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authorAdrian Chadd <adrian@FreeBSD.org>2011-12-31 22:35:46 +0000
committerAdrian Chadd <adrian@FreeBSD.org>2011-12-31 22:35:46 +0000
commit38f44a8c7c3367df45180852ee34d7d0a81b4ed7 (patch)
tree944912fd7cd4c5579637a369ce7483e251516f82 /linux/lib/xz/xz_dec_stream.c
downloadsrc-38f44a8c7c3367df45180852ee34d7d0a81b4ed7.tar.gz
src-38f44a8c7c3367df45180852ee34d7d0a81b4ed7.zip
This is from commit hash '48f4588342f4a4e0182a6740e25675fd8e6c6295'.
Notes
Notes: svn path=/vendor/xz-embedded/dist/; revision=229159 svn path=/vendor/xz-embedded/48f4588342f4a4e0182a6740e25675fd8e6c6295/; revision=229160; tag=vendor/xz-embedded/48f4588342f4a4e0182a6740e25675fd8e6c6295
Diffstat (limited to 'linux/lib/xz/xz_dec_stream.c')
-rw-r--r--linux/lib/xz/xz_dec_stream.c821
1 files changed, 821 insertions, 0 deletions
diff --git a/linux/lib/xz/xz_dec_stream.c b/linux/lib/xz/xz_dec_stream.c
new file mode 100644
index 000000000000..ac809b1e64f7
--- /dev/null
+++ b/linux/lib/xz/xz_dec_stream.c
@@ -0,0 +1,821 @@
+/*
+ * .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"
+
+/* 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;
+
+ /* CRC32 value in Block or Index */
+ uint32_t crc32;
+
+ /* 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 if presence of the CRC32
+ * 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->crc32 = xz_crc32(b->out + s->out_start,
+ b->out_pos - s->out_start, s->crc32);
+
+ 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;
+#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->crc32 = xz_crc32(b->in + s->in_start, in_used, s->crc32);
+}
+
+/*
+ * 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 input bytes match the value of s->crc32.
+ * s->pos must be zero when starting to validate the first byte.
+ */
+static enum xz_ret crc32_validate(struct xz_dec *s, struct xz_buf *b)
+{
+ do {
+ if (b->in_pos == b->in_size)
+ return XZ_OK;
+
+ if (((s->crc32 >> s->pos) & 0xFF) != b->in[b->in_pos++])
+ return XZ_DATA_ERROR;
+
+ s->pos += 8;
+
+ } while (s->pos < 32);
+
+ s->crc32 = 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 only none (Check ID = 0) and
+ * CRC32 (Check ID = 1). 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)
+ return XZ_UNSUPPORTED_CHECK;
+#else
+ if (s->check_type > XZ_CHECK_CRC32)
+ 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 = crc32_validate(s, b);
+ 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 = crc32_validate(s, b);
+ 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->crc32 = 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);
+ }
+}