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      1 /**
      2  * xzlib.c: front end for the transparent suport of lzma compression
      3  *          at the I/O layer, based on an example file from lzma project
      4  *
      5  * See Copyright for the status of this software.
      6  *
      7  * Anders F Bjorklund <afb (at) users.sourceforge.net>
      8  */
      9 #define IN_LIBXML
     10 #include "libxml.h"
     11 #ifdef LIBXML_LZMA_ENABLED
     12 
     13 #include <string.h>
     14 #ifdef HAVE_ERRNO_H
     15 #include <errno.h>
     16 #endif
     17 
     18 
     19 #ifdef HAVE_SYS_TYPES_H
     20 #include <sys/types.h>
     21 #endif
     22 #ifdef HAVE_SYS_STAT_H
     23 #include <sys/stat.h>
     24 #endif
     25 #ifdef HAVE_FCNTL_H
     26 #include <fcntl.h>
     27 #endif
     28 #ifdef HAVE_UNISTD_H
     29 #include <unistd.h>
     30 #endif
     31 #ifdef HAVE_STDLIB_H
     32 #include <stdlib.h>
     33 #endif
     34 #ifdef HAVE_ZLIB_H
     35 #include <zlib.h>
     36 #endif
     37 #ifdef HAVE_LZMA_H
     38 #include <lzma.h>
     39 #endif
     40 
     41 #include "xzlib.h"
     42 #include <libxml/xmlmemory.h>
     43 
     44 /* values for xz_state how */
     45 #define LOOK 0                  /* look for a gzip/lzma header */
     46 #define COPY 1                  /* copy input directly */
     47 #define GZIP 2                  /* decompress a gzip stream */
     48 #define LZMA 3                  /* decompress a lzma stream */
     49 
     50 /* internal lzma file state data structure */
     51 typedef struct {
     52     int mode;                   /* see lzma modes above */
     53     int fd;                     /* file descriptor */
     54     char *path;                 /* path or fd for error messages */
     55     uint64_t pos;               /* current position in uncompressed data */
     56     unsigned int size;          /* buffer size, zero if not allocated yet */
     57     unsigned int want;          /* requested buffer size, default is BUFSIZ */
     58     unsigned char *in;          /* input buffer */
     59     unsigned char *out;         /* output buffer (double-sized when reading) */
     60     unsigned char *next;        /* next output data to deliver or write */
     61     unsigned int have;          /* amount of output data unused at next */
     62     int eof;                    /* true if end of input file reached */
     63     uint64_t start;             /* where the lzma data started, for rewinding */
     64     uint64_t raw;               /* where the raw data started, for seeking */
     65     int how;                    /* 0: get header, 1: copy, 2: decompress */
     66     int direct;                 /* true if last read direct, false if lzma */
     67     /* seek request */
     68     uint64_t skip;              /* amount to skip (already rewound if backwards) */
     69     int seek;                   /* true if seek request pending */
     70     /* error information */
     71     int err;                    /* error code */
     72     char *msg;                  /* error message */
     73     /* lzma stream */
     74     int init;                   /* is the iniflate stream initialized */
     75     lzma_stream strm;           /* stream structure in-place (not a pointer) */
     76     char padding1[32];          /* padding allowing to cope with possible
     77                                    extensions of above structure without
     78 				   too much side effect */
     79 #ifdef HAVE_ZLIB_H
     80     /* zlib inflate or deflate stream */
     81     z_stream zstrm;             /* stream structure in-place (not a pointer) */
     82 #endif
     83     char padding2[32];          /* padding allowing to cope with possible
     84                                    extensions of above structure without
     85 				   too much side effect */
     86 } xz_state, *xz_statep;
     87 
     88 static void
     89 xz_error(xz_statep state, int err, const char *msg)
     90 {
     91     /* free previously allocated message and clear */
