325         0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
  326 };
  327 
  328 
  329 /* Macros for inflate() bit peeking and grabbing.
  330    The usage is:
  331 
  332         NEEDBITS(glbl,j)
  333         x = b & mask[j];
  334         DUMPBITS(j)
  335 
  336    where NEEDBITS makes sure that b has at least j bits in it, and
  337    DUMPBITS removes the bits from b.  The macros use the variable k
  338    for the number of bits in b.  Normally, b and k are register
  339    variables for speed, and are initialized at the begining of a
  340    routine that uses these macros from a global bit buffer and count.
  341 
  342    In order to not ask for more bits than there are in the compressed
  343    stream, the Huffman tables are constructed to only ask for just
  344    enough bits to make up the end-of-block code (value 256).  Then no
  345    bytes need to be "returned" to the buffer at the end of the last
  346    block.  See the huft_build() routine.
  347  */
  348 
  349 /*
  350  * The following 2 were global variables.
  351  * They are now fields of the inflate structure.
  352  */
  353 
  354 #define NEEDBITS(glbl,n) {                                              \
  355                 while(k<(n)) {                                          \
  356                         int c=(*glbl->gz_input)(glbl->gz_private);      \
  357                         if(c==GZ_EOF)                                   \
  358                                 return 1;                               \
  359                         b|=((ulg)c)<<k;                                 \
  360                         k+=8;                                           \
  361                 }                                                       \
  362         }
  363 
  364 #define DUMPBITS(n) {b>>=(n);k-=(n);}
  365 
  366 /*
  367    Huffman code decoding is performed using a multi-level table lookup.
  368    The fastest way to decode is to simply build a lookup table whose
  369    size is determined by the longest code.  However, the time it takes
  370    to build this table can also be a factor if the data being decoded
  371    is not very long.  The most common codes are necessarily the
  372    shortest codes, so those codes dominate the decoding time, and hence
  373    the speed.  The idea is you can have a shorter table that decodes the
  374    shorter, more probable codes, and then point to subsidiary tables for
  375    the longer codes.  The time it costs to decode the longer codes is
  376    then traded against the time it takes to make longer tables.
  377 
  378    This results of this trade are in the variables lbits and dbits
  379    below.  lbits is the number of bits the first level table for literal/
  380    length codes can decode in one step, and dbits is the same thing for
  381    the distance codes.  Subsequent tables are also less than or equal to
  382    those sizes.  These values may be adjusted either when all of the
  383    codes are shorter than that, in which case the longest code length in
  384    bits is used, or when the shortest code is *longer* than the requested
  385    table size, in which case the length of the shortest code in bits is
  386    used.
  387 
  388    There are two different values for the two tables, since they code a
  389    different number of possibilities each.  The literal/length table
  390    codes 286 possible values, or in a flat code, a little over eight
  391    bits.  The distance table codes 30 possible values, or a little less
  392    than five bits, flat.  The optimum values for speed end up being
  393    about one bit more than those, so lbits is 8+1 and dbits is 5+1.
  394    The optimum values may differ though from machine to machine, and
  395    possibly even between compilers.  Your mileage may vary.
  396  */
  397 
  398 static const int lbits = 9;     /* bits in base literal/length lookup table */
  399 static const int dbits = 6;     /* bits in base distance lookup table */
  400 
  401 
  402 /* If BMAX needs to be larger than 16, then h and x[] should be ulg. */
  403 #define BMAX 16                 /* maximum bit length of any code (16 for
  404                                  * explode) */
  405 #define N_MAX 288               /* maximum number of codes in any set */
  406 
  407 /* Given a list of code lengths and a maximum table size, make a set of
  408    tables to decode that set of codes.  Return zero on success, one if
  409    the given code set is incomplete (the tables are still built in this
  410    case), two if the input is invalid (all zero length codes or an
  411    oversubscribed set of lengths), and three if not enough memory.
