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File indexing completed on 2025-05-11 08:24:10

 /*
  * .xz Stream decoder
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
  *
  * This file has been put into the public domain.
  * You can do whatever you want with this file.
  */
 
 #include "xz_private.h"
 #include "xz_stream.h"
 
 #ifdef XZ_USE_CRC64
 #   define IS_CRC64(check_type) ((check_type) == XZ_CHECK_CRC64)
 #else
 #   define IS_CRC64(check_type) false
 #endif
 
 /* Hash used to validate the Index field */
 struct xz_dec_hash {
     vli_type unpadded;
     vli_type uncompressed;
     uint32_t crc32;
 };
 
 struct xz_dec {
     /* Position in dec_main() */
     enum {
         SEQ_STREAM_HEADER,
         SEQ_BLOCK_START,
         SEQ_BLOCK_HEADER,
         SEQ_BLOCK_UNCOMPRESS,
         SEQ_BLOCK_PADDING,
         SEQ_BLOCK_CHECK,
         SEQ_INDEX,
         SEQ_INDEX_PADDING,
         SEQ_INDEX_CRC32,
         SEQ_STREAM_FOOTER
     } sequence;
 
     /* Position in variable-length integers and Check fields */
     uint32_t pos;
 
     /* Variable-length integer decoded by dec_vli() */
     vli_type vli;
 
     /* Saved in_pos and out_pos */
     size_t in_start;
     size_t out_start;
 
 #ifdef XZ_USE_CRC64
     /* CRC32 or CRC64 value in Block or CRC32 value in Index */
     uint64_t crc;
 #else
     /* CRC32 value in Block or Index */
     uint32_t crc;
 #endif
 
     /* Type of the integrity check calculated from uncompressed data */
     enum xz_check check_type;
 
     /* Operation mode */
     enum xz_mode mode;
 
     /*
      * True if the next call to xz_dec_run() is allowed to return
      * XZ_BUF_ERROR.
      */
     bool allow_buf_error;
 
     /* Information stored in Block Header */
     struct {
         /*
          * Value stored in the Compressed Size field, or
          * VLI_UNKNOWN if Compressed Size is not present.
          */
         vli_type compressed;
 
         /*
          * Value stored in the Uncompressed Size field, or
          * VLI_UNKNOWN if Uncompressed Size is not present.
          */
         vli_type uncompressed;
 
         /* Size of the Block Header field */
         uint32_t size;
     } block_header;
 
     /* Information collected when decoding Blocks */
     struct {
         /* Observed compressed size of the current Block */
         vli_type compressed;
 
         /* Observed uncompressed size of the current Block */
         vli_type uncompressed;
 
         /* Number of Blocks decoded so far */
         vli_type count;
 
         /*
          * Hash calculated from the Block sizes. This is used to
          * validate the Index field.
          */
         struct xz_dec_hash hash;
     } block;
 
     /* Variables needed when verifying the Index field */
     struct {
         /* Position in dec_index() */
         enum {
             SEQ_INDEX_COUNT,
             SEQ_INDEX_UNPADDED,
             SEQ_INDEX_UNCOMPRESSED
         } sequence;
 
         /* Size of the Index in bytes */
         vli_type size;
 
         /* Number of Records (matches block.count in valid files) */
         vli_type count;
 
         /*
          * Hash calculated from the Records (matches block.hash in
          * valid files).
          */
         struct xz_dec_hash hash;
     } index;
 
     /*
      * Temporary buffer needed to hold Stream Header, Block Header,
      * and Stream Footer. The Block Header is the biggest (1 KiB)
      * so we reserve space according to that. buf[] has to be aligned
      * to a multiple of four bytes; the size_t variables before it
      * should guarantee this.
      */
     struct {
         size_t pos;
         size_t size;
         uint8_t buf[1024];
     } temp;
 
     struct xz_dec_lzma2 *lzma2;
 