     92     if (state->msg != NULL) {
     93         if (state->err != LZMA_MEM_ERROR)
     94             xmlFree(state->msg);
     95         state->msg = NULL;
     96     }
     97 
     98     /* set error code, and if no message, then done */
     99     state->err = err;
    100     if (msg == NULL)
    101         return;
    102 
    103     /* for an out of memory error, save as static string */
    104     if (err == LZMA_MEM_ERROR) {
    105         state->msg = (char *) msg;
    106         return;
    107     }
    108 
    109     /* construct error message with path */
    110     if ((state->msg =
    111          xmlMalloc(strlen(state->path) + strlen(msg) + 3)) == NULL) {
    112         state->err = LZMA_MEM_ERROR;
    113         state->msg = (char *) "out of memory";
    114         return;
    115     }
    116     strcpy(state->msg, state->path);
    117     strcat(state->msg, ": ");
    118     strcat(state->msg, msg);
    119     return;
    120 }
    121 
    122 static void
    123 xz_reset(xz_statep state)
    124 {
    125     state->have = 0;            /* no output data available */
    126     state->eof = 0;             /* not at end of file */
    127     state->how = LOOK;          /* look for gzip header */
    128     state->direct = 1;          /* default for empty file */
    129     state->seek = 0;            /* no seek request pending */
    130     xz_error(state, LZMA_OK, NULL);     /* clear error */
    131     state->pos = 0;             /* no uncompressed data yet */
    132     state->strm.avail_in = 0;   /* no input data yet */
    133 #ifdef HAVE_ZLIB_H
    134     state->zstrm.avail_in = 0;  /* no input data yet */
    135 #endif
    136 }
    137 
    138 static xzFile
    139 xz_open(const char *path, int fd, const char *mode ATTRIBUTE_UNUSED)
    140 {
    141     xz_statep state;
    142 
    143     /* allocate xzFile structure to return */
    144     state = xmlMalloc(sizeof(xz_state));
    145     if (state == NULL)
    146         return NULL;
    147     state->size = 0;            /* no buffers allocated yet */
    148     state->want = BUFSIZ;       /* requested buffer size */
    149     state->msg = NULL;          /* no error message yet */
    150     state->init = 0;            /* initialization of zlib data */
    151 
    152     /* save the path name for error messages */
    153     state->path = xmlMalloc(strlen(path) + 1);
    154     if (state->path == NULL) {
    155         xmlFree(state);
    156         return NULL;
    157     }
    158     strcpy(state->path, path);
    159 
    160     /* open the file with the appropriate mode (or just use fd) */
    161     state->fd = fd != -1 ? fd : open(path,
    162 #ifdef O_LARGEFILE
    163                                      O_LARGEFILE |
    164 #endif
    165 #ifdef O_BINARY
    166                                      O_BINARY |
    167 #endif
    168                                      O_RDONLY, 0666);
    169     if (state->fd == -1) {
    170         xmlFree(state->path);
    171         xmlFree(state);
    172         return NULL;
    173     }
    174 
    175     /* save the current position for rewinding (only if reading) */
    176     state->start = lseek(state->fd, 0, SEEK_CUR);
    177     if (state->start == (uint64_t) - 1)
    178         state->start = 0;
    179 
    180     /* initialize stream */
    181     xz_reset(state);
    182 
    183     /* return stream */
    184     return (xzFile) state;
    185 }
    186 
    187 static int
    188 xz_compressed(xzFile f) {
    189     xz_statep state;
    190 
    191     if (f == NULL)
    192         return(-1);
    193     state = (xz_statep) f;
    194     if (state->init <= 0)
    195         return(-1);
    196 
    197     switch (state->how) {
    198         case COPY:
    199 	    return(0);
    200 	case GZIP:
    201 	case LZMA:
    202 	    return(1);
    203     }
    204     return(-1);
    205 }
    206 
    207 xzFile
    208 __libxml2_xzopen(const char *path, const char *mode)
    209 {
    210     return xz_open(path, -1, mode);
    211 }
    212 
