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decompress_bunzip2: code shrink ~10 bytes

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Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko
2010-10-30 00:54:10 +02:00
parent 5d49b72f1a
commit 0c576975c8
1 changed files with 99 additions and 74 deletions
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173
archival/libunarchive/decompress_bunzip2.c
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@@ -151,8 +151,8 @@ static unsigned get_bits(bunzip_data *bd, int bits_wanted)
static int get_next_block(bunzip_data *bd) static int get_next_block(bunzip_data *bd)
{ {
struct group_data *hufGroup; struct group_data *hufGroup;
int dbufCount, nextSym, dbufSize, groupCount, *base, *limit, selector, int dbufCount, dbufSize, groupCount, *base, *limit, selector,
i, j, k, t, runPos, symCount, symTotal, nSelectors, byteCount[256]; i, j, t, runPos, symCount, symTotal, nSelectors, byteCount[256];
uint8_t uc, symToByte[256], mtfSymbol[256], *selectors; uint8_t uc, symToByte[256], mtfSymbol[256], *selectors;
uint32_t *dbuf; uint32_t *dbuf;
unsigned origPtr; unsigned origPtr;
@@ -161,9 +161,12 @@ static int get_next_block(bunzip_data *bd)
dbufSize = bd->dbufSize; dbufSize = bd->dbufSize;
selectors = bd->selectors; selectors = bd->selectors;
/* In bbox, we are ok with aborting through setjmp which is set up in start_bunzip */
#if 0
/* Reset longjmp I/O error handling */ /* Reset longjmp I/O error handling */
i = setjmp(bd->jmpbuf); i = setjmp(bd->jmpbuf);
if (i) return i; if (i) return i;
#endif
/* Read in header signature and CRC, then validate signature. /* Read in header signature and CRC, then validate signature.
(last block signature means CRC is for whole file, return now) */ (last block signature means CRC is for whole file, return now) */
@@ -185,16 +188,23 @@ static int get_next_block(bunzip_data *bd)
symbols to deal with, and writes a sparse bitfield indicating which symbols to deal with, and writes a sparse bitfield indicating which
values were present. We make a translation table to convert the symbols values were present. We make a translation table to convert the symbols
back to the corresponding bytes. */ back to the corresponding bytes. */
t = get_bits(bd, 16);
symTotal = 0; symTotal = 0;
for (i = 0; i < 16; i++) { i = 0;
if (t & (1 << (15-i))) { t = get_bits(bd, 16);
k = get_bits(bd, 16); do {
for (j = 0; j < 16; j++) if (t & (1 << 15)) {
if (k & (1 << (15-j))) unsigned inner_map = get_bits(bd, 16);
symToByte[symTotal++] = (16*i) + j; do {
if (inner_map & (1 << 15))
symToByte[symTotal++] = i;
inner_map <<= 1;
i++;
} while (i & 15);
i -= 16;
} }
} t <<= 1;
i += 16;
} while (i < 256);
/* How many different Huffman coding groups does this block use? */ /* How many different Huffman coding groups does this block use? */
groupCount = get_bits(bd, 3); groupCount = get_bits(bd, 3);
@@ -205,20 +215,24 @@ static int get_next_block(bunzip_data *bd)
group. Read in the group selector list, which is stored as MTF encoded group. Read in the group selector list, which is stored as MTF encoded
bit runs. (MTF=Move To Front, as each value is used it's moved to the bit runs. (MTF=Move To Front, as each value is used it's moved to the
start of the list.) */ start of the list.) */
for (i = 0; i < groupCount; i++)
mtfSymbol[i] = i;
nSelectors = get_bits(bd, 15); nSelectors = get_bits(bd, 15);
if (!nSelectors) return RETVAL_DATA_ERROR; if (!nSelectors)
for (i = 0; i < groupCount; i++) mtfSymbol[i] = i; return RETVAL_DATA_ERROR;
for (i = 0; i < nSelectors; i++) { for (i = 0; i < nSelectors; i++) {
uint8_t tmp_byte;
/* Get next value */ /* Get next value */
for (j = 0; get_bits(bd, 1); j++) int n = 0;
if (j >= groupCount) return RETVAL_DATA_ERROR; while (get_bits(bd, 1)) {