  412    The code with value 256 is special, and the tables are constructed
  413    so that no bits beyond that code are fetched when that code is
  414    decoded. */
  415 static int
  416 huft_build(glbl, b, n, s, d, e, t, m)
  417         struct inflate *glbl;
  418         unsigned       *b;      /* code lengths in bits (all assumed <= BMAX) */
  419         unsigned        n;      /* number of codes (assumed <= N_MAX) */
  420         unsigned        s;      /* number of simple-valued codes (0..s-1) */
  421         const ush      *d;      /* list of base values for non-simple codes */
  422         const ush      *e;      /* list of extra bits for non-simple codes */
  423         struct huft   **t;      /* result: starting table */
  424         int            *m;      /* maximum lookup bits, returns actual */
  425 {
  426         unsigned        a;      /* counter for codes of length k */
  427         unsigned        c[BMAX + 1];    /* bit length count table */
  428         unsigned        el;     /* length of EOB code (value 256) */
  429         unsigned        f;      /* i repeats in table every f entries */
  430         int             g;      /* maximum code length */
  431         int             h;      /* table level */
  432         register unsigned i;    /* counter, current code */
  433         register unsigned j;    /* counter */
  434         register int    k;      /* number of bits in current code */
  435         int             lx[BMAX + 1];   /* memory for l[-1..BMAX-1] */
  436         int            *l = lx + 1;     /* stack of bits per table */
  437         register unsigned *p;   /* pointer into c[], b[], or v[] */
  438         register struct huft *q;/* points to current table */
  439         struct huft     r;      /* table entry for structure assignment */
  440         struct huft    *u[BMAX];/* table stack */
  441         unsigned        v[N_MAX];       /* values in order of bit length */
  442         register int    w;      /* bits before this table == (l * h) */
  443         unsigned        x[BMAX + 1];    /* bit offsets, then code stack */
  444         unsigned       *xp;     /* pointer into x */
  445         int             y;      /* number of dummy codes added */
  446         unsigned        z;      /* number of entries in current table */
  447 
  448         /* Generate counts for each bit length */
  449         el = n > 256 ? b[256] : BMAX;   /* set length of EOB code, if any */
  450 #ifdef _KERNEL
  451         memzero((char *) c, sizeof(c));
  452 #else
  453         for (i = 0; i < BMAX+1; i++)
  454                 c [i] = 0;
  455 #endif
  456         p = b;
  457         i = n;
  458         do {
  459                 c[*p]++;
  460                 p++;            /* assume all entries <= BMAX */
  461         } while (--i);
  462         if (c[0] == n) {        /* null input--all zero length codes */
  463                 *t = (struct huft *) NULL;
  464                 *m = 0;
  465                 return 0;
  466         }
  467         /* Find minimum and maximum length, bound *m by those */
  468         for (j = 1; j <= BMAX; j++)
  469                 if (c[j])
  470                         break;
  471         k = j;                  /* minimum code length */
  472         if ((unsigned) *m < j)
  473                 *m = j;
  474         for (i = BMAX; i; i--)
  475                 if (c[i])
  476                         break;
  477         g = i;                  /* maximum code length */
  478         if ((unsigned) *m > i)
  479                 *m = i;
  480 
  481         /* Adjust last length count to fill out codes, if needed */
  482         for (y = 1 << j; j < i; j++, y <<= 1)
  483                 if ((y -= c[j]) < 0)
  484                         return 2;       /* bad input: more codes than bits */
  485         if ((y -= c[i]) < 0)
  486                 return 2;
  487         c[i] += y;
  488 
  489         /* Generate starting offsets into the value table for each length */
  490         x[1] = j = 0;
  491         p = c + 1;
  492         xp = x + 2;
  493         while (--i) {           /* note that i == g from above */
  494                 *xp++ = (j += *p++);
  495         }
  496 
  497         /* Make a table of values in order of bit lengths */
  498         p = b;
  499         i = 0;
  500         do {
  501                 if ((j = *p++) != 0)
  502                         v[x[j]++] = i;
  503         } while (++i < n);