    213 int
    214 __libxml2_xzcompressed(xzFile f) {
    215     return xz_compressed(f);
    216 }
    217 
    218 xzFile
    219 __libxml2_xzdopen(int fd, const char *mode)
    220 {
    221     char *path;                 /* identifier for error messages */
    222     xzFile xz;
    223 
    224     if (fd == -1 || (path = xmlMalloc(7 + 3 * sizeof(int))) == NULL)
    225         return NULL;
    226     sprintf(path, "<fd:%d>", fd);       /* for debugging */
    227     xz = xz_open(path, fd, mode);
    228     xmlFree(path);
    229     return xz;
    230 }
    231 
    232 static int
    233 xz_load(xz_statep state, unsigned char *buf, unsigned int len,
    234         unsigned int *have)
    235 {
    236     int ret;
    237 
    238     *have = 0;
    239     do {
    240         ret = read(state->fd, buf + *have, len - *have);
    241         if (ret <= 0)
    242             break;
    243         *have += ret;
    244     } while (*have < len);
    245     if (ret < 0) {
    246         xz_error(state, -1, strerror(errno));
    247         return -1;
    248     }
    249     if (ret == 0)
    250         state->eof = 1;
    251     return 0;
    252 }
    253 
    254 static int
    255 xz_avail(xz_statep state)
    256 {
    257     lzma_stream *strm = &(state->strm);
    258 
    259     if (state->err != LZMA_OK)
    260         return -1;
    261     if (state->eof == 0) {
    262         /* avail_in is size_t, which is not necessary sizeof(unsigned) */
    263         unsigned tmp = strm->avail_in;
    264 
    265         if (xz_load(state, state->in, state->size, &tmp) == -1) {
    266             strm->avail_in = tmp;
    267             return -1;
    268         }
    269         strm->avail_in = tmp;
    270         strm->next_in = state->in;
    271     }
    272     return 0;
    273 }
    274 
    275 #ifdef HAVE_ZLIB_H
    276 static int
    277 xz_avail_zstrm(xz_statep state)
    278 {
    279     int ret;
    280     state->strm.avail_in = state->zstrm.avail_in;
    281     state->strm.next_in = state->zstrm.next_in;
    282     ret = xz_avail(state);
    283     state->zstrm.avail_in = (uInt) state->strm.avail_in;
    284     state->zstrm.next_in = (Bytef *) state->strm.next_in;
    285     return ret;
    286 }
    287 #endif
    288 
    289 static int
    290 is_format_xz(xz_statep state)
    291 {
    292     lzma_stream *strm = &(state->strm);
    293 
    294     return strm->avail_in >= 6 && memcmp(state->in, "\3757zXZ", 6) == 0;
    295 }
    296 
    297 static int
    298 is_format_lzma(xz_statep state)
    299 {
    300     lzma_stream *strm = &(state->strm);
    301 
    302     lzma_filter filter;
    303     lzma_options_lzma *opt;
    304     uint32_t dict_size;
    305     uint64_t uncompressed_size;
    306     size_t i;
    307 
    308     if (strm->avail_in < 13)
    309         return 0;
    310 
    311     filter.id = LZMA_FILTER_LZMA1;
    312     if (lzma_properties_decode(&filter, NULL, state->in, 5) != LZMA_OK)
    313         return 0;
    314 
    315     opt = filter.options;
    316     dict_size = opt->dict_size;
    317     free(opt); /* we can't use xmlFree on a string returned by zlib */
    318 
    319     /* A hack to ditch tons of false positives: We allow only dictionary
    320      * sizes that are 2^n or 2^n + 2^(n-1) or UINT32_MAX. LZMA_Alone
    321      * created only files with 2^n, but accepts any dictionary size.
    322      * If someone complains, this will be reconsidered.
    323      */
    324     if (dict_size != UINT32_MAX) {
    325         uint32_t d = dict_size - 1;
    326 
    327         d |= d >> 2;
    328         d |= d >> 3;
    329         d |= d >> 4;
    330         d |= d >> 8;
    331         d |= d >> 16;
    332         ++d;
    333         if (d != dict_size || dict_size == 0)
    334             return 0;
    335     }
    336 
    337     /* Another hack to ditch false positives: Assume that if the
    338      * uncompressed size is known, it must be less than 256 GiB.
    339      * Again, if someone complains, this will be reconsidered.
