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 
   11 #include <sys/cdefs.h>
   12 __FBSDID("$FreeBSD: releng/8.1/sys/kern/inflate.c 199583 2009-11-20 15:27:52Z jhb $");
   13 
   14 #include <sys/param.h>
   15 #include <sys/inflate.h>
   16 #ifdef _KERNEL
   17 #include <sys/systm.h>
   18 #include <sys/kernel.h>
   19 #endif
   20 #include <sys/malloc.h>
   21 
   22 #ifdef _KERNEL
   23 static MALLOC_DEFINE(M_GZIP, "gzip_trees", "Gzip trees");
   24 #endif
   25 
   26 /* needed to make inflate() work */
   27 #define uch u_char
   28 #define ush u_short
   29 #define ulg u_long
   30 
   31 /* Stuff to make inflate() work */
   32 #ifdef _KERNEL
   33 #define memzero(dest,len)      bzero(dest,len)
   34 #endif
   35 #define NOMEMCPY
   36 #ifdef _KERNEL
   37 #define FPRINTF printf
   38 #else
   39 extern void putstr (char *);
   40 #define FPRINTF putstr
   41 #endif
   42 
   43 #define FLUSH(x,y) {                                            \
   44         int foo = (*x->gz_output)(x->gz_private,x->gz_slide,y); \
   45         if (foo)                                                \
   46                 return foo;                                     \
   47         }
   48 
   49 static const int qflag = 0;
   50 
   51 #ifndef _KERNEL /* want to use this file in kzip also */
   52 extern unsigned char *kzipmalloc (int);
   53 extern void kzipfree (void*);
   54 #define malloc(x, y, z) kzipmalloc((x))
   55 #define free(x, y) kzipfree((x))
   56 #endif
   57 
   58 /*
   59  * This came from unzip-5.12.  I have changed it the flow to pass
   60  * a structure pointer around, thus hopefully making it re-entrant.
   61  * Poul-Henning
   62  */
   63 
   64 /* inflate.c -- put in the public domain by Mark Adler
   65    version c14o, 23 August 1994 */
   66 
   67 /* You can do whatever you like with this source file, though I would
   68    prefer that if you modify it and redistribute it that you include
   69    comments to that effect with your name and the date.  Thank you.
   70 
   71    History:
   72    vers    date          who           what
   73    ----  ---------  --------------  ------------------------------------
   74     a    ~~ Feb 92  M. Adler        used full (large, one-step) lookup table
   75     b1   21 Mar 92  M. Adler        first version with partial lookup tables
   76     b2   21 Mar 92  M. Adler        fixed bug in fixed-code blocks
   77     b3   22 Mar 92  M. Adler        sped up match copies, cleaned up some
   78     b4   25 Mar 92  M. Adler        added prototypes; removed window[] (now
   79                                     is the responsibility of unzip.h--also
   80                                     changed name to slide[]), so needs diffs
   81                                     for unzip.c and unzip.h (this allows
   82                                     compiling in the small model on MSDOS);
   83                                     fixed cast of q in huft_build();
   84     b5   26 Mar 92  M. Adler        got rid of unintended macro recursion.
   85     b6   27 Mar 92  M. Adler        got rid of nextbyte() routine.  fixed
   86                                     bug in inflate_fixed().
   87     c1   30 Mar 92  M. Adler        removed lbits, dbits environment variables.
   88                                     changed BMAX to 16 for explode.  Removed
   89                                     OUTB usage, and replaced it with flush()--
   90                                     this was a 20% speed improvement!  Added
   91                                     an explode.c (to replace unimplod.c) that
   92                                     uses the huft routines here.  Removed
   93                                     register union.
   94     c2    4 Apr 92  M. Adler        fixed bug for file sizes a multiple of 32k.
   95     c3   10 Apr 92  M. Adler        reduced memory of code tables made by
   96                                     huft_build significantly (factor of two to
   97                                     three).
   98     c4   15 Apr 92  M. Adler        added NOMEMCPY do kill use of memcpy().
   99                                     worked around a Turbo C optimization bug.
  100     c5   21 Apr 92  M. Adler        added the GZ_WSIZE #define to allow reducing
  101                                     the 32K window size for specialized
  102                                     applications.
  103     c6   31 May 92  M. Adler        added some typecasts to eliminate warnings
  104     c7   27 Jun 92  G. Roelofs      added some more typecasts (444:  MSC bug).
  105     c8    5 Oct 92  J-l. Gailly     added ifdef'd code to deal with PKZIP bug.
  106     c9    9 Oct 92  M. Adler        removed a memory error message (~line 416).
  107     c10  17 Oct 92  G. Roelofs      changed ULONG/UWORD/byte to ulg/ush/uch,
  108                                     removed old inflate, renamed inflate_entry
  109                                     to inflate, added Mark's fix to a comment.
  110    c10.5 14 Dec 92  M. Adler        fix up error messages for incomplete trees.
  111     c11   2 Jan 93  M. Adler        fixed bug in detection of incomplete
  112                                     tables, and removed assumption that EOB is
  113                                     the longest code (bad assumption).
  114     c12   3 Jan 93  M. Adler        make tables for fixed blocks only once.
  115     c13   5 Jan 93  M. Adler        allow all zero length codes (pkzip 2.04c
  116                                     outputs one zero length code for an empty
  117                                     distance tree).
  118     c14  12 Mar 93  M. Adler        made inflate.c standalone with the
  119                                     introduction of inflate.h.
  120    c14b  16 Jul 93  G. Roelofs      added (unsigned) typecast to w at 470.
  121    c14c  19 Jul 93  J. Bush         changed v[N_MAX], l[288], ll[28x+3x] arrays
  122                                     to static for Amiga.
  123    c14d  13 Aug 93  J-l. Gailly     de-complicatified Mark's c[*p++]++ thing.
  124    c14e   8 Oct 93  G. Roelofs      changed memset() to memzero().
  125    c14f  22 Oct 93  G. Roelofs      renamed quietflg to qflag; made Trace()
  126                                     conditional; added inflate_free().