  504 
  505         /* Generate the Huffman codes and for each, make the table entries */
  506         x[0] = i = 0;           /* first Huffman code is zero */
  507         p = v;                  /* grab values in bit order */
  508         h = -1;                 /* no tables yet--level -1 */
  509         w = l[-1] = 0;          /* no bits decoded yet */
  510         u[0] = (struct huft *) NULL;    /* just to keep compilers happy */
  511         q = (struct huft *) NULL;       /* ditto */
  512         z = 0;                  /* ditto */
  513 
  514         /* go through the bit lengths (k already is bits in shortest code) */
  515         for (; k <= g; k++) {
  516                 a = c[k];
  517                 while (a--) {
  518                         /*
  519                          * here i is the Huffman code of length k bits for
  520                          * value *p
  521                          */
  522                         /* make tables up to required level */
  523                         while (k > w + l[h]) {
  524                                 w += l[h++];    /* add bits already decoded */
  525 
  526                                 /*
  527                                  * compute minimum size table less than or
  528                                  * equal to *m bits
  529                                  */
  530                                 z = (z = g - w) > (unsigned) *m ? *m : z;       /* upper limit */
  531                                 if ((f = 1 << (j = k - w)) > a + 1) {   /* try a k-w bit table *//* t
  532                                                                          * oo few codes for k-w
  533                                                                          * bit table */
  534                                         f -= a + 1;     /* deduct codes from
  535                                                          * patterns left */
  536                                         xp = c + k;
  537                                         while (++j < z) {       /* try smaller tables up
  538                                                                  * to z bits */
  539                                                 if ((f <<= 1) <= *++xp)
  540                                                         break;  /* enough codes to use
  541                                                                  * up j bits */
  542                                                 f -= *xp;       /* else deduct codes
  543                                                                  * from patterns */
  544                                         }
  545                                 }
  546                                 if ((unsigned) w + j > el && (unsigned) w < el)
  547                                         j = el - w;     /* make EOB code end at
  548                                                          * table */
  549                                 z = 1 << j;     /* table entries for j-bit
  550                                                  * table */
  551                                 l[h] = j;       /* set table size in stack */
  552 
  553                                 /* allocate and link in new table */
  554                                 if ((q = (struct huft *) malloc((z + 1) * sizeof(struct huft), M_GZIP, M_WAITOK)) ==
  555                                     (struct huft *) NULL) {
  556                                         if (h)
  557                                                 huft_free(glbl, u[0]);
  558                                         return 3;       /* not enough memory */
  559                                 }
  560                                 glbl->gz_hufts += z + 1;        /* track memory usage */
  561                                 *t = q + 1;     /* link to list for
  562                                                  * huft_free() */
  563                                 *(t = &(q->v.t)) = (struct huft *) NULL;
  564                                 u[h] = ++q;     /* table starts after link */
  565 
  566                                 /* connect to last table, if there is one */
  567                                 if (h) {
  568                                         x[h] = i;       /* save pattern for
  569                                                          * backing up */
  570                                         r.b = (uch) l[h - 1];   /* bits to dump before