    340      */
    341     uncompressed_size = 0;
    342     for (i = 0; i < 8; ++i)
    343         uncompressed_size |= (uint64_t) (state->in[5 + i]) << (i * 8);
    344 
    345     if (uncompressed_size != UINT64_MAX
    346         && uncompressed_size > (UINT64_C(1) << 38))
    347         return 0;
    348 
    349     return 1;
    350 }
    351 
    352 #ifdef HAVE_ZLIB_H
    353 
    354 /* Get next byte from input, or -1 if end or error. */
    355 #define NEXT() ((strm->avail_in == 0 && xz_avail(state) == -1) ? -1 : \
    356                 (strm->avail_in == 0 ? -1 : \
    357                  (strm->avail_in--, *(strm->next_in)++)))
    358 /* Same thing, but from zstrm */
    359 #define NEXTZ() ((strm->avail_in == 0 && xz_avail_zstrm(state) == -1) ? -1 : \
    360                 (strm->avail_in == 0 ? -1 : \
    361                  (strm->avail_in--, *(strm->next_in)++)))
    362 
    363 /* Get a four-byte little-endian integer and return 0 on success and the value
    364    in *ret.  Otherwise -1 is returned and *ret is not modified. */
    365 static int
    366 gz_next4(xz_statep state, unsigned long *ret)
    367 {
    368     int ch;
    369     unsigned long val;
    370     z_streamp strm = &(state->zstrm);
    371 
    372     val = NEXTZ();
    373     val += (unsigned) NEXTZ() << 8;
    374     val += (unsigned long) NEXTZ() << 16;
    375     ch = NEXTZ();
    376     if (ch == -1)
    377         return -1;
    378     val += (unsigned long) ch << 24;
    379     *ret = val;
    380     return 0;
    381 }
    382 #endif
    383 
    384 static int
    385 xz_head(xz_statep state)
    386 {
    387     lzma_stream *strm = &(state->strm);
    388     lzma_stream init = LZMA_STREAM_INIT;
    389     int flags;
    390     unsigned len;
    391 
    392     /* allocate read buffers and inflate memory */
    393     if (state->size == 0) {
    394         /* allocate buffers */
    395         state->in = xmlMalloc(state->want);
    396         state->out = xmlMalloc(state->want << 1);
    397         if (state->in == NULL || state->out == NULL) {
    398             if (state->out != NULL)
    399                 xmlFree(state->out);
    400             if (state->in != NULL)
    401                 xmlFree(state->in);
    402             xz_error(state, LZMA_MEM_ERROR, "out of memory");
    403             return -1;
    404         }
    405         state->size = state->want;
    406 
    407         /* allocate decoder memory */
    408         state->strm = init;
    409         state->strm.avail_in = 0;
    410         state->strm.next_in = NULL;
    411         if (lzma_auto_decoder(&state->strm, UINT64_MAX, 0) != LZMA_OK) {
    412             xmlFree(state->out);
    413             xmlFree(state->in);
    414             state->size = 0;
    415             xz_error(state, LZMA_MEM_ERROR, "out of memory");
    416             return -1;
    417         }
    418 #ifdef HAVE_ZLIB_H
    419         /* allocate inflate memory */
    420         state->zstrm.zalloc = Z_NULL;
    421         state->zstrm.zfree = Z_NULL;
    422         state->zstrm.opaque = Z_NULL;
    423         state->zstrm.avail_in = 0;
    424         state->zstrm.next_in = Z_NULL;
    425         if (state->init == 0) {
    426             if (inflateInit2(&(state->zstrm), -15) != Z_OK) {/* raw inflate */
    427                 xmlFree(state->out);
    428                 xmlFree(state->in);
    429                 state->size = 0;
    430                 xz_error(state, LZMA_MEM_ERROR, "out of memory");
    431                 return -1;
    432             }
    433             state->init = 1;
    434         }
    435 #endif
    436     }
    437 
    438     /* get some data in the input buffer */
    439     if (strm->avail_in == 0) {
    440         if (xz_avail(state) == -1)
    441             return -1;
    442         if (strm->avail_in == 0)
    443             return 0;
    444     }
    445 
    446     /* look for the xz magic header bytes */
    447     if (is_format_xz(state) || is_format_lzma(state)) {
    448         state->how = LZMA;
    449         state->direct = 0;
    450         return 0;
    451     }
    452 #ifdef HAVE_ZLIB_H
    453     /* look for the gzip magic header bytes 31 and 139 */
    454     if (strm->next_in[0] == 31) {
    455         strm->avail_in--;
    456         strm->next_in++;
    457         if (strm->avail_in == 0 && xz_avail(state) == -1)