  127    c14g  28 Oct 93  G. Roelofs      changed l/(lx+1) macro to pointer (Cray bug)
  128    c14h   7 Dec 93  C. Ghisler      huft_build() optimizations.
  129    c14i   9 Jan 94  A. Verheijen    set fixed_t{d,l} to NULL after freeing;
  130                     G. Roelofs      check NEXTBYTE macro for GZ_EOF.
  131    c14j  23 Jan 94  G. Roelofs      removed Ghisler "optimizations"; ifdef'd
  132                                     GZ_EOF check.
  133    c14k  27 Feb 94  G. Roelofs      added some typecasts to avoid warnings.
  134    c14l   9 Apr 94  G. Roelofs      fixed split comments on preprocessor lines
  135                                     to avoid bug in Encore compiler.
  136    c14m   7 Jul 94  P. Kienitz      modified to allow assembler version of
  137                                     inflate_codes() (define ASM_INFLATECODES)
  138    c14n  22 Jul 94  G. Roelofs      changed fprintf to FPRINTF for DLL versions
  139    c14o  23 Aug 94  C. Spieler      added a newline to a debug statement;
  140                     G. Roelofs      added another typecast to avoid MSC warning
  141  */
  142 
  143 
  144 /*
  145    Inflate deflated (PKZIP's method 8 compressed) data.  The compression
  146    method searches for as much of the current string of bytes (up to a
  147    length of 258) in the previous 32K bytes.  If it doesn't find any
  148    matches (of at least length 3), it codes the next byte.  Otherwise, it
  149    codes the length of the matched string and its distance backwards from
  150    the current position.  There is a single Huffman code that codes both
  151    single bytes (called "literals") and match lengths.  A second Huffman
  152    code codes the distance information, which follows a length code.  Each
  153    length or distance code actually represents a base value and a number
  154    of "extra" (sometimes zero) bits to get to add to the base value.  At
  155    the end of each deflated block is a special end-of-block (EOB) literal/
  156    length code.  The decoding process is basically: get a literal/length
  157    code; if EOB then done; if a literal, emit the decoded byte; if a
  158    length then get the distance and emit the referred-to bytes from the
  159    sliding window of previously emitted data.
  160 
  161    There are (currently) three kinds of inflate blocks: stored, fixed, and
  162    dynamic.  The compressor outputs a chunk of data at a time and decides
  163    which method to use on a chunk-by-chunk basis.  A chunk might typically
  164    be 32K to 64K, uncompressed.  If the chunk is uncompressible, then the
  165    "stored" method is used.  In this case, the bytes are simply stored as
  166    is, eight bits per byte, with none of the above coding.  The bytes are
  167    preceded by a count, since there is no longer an EOB code.
  168 
  169    If the data is compressible, then either the fixed or dynamic methods
  170    are used.  In the dynamic method, the compressed data is preceded by
  171    an encoding of the literal/length and distance Huffman codes that are
  172    to be used to decode this block.  The representation is itself Huffman
  173    coded, and so is preceded by a description of that code.  These code
  174    descriptions take up a little space, and so for small blocks, there is
  175    a predefined set of codes, called the fixed codes.  The fixed method is
  176    used if the block ends up smaller that way (usually for quite small
  177    chunks); otherwise the dynamic method is used.  In the latter case, the
  178    codes are customized to the probabilities in the current block and so
  179    can code it much better than the pre-determined fixed codes can.
  180 
  181    The Huffman codes themselves are decoded using a mutli-level table
  182    lookup, in order to maximize the speed of decoding plus the speed of
  183    building the decoding tables.  See the comments below that precede the
  184    lbits and dbits tuning parameters.
  185  */
  186 
  187 
  188 /*
  189    Notes beyond the 1.93a appnote.txt:
  190 
  191    1. Distance pointers never point before the beginning of the output
  192       stream.
  193    2. Distance pointers can point back across blocks, up to 32k away.
  194    3. There is an implied maximum of 7 bits for the bit length table and
  195       15 bits for the actual data.
  196    4. If only one code exists, then it is encoded using one bit.  (Zero
  197       would be more efficient, but perhaps a little confusing.)  If two
  198       codes exist, they are coded using one bit each (0 and 1).
  199    5. There is no way of sending zero distance codes--a dummy must be
  200       sent if there are none.  (History: a pre 2.0 version of PKZIP would
  201       store blocks with no distance codes, but this was discovered to be
  202       too harsh a criterion.)  Valid only for 1.93a.  2.04c does allow
  203       zero distance codes, which is sent as one code of zero bits in
  204       length.
  205    6. There are up to 286 literal/length codes.  Code 256 represents the
  206       end-of-block.  Note however that the static length tree defines
  207       288 codes just to fill out the Huffman codes.  Codes 286 and 287
  208       cannot be used though, since there is no length base or extra bits
  209       defined for them.  Similarily, there are up to 30 distance codes.
  210       However, static trees define 32 codes (all 5 bits) to fill out the
  211       Huffman codes, but the last two had better not show up in the data.
  212    7. Unzip can check dynamic Huffman blocks for complete code sets.
  213       The exception is that a single code would not be complete (see #4).
  214    8. The five bits following the block type is really the number of
  215       literal codes sent minus 257.
  216    9. Length codes 8,16,16 are interpreted as 13 length codes of 8 bits
  217       (1+6+6).  Therefore, to output three times the length, you output
  218       three codes (1+1+1), whereas to output four times the same length,
  219       you only need two codes (1+3).  Hmm.
  220   10. In the tree reconstruction algorithm, Code = Code + Increment
  221       only if BitLength(i) is not zero.  (Pretty obvious.)
  222   11. Correction: 4 Bits: # of Bit Length codes - 4     (4 - 19)
  223   12. Note: length code 284 can represent 227-258, but length code 285
  224       really is 258.  The last length deserves its own, short code
  225       since it gets used a lot in very redundant files.  The length
  226       258 is special since 258 - 3 (the min match length) is 255.
