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-rw-r--r--src/liblzma/subblock/subblock_encoder.c170
1 files changed, 119 insertions, 51 deletions
diff --git a/src/liblzma/subblock/subblock_encoder.c b/src/liblzma/subblock/subblock_encoder.c
index d033ea2c..6fc420b5 100644
--- a/src/liblzma/subblock/subblock_encoder.c
+++ b/src/liblzma/subblock/subblock_encoder.c
@@ -21,17 +21,27 @@
#include "raw_encoder.h"
+/// Maximum number of repeats that a single Repeating Data can indicate.
+/// This is directly from the file format specification.
#define REPEAT_COUNT_MAX (1U << 28)
-/// Number of bytes the data chunk being repeated must be before we care
-/// about alignment. This is somewhat arbitrary. It just doesn't make sense
-/// to waste bytes for alignment when the data chunk is very small.
-///
-/// TODO Rename and use this also for Subblock Data?
-#define RLE_MIN_SIZE_FOR_ALIGN 3
+/// Number of bytes the data chunk (not including the header part) must be
+/// before we care about alignment. This is somewhat arbitrary. It just
+/// doesn't make sense to waste bytes for alignment when the data chunk
+/// is very small.
+#define MIN_CHUNK_SIZE_FOR_ALIGN 4
+
+/// Number of bytes of the header part of Subblock Type `Data'. This is
+/// used as the `skew' argument for subblock_align().
+#define ALIGN_SKEW_DATA 4
+
+/// Like above but for Repeating Data.
+#define ALIGN_SKEW_REPEATING_DATA 5
+/// Writes one byte to output buffer and updates the alignment counter.
#define write_byte(b) \
do { \
+ assert(*out_pos < out_size); \
out[*out_pos] = b; \
++*out_pos; \
++coder->alignment.out_pos; \
@@ -77,10 +87,6 @@ struct lzma_coder_s {
/// LZMA_SUBBLOCK_ALIGNMENT_DEFAULT if options is NULL.
uint32_t multiple;
- /// Number of input bytes that we have already read but
- /// not yet started writing out.
- uint32_t in_pending;
-
/// Number of input bytes which we have processed and started
/// writing out. 32-bit integer is enough since we care only
/// about the lowest bits when fixing alignment.
@@ -100,6 +106,12 @@ struct lzma_coder_s {
/// Allocated size of the buffer.
size_t limit;
+
+ /// Number of input bytes that we have already read but
+ /// not yet started writing out. This can be different
+ /// to `size' when using Subfilter. That's why we track
+ /// in_pending separately for RLE (see below).
+ uint32_t in_pending;
} subblock;
struct {
@@ -112,7 +124,10 @@ struct lzma_coder_s {
/// Number of times the first `size' bytes of buffer[]
/// will be repeated.
- lzma_vli count;
+ uint64_t count;
+
+ /// Like subblock.in_pending above, but for RLE.
+ uint32_t in_pending;
} rle;
struct {
@@ -156,6 +171,7 @@ struct lzma_coder_s {
} subfilter;
+ /// Temporary buffer used when we are not the last filter in the chain.
struct {
size_t pos;
size_t size;
@@ -170,27 +186,28 @@ struct lzma_coder_s {
/// a multiple of coder->alignment.multiple.
static bool
subblock_align(lzma_coder *coder, uint8_t *restrict out,
- size_t *restrict out_pos, size_t out_size, uint32_t skew)
+ size_t *restrict out_pos, size_t out_size,
+ size_t chunk_size, uint32_t skew)
{
assert(*out_pos < out_size);
- const uint32_t target = coder->alignment.in_pos
- % coder->alignment.multiple;
+ // Fix the alignment only if it makes sense at least a little.
+ if (chunk_size >= MIN_CHUNK_SIZE_FOR_ALIGN) {
+ const uint32_t target = coder->alignment.in_pos
+ % coder->alignment.multiple;
- while ((coder->alignment.out_pos + skew)
- % coder->alignment.multiple != target) {
- // Zero indicates padding.