  571                                                                  * this table */
  572                                         r.e = (uch) (16 + j);   /* bits in this table */
  573                                         r.v.t = q;      /* pointer to this table */
  574                                         j = (i & ((1 << w) - 1)) >> (w - l[h - 1]);
  575                                         u[h - 1][j] = r;        /* connect to last table */
  576                                 }
  577                         }
  578 
  579                         /* set up table entry in r */
  580                         r.b = (uch) (k - w);
  581                         if (p >= v + n)
  582                                 r.e = 99;       /* out of values--invalid
  583                                                  * code */
  584                         else if (*p < s) {
  585                                 r.e = (uch) (*p < 256 ? 16 : 15);       /* 256 is end-of-block
  586                                                                          * code */
  587                                 r.v.n = *p++;   /* simple code is just the
  588                                                  * value */
  589                         } else {
  590                                 r.e = (uch) e[*p - s];  /* non-simple--look up
  591                                                          * in lists */
  592                                 r.v.n = d[*p++ - s];
  593                         }
  594 
  595                         /* fill code-like entries with r */
  596                         f = 1 << (k - w);
  597                         for (j = i >> w; j < z; j += f)
  598                                 q[j] = r;
  599 
  600                         /* backwards increment the k-bit code i */
  601                         for (j = 1 << (k - 1); i & j; j >>= 1)
  602                                 i ^= j;
  603                         i ^= j;
  604 
  605                         /* backup over finished tables */
  606                         while ((i & ((1 << w) - 1)) != x[h])
  607                                 w -= l[--h];    /* don't need to update q */
  608                 }
  609         }
  610 
  611         /* return actual size of base table */
  612         *m = l[0];
  613 
  614         /* Return true (1) if we were given an incomplete table */
  615         return y != 0 && g != 1;
  616 }
  617 
  618 static int
  619 huft_free(glbl, t)
  620         struct inflate *glbl;
  621         struct huft    *t;      /* table to free */
  622 /* Free the malloc'ed tables built by huft_build(), which makes a linked
  623    list of the tables it made, with the links in a dummy first entry of
  624    each table. */
  625 {
  626         register struct huft *p, *q;
  627 
  628         /* Go through linked list, freeing from the malloced (t[-1]) address. */
  629         p = t;
  630         while (p != (struct huft *) NULL) {
  631                 q = (--p)->v.t;
  632                 free(p, M_GZIP);
  633                 p = q;
  634         }
  635         return 0;
  636 }
  637 
  638 /* inflate (decompress) the codes in a deflated (compressed) block.
  639    Return an error code or zero if it all goes ok. */
  640 static int
  641 inflate_codes(glbl, tl, td, bl, bd)
  642         struct inflate *glbl;
  643         struct huft    *tl, *td;/* literal/length and distance decoder tables */
  644         int             bl, bd; /* number of bits decoded by tl[] and td[] */
  645 {
  646         register unsigned e;    /* table entry flag/number of extra bits */
  647         unsigned        n, d;   /* length and index for copy */
  648         unsigned        w;      /* current window position */
  649         struct huft    *t;      /* pointer to table entry */
  650         unsigned        ml, md; /* masks for bl and bd bits */
  651         register ulg    b;      /* bit buffer */
  652         register unsigned k;    /* number of bits in bit buffer */
  653 
  654         /* make local copies of globals */
  655         b = glbl->gz_bb;                        /* initialize bit buffer */
  656         k = glbl->gz_bk;
  657         w = glbl->gz_wp;        /* initialize window position */
  658 
  659         /* inflate the coded data */
  660         ml = mask[bl];          /* precompute masks for speed */
  661         md = mask[bd];
  662         while (1) {             /* do until end of block */