if (n >= groupCount) return RETVAL_DATA_ERROR;
n++;
}
/* Decode MTF to get the next selector */ /* Decode MTF to get the next selector */
uc = mtfSymbol[j]; tmp_byte = mtfSymbol[n];
for (; j; j--) while (--n >= 0)
mtfSymbol[j] = mtfSymbol[j-1]; mtfSymbol[n + 1] = mtfSymbol[n];
mtfSymbol[0] = selectors[i] = uc; mtfSymbol[0] = selectors[i] = tmp_byte;
} }
/* Read the Huffman coding tables for each group, which code for symTotal /* Read the Huffman coding tables for each group, which code for symTotal
@@ -239,20 +253,21 @@ static int get_next_block(bunzip_data *bd)
t = get_bits(bd, 5) - 1; t = get_bits(bd, 5) - 1;
for (i = 0; i < symCount; i++) { for (i = 0; i < symCount; i++) {
for (;;) { for (;;) {
int two_bits;
if ((unsigned)t > (MAX_HUFCODE_BITS-1)) if ((unsigned)t > (MAX_HUFCODE_BITS-1))
return RETVAL_DATA_ERROR; return RETVAL_DATA_ERROR;
/* If first bit is 0, stop. Else second bit indicates whether /* If first bit is 0, stop. Else second bit indicates whether
to increment or decrement the value. Optimization: grab 2 to increment or decrement the value. Optimization: grab 2
bits and unget the second if the first was 0. */ bits and unget the second if the first was 0. */
k = get_bits(bd, 2); two_bits = get_bits(bd, 2);
if (k < 2) { if (two_bits < 2) {
bd->inbufBitCount++; bd->inbufBitCount++;
break; break;
} }
/* Add one if second bit 1, else subtract 1. Avoids if/else */ /* Add one if second bit 1, else subtract 1. Avoids if/else */
t += (((k+1) & 2) - 1); t += (((two_bits+1) & 2) - 1);
} }
/* Correct for the initial -1, to get the final symbol length */ /* Correct for the initial -1, to get the final symbol length */
@@ -282,17 +297,18 @@ static int get_next_block(bunzip_data *bd)
/* Note that minLen can't be smaller than 1, so we adjust the base /* Note that minLen can't be smaller than 1, so we adjust the base
and limit array pointers so we're not always wasting the first and limit array pointers so we're not always wasting the first
entry. We do this again when using them (during symbol decoding).*/ entry. We do this again when using them (during symbol decoding). */
base = hufGroup->base - 1; base = hufGroup->base - 1;
limit = hufGroup->limit - 1; limit = hufGroup->limit - 1;
/* Calculate permute[]. Concurently, initialize temp[] and limit[]. */ /* Calculate permute[]. Concurently, initialize temp[] and limit[]. */
pp = 0; pp = 0;
for (i = minLen; i <= maxLen; i++) { for (i = minLen; i <= maxLen; i++) {
int k;
temp[i] = limit[i] = 0; temp[i] = limit[i] = 0;
for (t = 0; t < symCount; t++) for (k = 0; k < symCount; k++)
if (length[t] == i) if (length[k] == i)
hufGroup->permute[pp++] = t; hufGroup->permute[pp++] = k;
} }
/* Count symbols coded for at each bit length */ /* Count symbols coded for at each bit length */
@@ -305,8 +321,10 @@ static int get_next_block(bunzip_data *bd)
* base[] (number of symbols to ignore at each bit length, which is * base[] (number of symbols to ignore at each bit length, which is
* limit minus the cumulative count of symbols coded for already). */ * limit minus the cumulative count of symbols coded for already). */
pp = t = 0; pp = t = 0;
for (i = minLen; i < maxLen; i++) { for (i = minLen; i < maxLen;) {
pp += temp[i]; unsigned temp_i = temp[i];
pp += temp_i;
/* We read the largest possible symbol size and then unget bits /* We read the largest possible symbol size and then unget bits
after determining how many we need, and those extra bits could after determining how many we need, and those extra bits could
@@ -316,8 +334,8 @@ static int get_next_block(bunzip_data *bd)
don't affect the value>limit[length] comparison. */ don't affect the value>limit[length] comparison. */
limit[i] = (pp << (maxLen - i)) - 1; limit[i] = (pp << (maxLen - i)) - 1;
pp <<= 1; pp <<= 1;