    458             return -1;
    459         if (strm->avail_in && strm->next_in[0] == 139) {
    460             /* we have a gzip header, woo hoo! */
    461             strm->avail_in--;
    462             strm->next_in++;
    463 
    464             /* skip rest of header */
    465             if (NEXT() != 8) {  /* compression method */
    466                 xz_error(state, LZMA_DATA_ERROR,
    467                          "unknown compression method");
    468                 return -1;
    469             }
    470             flags = NEXT();
    471             if (flags & 0xe0) { /* reserved flag bits */
    472                 xz_error(state, LZMA_DATA_ERROR,
    473                          "unknown header flags set");
    474                 return -1;
    475             }
    476             NEXT();             /* modification time */
    477             NEXT();
    478             NEXT();
    479             NEXT();
    480             NEXT();             /* extra flags */
    481             NEXT();             /* operating system */
    482             if (flags & 4) {    /* extra field */
    483                 len = (unsigned) NEXT();
    484                 len += (unsigned) NEXT() << 8;
    485                 while (len--)
    486                     if (NEXT() < 0)
    487                         break;
    488             }
    489             if (flags & 8)      /* file name */
    490                 while (NEXT() > 0) ;
    491             if (flags & 16)     /* comment */
    492                 while (NEXT() > 0) ;
    493             if (flags & 2) {    /* header crc */
    494                 NEXT();
    495                 NEXT();
    496             }
    497             /* an unexpected end of file is not checked for here -- it will be
    498              * noticed on the first request for uncompressed data */
    499 
    500             /* set up for decompression */
    501             inflateReset(&state->zstrm);
    502             state->zstrm.adler = crc32(0L, Z_NULL, 0);
    503             state->how = GZIP;
    504             state->direct = 0;
    505             return 0;
    506         } else {
    507             /* not a gzip file -- save first byte (31) and fall to raw i/o */
    508             state->out[0] = 31;
    509             state->have = 1;
    510         }
    511     }
    512 #endif
    513 
    514     /* doing raw i/o, save start of raw data for seeking, copy any leftover
    515      * input to output -- this assumes that the output buffer is larger than
    516      * the input buffer, which also assures space for gzungetc() */
    517     state->raw = state->pos;
    518     state->next = state->out;
    519     if (strm->avail_in) {
    520         memcpy(state->next + state->have, strm->next_in, strm->avail_in);
    521         state->have += strm->avail_in;
    522         strm->avail_in = 0;
    523     }
    524     state->how = COPY;
    525     state->direct = 1;
    526     return 0;
    527 }
    528 
    529 static int
    530 xz_decomp(xz_statep state)
    531 {
    532     int ret;
    533     unsigned had;
    534     unsigned long crc, len;
    535     lzma_stream *strm = &(state->strm);
    536 
    537     lzma_action action = LZMA_RUN;
    538 
    539     /* fill output buffer up to end of deflate stream */
    540     had = strm->avail_out;
    541     do {
    542         /* get more input for inflate() */
    543         if (strm->avail_in == 0 && xz_avail(state) == -1)
    544             return -1;
    545         if (strm->avail_in == 0) {
    546             xz_error(state, LZMA_DATA_ERROR, "unexpected end of file");
    547             return -1;
    548         }
    549         if (state->eof)
    550             action = LZMA_FINISH;
    551 
    552         /* decompress and handle errors */
    553 #ifdef HAVE_ZLIB_H
    554         if (state->how == GZIP) {
    555             state->zstrm.avail_in = (uInt) state->strm.avail_in;
    556             state->zstrm.next_in = (Bytef *) state->strm.next_in;
    557             state->zstrm.avail_out = (uInt) state->strm.avail_out;
    558             state->zstrm.next_out = (Bytef *) state->strm.next_out;
    559             ret = inflate(&state->zstrm, Z_NO_FLUSH);
    560             if (ret == Z_STREAM_ERROR || ret == Z_NEED_DICT) {
    561                 xz_error(state, Z_STREAM_ERROR,