  227   13. The literal/length and distance code bit lengths are read as a
  228       single stream of lengths.  It is possible (and advantageous) for
  229       a repeat code (16, 17, or 18) to go across the boundary between
  230       the two sets of lengths.
  231  */
  232 
  233 
  234 #define PKZIP_BUG_WORKAROUND    /* PKZIP 1.93a problem--live with it */
  235 
  236 /*
  237     inflate.h must supply the uch slide[GZ_WSIZE] array and the NEXTBYTE,
  238     FLUSH() and memzero macros.  If the window size is not 32K, it
  239     should also define GZ_WSIZE.  If INFMOD is defined, it can include
  240     compiled functions to support the NEXTBYTE and/or FLUSH() macros.
  241     There are defaults for NEXTBYTE and FLUSH() below for use as
  242     examples of what those functions need to do.  Normally, you would
  243     also want FLUSH() to compute a crc on the data.  inflate.h also
  244     needs to provide these typedefs:
  245 
  246         typedef unsigned char uch;
  247         typedef unsigned short ush;
  248         typedef unsigned long ulg;
  249 
  250     This module uses the external functions malloc() and free() (and
  251     probably memset() or bzero() in the memzero() macro).  Their
  252     prototypes are normally found in <string.h> and <stdlib.h>.
  253  */
  254 #define INFMOD                  /* tell inflate.h to include code to be
  255                                  * compiled */
  256 
  257 /* Huffman code lookup table entry--this entry is four bytes for machines
  258    that have 16-bit pointers (e.g. PC's in the small or medium model).
  259    Valid extra bits are 0..13.  e == 15 is EOB (end of block), e == 16
  260    means that v is a literal, 16 < e < 32 means that v is a pointer to
  261    the next table, which codes e - 16 bits, and lastly e == 99 indicates
  262    an unused code.  If a code with e == 99 is looked up, this implies an
  263    error in the data. */
  264 struct huft {
  265         uch             e;      /* number of extra bits or operation */
  266         uch             b;      /* number of bits in this code or subcode */
  267         union {
  268                 ush             n;      /* literal, length base, or distance
  269                                          * base */
  270                 struct huft    *t;      /* pointer to next level of table */
  271         }               v;
  272 };
  273 
  274 
  275 /* Function prototypes */
  276 static int huft_build(struct inflate *, unsigned *, unsigned, unsigned, const ush *, const ush *, struct huft **, int *);
  277 static int huft_free(struct inflate *, struct huft *);
  278 static int inflate_codes(struct inflate *, struct huft *, struct huft *, int, int);
  279 static int inflate_stored(struct inflate *);
  280 static int xinflate(struct inflate *);
  281 static int inflate_fixed(struct inflate *);
  282 static int inflate_dynamic(struct inflate *);
  283 static int inflate_block(struct inflate *, int *);
  284 
  285 /* The inflate algorithm uses a sliding 32K byte window on the uncompressed
  286    stream to find repeated byte strings.  This is implemented here as a
  287    circular buffer.  The index is updated simply by incrementing and then
  288    and'ing with 0x7fff (32K-1). */
  289 /* It is left to other modules to supply the 32K area.  It is assumed
  290    to be usable as if it were declared "uch slide[32768];" or as just
  291    "uch *slide;" and then malloc'ed in the latter case.  The definition
  292    must be in unzip.h, included above. */
  293 
  294 
  295 /* Tables for deflate from PKZIP's appnote.txt. */
  296 
  297 /* Order of the bit length code lengths */
  298 static const unsigned border[] = {
  299         16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
  300 
  301 static const ush cplens[] = {   /* Copy lengths for literal codes 257..285 */
  302         3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
  303         35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
  304  /* note: see note #13 above about the 258 in this list. */
  305 
  306 static const ush cplext[] = {   /* Extra bits for literal codes 257..285 */
  307         0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
  308         3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 99, 99}; /* 99==invalid */
  309 
  310 static const ush cpdist[] = {   /* Copy offsets for distance codes 0..29 */
  311         1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
  312         257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
  313         8193, 12289, 16385, 24577};
  314 
  315 static const ush cpdext[] = {   /* Extra bits for distance codes */
  316         0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
  317         7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
  318         12, 12, 13, 13};
  319 
  320 /* And'ing with mask[n] masks the lower n bits */
  321 static const ush mask[] = {
  322         0x0000,
  323         0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
  324         0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
  325 };
  326 
  327 
  328 /* Macros for inflate() bit peeking and grabbing.
  329    The usage is:
  330 
  331         NEEDBITS(glbl,j)
  332         x = b & mask[j];
  333         DUMPBITS(j)
  334 
  335    where NEEDBITS makes sure that b has at least j bits in it, and
  336    DUMPBITS removes the bits from b.  The macros use the variable k
  337    for the number of bits in b.  Normally, b and k are register
  338    variables for speed, and are initialized at the begining of a
  339    routine that uses these macros from a global bit buffer and count.
  340 
  341    In order to not ask for more bits than there are in the compressed
  342    stream, the Huffman tables are constructed to only ask for just
  343    enough bits to make up the end-of-block code (value 256).  Then no
  344    bytes need to be "returned" to the buffer at the end of the last
  345    block.  See the huft_build() routine.
  346  */
  347 
  348 /*
  349  * The following 2 were global variables.
  350  * They are now fields of the inflate structure.
  351  */
  352 
  353 #define NEEDBITS(glbl,n) {                                              \
  354                 while(k<(n)) {                                          \
  355                         int c=(*glbl->gz_input)(glbl->gz_private);      \
  356                         if(c==GZ_EOF)                                   \
  357                                 return 1;                               \
  358                         b|=((ulg)c)<<k;                                 \
  359                         k+=8;                                           \
  360                 }                                                       \
  361         }
  362 
  363 #define DUMPBITS(n) {b>>=(n);k-=(n);}
  364 
  365 /*
  366    Huffman code decoding is performed using a multi-level table lookup.
  367    The fastest way to decode is to simply build a lookup table whose
  368    size is determined by the longest code.  However, the time it takes
  369    to build this table can also be a factor if the data being decoded
  370    is not very long.  The most common codes are necessarily the
  371    shortest codes, so those codes dominate the decoding time, and hence
  372    the speed.  The idea is you can have a shorter table that decodes the
  373    shorter, more probable codes, and then point to subsidiary tables for
  374    the longer codes.  The time it costs to decode the longer codes is
  375    then traded against the time it takes to make longer tables.