  663                 NEEDBITS(glbl, (unsigned) bl)
  664                         if ((e = (t = tl + ((unsigned) b & ml))->e) > 16)
  665                         do {
  666                                 if (e == 99)
  667                                         return 1;
  668                                 DUMPBITS(t->b)
  669                                         e -= 16;
  670                                 NEEDBITS(glbl, e)
  671                         } while ((e = (t = t->v.t + ((unsigned) b & mask[e]))->e) > 16);
  672                 DUMPBITS(t->b)
  673                         if (e == 16) {  /* then it's a literal */
  674                         glbl->gz_slide[w++] = (uch) t->v.n;
  675                         if (w == GZ_WSIZE) {
  676                                 FLUSH(glbl, w);
  677                                 w = 0;
  678                         }
  679                 } else {        /* it's an EOB or a length */
  680                         /* exit if end of block */
  681                         if (e == 15)
  682                                 break;
  683 
  684                         /* get length of block to copy */
  685                         NEEDBITS(glbl, e)
  686                                 n = t->v.n + ((unsigned) b & mask[e]);
  687                         DUMPBITS(e);
  688 
  689                         /* decode distance of block to copy */
  690                         NEEDBITS(glbl, (unsigned) bd)
  691                                 if ((e = (t = td + ((unsigned) b & md))->e) > 16)
  692                                 do {
  693                                         if (e == 99)
  694                                                 return 1;
  695                                         DUMPBITS(t->b)
  696                                                 e -= 16;
  697                                         NEEDBITS(glbl, e)
  698                                 } while ((e = (t = t->v.t + ((unsigned) b & mask[e]))->e) > 16);
  699                         DUMPBITS(t->b)
  700                                 NEEDBITS(glbl, e)
  701                                 d = w - t->v.n - ((unsigned) b & mask[e]);
  702                         DUMPBITS(e)
  703                         /* do the copy */
  704                                 do {
  705                                 n -= (e = (e = GZ_WSIZE - ((d &= GZ_WSIZE - 1) > w ? d : w)) > n ? n : e);
  706 #ifndef NOMEMCPY
  707                                 if (w - d >= e) {       /* (this test assumes
  708                                                          * unsigned comparison) */
  709                                         memcpy(glbl->gz_slide + w, glbl->gz_slide + d, e);
  710                                         w += e;
  711                                         d += e;
  712                                 } else  /* do it slow to avoid memcpy()
  713                                          * overlap */
  714 #endif                          /* !NOMEMCPY */
  715                                         do {
  716                                                 glbl->gz_slide[w++] = glbl->gz_slide[d++];
  717                                         } while (--e);
  718                                 if (w == GZ_WSIZE) {
  719                                         FLUSH(glbl, w);
  720                                         w = 0;
  721                                 }
  722                         } while (n);
  723                 }
  724         }
  725 
  726         /* restore the globals from the locals */
  727         glbl->gz_wp = w;        /* restore global window pointer */
  728         glbl->gz_bb = b;                        /* restore global bit buffer */
  729         glbl->gz_bk = k;
  730 
  731         /* done */
  732         return 0;
  733 }
  734 
  735 /* "decompress" an inflated type 0 (stored) block. */
  736 static int
  737 inflate_stored(glbl)
  738         struct inflate *glbl;
  739 {
  740         unsigned        n;      /* number of bytes in block */
  741         unsigned        w;      /* current window position */
  742         register ulg    b;      /* bit buffer */
  743         register unsigned k;    /* number of bits in bit buffer */
  744 
  745         /* make local copies of globals */
  746         b = glbl->gz_bb;                        /* initialize bit buffer */
  747         k = glbl->gz_bk;
  748         w = glbl->gz_wp;        /* initialize window position */