- write_byte(0x00);
+ while ((coder->alignment.out_pos + skew)
+ % coder->alignment.multiple != target) {
+ // Zero indicates padding.
+ write_byte(0x00);
- // Check if output buffer got full and indicate it to
- // the caller.
- if (*out_pos == out_size)
- return true;
+ // Check if output buffer got full and indicate it to
+ // the caller.
+ if (*out_pos == out_size)
+ return true;
+ }
}
- coder->alignment.in_pos += coder->alignment.in_pending;
- coder->alignment.in_pending = 0;
-
// Output buffer is not full.
return false;
}
@@ -245,10 +262,20 @@ subblock_rle_flush(lzma_coder *coder)
}
}
- if (coder->rle.count > REPEAT_COUNT_MAX)
+ if (coder->rle.count == 1) {
+ // The buffer should be repeated only once. It is
+ // waste of space to use Repeating Data. Instead,
+ // write a regular Data Subblock. See SEQ_RLE_COUNT_0
+ // in subblock_buffer() for more info.
+ coder->tmp = coder->rle.size - 1;
+ } else if (coder->rle.count > REPEAT_COUNT_MAX) {
+ // There's so much to repeat that it doesn't fit into
+ // 28-bit integer. We will write two or more Subblocks
+ // of type Repeating Data.
coder->tmp = REPEAT_COUNT_MAX - 1;
- else
+ } else {
coder->tmp = coder->rle.count - 1;
+ }
coder->sequence = SEQ_RLE_COUNT_0;
@@ -372,7 +399,7 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
assert(coder->subfilter.subcoder.code == NULL);
// No Subfilter is enabled, just copy the data as is.
- coder->alignment.in_pending += bufcpy(
+ coder->subblock.in_pending += bufcpy(
in, in_pos, in_size,
coder->subblock.data,
&coder->subblock.size,
@@ -415,7 +442,7 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
? LZMA_FINISH : action);
const size_t in_used = *in_pos - in_start;
- coder->alignment.in_pending += in_used;
+ coder->subblock.in_pending += in_used;
if (in_used > 0)
coder->subfilter.got_input = true;
@@ -527,16 +554,21 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
coder->rle.size);
// Test if coder->subblock.data is repeating.
+ // If coder->rle.count would overflow, we
+ // force flushing. Forced flushing shouldn't
+ // really happen in real-world situations.
const size_t count = coder->subblock.size
/ coder->rle.size;
- if (is_repeating(coder->rle.buffer,
- coder->rle.size,
- coder->subblock.data, count)) {
- if (LZMA_VLI_VALUE_MAX - count
- < coder->rle.count)
- return LZMA_PROG_ERROR;
-
+ if (UINT64_MAX - count > coder->rle.count
+ && is_repeating(
+ coder->rle.buffer,
+ coder->rle.size,
+ coder->subblock.data,
+ count)) {
coder->rle.count += count;
+ coder->rle.in_pending += coder
+ ->subblock.in_pending;
+ coder->subblock.in_pending = 0;
coder->subblock.size = 0;
} else if (coder->rle.count > 0) {
@@ -621,17 +653,42 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
break;
case SEQ_RLE_COUNT_0:
- // Make the Data field properly aligned, but only if the data
- // chunk to be repeated isn't extremely small. We have four
- // bytes for Count and one byte for Size, thus the number five.
- if (coder->rle.size >= RLE_MIN_SIZE_FOR_ALIGN
- && subblock_align(
- coder, out, out_pos, out_size, 5))
- return LZMA_OK;
-
assert(coder->rle.count > 0);
- write_byte(0x30 | (coder->tmp & 0x0F));
+ if (coder->rle.count == 1) {
+ // The buffer should be repeated only once. Fix
+ // the alignment and write the first byte of
+ // Subblock Type `Data'.
+ if (subblock_align(coder, out, out_pos, out_size,
+ coder->rle.size, ALIGN_SKEW_DATA))
+ return LZMA_OK;
+
+ write_byte(0x20 | (coder->tmp & 0x0F));
+
+ } else {
+ // We have something to actually repeat, which should
+ // mean that it takes less space with run-length
+ // encoding.