  376 
  377    This results of this trade are in the variables lbits and dbits
  378    below.  lbits is the number of bits the first level table for literal/
  379    length codes can decode in one step, and dbits is the same thing for
  380    the distance codes.  Subsequent tables are also less than or equal to
  381    those sizes.  These values may be adjusted either when all of the
  382    codes are shorter than that, in which case the longest code length in
  383    bits is used, or when the shortest code is *longer* than the requested
  384    table size, in which case the length of the shortest code in bits is
  385    used.
  386 
  387    There are two different values for the two tables, since they code a
  388    different number of possibilities each.  The literal/length table
  389    codes 286 possible values, or in a flat code, a little over eight
  390    bits.  The distance table codes 30 possible values, or a little less
  391    than five bits, flat.  The optimum values for speed end up being
  392    about one bit more than those, so lbits is 8+1 and dbits is 5+1.
  393    The optimum values may differ though from machine to machine, and
  394    possibly even between compilers.  Your mileage may vary.
  395  */
  396 
  397 static const int lbits = 9;     /* bits in base literal/length lookup table */
  398 static const int dbits = 6;     /* bits in base distance lookup table */
  399 
  400 
  401 /* If BMAX needs to be larger than 16, then h and x[] should be ulg. */
  402 #define BMAX 16                 /* maximum bit length of any code (16 for
  403                                  * explode) */
  404 #define N_MAX 288               /* maximum number of codes in any set */
  405 
  406 /* Given a list of code lengths and a maximum table size, make a set of
  407    tables to decode that set of codes.  Return zero on success, one if
  408    the given code set is incomplete (the tables are still built in this
  409    case), two if the input is invalid (all zero length codes or an
  410    oversubscribed set of lengths), and three if not enough memory.
  411    The code with value 256 is special, and the tables are constructed
  412    so that no bits beyond that code are fetched when that code is
  413    decoded. */
  414 static int
  415 huft_build(glbl, b, n, s, d, e, t, m)
  416         struct inflate *glbl;
  417         unsigned       *b;      /* code lengths in bits (all assumed <= BMAX) */
  418         unsigned        n;      /* number of codes (assumed <= N_MAX) */
  419         unsigned        s;      /* number of simple-valued codes (0..s-1) */
  420         const ush      *d;      /* list of base values for non-simple codes */
  421         const ush      *e;      /* list of extra bits for non-simple codes */
  422         struct huft   **t;      /* result: starting table */
  423         int            *m;      /* maximum lookup bits, returns actual */
  424 {
  425         unsigned        a;      /* counter for codes of length k */
  426         unsigned        c[BMAX + 1];    /* bit length count table */
  427         unsigned        el;     /* length of EOB code (value 256) */
  428         unsigned        f;      /* i repeats in table every f entries */
  429         int             g;      /* maximum code length */
  430         int             h;      /* table level */
  431         register unsigned i;    /* counter, current code */
  432         register unsigned j;    /* counter */
  433         register int    k;      /* number of bits in current code */
  434         int             lx[BMAX + 1];   /* memory for l[-1..BMAX-1] */
  435         int            *l = lx + 1;     /* stack of bits per table */
  436         register unsigned *p;   /* pointer into c[], b[], or v[] */
  437         register struct huft *q;/* points to current table */
  438         struct huft     r;      /* table entry for structure assignment */
  439         struct huft    *u[BMAX];/* table stack */
  440         unsigned        v[N_MAX];       /* values in order of bit length */
  441         register int    w;      /* bits before this table == (l * h) */
  442         unsigned        x[BMAX + 1];    /* bit offsets, then code stack */
  443         unsigned       *xp;     /* pointer into x */
  444         int             y;      /* number of dummy codes added */
  445         unsigned        z;      /* number of entries in current table */
  446 
  447         /* Generate counts for each bit length */
  448         el = n > 256 ? b[256] : BMAX;   /* set length of EOB code, if any */
  449 #ifdef _KERNEL
  450         memzero((char *) c, sizeof(c));
  451 #else
  452         for (i = 0; i < BMAX+1; i++)
  453                 c [i] = 0;
  454 #endif
  455         p = b;
  456         i = n;
  457         do {
  458                 c[*p]++;
  459                 p++;            /* assume all entries <= BMAX */
  460         } while (--i);
  461         if (c[0] == n) {        /* null input--all zero length codes */
  462                 *t = (struct huft *) NULL;
  463                 *m = 0;
  464                 return 0;
  465         }
  466         /* Find minimum and maximum length, bound *m by those */
  467         for (j = 1; j <= BMAX; j++)
  468                 if (c[j])
  469                         break;
  470         k = j;                  /* minimum code length */
  471         if ((unsigned) *m < j)
  472                 *m = j;
  473         for (i = BMAX; i; i--)
  474                 if (c[i])
  475                         break;
  476         g = i;                  /* maximum code length */
  477         if ((unsigned) *m > i)
  478                 *m = i;
  479 
  480         /* Adjust last length count to fill out codes, if needed */
  481         for (y = 1 << j; j < i; j++, y <<= 1)
  482                 if ((y -= c[j]) < 0)
  483                         return 2;       /* bad input: more codes than bits */
  484         if ((y -= c[i]) < 0)
  485                 return 2;
  486         c[i] += y;
  487 
  488         /* Generate starting offsets into the value table for each length */
  489         x[1] = j = 0;
  490         p = c + 1;
  491         xp = x + 2;
  492         while (--i) {           /* note that i == g from above */
  493                 *xp++ = (j += *p++);
  494         }
  495 
  496         /* Make a table of values in order of bit lengths */
  497         p = b;
  498         i = 0;
  499         do {
  500                 if ((j = *p++) != 0)
  501                         v[x[j]++] = i;
  502         } while (++i < n);
  503 
  504         /* Generate the Huffman codes and for each, make the table entries */
  505         x[0] = i = 0;           /* first Huffman code is zero */
  506         p = v;                  /* grab values in bit order */
  507         h = -1;                 /* no tables yet--level -1 */
  508         w = l[-1] = 0;          /* no bits decoded yet */
  509         u[0] = (struct huft *) NULL;    /* just to keep compilers happy */
  510         q = (struct huft *) NULL;       /* ditto */
  511         z = 0;                  /* ditto */
  512 
