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annotate zlib/inftrees.c @ 1692:5dacaef602a7 segacd

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Merge from default
author Michael Pavone <pavone@retrodev.com>
date Sat, 05 Jan 2019 00:58:08 -0800
parents 00d788dac91a
children
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1 /* inftrees.c -- generate Huffman trees for efficient decoding
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2 * Copyright (C) 1995-2017 Mark Adler
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3 * For conditions of distribution and use, see copyright notice in zlib.h
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4 */
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5
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6 #include "zutil.h"
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7 #include "inftrees.h"
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8
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9 #define MAXBITS 15
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10
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11 const char inflate_copyright[] =
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12 " inflate 1.2.11 Copyright 1995-2017 Mark Adler ";
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13 /*
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14 If you use the zlib library in a product, an acknowledgment is welcome
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15 in the documentation of your product. If for some reason you cannot
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16 include such an acknowledgment, I would appreciate that you keep this
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17 copyright string in the executable of your product.
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18 */
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19
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20 /*
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21 Build a set of tables to decode the provided canonical Huffman code.
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22 The code lengths are lens[0..codes-1]. The result starts at *table,
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23 whose indices are 0..2^bits-1. work is a writable array of at least
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24 lens shorts, which is used as a work area. type is the type of code
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25 to be generated, CODES, LENS, or DISTS. On return, zero is success,
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26 -1 is an invalid code, and +1 means that ENOUGH isn't enough. table
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27 on return points to the next available entry's address. bits is the
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28 requested root table index bits, and on return it is the actual root
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29 table index bits. It will differ if the request is greater than the
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30 longest code or if it is less than the shortest code.
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31 */
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32 int ZLIB_INTERNAL inflate_table(type, lens, codes, table, bits, work)
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33 codetype type;
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34 unsigned short FAR *lens;
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35 unsigned codes;
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36 code FAR * FAR *table;
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37 unsigned FAR *bits;
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38 unsigned short FAR *work;
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39 {
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40 unsigned len; /* a code's length in bits */
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41 unsigned sym; /* index of code symbols */
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42 unsigned min, max; /* minimum and maximum code lengths */
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43 unsigned root; /* number of index bits for root table */
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44 unsigned curr; /* number of index bits for current table */
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45 unsigned drop; /* code bits to drop for sub-table */
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46 int left; /* number of prefix codes available */
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47 unsigned used; /* code entries in table used */
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48 unsigned huff; /* Huffman code */
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49 unsigned incr; /* for incrementing code, index */
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50 unsigned fill; /* index for replicating entries */
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51 unsigned low; /* low bits for current root entry */
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52 unsigned mask; /* mask for low root bits */
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53 code here; /* table entry for duplication */
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54 code FAR *next; /* next available space in table */
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55 const unsigned short FAR *base; /* base value table to use */
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56 const unsigned short FAR *extra; /* extra bits table to use */
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57 unsigned match; /* use base and extra for symbol >= match */
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58 unsigned short count[MAXBITS+1]; /* number of codes of each length */
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59 unsigned short offs[MAXBITS+1]; /* offsets in table for each length */
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60 static const unsigned short lbase[31] = { /* Length codes 257..285 base */
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61 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
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62 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
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63 static const unsigned short lext[31] = { /* Length codes 257..285 extra */
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64 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
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65 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 77, 202};
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66 static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
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67 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
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68 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
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69 8193, 12289, 16385, 24577, 0, 0};
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70 static const unsigned short dext[32] = { /* Distance codes 0..29 extra */
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71 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
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72 23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
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73 28, 28, 29, 29, 64, 64};
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74
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75 /*
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76 Process a set of code lengths to create a canonical Huffman code. The
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77 code lengths are lens[0..codes-1]. Each length corresponds to the
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78 symbols 0..codes-1. The Huffman code is generated by first sorting the
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79 symbols by length from short to long, and retaining the symbol order
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80 for codes with equal lengths. Then the code starts with all zero bits
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81 for the first code of the shortest length, and the codes are integer
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82 increments for the same length, and zeros are appended as the length
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83 increases. For the deflate format, these bits are stored backwards
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84 from their more natural integer increment ordering, and so when the
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85 decoding tables are built in the large loop below, the integer codes
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86 are incremented backwards.