+ if (subblock_align(coder, out, out_pos, out_size,
+ coder->rle.size,
+ ALIGN_SKEW_REPEATING_DATA))
+ return LZMA_OK;
+
+ write_byte(0x30 | (coder->tmp & 0x0F));
+ }
+
+ // NOTE: If we have to write more than one Repeating Data
+ // due to rle.count > REPEAT_COUNT_MAX, the subsequent
+ // Repeating Data Subblocks may get wrong alignment, because
+ // we add rle.in_pending to alignment.in_pos at once instead
+ // of adding only as much as this particular Repeating Data
+ // consumed input data. Correct alignment is always restored
+ // after all the required Repeating Data Subblocks have been
+ // written. This problem occurs in such a weird cases that
+ // it's not worth fixing.
+ coder->alignment.out_pos += coder->rle.size;
+ coder->alignment.in_pos += coder->rle.in_pending;
+ coder->rle.in_pending = 0;
coder->sequence = SEQ_RLE_COUNT_1;
break;
@@ -649,12 +706,18 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
case SEQ_RLE_COUNT_3:
write_byte(coder->tmp >> 20);
+ // Again, see if we are writing regular Data or Repeating Data.
+ // In the former case, we skip SEQ_RLE_SIZE.
+ if (coder->rle.count == 1)
+ coder->sequence = SEQ_RLE_DATA;
+ else
+ coder->sequence = SEQ_RLE_SIZE;
+
if (coder->rle.count > REPEAT_COUNT_MAX)
coder->rle.count -= REPEAT_COUNT_MAX;
else
coder->rle.count = 0;
- coder->sequence = SEQ_RLE_SIZE;
break;
case SEQ_RLE_SIZE:
@@ -670,17 +733,20 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
if (coder->pos < coder->rle.size)
return LZMA_OK;
- coder->alignment.out_pos += coder->rle.size;
-
coder->pos = 0;
coder->sequence = SEQ_FLUSH;
break;
case SEQ_DATA_SIZE_0:
// We need four bytes for the Size field.
- if (subblock_align(coder, out, out_pos, out_size, 4))
+ if (subblock_align(coder, out, out_pos, out_size,
+ coder->subblock.size, ALIGN_SKEW_DATA))
return LZMA_OK;
+ coder->alignment.out_pos += coder->subblock.size;
+ coder->alignment.in_pos += coder->subblock.in_pending;
+ coder->subblock.in_pending = 0;
+
write_byte(0x20 | (coder->tmp & 0x0F));
coder->sequence = SEQ_DATA_SIZE_1;
break;
@@ -706,7 +772,6 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
if (coder->pos < coder->subblock.size)
return LZMA_OK;
- coder->alignment.out_pos += coder->subblock.size;
coder->subblock.size = 0;
coder->pos = 0;
coder->sequence = SEQ_FLUSH;
@@ -714,7 +779,9 @@ subblock_buffer(lzma_coder *coder, lzma_allocator *allocator,
case SEQ_SUBFILTER_INIT: {
assert(coder->subblock.size == 0);
+ assert(coder->subblock.in_pending == 0);
assert(coder->rle.count == 0);
+ assert(coder->rle.in_pending == 0);
assert(coder->subfilter.mode == SUB_SET);
assert(coder->options != NULL);
@@ -884,11 +951,12 @@ lzma_subblock_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
== LZMA_VLI_VALUE_UNKNOWN;
next->coder->pos = 0;
- next->coder->alignment.in_pending = 0;
next->coder->alignment.in_pos = 0;
next->coder->alignment.out_pos = 0;
next->coder->subblock.size = 0;
+ next->coder->subblock.in_pending = 0;
next->coder->rle.count = 0;
+ next->coder->rle.in_pending = 0;
next->coder->subfilter.mode = SUB_NONE;
next->coder->subfilter.mode_locked = false;
generated by cgit v1.2.3 (git 2.25.1) at 2024-09-20 15:36:35 +0000