  749 
  750         /* go to byte boundary */
  751         n = k & 7;
  752         DUMPBITS(n);
  753 
  754         /* get the length and its complement */
  755         NEEDBITS(glbl, 16)
  756                 n = ((unsigned) b & 0xffff);
  757         DUMPBITS(16)
  758                 NEEDBITS(glbl, 16)
  759                 if (n != (unsigned) ((~b) & 0xffff))
  760                 return 1;       /* error in compressed data */
  761         DUMPBITS(16)
  762         /* read and output the compressed data */
  763                 while (n--) {
  764                 NEEDBITS(glbl, 8)
  765                         glbl->gz_slide[w++] = (uch) b;
  766                 if (w == GZ_WSIZE) {
  767                         FLUSH(glbl, w);
  768                         w = 0;
  769                 }
  770                 DUMPBITS(8)
  771         }
  772 
  773         /* restore the globals from the locals */
  774         glbl->gz_wp = w;        /* restore global window pointer */
  775         glbl->gz_bb = b;                        /* restore global bit buffer */
  776         glbl->gz_bk = k;
  777         return 0;
  778 }
  779 
  780 /* decompress an inflated type 1 (fixed Huffman codes) block.  We should
  781    either replace this with a custom decoder, or at least precompute the
  782    Huffman tables. */
  783 static int
  784 inflate_fixed(glbl)
  785         struct inflate *glbl;
  786 {
  787         /* if first time, set up tables for fixed blocks */
  788         if (glbl->gz_fixed_tl == (struct huft *) NULL) {
  789                 int             i;      /* temporary variable */
  790                 static unsigned l[288]; /* length list for huft_build */
  791 
  792                 /* literal table */
  793                 for (i = 0; i < 144; i++)
  794                         l[i] = 8;
  795                 for (; i < 256; i++)
  796                         l[i] = 9;
  797                 for (; i < 280; i++)
  798                         l[i] = 7;
  799                 for (; i < 288; i++)    /* make a complete, but wrong code
  800                                          * set */
  801                         l[i] = 8;
  802                 glbl->gz_fixed_bl = 7;
  803                 if ((i = huft_build(glbl, l, 288, 257, cplens, cplext,
  804                             &glbl->gz_fixed_tl, &glbl->gz_fixed_bl)) != 0) {
  805                         glbl->gz_fixed_tl = (struct huft *) NULL;
  806                         return i;
  807                 }
  808                 /* distance table */
  809                 for (i = 0; i < 30; i++)        /* make an incomplete code
  810                                                  * set */
  811                         l[i] = 5;
  812                 glbl->gz_fixed_bd = 5;
  813                 if ((i = huft_build(glbl, l, 30, 0, cpdist, cpdext,
  814                              &glbl->gz_fixed_td, &glbl->gz_fixed_bd)) > 1) {
  815                         huft_free(glbl, glbl->gz_fixed_tl);
  816                         glbl->gz_fixed_tl = (struct huft *) NULL;
  817                         return i;
  818                 }
  819         }
  820         /* decompress until an end-of-block code */
  821         return inflate_codes(glbl, glbl->gz_fixed_tl, glbl->gz_fixed_td, glbl->gz_fixed_bl, glbl->gz_fixed_bd) != 0;
  822 }
  823 
  824 /* decompress an inflated type 2 (dynamic Huffman codes) block. */
  825 static int
  826 inflate_dynamic(glbl)
  827         struct inflate *glbl;
  828 {
  829         int             i;      /* temporary variables */
  830         unsigned        j;
  831         unsigned        l;      /* last length */
  832         unsigned        m;      /* mask for bit lengths table */
  833         unsigned        n;      /* number of lengths to get */
  834         struct huft    *tl;     /* literal/length code table */
  835         struct huft    *td;     /* distance code table */
  836         int             bl;     /* lookup bits for tl */
  837         int             bd;     /* lookup bits for td */
  838         unsigned        nb;     /* number of bit length codes */
  839         unsigned        nl;     /* number of literal/length codes */
  840         unsigned        nd;     /* number of distance codes */
  841 #ifdef PKZIP_BUG_WORKAROUND
  842         unsigned        ll[288 + 32];   /* literal/length and distance code
  843                                          * lengths */
  844 #else