    562                          "internal error: inflate stream corrupt");
    563                 return -1;
    564             }
    565             if (ret == Z_MEM_ERROR)
    566                 ret = LZMA_MEM_ERROR;
    567             if (ret == Z_DATA_ERROR)
    568                 ret = LZMA_DATA_ERROR;
    569             if (ret == Z_STREAM_END)
    570                 ret = LZMA_STREAM_END;
    571             state->strm.avail_in = state->zstrm.avail_in;
    572             state->strm.next_in = state->zstrm.next_in;
    573             state->strm.avail_out = state->zstrm.avail_out;
    574             state->strm.next_out = state->zstrm.next_out;
    575         } else                  /* state->how == LZMA */
    576 #endif
    577             ret = lzma_code(strm, action);
    578         if (ret == LZMA_MEM_ERROR) {
    579             xz_error(state, LZMA_MEM_ERROR, "out of memory");
    580             return -1;
    581         }
    582         if (ret == LZMA_DATA_ERROR) {
    583             xz_error(state, LZMA_DATA_ERROR, "compressed data error");
    584             return -1;
    585         }
    586         if (ret == LZMA_PROG_ERROR) {
    587             xz_error(state, LZMA_PROG_ERROR, "compression error");
    588             return -1;
    589         }
    590     } while (strm->avail_out && ret != LZMA_STREAM_END);
    591 
    592     /* update available output and crc check value */
    593     state->have = had - strm->avail_out;
    594     state->next = strm->next_out - state->have;
    595 #ifdef HAVE_ZLIB_H
    596     state->zstrm.adler =
    597         crc32(state->zstrm.adler, state->next, state->have);
    598 #endif
    599 
    600     if (ret == LZMA_STREAM_END) {
    601 #ifdef HAVE_ZLIB_H
    602         if (state->how == GZIP) {
    603             if (gz_next4(state, &crc) == -1 || gz_next4(state, &len) == -1) {
    604                 xz_error(state, LZMA_DATA_ERROR, "unexpected end of file");
    605                 return -1;
    606             }
    607             if (crc != state->zstrm.adler) {
    608                 xz_error(state, LZMA_DATA_ERROR, "incorrect data check");
    609                 return -1;
    610             }
    611             if (len != (state->zstrm.total_out & 0xffffffffL)) {
    612                 xz_error(state, LZMA_DATA_ERROR, "incorrect length check");
    613                 return -1;
    614             }
    615             state->strm.avail_in = 0;
    616             state->strm.next_in = NULL;
    617             state->strm.avail_out = 0;
    618             state->strm.next_out = NULL;
    619         } else
    620 #endif
    621         if (strm->avail_in != 0 || !state->eof) {
    622             xz_error(state, LZMA_DATA_ERROR, "trailing garbage");
    623             return -1;
    624         }
    625         state->how = LOOK;      /* ready for next stream, once have is 0 (leave
    626                                  * state->direct unchanged to remember how) */
    627     }
    628 
    629     /* good decompression */
    630     return 0;
    631 }
    632 
    633 static int
    634 xz_make(xz_statep state)
    635 {
    636     lzma_stream *strm = &(state->strm);
    637 
    638     if (state->how == LOOK) {   /* look for lzma / gzip header */
    639         if (xz_head(state) == -1)
    640             return -1;
    641         if (state->have)        /* got some data from xz_head() */
    642             return 0;
    643     }
    644     if (state->how == COPY) {   /* straight copy */
    645         if (xz_load(state, state->out, state->size << 1, &(state->have)) ==
    646             -1)
    647             return -1;
    648         state->next = state->out;
    649     } else if (state->how == LZMA || state->how == GZIP) {      /* decompress */
    650         strm->avail_out = state->size << 1;
    651         strm->next_out = state->out;
    652         if (xz_decomp(state) == -1)
    653             return -1;
    654     }
    655     return 0;
    656 }
    657 
    658 static int
    659 xz_skip(xz_statep state, uint64_t len)
    660 {
    661     unsigned n;
    662 
    663     /* skip over len bytes or reach end-of-file, whichever comes first */
    664     while (len)
    665         /* skip over whatever is in output buffer */
    666         if (state->have) {
    667             n = (uint64_t) state->have > len ?