  513         /* go through the bit lengths (k already is bits in shortest code) */
  514         for (; k <= g; k++) {
  515                 a = c[k];
  516                 while (a--) {
  517                         /*
  518                          * here i is the Huffman code of length k bits for
  519                          * value *p
  520                          */
  521                         /* make tables up to required level */
  522                         while (k > w + l[h]) {
  523                                 w += l[h++];    /* add bits already decoded */
  524 
  525                                 /*
  526                                  * compute minimum size table less than or
  527                                  * equal to *m bits
  528                                  */
  529                                 z = (z = g - w) > (unsigned) *m ? *m : z;       /* upper limit */
  530                                 if ((f = 1 << (j = k - w)) > a + 1) {   /* try a k-w bit table *//* t
  531                                                                          * oo few codes for k-w
  532                                                                          * bit table */
  533                                         f -= a + 1;     /* deduct codes from
  534                                                          * patterns left */
  535                                         xp = c + k;
  536                                         while (++j < z) {       /* try smaller tables up
  537                                                                  * to z bits */
  538                                                 if ((f <<= 1) <= *++xp)
  539                                                         break;  /* enough codes to use
  540                                                                  * up j bits */
  541                                                 f -= *xp;       /* else deduct codes
  542                                                                  * from patterns */
  543                                         }
  544                                 }
  545                                 if ((unsigned) w + j > el && (unsigned) w < el)
  546                                         j = el - w;     /* make EOB code end at
  547                                                          * table */
  548                                 z = 1 << j;     /* table entries for j-bit
  549                                                  * table */
  550                                 l[h] = j;       /* set table size in stack */
  551 
  552                                 /* allocate and link in new table */
  553                                 if ((q = (struct huft *) malloc((z + 1) * sizeof(struct huft), M_GZIP, M_WAITOK)) ==
  554                                     (struct huft *) NULL) {
  555                                         if (h)
  556                                                 huft_free(glbl, u[0]);
  557                                         return 3;       /* not enough memory */
  558                                 }
  559                                 glbl->gz_hufts += z + 1;        /* track memory usage */
  560                                 *t = q + 1;     /* link to list for
  561                                                  * huft_free() */
  562                                 *(t = &(q->v.t)) = (struct huft *) NULL;
  563                                 u[h] = ++q;     /* table starts after link */
  564 
  565                                 /* connect to last table, if there is one */
  566                                 if (h) {
  567                                         x[h] = i;       /* save pattern for
  568                                                          * backing up */
  569                                         r.b = (uch) l[h - 1];   /* bits to dump before
  570                                                                  * this table */
  571                                         r.e = (uch) (16 + j);   /* bits in this table */
  572                                         r.v.t = q;      /* pointer to this table */
  573                                         j = (i & ((1 << w) - 1)) >> (w - l[h - 1]);
  574                                         u[h - 1][j] = r;        /* connect to last table */
  575                                 }
  576                         }
  577 
  578                         /* set up table entry in r */
  579                         r.b = (uch) (k - w);
  580                         if (p >= v + n)
  581                                 r.e = 99;       /* out of values--invalid
  582                                                  * code */
  583                         else if (*p < s) {
  584                                 r.e = (uch) (*p < 256 ? 16 : 15);       /* 256 is end-of-block
  585                                                                          * code */
  586                                 r.v.n = *p++;   /* simple code is just the
  587                                                  * value */
  588                         } else {
  589                                 r.e = (uch) e[*p - s];  /* non-simple--look up
  590                                                          * in lists */
  591                                 r.v.n = d[*p++ - s];
  592                         }
  593 
  594                         /* fill code-like entries with r */
  595                         f = 1 << (k - w);
  596                         for (j = i >> w; j < z; j += f)
  597                                 q[j] = r;
  598 
  599                         /* backwards increment the k-bit code i */
  600                         for (j = 1 << (k - 1); i & j; j >>= 1)
  601                                 i ^= j;
  602                         i ^= j;
  603 
  604                         /* backup over finished tables */
  605                         while ((i & ((1 << w) - 1)) != x[h])
  606                                 w -= l[--h];    /* don't need to update q */
  607                 }
  608         }
  609 
  610         /* return actual size of base table */
  611         *m = l[0];
  612 
  613         /* Return true (1) if we were given an incomplete table */
  614         return y != 0 && g != 1;
  615 }
  616 
  617 static int
  618 huft_free(glbl, t)
  619         struct inflate *glbl;
  620         struct huft    *t;      /* table to free */
  621 /* Free the malloc'ed tables built by huft_build(), which makes a linked
  622    list of the tables it made, with the links in a dummy first entry of
  623    each table. */
  624 {
  625         register struct huft *p, *q;
  626 
  627         /* Go through linked list, freeing from the malloced (t[-1]) address. */
  628         p = t;
  629         while (p != (struct huft *) NULL) {
  630                 q = (--p)->v.t;
  631                 free(p, M_GZIP);
  632                 p = q;
  633         }
  634         return 0;
  635 }
  636 
  637 /* inflate (decompress) the codes in a deflated (compressed) block.