  845         unsigned        ll[286 + 30];   /* literal/length and distance code
  846                                          * lengths */
  847 #endif
  848         register ulg    b;      /* bit buffer */
  849         register unsigned k;    /* number of bits in bit buffer */
  850 
  851         /* make local bit buffer */
  852         b = glbl->gz_bb;
  853         k = glbl->gz_bk;
  854 
  855         /* read in table lengths */
  856         NEEDBITS(glbl, 5)
  857                 nl = 257 + ((unsigned) b & 0x1f);       /* number of
  858                                                          * literal/length codes */
  859         DUMPBITS(5)
  860                 NEEDBITS(glbl, 5)
  861                 nd = 1 + ((unsigned) b & 0x1f); /* number of distance codes */
  862         DUMPBITS(5)
  863                 NEEDBITS(glbl, 4)
  864                 nb = 4 + ((unsigned) b & 0xf);  /* number of bit length codes */
  865         DUMPBITS(4)
  866 #ifdef PKZIP_BUG_WORKAROUND
  867                 if (nl > 288 || nd > 32)
  868 #else
  869                 if (nl > 286 || nd > 30)
  870 #endif
  871                 return 1;       /* bad lengths */
  872         /* read in bit-length-code lengths */
  873         for (j = 0; j < nb; j++) {
  874                 NEEDBITS(glbl, 3)
  875                         ll[border[j]] = (unsigned) b & 7;
  876                 DUMPBITS(3)
  877         }
  878         for (; j < 19; j++)
  879                 ll[border[j]] = 0;
  880 
  881         /* build decoding table for trees--single level, 7 bit lookup */
  882         bl = 7;
  883         if ((i = huft_build(glbl, ll, 19, 19, NULL, NULL, &tl, &bl)) != 0) {
  884                 if (i == 1)
  885                         huft_free(glbl, tl);
  886                 return i;       /* incomplete code set */
  887         }
  888         /* read in literal and distance code lengths */
  889         n = nl + nd;
  890         m = mask[bl];
  891         i = l = 0;
  892         while ((unsigned) i < n) {
  893                 NEEDBITS(glbl, (unsigned) bl)
  894                         j = (td = tl + ((unsigned) b & m))->b;
  895                 DUMPBITS(j)
  896                         j = td->v.n;
  897                 if (j < 16)     /* length of code in bits (0..15) */
  898                         ll[i++] = l = j;        /* save last length in l */
  899                 else if (j == 16) {     /* repeat last length 3 to 6 times */
  900                         NEEDBITS(glbl, 2)
  901                                 j = 3 + ((unsigned) b & 3);
  902                         DUMPBITS(2)
  903                                 if ((unsigned) i + j > n)
  904                                 return 1;
  905                         while (j--)
  906                                 ll[i++] = l;
  907                 } else if (j == 17) {   /* 3 to 10 zero length codes */
  908                         NEEDBITS(glbl, 3)
  909                                 j = 3 + ((unsigned) b & 7);
  910                         DUMPBITS(3)
  911                                 if ((unsigned) i + j > n)
  912                                 return 1;
  913                         while (j--)
  914                                 ll[i++] = 0;
  915                         l = 0;
  916                 } else {        /* j == 18: 11 to 138 zero length codes */
  917                         NEEDBITS(glbl, 7)
  918                                 j = 11 + ((unsigned) b & 0x7f);
  919                         DUMPBITS(7)
  920                                 if ((unsigned) i + j > n)
  921                                 return 1;
  922                         while (j--)
  923                                 ll[i++] = 0;
  924                         l = 0;
  925                 }
  926         }
  927 
  928         /* free decoding table for trees */
  929         huft_free(glbl, tl);
  930 
  931         /* restore the global bit buffer */
  932         glbl->gz_bb = b;
  933         glbl->gz_bk = k;
  934 
  935         /* build the decoding tables for literal/length and distance codes */
  936         bl = lbits;
  937         i = huft_build(glbl, ll, nl, 257, cplens, cplext, &tl, &bl);
  938         if (i != 0) {
  939                 if (i == 1 && !qflag) {
  940                         FPRINTF("(incomplete l-tree)  ");
  941                         huft_free(glbl, tl);
  942                 }
  943                 return i;       /* incomplete code set */