 #ifdef XZ_DEC_BCJ
     struct xz_dec_bcj *bcj;
     bool bcj_active;
 #endif
 };
 
 #ifdef XZ_DEC_ANY_CHECK
 /* Sizes of the Check field with different Check IDs */
 static const uint8_t check_sizes[16] = {
     0,
     4, 4, 4,
     8, 8, 8,
     16, 16, 16,
     32, 32, 32,
     64, 64, 64
 };
 #endif
 
 /*
  * Fill s->temp by copying data starting from b->in[b->in_pos]. Caller
  * must have set s->temp.pos to indicate how much data we are supposed
  * to copy into s->temp.buf. Return true once s->temp.pos has reached
  * s->temp.size.
  */
 static bool fill_temp(struct xz_dec *s, struct xz_buf *b)
 {
     size_t copy_size = min_t(size_t,
             b->in_size - b->in_pos, s->temp.size - s->temp.pos);
 
     memcpy(s->temp.buf + s->temp.pos, b->in + b->in_pos, copy_size);
     b->in_pos += copy_size;
     s->temp.pos += copy_size;
 
     if (s->temp.pos == s->temp.size) {
         s->temp.pos = 0;
         return true;
     }
 
     return false;
 }
 
 /* Decode a variable-length integer (little-endian base-128 encoding) */
 static enum xz_ret dec_vli(struct xz_dec *s, const uint8_t *in,
                size_t *in_pos, size_t in_size)
 {
     uint8_t byte;
 
     if (s->pos == 0)
         s->vli = 0;
 
     while (*in_pos < in_size) {
         byte = in[*in_pos];
         ++*in_pos;
 
         s->vli |= (vli_type)(byte & 0x7F) << s->pos;
 
         if ((byte & 0x80) == 0) {
             /* Don't allow non-minimal encodings. */
             if (byte == 0 && s->pos != 0)
                 return XZ_DATA_ERROR;
 
             s->pos = 0;
             return XZ_STREAM_END;
         }
 
         s->pos += 7;
         if (s->pos == 7 * VLI_BYTES_MAX)
             return XZ_DATA_ERROR;
     }
 
     return XZ_OK;
 }
 
 /*
  * Decode the Compressed Data field from a Block. Update and validate
  * the observed compressed and uncompressed sizes of the Block so that
  * they don't exceed the values possibly stored in the Block Header
  * (validation assumes that no integer overflow occurs, since vli_type
  * is normally uint64_t). Update the CRC32 or CRC64 value if presence of
  * the CRC32 or CRC64 field was indicated in Stream Header.
  *
  * Once the decoding is finished, validate that the observed sizes match
  * the sizes possibly stored in the Block Header. Update the hash and
  * Block count, which are later used to validate the Index field.
  */
 static enum xz_ret dec_block(struct xz_dec *s, struct xz_buf *b)
 {
     enum xz_ret ret;
 
     s->in_start = b->in_pos;
     s->out_start = b->out_pos;
 
 #ifdef XZ_DEC_BCJ
     if (s->bcj_active)
         ret = xz_dec_bcj_run(s->bcj, s->lzma2, b);
     else
 #endif
         ret = xz_dec_lzma2_run(s->lzma2, b);
 
     s->block.compressed += b->in_pos - s->in_start;
     s->block.uncompressed += b->out_pos - s->out_start;
 
     /*
      * There is no need to separately check for VLI_UNKNOWN, since
      * the observed sizes are always smaller than VLI_UNKNOWN.
      */
     if (s->block.compressed > s->block_header.compressed
             || s->block.uncompressed
                 > s->block_header.uncompressed)
         return XZ_DATA_ERROR;
 
     if (s->check_type == XZ_CHECK_CRC32)
         s->crc = xz_crc32(b->out + s->out_start,
                 b->out_pos - s->out_start, s->crc);
 #ifdef XZ_USE_CRC64
     else if (s->check_type == XZ_CHECK_CRC64)
         s->crc = xz_crc64(b->out + s->out_start,
                 b->out_pos - s->out_start, s->crc);
 #endif
 