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87
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88 This routine assumes, but does not check, that all of the entries in
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89 lens[] are in the range 0..MAXBITS. The caller must assure this.
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90 1..MAXBITS is interpreted as that code length. zero means that that
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91 symbol does not occur in this code.
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92
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93 The codes are sorted by computing a count of codes for each length,
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94 creating from that a table of starting indices for each length in the
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95 sorted table, and then entering the symbols in order in the sorted
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96 table. The sorted table is work[], with that space being provided by
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97 the caller.
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98
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99 The length counts are used for other purposes as well, i.e. finding
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100 the minimum and maximum length codes, determining if there are any
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101 codes at all, checking for a valid set of lengths, and looking ahead
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102 at length counts to determine sub-table sizes when building the
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103 decoding tables.
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104 */
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105
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106 /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
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107 for (len = 0; len <= MAXBITS; len++)
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108 count[len] = 0;
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109 for (sym = 0; sym < codes; sym++)
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110 count[lens[sym]]++;
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111
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112 /* bound code lengths, force root to be within code lengths */
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113 root = *bits;
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114 for (max = MAXBITS; max >= 1; max--)
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115 if (count[max] != 0) break;
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116 if (root > max) root = max;
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117 if (max == 0) { /* no symbols to code at all */
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118 here.op = (unsigned char)64; /* invalid code marker */
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119 here.bits = (unsigned char)1;
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120 here.val = (unsigned short)0;
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121 *(*table)++ = here; /* make a table to force an error */
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122 *(*table)++ = here;
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123 *bits = 1;
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124 return 0; /* no symbols, but wait for decoding to report error */
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125 }
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126 for (min = 1; min < max; min++)
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127 if (count[min] != 0) break;
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128 if (root < min) root = min;
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129
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130 /* check for an over-subscribed or incomplete set of lengths */
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131 left = 1;
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132 for (len = 1; len <= MAXBITS; len++) {
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133 left <<= 1;
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134 left -= count[len];
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135 if (left < 0) return -1; /* over-subscribed */
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136 }
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137 if (left > 0 && (type == CODES || max != 1))
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Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
138 return -1; /* incomplete set */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
139
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
140 /* generate offsets into symbol table for each length for sorting */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
141 offs[1] = 0;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
142 for (len = 1; len < MAXBITS; len++)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
143 offs[len + 1] = offs[len] + count[len];
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
144
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
145 /* sort symbols by length, by symbol order within each length */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
146 for (sym = 0; sym < codes; sym++)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
147 if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
148
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
149 /*
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
150 Create and fill in decoding tables. In this loop, the table being
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
151 filled is at next and has curr index bits. The code being used is huff
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
152 with length len. That code is converted to an index by dropping drop
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
153 bits off of the bottom. For codes where len is less than drop + curr,
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
154 those top drop + curr - len bits are incremented through all values to
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
155 fill the table with replicated entries.
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
156
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
157 root is the number of index bits for the root table. When len exceeds
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
158 root, sub-tables are created pointed to by the root entry with an index
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
159 of the low root bits of huff. This is saved in low to check for when a
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
160 new sub-table should be started. drop is zero when the root table is
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
161 being filled, and drop is root when sub-tables are being filled.
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
162
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
163 When a new sub-table is needed, it is necessary to look ahead in the
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
164 code lengths to determine what size sub-table is needed. The length
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
165 counts are used for this, and so count[] is decremented as codes are
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
166 entered in the tables.
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
167
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
168 used keeps track of how many table entries have been allocated from the
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
169 provided *table space. It is checked for LENS and DIST tables against
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
170 the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
171 the initial root table size constants. See the comments in inftrees.h
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
172 for more information.
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
173
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
174 sym increments through all symbols, and the loop terminates when
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
175 all codes of length max, i.e. all codes, have been processed. This
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
176 routine permits incomplete codes, so another loop after this one fills
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
177 in the rest of the decoding tables with invalid code markers.
