diff options
Diffstat (limited to 'archival/libunarchive/decompress_bunzip2.c')
| -rw-r--r-- | archival/libunarchive/decompress_bunzip2.c | 36 |
1 files changed, 18 insertions, 18 deletions
diff --git a/archival/libunarchive/decompress_bunzip2.c b/archival/libunarchive/decompress_bunzip2.c index af16533..4b8ceb8 100644 --- a/archival/libunarchive/decompress_bunzip2.c +++ b/archival/libunarchive/decompress_bunzip2.c @@ -13,7 +13,7 @@ /* Size and speed optimizations by Manuel Novoa III (mjn3@codepoet.org). - More efficient reading of huffman codes, a streamlined read_bunzip() + More efficient reading of Huffman codes, a streamlined read_bunzip() function, and various other tweaks. In (limited) tests, approximately 20% faster than bzcat on x86 and about 10% faster on arm. @@ -49,10 +49,10 @@ #include "libbb.h" -/* Constants for huffman coding */ +/* Constants for Huffman coding */ #define MAX_GROUPS 6 #define GROUP_SIZE 50 /* 64 would have been more efficient */ -#define MAX_HUFCODE_BITS 20 /* Longest huffman code allowed */ +#define MAX_HUFCODE_BITS 20 /* Longest Huffman code allowed */ #define MAX_SYMBOLS 258 /* 256 literals + RUNA + RUNB */ #define SYMBOL_RUNA 0 #define SYMBOL_RUNB 1 @@ -70,7 +70,7 @@ /* Other housekeeping constants */ #define IOBUF_SIZE 4096 -/* This is what we know about each huffman coding group */ +/* This is what we know about each Huffman coding group */ struct group_data { /* We have an extra slot at the end of limit[] for a sentinal value. */ int limit[MAX_HUFCODE_BITS+1],base[MAX_HUFCODE_BITS],permute[MAX_SYMBOLS]; @@ -92,7 +92,7 @@ typedef struct { unsigned int *dbuf, dbufSize; /* These things are a bit too big to go on the stack */ unsigned char selectors[32768]; /* nSelectors=15 bits */ - struct group_data groups[MAX_GROUPS]; /* huffman coding tables */ + struct group_data groups[MAX_GROUPS]; /* Huffman coding tables */ /* For I/O error handling */ jmp_buf jmpbuf; } bunzip_data; @@ -172,10 +172,10 @@ static int get_next_block(bunzip_data *bd) if(k&(1<<(15-j))) symToByte[symTotal++]=(16*i)+j; } } - /* 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); if (groupCount<2 || groupCount>MAX_GROUPS) return RETVAL_DATA_ERROR; - /* nSelectors: Every GROUP_SIZE many symbols we select a new huffman coding + /* nSelectors: Every GROUP_SIZE many symbols we select a new Huffman coding 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 start of the list.) */ @@ -189,13 +189,13 @@ static int get_next_block(bunzip_data *bd) for(;j;j--) mtfSymbol[j] = mtfSymbol[j-1]; mtfSymbol[0]=selectors[i]=uc; } - /* Read the huffman coding tables for each group, which code for symTotal + /* Read the Huffman coding tables for each group, which code for symTotal literal symbols, plus two run symbols (RUNA, RUNB) */ symCount=symTotal+2; for (j=0; j<groupCount; j++) { unsigned char length[MAX_SYMBOLS],temp[MAX_HUFCODE_BITS+1]; int minLen, maxLen, pp; - /* Read huffman code lengths for each symbol. They're stored in + /* Read Huffman code lengths for each symbol. They're stored in a way similar to mtf; record a starting value for the first symbol, and an offset from the previous value for everys symbol after that. (Subtracting 1 before the loop and then adding it back at the end is @@ -228,12 +228,12 @@ static int get_next_block(bunzip_data *bd) } /* Calculate permute[], base[], and limit[] tables from length[]. * - * permute[] is the lookup table for converting huffman coded symbols + * permute[] is the lookup table for converting Huffman coded symbols * into decoded symbols. base[] is the amount to subtract from the - * value of a huffman symbol of a given length when using permute[]. + * value of a Huffman symbol of a given length when using permute[]. * * limit[] indicates the largest numerical value a symbol with a given - * number of bits can have. This is how the huffman codes can vary in + * number of bits can have. This is how the Huffman codes can vary in * length: each code with a value>limit[length] needs another bit. */ hufGroup=bd->groups+j; @@ -275,7 +275,7 @@ static int get_next_block(bunzip_data *bd) base[minLen]=0; } /* We've finished reading and digesting the block header. Now read this - block's huffman coded symbols from the file and undo the huffman coding + block's Huffman coded symbols from the file and undo the Huffman coding and run length encoding, saving the result into dbuf[dbufCount++]=uc */ /* Initialize symbol occurrence counters and symbol Move To Front table */ @@ -286,7 +286,7 @@ static int get_next_block(bunzip_data *bd) /* Loop through compressed symbols. */ runPos=dbufCount=symCount=selector=0; for(;;) { - /* Determine which huffman coding group to use. */ + /* Determine which Huffman coding group to use. */ if(!(symCount--)) { symCount=GROUP_SIZE-1; if(selector>=nSelectors) return RETVAL_DATA_ERROR; @@ -294,7 +294,7 @@ static int get_next_block(bunzip_data *bd) base=hufGroup->base-1; limit=hufGroup->limit-1; } - /* 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 to read minLen bits and then an additional bit at a time, testing as we go. Because there is a trailing last block (with file CRC), @@ -383,7 +383,7 @@ got_huff_bits: byteCount[uc]++; dbuf[dbufCount++] = (unsigned int)uc; } - /* 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 runs) for this block from the input stream, and decoded them into the intermediate buffer. There are dbufCount many decoded bytes in dbuf[]. Now undo the Burrows-Wheeler transform on dbuf. @@ -439,7 +439,7 @@ static int read_bunzip(bunzip_data *bd, char *outbuf, int len) /* We will always have pending decoded data to write into the output buffer unless this is the very first call (in which case we haven't - huffman-decoded a block into the intermediate buffer yet). */ + Huffman-decoded a block into the intermediate buffer yet). */ if (bd->writeCopies) { /* Inside the loop, writeCopies means extra copies (beyond 1) */ @@ -495,7 +495,7 @@ decode_next_byte: } } - /* Refill the intermediate buffer by huffman-decoding next block of input */ + /* Refill the intermediate buffer by Huffman-decoding next block of input */ /* (previous is just a convenient unused temp variable here) */ previous=get_next_block(bd); if(previous) { |