     if (ret == XZ_STREAM_END) {
         if (s->block_header.compressed != VLI_UNKNOWN
                 && s->block_header.compressed
                     != s->block.compressed)
             return XZ_DATA_ERROR;
 
         if (s->block_header.uncompressed != VLI_UNKNOWN
                 && s->block_header.uncompressed
                     != s->block.uncompressed)
             return XZ_DATA_ERROR;
 
         s->block.hash.unpadded += s->block_header.size
                 + s->block.compressed;
 
 #ifdef XZ_DEC_ANY_CHECK
         s->block.hash.unpadded += check_sizes[s->check_type];
 #else
         if (s->check_type == XZ_CHECK_CRC32)
             s->block.hash.unpadded += 4;
         else if (IS_CRC64(s->check_type))
             s->block.hash.unpadded += 8;
 #endif
 
         s->block.hash.uncompressed += s->block.uncompressed;
         s->block.hash.crc32 = xz_crc32(
                 (const uint8_t *)&s->block.hash,
                 sizeof(s->block.hash), s->block.hash.crc32);
 
         ++s->block.count;
     }
 
     return ret;
 }
 
 /* Update the Index size and the CRC32 value. */
 static void index_update(struct xz_dec *s, const struct xz_buf *b)
 {
     size_t in_used = b->in_pos - s->in_start;
     s->index.size += in_used;
     s->crc = xz_crc32(b->in + s->in_start, in_used, s->crc);
 }
 
 /*
  * Decode the Number of Records, Unpadded Size, and Uncompressed Size
  * fields from the Index field. That is, Index Padding and CRC32 are not
  * decoded by this function.
  *
  * This can return XZ_OK (more input needed), XZ_STREAM_END (everything
  * successfully decoded), or XZ_DATA_ERROR (input is corrupt).
  */
 static enum xz_ret dec_index(struct xz_dec *s, struct xz_buf *b)
 {
     enum xz_ret ret;
 
     do {
         ret = dec_vli(s, b->in, &b->in_pos, b->in_size);
         if (ret != XZ_STREAM_END) {
             index_update(s, b);
             return ret;
         }
 
         switch (s->index.sequence) {
         case SEQ_INDEX_COUNT:
             s->index.count = s->vli;
 
             /*
              * Validate that the Number of Records field
              * indicates the same number of Records as
              * there were Blocks in the Stream.
              */
             if (s->index.count != s->block.count)
                 return XZ_DATA_ERROR;
 
             s->index.sequence = SEQ_INDEX_UNPADDED;
             break;
 
         case SEQ_INDEX_UNPADDED:
             s->index.hash.unpadded += s->vli;
             s->index.sequence = SEQ_INDEX_UNCOMPRESSED;
             break;
 
         case SEQ_INDEX_UNCOMPRESSED:
             s->index.hash.uncompressed += s->vli;
             s->index.hash.crc32 = xz_crc32(
                     (const uint8_t *)&s->index.hash,
                     sizeof(s->index.hash),
                     s->index.hash.crc32);
             --s->index.count;
             s->index.sequence = SEQ_INDEX_UNPADDED;
             break;
         }
     } while (s->index.count > 0);
 
     return XZ_STREAM_END;
 }
 
 /*
  * Validate that the next four or eight input bytes match the value
  * of s->crc. s->pos must be zero when starting to validate the first byte.
  * The "bits" argument allows using the same code for both CRC32 and CRC64.
  */
 static enum xz_ret crc_validate(struct xz_dec *s, struct xz_buf *b,
                 uint32_t bits)
 {
     do {
         if (b->in_pos == b->in_size)
             return XZ_OK;
 
         if (((s->crc >> s->pos) & 0xFF) != b->in[b->in_pos++])
             return XZ_DATA_ERROR;
 
         s->pos += 8;
 