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
178 */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
179
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
180 /* set up for code type */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
181 switch (type) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
182 case CODES:
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
183 base = extra = work; /* dummy value--not used */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
184 match = 20;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
185 break;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
186 case LENS:
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
187 base = lbase;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
188 extra = lext;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
189 match = 257;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
190 break;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
191 default: /* DISTS */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
192 base = dbase;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
193 extra = dext;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
194 match = 0;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
195 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
196
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
197 /* initialize state for loop */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
198 huff = 0; /* starting code */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
199 sym = 0; /* starting code symbol */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
200 len = min; /* starting code length */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
201 next = *table; /* current table to fill in */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
202 curr = root; /* current table index bits */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
203 drop = 0; /* current bits to drop from code for index */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
204 low = (unsigned)(-1); /* trigger new sub-table when len > root */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
205 used = 1U << root; /* use root table entries */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
206 mask = used - 1; /* mask for comparing low */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
207
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
208 /* check available table space */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
209 if ((type == LENS && used > ENOUGH_LENS) ||
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
210 (type == DISTS && used > ENOUGH_DISTS))
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
211 return 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
212
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
213 /* process all codes and make table entries */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
214 for (;;) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
215 /* create table entry */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
216 here.bits = (unsigned char)(len - drop);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
217 if (work[sym] + 1U < match) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
218 here.op = (unsigned char)0;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
219 here.val = work[sym];
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
220 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
221 else if (work[sym] >= match) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
222 here.op = (unsigned char)(extra[work[sym] - match]);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
223 here.val = base[work[sym] - match];
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
224 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
225 else {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
226 here.op = (unsigned char)(32 + 64); /* end of block */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
227 here.val = 0;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
228 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
229
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
230 /* replicate for those indices with low len bits equal to huff */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
231 incr = 1U << (len - drop);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
232 fill = 1U << curr;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
233 min = fill; /* save offset to next table */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
234 do {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
235 fill -= incr;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
236 next[(huff >> drop) + fill] = here;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
237 } while (fill != 0);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
238
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
239 /* backwards increment the len-bit code huff */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
240 incr = 1U << (len - 1);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
241 while (huff & incr)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
242 incr >>= 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
243 if (incr != 0) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
244 huff &= incr - 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
245 huff += incr;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
246 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
247 else
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
248 huff = 0;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
249
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
250 /* go to next symbol, update count, len */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
251 sym++;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
252 if (--(count[len]) == 0) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
253 if (len == max) break;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
254 len = lens[work[sym]];
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
255 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
256
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
257 /* create new sub-table if needed */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
258 if (len > root && (huff & mask) != low) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
259 /* if first time, transition to sub-tables */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
260 if (drop == 0)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
261 drop = root;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
262
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
263 /* increment past last table */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
264 next += min; /* here min is 1 << curr */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
265
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
266 /* determine length of next table */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
267 curr = len - drop;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
268 left = (int)(1 << curr);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
269 while (curr + drop < max) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
270 left -= count[curr + drop];
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
271 if (left <= 0) break;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
272 curr++;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
273 left <<= 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
274 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
275
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
276 /* check for enough space */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
277 used += 1U << curr;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
278 if ((type == LENS && used > ENOUGH_LENS) ||
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
279 (type == DISTS && used > ENOUGH_DISTS))
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
280 return 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
281
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
282 /* point entry in root table to sub-table */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
283 low = huff & mask;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
284 (*table)[low].op = (unsigned char)curr;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
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285 (*table)[low].bits = (unsigned char)root;
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286 (*table)[low].val = (unsigned short)(next - *table);
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287 }
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288 }
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289
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290 /* fill in remaining table entry if code is incomplete (guaranteed to have
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291 at most one remaining entry, since if the code is incomplete, the
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292 maximum code length that was allowed to get this far is one bit) */
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293 if (huff != 0) {
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294 here.op = (unsigned char)64; /* invalid code marker */
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295 here.bits = (unsigned char)(len - drop);
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296 here.val = (unsigned short)0;
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297 next[huff] = here;
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298 }
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299
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300 /* set return parameters */
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301 *table += used;
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302 *bits = root;
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303 return 0;
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304 }