  944         }
  945         bd = dbits;
  946         i = huft_build(glbl, ll + nl, nd, 0, cpdist, cpdext, &td, &bd);
  947         if (i != 0) {
  948                 if (i == 1 && !qflag) {
  949                         FPRINTF("(incomplete d-tree)  ");
  950 #ifdef PKZIP_BUG_WORKAROUND
  951                         i = 0;
  952                 }
  953 #else
  954                         huft_free(glbl, td);
  955                 }
  956                 huft_free(glbl, tl);
  957                 return i;       /* incomplete code set */
  958 #endif
  959         }
  960         /* decompress until an end-of-block code */
  961         if (inflate_codes(glbl, tl, td, bl, bd))
  962                 return 1;
  963 
  964         /* free the decoding tables, return */
  965         huft_free(glbl, tl);
  966         huft_free(glbl, td);
  967         return 0;
  968 }
  969 
  970 /* decompress an inflated block */
  971 static int
  972 inflate_block(glbl, e)
  973         struct inflate *glbl;
  974         int            *e;      /* last block flag */
  975 {
  976         unsigned        t;      /* block type */
  977         register ulg    b;      /* bit buffer */
  978         register unsigned k;    /* number of bits in bit buffer */
  979 
  980         /* make local bit buffer */
  981         b = glbl->gz_bb;
  982         k = glbl->gz_bk;
  983 
  984         /* read in last block bit */
  985         NEEDBITS(glbl, 1)
  986                 * e = (int) b & 1;
  987         DUMPBITS(1)
  988         /* read in block type */
  989                 NEEDBITS(glbl, 2)
  990                 t = (unsigned) b & 3;
  991         DUMPBITS(2)
  992         /* restore the global bit buffer */
  993                 glbl->gz_bb = b;
  994         glbl->gz_bk = k;
  995 
  996         /* inflate that block type */
  997         if (t == 2)
  998                 return inflate_dynamic(glbl);
  999         if (t == 0)
 1000                 return inflate_stored(glbl);
 1001         if (t == 1)
 1002                 return inflate_fixed(glbl);
 1003         /* bad block type */
 1004         return 2;
 1005 }
 1006 
 1007 
 1008 
 1009 /* decompress an inflated entry */
 1010 static int
 1011 xinflate(glbl)
 1012         struct inflate *glbl;
 1013 {
 1014         int             e;      /* last block flag */
 1015         int             r;      /* result code */
 1016         unsigned        h;      /* maximum struct huft's malloc'ed */
 1017 
 1018         glbl->gz_fixed_tl = (struct huft *) NULL;
 1019 
 1020         /* initialize window, bit buffer */
 1021         glbl->gz_wp = 0;
 1022         glbl->gz_bk = 0;
 1023         glbl->gz_bb = 0;
 1024 
 1025         /* decompress until the last block */
 1026         h = 0;
 1027         do {
 1028                 glbl->gz_hufts = 0;
 1029                 if ((r = inflate_block(glbl, &e)) != 0)
 1030                         return r;
 1031                 if (glbl->gz_hufts > h)
 1032                         h = glbl->gz_hufts;
 1033         } while (!e);
 1034 
 1035         /* flush out slide */
 1036         FLUSH(glbl, glbl->gz_wp);
 1037 
 1038         /* return success */
 1039         return 0;
 1040 }
 1041 
 1042 /* Nobody uses this - why not? */
 1043 int
 1044 inflate(glbl)
 1045         struct inflate *glbl;
 1046 {
 1047         int             i;
 1048 #ifdef _KERNEL
 1049         u_char          *p = NULL;
 1050 
 1051         if (!glbl->gz_slide)
 1052                 p = glbl->gz_slide = malloc(GZ_WSIZE, M_GZIP, M_WAITOK);
 1053 #endif
 1054         if (!glbl->gz_slide)
 1055 #ifdef _KERNEL
 1056                 return(ENOMEM);
 1057 #else
 1058                 return 3; /* kzip expects 3 */
 1059 #endif
 1060         i = xinflate(glbl);
 1061 
 1062         if (glbl->gz_fixed_td != (struct huft *) NULL) {
 1063                 huft_free(glbl, glbl->gz_fixed_td);
 1064                 glbl->gz_fixed_td = (struct huft *) NULL;
 1065         }
 1066         if (glbl->gz_fixed_tl != (struct huft *) NULL) {
 1067                 huft_free(glbl, glbl->gz_fixed_tl);
 1068                 glbl->gz_fixed_tl = (struct huft *) NULL;
 1069         }
 1070 #ifdef _KERNEL
 1071         if (p == glbl->gz_slide) {
 1072                 free(glbl->gz_slide, M_GZIP);
 1073                 glbl->gz_slide = NULL;
 1074         }
 1075 #endif
 1076         return i;
 1077 }
 1078 /* ----------------------- END INFLATE.C */

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