     } while (s->pos < bits);
 
     s->crc = 0;
     s->pos = 0;
 
     return XZ_STREAM_END;
 }
 
 #ifdef XZ_DEC_ANY_CHECK
 /*
  * Skip over the Check field when the Check ID is not supported.
  * Returns true once the whole Check field has been skipped over.
  */
 static bool check_skip(struct xz_dec *s, struct xz_buf *b)
 {
     while (s->pos < check_sizes[s->check_type]) {
         if (b->in_pos == b->in_size)
             return false;
 
         ++b->in_pos;
         ++s->pos;
     }
 
     s->pos = 0;
 
     return true;
 }
 #endif
 
 /* Decode the Stream Header field (the first 12 bytes of the .xz Stream). */
 static enum xz_ret dec_stream_header(struct xz_dec *s)
 {
     if (!memeq(s->temp.buf, HEADER_MAGIC, HEADER_MAGIC_SIZE))
         return XZ_FORMAT_ERROR;
 
     if (xz_crc32(s->temp.buf + HEADER_MAGIC_SIZE, 2, 0)
             != get_le32(s->temp.buf + HEADER_MAGIC_SIZE + 2))
         return XZ_DATA_ERROR;
 
     if (s->temp.buf[HEADER_MAGIC_SIZE] != 0)
         return XZ_OPTIONS_ERROR;
 
     /*
      * Of integrity checks, we support none (Check ID = 0),
      * CRC32 (Check ID = 1), and optionally CRC64 (Check ID = 4).
      * However, if XZ_DEC_ANY_CHECK is defined, we will accept other
      * check types too, but then the check won't be verified and
      * a warning (XZ_UNSUPPORTED_CHECK) will be given.
      */
     s->check_type = s->temp.buf[HEADER_MAGIC_SIZE + 1];
 
 #ifdef XZ_DEC_ANY_CHECK
     if (s->check_type > XZ_CHECK_MAX)
         return XZ_OPTIONS_ERROR;
 
     if (s->check_type > XZ_CHECK_CRC32 && !IS_CRC64(s->check_type))
         return XZ_UNSUPPORTED_CHECK;
 #else
     if (s->check_type > XZ_CHECK_CRC32 && !IS_CRC64(s->check_type))
         return XZ_OPTIONS_ERROR;
 #endif
 
     return XZ_OK;
 }
 
 /* Decode the Stream Footer field (the last 12 bytes of the .xz Stream) */
 static enum xz_ret dec_stream_footer(struct xz_dec *s)
 {
     if (!memeq(s->temp.buf + 10, FOOTER_MAGIC, FOOTER_MAGIC_SIZE))
         return XZ_DATA_ERROR;
 
     if (xz_crc32(s->temp.buf + 4, 6, 0) != get_le32(s->temp.buf))
         return XZ_DATA_ERROR;
 
     /*
      * Validate Backward Size. Note that we never added the size of the
      * Index CRC32 field to s->index.size, thus we use s->index.size / 4
      * instead of s->index.size / 4 - 1.
      */
     if ((s->index.size >> 2) != get_le32(s->temp.buf + 4))
         return XZ_DATA_ERROR;
 
     if (s->temp.buf[8] != 0 || s->temp.buf[9] != s->check_type)
         return XZ_DATA_ERROR;
 
     /*
      * Use XZ_STREAM_END instead of XZ_OK to be more convenient
      * for the caller.
      */
     return XZ_STREAM_END;
 }
 
 /* Decode the Block Header and initialize the filter chain. */
 static enum xz_ret dec_block_header(struct xz_dec *s)
 {
     enum xz_ret ret;
 
     /*
      * Validate the CRC32. We know that the temp buffer is at least
      * eight bytes so this is safe.
      */
     s->temp.size -= 4;
     if (xz_crc32(s->temp.buf, s->temp.size, 0)
             != get_le32(s->temp.buf + s->temp.size))
         return XZ_DATA_ERROR;
 
     s->temp.pos = 2;
 