  638    Return an error code or zero if it all goes ok. */
  639 static int
  640 inflate_codes(glbl, tl, td, bl, bd)
  641         struct inflate *glbl;
  642         struct huft    *tl, *td;/* literal/length and distance decoder tables */
  643         int             bl, bd; /* number of bits decoded by tl[] and td[] */
  644 {
  645         register unsigned e;    /* table entry flag/number of extra bits */
  646         unsigned        n, d;   /* length and index for copy */
  647         unsigned        w;      /* current window position */
  648         struct huft    *t;      /* pointer to table entry */
  649         unsigned        ml, md; /* masks for bl and bd bits */
  650         register ulg    b;      /* bit buffer */
  651         register unsigned k;    /* number of bits in bit buffer */
  652 
  653         /* make local copies of globals */
  654         b = glbl->gz_bb;                        /* initialize bit buffer */
  655         k = glbl->gz_bk;
  656         w = glbl->gz_wp;        /* initialize window position */
  657 
  658         /* inflate the coded data */
  659         ml = mask[bl];          /* precompute masks for speed */
  660         md = mask[bd];
  661         while (1) {             /* do until end of block */
  662                 NEEDBITS(glbl, (unsigned) bl)
  663                         if ((e = (t = tl + ((unsigned) b & ml))->e) > 16)
  664                         do {
  665                                 if (e == 99)
  666                                         return 1;
  667                                 DUMPBITS(t->b)
  668                                         e -= 16;
  669                                 NEEDBITS(glbl, e)
  670                         } while ((e = (t = t->v.t + ((unsigned) b & mask[e]))->e) > 16);
  671                 DUMPBITS(t->b)
  672                         if (e == 16) {  /* then it's a literal */
  673                         glbl->gz_slide[w++] = (uch) t->v.n;
  674                         if (w == GZ_WSIZE) {
  675                                 FLUSH(glbl, w);
  676                                 w = 0;
  677                         }
  678                 } else {        /* it's an EOB or a length */
  679                         /* exit if end of block */
  680                         if (e == 15)
  681                                 break;
  682 
  683                         /* get length of block to copy */
  684                         NEEDBITS(glbl, e)
  685                                 n = t->v.n + ((unsigned) b & mask[e]);
  686                         DUMPBITS(e);
  687 
  688                         /* decode distance of block to copy */
  689                         NEEDBITS(glbl, (unsigned) bd)
  690                                 if ((e = (t = td + ((unsigned) b & md))->e) > 16)
  691                                 do {
  692                                         if (e == 99)
  693                                                 return 1;
  694                                         DUMPBITS(t->b)
  695                                                 e -= 16;
  696                                         NEEDBITS(glbl, e)
  697                                 } while ((e = (t = t->v.t + ((unsigned) b & mask[e]))->e) > 16);
  698                         DUMPBITS(t->b)
  699                                 NEEDBITS(glbl, e)
  700                                 d = w - t->v.n - ((unsigned) b & mask[e]);
  701                         DUMPBITS(e)
  702                         /* do the copy */
  703                                 do {
  704                                 n -= (e = (e = GZ_WSIZE - ((d &= GZ_WSIZE - 1) > w ? d : w)) > n ? n : e);
  705 #ifndef NOMEMCPY
  706                                 if (w - d >= e) {       /* (this test assumes
  707                                                          * unsigned comparison) */
  708                                         memcpy(glbl->gz_slide + w, glbl->gz_slide + d, e);
  709                                         w += e;
  710                                         d += e;
  711                                 } else  /* do it slow to avoid memcpy()
  712                                          * overlap */
  713 #endif                          /* !NOMEMCPY */
  714                                         do {
  715                                                 glbl->gz_slide[w++] = glbl->gz_slide[d++];
  716                                         } while (--e);
  717                                 if (w == GZ_WSIZE) {
  718                                         FLUSH(glbl, w);
  719                                         w = 0;
  720                                 }
  721                         } while (n);
  722                 }
  723         }
  724 
  725         /* restore the globals from the locals */
  726         glbl->gz_wp = w;        /* restore global window pointer */
  727         glbl->gz_bb = b;                        /* restore global bit buffer */
  728         glbl->gz_bk = k;
  729 
  730         /* done */
  731         return 0;
  732 }
  733 
  734 /* "decompress" an inflated type 0 (stored) block. */
  735 static int
  736 inflate_stored(glbl)
  737         struct inflate *glbl;
  738 {
  739         unsigned        n;      /* number of bytes in block */
  740         unsigned        w;      /* current window position */
  741         register ulg    b;      /* bit buffer */
  742         register unsigned k;    /* number of bits in bit buffer */
  743 
  744         /* make local copies of globals */
  745         b = glbl->gz_bb;                        /* initialize bit buffer */
  746         k = glbl->gz_bk;
  747         w = glbl->gz_wp;        /* initialize window position */
  748 
  749         /* go to byte boundary */
  750         n = k & 7;
  751         DUMPBITS(n);
  752 
  753         /* get the length and its complement */
  754         NEEDBITS(glbl, 16)
  755                 n = ((unsigned) b & 0xffff);
  756         DUMPBITS(16)
  757                 NEEDBITS(glbl, 16)
  758                 if (n != (unsigned) ((~b) & 0xffff))
  759                 return 1;       /* error in compressed data */
  760         DUMPBITS(16)
  761         /* read and output the compressed data */
  762                 while (n--) {
  763                 NEEDBITS(glbl, 8)
  764                         glbl->gz_slide[w++] = (uch) b;