t += temp[i]; t += temp_i;
base[i+1] = pp - t; base[++i] = pp - t;
} }
limit[maxLen+1] = INT_MAX; /* Sentinel value for reading next sym. */ limit[maxLen+1] = INT_MAX; /* Sentinel value for reading next sym. */
limit[maxLen] = pp + temp[maxLen] - 1; limit[maxLen] = pp + temp[maxLen] - 1;
@@ -329,9 +347,9 @@ static int get_next_block(bunzip_data *bd)
and run length encoding, saving the result into dbuf[dbufCount++] = uc */ and run length encoding, saving the result into dbuf[dbufCount++] = uc */
/* Initialize symbol occurrence counters and symbol Move To Front table */ /* Initialize symbol occurrence counters and symbol Move To Front table */
memset(byteCount, 0, sizeof(byteCount)); /* smaller, maybe slower? */ /*memset(byteCount, 0, sizeof(byteCount)); - smaller, but slower */
for (i = 0; i < 256; i++) { for (i = 0; i < 256; i++) {
//byteCount[i] = 0; byteCount[i] = 0;
mtfSymbol[i] = (uint8_t)i; mtfSymbol[i] = (uint8_t)i;
} }
@@ -339,6 +357,7 @@ static int get_next_block(bunzip_data *bd)
runPos = dbufCount = selector = 0; runPos = dbufCount = selector = 0;
for (;;) { for (;;) {
int nextSym;
/* Fetch next Huffman coding group from list. */ /* Fetch next Huffman coding group from list. */
symCount = GROUP_SIZE - 1; symCount = GROUP_SIZE - 1;
@@ -346,44 +365,49 @@ static int get_next_block(bunzip_data *bd)
hufGroup = bd->groups + selectors[selector++]; hufGroup = bd->groups + selectors[selector++];
base = hufGroup->base - 1; base = hufGroup->base - 1;
limit = hufGroup->limit - 1; limit = hufGroup->limit - 1;
continue_this_group:
continue_this_group:
/* Read next Huffman-coded symbol. */ /* Read next Huffman-coded symbol. */
/* Note: It is far cheaper to read maxLen bits and back up than it is /* Note: It is far cheaper to read maxLen bits and back up than it is
to read minLen bits and then an additional bit at a time, testing to read minLen bits and then add additional bit at a time, testing
as we go. Because there is a trailing last block (with file CRC), as we go. Because there is a trailing last block (with file CRC),
there is no danger of the overread causing an unexpected EOF for a there is no danger of the overread causing an unexpected EOF for a
valid compressed file. As a further optimization, we do the read valid compressed file.
inline (falling back to a call to get_bits if the buffer runs
dry). The following (up to got_huff_bits:) is equivalent to
j = get_bits(bd, hufGroup->maxLen);
*/ */
while ((int)(bd->inbufBitCount) < hufGroup->maxLen) { if (1) {
if (bd->inbufPos == bd->inbufCount) { /* As a further optimization, we do the read inline
j = get_bits(bd, hufGroup->maxLen); (falling back to a call to get_bits if the buffer runs dry).
goto got_huff_bits; */
} int new_cnt;
bd->inbufBits = (bd->inbufBits << 8) | bd->inbuf[bd->inbufPos++]; while ((new_cnt = bd->inbufBitCount - hufGroup->maxLen) < 0) {
bd->inbufBitCount += 8; /* bd->inbufBitCount < hufGroup->maxLen */
}; if (bd->inbufPos == bd->inbufCount) {
bd->inbufBitCount -= hufGroup->maxLen; nextSym = get_bits(bd, hufGroup->maxLen);
j = (bd->inbufBits >> bd->inbufBitCount) & ((1 << hufGroup->maxLen) - 1); goto got_huff_bits;
}
got_huff_bits: bd->inbufBits = (bd->inbufBits << 8) | bd->inbuf[bd->inbufPos++];
bd->inbufBitCount += 8;
/* Figure how how many bits are in next symbol and unget extras */ };
bd->inbufBitCount = new_cnt; /* "bd->inbufBitCount -= hufGroup->maxLen;" */
nextSym = (bd->inbufBits >> new_cnt) & ((1 << hufGroup->maxLen) - 1);
got_huff_bits: ;
} else { /* unoptimized equivalent */
nextSym = get_bits(bd, hufGroup->maxLen);
}
/* Figure how many bits are in next symbol and unget extras */
i = hufGroup->minLen; i = hufGroup->minLen;
while (j > limit[i]) ++i; while (nextSym > limit[i]) ++i;
bd->inbufBitCount += (hufGroup->maxLen - i); j = hufGroup->maxLen - i;