     /*
      * Catch unsupported Block Flags. We support only one or two filters
      * in the chain, so we catch that with the same test.
      */
 #ifdef XZ_DEC_BCJ
     if (s->temp.buf[1] & 0x3E)
 #else
     if (s->temp.buf[1] & 0x3F)
 #endif
         return XZ_OPTIONS_ERROR;
 
     /* Compressed Size */
     if (s->temp.buf[1] & 0x40) {
         if (dec_vli(s, s->temp.buf, &s->temp.pos, s->temp.size)
                     != XZ_STREAM_END)
             return XZ_DATA_ERROR;
 
         s->block_header.compressed = s->vli;
     } else {
         s->block_header.compressed = VLI_UNKNOWN;
     }
 
     /* Uncompressed Size */
     if (s->temp.buf[1] & 0x80) {
         if (dec_vli(s, s->temp.buf, &s->temp.pos, s->temp.size)
                 != XZ_STREAM_END)
             return XZ_DATA_ERROR;
 
         s->block_header.uncompressed = s->vli;
     } else {
         s->block_header.uncompressed = VLI_UNKNOWN;
     }
 
 #ifdef XZ_DEC_BCJ
     /* If there are two filters, the first one must be a BCJ filter. */
     s->bcj_active = s->temp.buf[1] & 0x01;
     if (s->bcj_active) {
         if (s->temp.size - s->temp.pos < 2)
             return XZ_OPTIONS_ERROR;
 
         ret = xz_dec_bcj_reset(s->bcj, s->temp.buf[s->temp.pos++]);
         if (ret != XZ_OK)
             return ret;
 
         /*
          * We don't support custom start offset,
          * so Size of Properties must be zero.
          */
         if (s->temp.buf[s->temp.pos++] != 0x00)
             return XZ_OPTIONS_ERROR;
     }
 #endif
 
     /* Valid Filter Flags always take at least two bytes. */
     if (s->temp.size - s->temp.pos < 2)
         return XZ_DATA_ERROR;
 
     /* Filter ID = LZMA2 */
     if (s->temp.buf[s->temp.pos++] != 0x21)
         return XZ_OPTIONS_ERROR;
 
     /* Size of Properties = 1-byte Filter Properties */
     if (s->temp.buf[s->temp.pos++] != 0x01)
         return XZ_OPTIONS_ERROR;
 
     /* Filter Properties contains LZMA2 dictionary size. */
     if (s->temp.size - s->temp.pos < 1)
         return XZ_DATA_ERROR;
 
     ret = xz_dec_lzma2_reset(s->lzma2, s->temp.buf[s->temp.pos++]);
     if (ret != XZ_OK)
         return ret;
 
     /* The rest must be Header Padding. */
     while (s->temp.pos < s->temp.size)
         if (s->temp.buf[s->temp.pos++] != 0x00)
             return XZ_OPTIONS_ERROR;
 
     s->temp.pos = 0;
     s->block.compressed = 0;
     s->block.uncompressed = 0;
 
     return XZ_OK;
 }
 
 static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 {
     enum xz_ret ret;
 
     /*
      * Store the start position for the case when we are in the middle
      * of the Index field.
      */
     s->in_start = b->in_pos;
 
     while (true) {
         switch (s->sequence) {
         case SEQ_STREAM_HEADER:
             /*
              * Stream Header is copied to s->temp, and then
              * decoded from there. This way if the caller
              * gives us only little input at a time, we can
              * still keep the Stream Header decoding code
              * simple. Similar approach is used in many places
              * in this file.
              */
             if (!fill_temp(s, b))
                 return XZ_OK;
 