  765                 if (w == GZ_WSIZE) {
  766                         FLUSH(glbl, w);
  767                         w = 0;
  768                 }
  769                 DUMPBITS(8)
  770         }
  771 
  772         /* restore the globals from the locals */
  773         glbl->gz_wp = w;        /* restore global window pointer */
  774         glbl->gz_bb = b;                        /* restore global bit buffer */
  775         glbl->gz_bk = k;
  776         return 0;
  777 }
  778 
  779 /* decompress an inflated type 1 (fixed Huffman codes) block.  We should
  780    either replace this with a custom decoder, or at least precompute the
  781    Huffman tables. */
  782 static int
  783 inflate_fixed(glbl)
  784         struct inflate *glbl;
  785 {
  786         /* if first time, set up tables for fixed blocks */
  787         if (glbl->gz_fixed_tl == (struct huft *) NULL) {
  788                 int             i;      /* temporary variable */
  789                 static unsigned l[288]; /* length list for huft_build */
  790 
  791                 /* literal table */
  792                 for (i = 0; i < 144; i++)
  793                         l[i] = 8;
  794                 for (; i < 256; i++)
  795                         l[i] = 9;
  796                 for (; i < 280; i++)
  797                         l[i] = 7;
  798                 for (; i < 288; i++)    /* make a complete, but wrong code
  799                                          * set */
  800                         l[i] = 8;
  801                 glbl->gz_fixed_bl = 7;
  802                 if ((i = huft_build(glbl, l, 288, 257, cplens, cplext,
  803                             &glbl->gz_fixed_tl, &glbl->gz_fixed_bl)) != 0) {
  804                         glbl->gz_fixed_tl = (struct huft *) NULL;
  805                         return i;
  806                 }
  807                 /* distance table */
  808                 for (i = 0; i < 30; i++)        /* make an incomplete code
  809                                                  * set */
  810                         l[i] = 5;
  811                 glbl->gz_fixed_bd = 5;
  812                 if ((i = huft_build(glbl, l, 30, 0, cpdist, cpdext,
  813                              &glbl->gz_fixed_td, &glbl->gz_fixed_bd)) > 1) {
  814                         huft_free(glbl, glbl->gz_fixed_tl);
  815                         glbl->gz_fixed_tl = (struct huft *) NULL;
  816                         return i;
  817                 }
  818         }
  819         /* decompress until an end-of-block code */
  820         return inflate_codes(glbl, glbl->gz_fixed_tl, glbl->gz_fixed_td, glbl->gz_fixed_bl, glbl->gz_fixed_bd) != 0;
  821 }
  822 
  823 /* decompress an inflated type 2 (dynamic Huffman codes) block. */
  824 static int
  825 inflate_dynamic(glbl)
  826         struct inflate *glbl;
  827 {
  828         int             i;      /* temporary variables */
  829         unsigned        j;
  830         unsigned        l;      /* last length */
  831         unsigned        m;      /* mask for bit lengths table */
  832         unsigned        n;      /* number of lengths to get */
  833         struct huft    *tl;     /* literal/length code table */
  834         struct huft    *td;     /* distance code table */
  835         int             bl;     /* lookup bits for tl */
  836         int             bd;     /* lookup bits for td */
  837         unsigned        nb;     /* number of bit length codes */
  838         unsigned        nl;     /* number of literal/length codes */
  839         unsigned        nd;     /* number of distance codes */
  840 #ifdef PKZIP_BUG_WORKAROUND
  841         unsigned        ll[288 + 32];   /* literal/length and distance code
  842                                          * lengths */
  843 #else
  844         unsigned        ll[286 + 30];   /* literal/length and distance code
  845                                          * lengths */
  846 #endif
  847         register ulg    b;      /* bit buffer */
  848         register unsigned k;    /* number of bits in bit buffer */
  849 
  850         /* make local bit buffer */
  851         b = glbl->gz_bb;
  852         k = glbl->gz_bk;
  853 
  854         /* read in table lengths */
  855         NEEDBITS(glbl, 5)
  856                 nl = 257 + ((unsigned) b & 0x1f);       /* number of
  857                                                          * literal/length codes */
  858         DUMPBITS(5)
  859                 NEEDBITS(glbl, 5)
  860                 nd = 1 + ((unsigned) b & 0x1f); /* number of distance codes */
  861         DUMPBITS(5)
  862                 NEEDBITS(glbl, 4)
  863                 nb = 4 + ((unsigned) b & 0xf);  /* number of bit length codes */
  864         DUMPBITS(4)
  865 #ifdef PKZIP_BUG_WORKAROUND
  866                 if (nl > 288 || nd > 32)
  867 #else
  868                 if (nl > 286 || nd > 30)
  869 #endif
  870                 return 1;       /* bad lengths */
  871         /* read in bit-length-code lengths */
  872         for (j = 0; j < nb; j++) {
  873                 NEEDBITS(glbl, 3)
  874                         ll[border[j]] = (unsigned) b & 7;
  875                 DUMPBITS(3)
  876         }
  877         for (; j < 19; j++)
  878                 ll[border[j]] = 0;
  879 
  880         /* build decoding table for trees--single level, 7 bit lookup */
  881         bl = 7;
  882         if ((i = huft_build(glbl, ll, 19, 19, NULL, NULL, &tl, &bl)) != 0) {
  883                 if (i == 1)
  884                         huft_free(glbl, tl);
  885                 return i;       /* incomplete code set */
  886         }
  887         /* read in literal and distance code lengths */
  888         n = nl + nd;
  889         m = mask[bl];
  890         i = l = 0;
  891         while ((unsigned) i < n) {
  892                 NEEDBITS(glbl, (unsigned) bl)
  893                         j = (td = tl + ((unsigned) b & m))->b;
  894                 DUMPBITS(j)
  895                         j = td->v.n;
  896                 if (j < 16)     /* length of code in bits (0..15) */
  897                         ll[i++] = l = j;        /* save last length in l */
  898                 else if (j == 16) {     /* repeat last length 3 to 6 times */
  899                         NEEDBITS(glbl, 2)
  900                                 j = 3 + ((unsigned) b & 3);