if (j < 0)
return RETVAL_DATA_ERROR;
bd->inbufBitCount += j;
/* Huffman decode value to get nextSym (with bounds checking) */ /* Huffman decode value to get nextSym (with bounds checking) */
if (i > hufGroup->maxLen) nextSym = (nextSym >> j) - base[i];
if ((unsigned)nextSym >= MAX_SYMBOLS)
return RETVAL_DATA_ERROR; return RETVAL_DATA_ERROR;
j = (j >> (hufGroup->maxLen - i)) - base[i]; nextSym = hufGroup->permute[nextSym];
if ((unsigned)j >= MAX_SYMBOLS)
return RETVAL_DATA_ERROR;
nextSym = hufGroup->permute[j];
/* We have now decoded the symbol, which indicates either a new literal /* We have now decoded the symbol, which indicates either a new literal
byte, or a repeated run of the most recent literal byte. First, byte, or a repeated run of the most recent literal byte. First,
@@ -392,7 +416,7 @@ static int get_next_block(bunzip_data *bd)
if ((unsigned)nextSym <= SYMBOL_RUNB) { /* RUNA or RUNB */ if ((unsigned)nextSym <= SYMBOL_RUNB) { /* RUNA or RUNB */
/* If this is the start of a new run, zero out counter */ /* If this is the start of a new run, zero out counter */
if (!runPos) { if (runPos == 0) {
runPos = 1; runPos = 1;
t = 0; t = 0;
} }
@@ -413,13 +437,13 @@ static int get_next_block(bunzip_data *bd)
how many times to repeat the last literal, so append that many how many times to repeat the last literal, so append that many
copies to our buffer of decoded symbols (dbuf) now. (The last copies to our buffer of decoded symbols (dbuf) now. (The last
literal used is the one at the head of the mtfSymbol array.) */ literal used is the one at the head of the mtfSymbol array.) */
if (runPos) { if (runPos != 0) {
runPos = 0; uint8_t tmp_byte;
if (dbufCount + t >= dbufSize) return RETVAL_DATA_ERROR; if (dbufCount + t >= dbufSize) return RETVAL_DATA_ERROR;
tmp_byte = symToByte[mtfSymbol[0]];
uc = symToByte[mtfSymbol[0]]; byteCount[tmp_byte] += t;
byteCount[uc] += t; while (--t >= 0) dbuf[dbufCount++] = tmp_byte;
while (t--) dbuf[dbufCount++] = uc; runPos = 0;
} }
/* Is this the terminating symbol? */ /* Is this the terminating symbol? */
@@ -448,12 +472,12 @@ static int get_next_block(bunzip_data *bd)
/* We have our literal byte. Save it into dbuf. */ /* We have our literal byte. Save it into dbuf. */
byteCount[uc]++; byteCount[uc]++;
dbuf[dbufCount++] = (unsigned)uc; dbuf[dbufCount++] = (uint32_t)uc;
/* Skip group initialization if we're not done with this group. Done /* Skip group initialization if we're not done with this group. Done
* this way to avoid compiler warning. */ * this way to avoid compiler warning. */
end_of_huffman_loop: end_of_huffman_loop:
if (symCount--) goto continue_this_group; if (--symCount >= 0) goto continue_this_group;
} }
/* At this point, we've read all the Huffman-coded symbols (and repeated /* At this point, we've read all the Huffman-coded symbols (and repeated
@@ -466,16 +490,17 @@ static int get_next_block(bunzip_data *bd)
/* Turn byteCount into cumulative occurrence counts of 0 to n-1. */ /* Turn byteCount into cumulative occurrence counts of 0 to n-1. */
j = 0; j = 0;
for (i = 0; i < 256; i++) { for (i = 0; i < 256; i++) {
k = j + byteCount[i]; int tmp_count = j + byteCount[i];
byteCount[i] = j; byteCount[i] = j;
j = k; j = tmp_count;
} }
/* Figure out what order dbuf would be in if we sorted it. */ /* Figure out what order dbuf would be in if we sorted it. */
for (i = 0; i < dbufCount; i++) { for (i = 0; i < dbufCount; i++) {
uc = (uint8_t)dbuf[i]; uint8_t tmp_byte = (uint8_t)dbuf[i];
dbuf[byteCount[uc]] |= (i << 8); int tmp_count = byteCount[tmp_byte];
byteCount[uc]++; dbuf[tmp_count] |= (i << 8);
byteCount[tmp_byte] = tmp_count + 1;
} }
/* Decode first byte by hand to initialize "previous" byte. Note that it /* Decode first byte by hand to initialize "previous" byte. Note that it