             /*
              * If dec_stream_header() returns
              * XZ_UNSUPPORTED_CHECK, it is still possible
              * to continue decoding if working in multi-call
              * mode. Thus, update s->sequence before calling
              * dec_stream_header().
              */
             s->sequence = SEQ_BLOCK_START;
 
             ret = dec_stream_header(s);
             if (ret != XZ_OK)
                 return ret;
 
         case SEQ_BLOCK_START:
             /* We need one byte of input to continue. */
             if (b->in_pos == b->in_size)
                 return XZ_OK;
 
             /* See if this is the beginning of the Index field. */
             if (b->in[b->in_pos] == 0) {
                 s->in_start = b->in_pos++;
                 s->sequence = SEQ_INDEX;
                 break;
             }
 
             /*
              * Calculate the size of the Block Header and
              * prepare to decode it.
              */
             s->block_header.size
                 = ((uint32_t)b->in[b->in_pos] + 1) * 4;
 
             s->temp.size = s->block_header.size;
             s->temp.pos = 0;
             s->sequence = SEQ_BLOCK_HEADER;
 
         case SEQ_BLOCK_HEADER:
             if (!fill_temp(s, b))
                 return XZ_OK;
 
             ret = dec_block_header(s);
             if (ret != XZ_OK)
                 return ret;
 
             s->sequence = SEQ_BLOCK_UNCOMPRESS;
 
         case SEQ_BLOCK_UNCOMPRESS:
             ret = dec_block(s, b);
             if (ret != XZ_STREAM_END)
                 return ret;
 
             s->sequence = SEQ_BLOCK_PADDING;
 
         case SEQ_BLOCK_PADDING:
             /*
              * Size of Compressed Data + Block Padding
              * must be a multiple of four. We don't need
              * s->block.compressed for anything else
              * anymore, so we use it here to test the size
              * of the Block Padding field.
              */
             while (s->block.compressed & 3) {
                 if (b->in_pos == b->in_size)
                     return XZ_OK;
 
                 if (b->in[b->in_pos++] != 0)
                     return XZ_DATA_ERROR;
 
                 ++s->block.compressed;
             }
 
             s->sequence = SEQ_BLOCK_CHECK;
 
         case SEQ_BLOCK_CHECK:
             if (s->check_type == XZ_CHECK_CRC32) {
                 ret = crc_validate(s, b, 32);
                 if (ret != XZ_STREAM_END)
                     return ret;
             }
             else if (IS_CRC64(s->check_type)) {
                 ret = crc_validate(s, b, 64);
                 if (ret != XZ_STREAM_END)
                     return ret;
             }
 #ifdef XZ_DEC_ANY_CHECK
             else if (!check_skip(s, b)) {
                 return XZ_OK;
             }
 #endif
 
             s->sequence = SEQ_BLOCK_START;
             break;
 
         case SEQ_INDEX:
             ret = dec_index(s, b);
             if (ret != XZ_STREAM_END)
                 return ret;
 
             s->sequence = SEQ_INDEX_PADDING;
 
         case SEQ_INDEX_PADDING:
             while ((s->index.size + (b->in_pos - s->in_start))
                     & 3) {
                 if (b->in_pos == b->in_size) {
                     index_update(s, b);
                     return XZ_OK;
                 }
 
                 if (b->in[b->in_pos++] != 0)
                     return XZ_DATA_ERROR;
             }
 
             /* Finish the CRC32 value and Index size. */
             index_update(s, b);
 
             /* Compare the hashes to validate the Index field. */
             if (!memeq(&s->block.hash, &s->index.hash,
                     sizeof(s->block.hash)))
                 return XZ_DATA_ERROR;
 
             s->sequence = SEQ_INDEX_CRC32;
 
         case SEQ_INDEX_CRC32:
             ret = crc_validate(s, b, 32);
             if (ret != XZ_STREAM_END)
                 return ret;
 
             s->temp.size = STREAM_HEADER_SIZE;
             s->sequence = SEQ_STREAM_FOOTER;
 
         case SEQ_STREAM_FOOTER:
             if (!fill_temp(s, b))
                 return XZ_OK;
 