    668                 (unsigned) len : state->have;
    669             state->have -= n;
    670             state->next += n;
    671             state->pos += n;
    672             len -= n;
    673         }
    674 
    675     /* output buffer empty -- return if we're at the end of the input */
    676         else if (state->eof && state->strm.avail_in == 0)
    677             break;
    678 
    679     /* need more data to skip -- load up output buffer */
    680         else {
    681             /* get more output, looking for header if required */
    682             if (xz_make(state) == -1)
    683                 return -1;
    684         }
    685     return 0;
    686 }
    687 
    688 int
    689 __libxml2_xzread(xzFile file, void *buf, unsigned len)
    690 {
    691     unsigned got, n;
    692     xz_statep state;
    693     lzma_stream *strm;
    694 
    695     /* get internal structure */
    696     if (file == NULL)
    697         return -1;
    698     state = (xz_statep) file;
    699     strm = &(state->strm);
    700 
    701     /* check that we're reading and that there's no error */
    702     if (state->err != LZMA_OK)
    703         return -1;
    704 
    705     /* since an int is returned, make sure len fits in one, otherwise return
    706      * with an error (this avoids the flaw in the interface) */
    707     if ((int) len < 0) {
    708         xz_error(state, LZMA_BUF_ERROR,
    709                  "requested length does not fit in int");
    710         return -1;
    711     }
    712 
    713     /* if len is zero, avoid unnecessary operations */
    714     if (len == 0)
    715         return 0;
    716 
    717     /* process a skip request */
    718     if (state->seek) {
    719         state->seek = 0;
    720         if (xz_skip(state, state->skip) == -1)
    721             return -1;
    722     }
    723 
    724     /* get len bytes to buf, or less than len if at the end */
    725     got = 0;
    726     do {
    727         /* first just try copying data from the output buffer */
    728         if (state->have) {
    729             n = state->have > len ? len : state->have;
    730             memcpy(buf, state->next, n);
    731             state->next += n;
    732             state->have -= n;
    733         }
    734 
    735         /* output buffer empty -- return if we're at the end of the input */
    736         else if (state->eof && strm->avail_in == 0)
    737             break;
    738 
    739         /* need output data -- for small len or new stream load up our output
    740          * buffer */
    741         else if (state->how == LOOK || len < (state->size << 1)) {
    742             /* get more output, looking for header if required */
    743             if (xz_make(state) == -1)
    744                 return -1;
    745             continue;           /* no progress yet -- go back to memcpy() above */
    746             /* the copy above assures that we will leave with space in the
    747              * output buffer, allowing at least one gzungetc() to succeed */
    748         }
    749 
    750         /* large len -- read directly into user buffer */
    751         else if (state->how == COPY) {  /* read directly */
    752             if (xz_load(state, buf, len, &n) == -1)
    753                 return -1;
    754         }
    755 
    756         /* large len -- decompress directly into user buffer */
    757         else {                  /* state->how == LZMA */
    758             strm->avail_out = len;
    759             strm->next_out = buf;
    760             if (xz_decomp(state) == -1)
    761                 return -1;
    762             n = state->have;
    763             state->have = 0;
    764         }
    765 
    766         /* update progress */
    767         len -= n;
    768         buf = (char *) buf + n;
    769         got += n;
    770         state->pos += n;
    771     } while (len);
    772 
    773     /* return number of bytes read into user buffer (will fit in int) */
    774     return (int) got;
    775 }
    776 
    777 int
    778 __libxml2_xzclose(xzFile file)
    779 {
    780     int ret;
    781     xz_statep state;
    782 
    783     /* get internal structure */
    784     if (file == NULL)
    785         return LZMA_DATA_ERROR;
    786     state = (xz_statep) file;
    787 
    788     /* free memory and close file */
    789     if (state->size) {
    790         lzma_end(&(state->strm));
    791 #ifdef HAVE_ZLIB_H
    792         if (state->init == 1)
    793             inflateEnd(&(state->zstrm));
    794         state->init = 0;
    795 #endif
    796         xmlFree(state->out);
    797         xmlFree(state->in);
    798     }
    799     xmlFree(state->path);
    800     ret = close(state->fd);
    801     xmlFree(state);
    802     return ret ? ret : LZMA_OK;
    803 }
    804 #endif /* LIBXML_LZMA_ENABLED */
    805