  901                         DUMPBITS(2)
  902                                 if ((unsigned) i + j > n)
  903                                 return 1;
  904                         while (j--)
  905                                 ll[i++] = l;
  906                 } else if (j == 17) {   /* 3 to 10 zero length codes */
  907                         NEEDBITS(glbl, 3)
  908                                 j = 3 + ((unsigned) b & 7);
  909                         DUMPBITS(3)
  910                                 if ((unsigned) i + j > n)
  911                                 return 1;
  912                         while (j--)
  913                                 ll[i++] = 0;
  914                         l = 0;
  915                 } else {        /* j == 18: 11 to 138 zero length codes */
  916                         NEEDBITS(glbl, 7)
  917                                 j = 11 + ((unsigned) b & 0x7f);
  918                         DUMPBITS(7)
  919                                 if ((unsigned) i + j > n)
  920                                 return 1;
  921                         while (j--)
  922                                 ll[i++] = 0;
  923                         l = 0;
  924                 }
  925         }
  926 
  927         /* free decoding table for trees */
  928         huft_free(glbl, tl);
  929 
  930         /* restore the global bit buffer */
  931         glbl->gz_bb = b;
  932         glbl->gz_bk = k;
  933 
  934         /* build the decoding tables for literal/length and distance codes */
  935         bl = lbits;
  936         i = huft_build(glbl, ll, nl, 257, cplens, cplext, &tl, &bl);
  937         if (i != 0) {
  938                 if (i == 1 && !qflag) {
  939                         FPRINTF("(incomplete l-tree)  ");
  940                         huft_free(glbl, tl);
  941                 }
  942                 return i;       /* incomplete code set */
  943         }
  944         bd = dbits;
  945         i = huft_build(glbl, ll + nl, nd, 0, cpdist, cpdext, &td, &bd);
  946         if (i != 0) {
  947                 if (i == 1 && !qflag) {
  948                         FPRINTF("(incomplete d-tree)  ");
  949 #ifdef PKZIP_BUG_WORKAROUND
  950                         i = 0;
  951                 }
  952 #else
  953                         huft_free(glbl, td);
  954                 }
  955                 huft_free(glbl, tl);
  956                 return i;       /* incomplete code set */
  957 #endif
  958         }
  959         /* decompress until an end-of-block code */
  960         if (inflate_codes(glbl, tl, td, bl, bd))
  961                 return 1;
  962 
  963         /* free the decoding tables, return */
  964         huft_free(glbl, tl);
  965         huft_free(glbl, td);
  966         return 0;
  967 }
  968 
  969 /* decompress an inflated block */
  970 static int
  971 inflate_block(glbl, e)
  972         struct inflate *glbl;
  973         int            *e;      /* last block flag */
  974 {
  975         unsigned        t;      /* block type */
  976         register ulg    b;      /* bit buffer */
  977         register unsigned k;    /* number of bits in bit buffer */
  978 
  979         /* make local bit buffer */
  980         b = glbl->gz_bb;
  981         k = glbl->gz_bk;
  982 
  983         /* read in last block bit */
  984         NEEDBITS(glbl, 1)
  985                 * e = (int) b & 1;
  986         DUMPBITS(1)
  987         /* read in block type */
  988                 NEEDBITS(glbl, 2)
  989                 t = (unsigned) b & 3;
  990         DUMPBITS(2)
  991         /* restore the global bit buffer */
  992                 glbl->gz_bb = b;
  993         glbl->gz_bk = k;
  994 
  995         /* inflate that block type */
  996         if (t == 2)
  997                 return inflate_dynamic(glbl);
  998         if (t == 0)
  999                 return inflate_stored(glbl);
 1000         if (t == 1)
 1001                 return inflate_fixed(glbl);
 1002         /* bad block type */
 1003         return 2;
 1004 }
 1005 
 1006 
 1007 
 1008 /* decompress an inflated entry */
 1009 static int
 1010 xinflate(glbl)
 1011         struct inflate *glbl;
 1012 {
 1013         int             e;      /* last block flag */
 1014         int             r;      /* result code */
 1015         unsigned        h;      /* maximum struct huft's malloc'ed */
 1016 
 1017         glbl->gz_fixed_tl = (struct huft *) NULL;
 1018 
 1019         /* initialize window, bit buffer */
 1020         glbl->gz_wp = 0;
 1021         glbl->gz_bk = 0;
 1022         glbl->gz_bb = 0;
 1023 
 1024         /* decompress until the last block */
 1025         h = 0;
 1026         do {
 1027                 glbl->gz_hufts = 0;
 1028                 if ((r = inflate_block(glbl, &e)) != 0)
 1029                         return r;
 1030                 if (glbl->gz_hufts > h)
 1031                         h = glbl->gz_hufts;
 1032         } while (!e);
 1033 
 1034         /* flush out slide */
 1035         FLUSH(glbl, glbl->gz_wp);
 1036 
 1037         /* return success */
 1038         return 0;
 1039 }
 1040 
 1041 /* Nobody uses this - why not? */
 1042 int
 1043 inflate(glbl)
 1044         struct inflate *glbl;
 1045 {
 1046         int             i;
 1047 #ifdef _KERNEL
 1048         u_char          *p = NULL;
 1049 
 1050         if (!glbl->gz_slide)
 1051                 p = glbl->gz_slide = malloc(GZ_WSIZE, M_GZIP, M_WAITOK);
 1052 #endif
 1053         if (!glbl->gz_slide)
 1054 #ifdef _KERNEL
 1055                 return(ENOMEM);
 1056 #else
 1057                 return 3; /* kzip expects 3 */
 1058 #endif
 1059         i = xinflate(glbl);
 1060 
 1061         if (glbl->gz_fixed_td != (struct huft *) NULL) {
 1062                 huft_free(glbl, glbl->gz_fixed_td);
 1063                 glbl->gz_fixed_td = (struct huft *) NULL;
 1064         }
 1065         if (glbl->gz_fixed_tl != (struct huft *) NULL) {
 1066                 huft_free(glbl, glbl->gz_fixed_tl);
 1067                 glbl->gz_fixed_tl = (struct huft *) NULL;
 1068         }
 1069 #ifdef _KERNEL
 1070         if (p == glbl->gz_slide) {
 1071                 free(glbl->gz_slide, M_GZIP);
 1072                 glbl->gz_slide = NULL;
 1073         }
 1074 #endif
 1075         return i;
 1076 }
 1077 /* ----------------------- END INFLATE.C */

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