             return dec_stream_footer(s);
         }
     }
 
     /* Never reached */
 }
 
 /*
  * xz_dec_run() is a wrapper for dec_main() to handle some special cases in
  * multi-call and single-call decoding.
  *
  * In multi-call mode, we must return XZ_BUF_ERROR when it seems clear that we
  * are not going to make any progress anymore. This is to prevent the caller
  * from calling us infinitely when the input file is truncated or otherwise
  * corrupt. Since zlib-style API allows that the caller fills the input buffer
  * only when the decoder doesn't produce any new output, we have to be careful
  * to avoid returning XZ_BUF_ERROR too easily: XZ_BUF_ERROR is returned only
  * after the second consecutive call to xz_dec_run() that makes no progress.
  *
  * In single-call mode, if we couldn't decode everything and no error
  * occurred, either the input is truncated or the output buffer is too small.
  * Since we know that the last input byte never produces any output, we know
  * that if all the input was consumed and decoding wasn't finished, the file
  * must be corrupt. Otherwise the output buffer has to be too small or the
  * file is corrupt in a way that decoding it produces too big output.
  *
  * If single-call decoding fails, we reset b->in_pos and b->out_pos back to
  * their original values. This is because with some filter chains there won't
  * be any valid uncompressed data in the output buffer unless the decoding
  * actually succeeds (that's the price to pay of using the output buffer as
  * the workspace).
  */
 XZ_EXTERN enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b)
 {
     size_t in_start;
     size_t out_start;
     enum xz_ret ret;
 
     if (DEC_IS_SINGLE(s->mode))
         xz_dec_reset(s);
 
     in_start = b->in_pos;
     out_start = b->out_pos;
     ret = dec_main(s, b);
 
     if (DEC_IS_SINGLE(s->mode)) {
         if (ret == XZ_OK)
             ret = b->in_pos == b->in_size
                     ? XZ_DATA_ERROR : XZ_BUF_ERROR;
 
         if (ret != XZ_STREAM_END) {
             b->in_pos = in_start;
             b->out_pos = out_start;
         }
 
     } else if (ret == XZ_OK && in_start == b->in_pos
             && out_start == b->out_pos) {
         if (s->allow_buf_error)
             ret = XZ_BUF_ERROR;
 
         s->allow_buf_error = true;
     } else {
         s->allow_buf_error = false;
     }
 
     return ret;
 }
 
 XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max)
 {
     struct xz_dec *s = kmalloc(sizeof(*s), GFP_KERNEL);
     if (s == NULL)
         return NULL;
 
     s->mode = mode;
 
 #ifdef XZ_DEC_BCJ
     s->bcj = xz_dec_bcj_create(DEC_IS_SINGLE(mode));
     if (s->bcj == NULL)
         goto error_bcj;
 #endif
 
     s->lzma2 = xz_dec_lzma2_create(mode, dict_max);
     if (s->lzma2 == NULL)
         goto error_lzma2;
 
     xz_dec_reset(s);
     return s;
 
 error_lzma2:
 #ifdef XZ_DEC_BCJ
     xz_dec_bcj_end(s->bcj);
 error_bcj:
 #endif
     kfree(s);
     return NULL;
 }
 
 XZ_EXTERN void xz_dec_reset(struct xz_dec *s)
 {
     s->sequence = SEQ_STREAM_HEADER;
     s->allow_buf_error = false;
     s->pos = 0;
     s->crc = 0;
     memzero(&s->block, sizeof(s->block));
     memzero(&s->index, sizeof(s->index));
     s->temp.pos = 0;
     s->temp.size = STREAM_HEADER_SIZE;
 }
 
 XZ_EXTERN void xz_dec_end(struct xz_dec *s)
 {
     if (s != NULL) {
         xz_dec_lzma2_end(s->lzma2);
 #ifdef XZ_DEC_BCJ
         xz_dec_bcj_end(s->bcj);
 #endif
         kfree(s);
     }
 }

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