Mercurial > repos > blastem
annotate zlib/inffast.c @ 1790:a29f35c47da4
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author | Michael Pavone <pavone@retrodev.com> |
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date | Wed, 20 Mar 2019 09:35:17 -0700 |
parents | 00d788dac91a |
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1 /* inffast.c -- fast 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 #include "inflate.h" |
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9 #include "inffast.h" |
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10 |
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11 #ifdef ASMINF |
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12 # pragma message("Assembler code may have bugs -- use at your own risk") |
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13 #else |
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14 |
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15 /* |
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16 Decode literal, length, and distance codes and write out the resulting |
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17 literal and match bytes until either not enough input or output is |
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18 available, an end-of-block is encountered, or a data error is encountered. |
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19 When large enough input and output buffers are supplied to inflate(), for |
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20 example, a 16K input buffer and a 64K output buffer, more than 95% of the |
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21 inflate execution time is spent in this routine. |
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22 |
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23 Entry assumptions: |
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24 |
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25 state->mode == LEN |
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26 strm->avail_in >= 6 |
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27 strm->avail_out >= 258 |
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28 start >= strm->avail_out |
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29 state->bits < 8 |
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30 |
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31 On return, state->mode is one of: |
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32 |
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33 LEN -- ran out of enough output space or enough available input |
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34 TYPE -- reached end of block code, inflate() to interpret next block |
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35 BAD -- error in block data |
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36 |
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37 Notes: |
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38 |
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39 - The maximum input bits used by a length/distance pair is 15 bits for the |
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40 length code, 5 bits for the length extra, 15 bits for the distance code, |
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41 and 13 bits for the distance extra. This totals 48 bits, or six bytes. |
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42 Therefore if strm->avail_in >= 6, then there is enough input to avoid |
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43 checking for available input while decoding. |
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44 |
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45 - The maximum bytes that a single length/distance pair can output is 258 |
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46 bytes, which is the maximum length that can be coded. inflate_fast() |
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47 requires strm->avail_out >= 258 for each loop to avoid checking for |
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48 output space. |
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49 */ |
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50 void ZLIB_INTERNAL inflate_fast(strm, start) |
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51 z_streamp strm; |
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52 unsigned start; /* inflate()'s starting value for strm->avail_out */ |
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53 { |
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54 struct inflate_state FAR *state; |
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55 z_const unsigned char FAR *in; /* local strm->next_in */ |
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56 z_const unsigned char FAR *last; /* have enough input while in < last */ |
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57 unsigned char FAR *out; /* local strm->next_out */ |
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58 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */ |
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59 unsigned char FAR *end; /* while out < end, enough space available */ |
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60 #ifdef INFLATE_STRICT |
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61 unsigned dmax; /* maximum distance from zlib header */ |
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62 #endif |
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63 unsigned wsize; /* window size or zero if not using window */ |
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64 unsigned whave; /* valid bytes in the window */ |
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65 unsigned wnext; /* window write index */ |
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66 unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */ |
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67 unsigned long hold; /* local strm->hold */ |
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68 unsigned bits; /* local strm->bits */ |
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69 code const FAR *lcode; /* local strm->lencode */ |
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70 code const FAR *dcode; /* local strm->distcode */ |
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71 unsigned lmask; /* mask for first level of length codes */ |
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72 unsigned dmask; /* mask for first level of distance codes */ |
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73 code here; /* retrieved table entry */ |
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74 unsigned op; /* code bits, operation, extra bits, or */ |
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75 /* window position, window bytes to copy */ |
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76 unsigned len; /* match length, unused bytes */ |
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77 unsigned dist; /* match distance */ |
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78 unsigned char FAR *from; /* where to copy match from */ |
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79 |
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80 /* copy state to local variables */ |
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81 state = (struct inflate_state FAR *)strm->state; |
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82 in = strm->next_in; |
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83 last = in + (strm->avail_in - 5); |
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84 out = strm->next_out; |
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85 beg = out - (start - strm->avail_out); |
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86 end = out + (strm->avail_out - 257); |
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87 #ifdef INFLATE_STRICT |
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88 dmax = state->dmax; |
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89 #endif |
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90 wsize = state->wsize; |
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91 whave = state->whave; |
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92 wnext = state->wnext; |
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93 window = state->window; |
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94 hold = state->hold; |
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95 bits = state->bits; |
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96 lcode = state->lencode; |
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97 dcode = state->distcode; |
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98 lmask = (1U << state->lenbits) - 1; |
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99 dmask = (1U << state->distbits) - 1; |
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100 |
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101 /* decode literals and length/distances until end-of-block or not enough |
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102 input data or output space */ |
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103 do { |
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104 if (bits < 15) { |
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105 hold += (unsigned long)(*in++) << bits; |
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106 bits += 8; |
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107 hold += (unsigned long)(*in++) << bits; |
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108 bits += 8; |
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109 } |
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110 here = lcode[hold & lmask]; |
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111 dolen: |
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112 op = (unsigned)(here.bits); |
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113 hold >>= op; |
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114 bits -= op; |
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115 op = (unsigned)(here.op); |
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116 if (op == 0) { /* literal */ |
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117 Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ? |
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118 "inflate: literal '%c'\n" : |
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119 "inflate: literal 0x%02x\n", here.val)); |
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120 *out++ = (unsigned char)(here.val); |
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121 } |
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122 else if (op & 16) { /* length base */ |
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123 len = (unsigned)(here.val); |
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124 op &= 15; /* number of extra bits */ |
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125 if (op) { |
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parents:
diff
changeset
|
126 if (bits < op) { |
00d788dac91a
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parents:
diff
changeset
|
127 hold += (unsigned long)(*in++) << bits; |
00d788dac91a
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parents:
diff
changeset
|
128 bits += 8; |
00d788dac91a
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parents:
diff
changeset
|
129 } |
00d788dac91a
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parents:
diff
changeset
|
130 len += (unsigned)hold & ((1U << op) - 1); |
00d788dac91a
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parents:
diff
changeset
|
131 hold >>= op; |
00d788dac91a
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parents:
diff
changeset
|
132 bits -= op; |
00d788dac91a
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parents:
diff
changeset
|
133 } |
00d788dac91a
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parents:
diff
changeset
|
134 Tracevv((stderr, "inflate: length %u\n", len)); |
00d788dac91a
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parents:
diff
changeset
|
135 if (bits < 15) { |
00d788dac91a
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parents:
diff
changeset
|
136 hold += (unsigned long)(*in++) << bits; |
00d788dac91a
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parents:
diff
changeset
|
137 bits += 8; |
00d788dac91a
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parents:
diff
changeset
|
138 hold += (unsigned long)(*in++) << bits; |
00d788dac91a
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parents:
diff
changeset
|
139 bits += 8; |
00d788dac91a
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parents:
diff
changeset
|
140 } |
00d788dac91a
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parents:
diff
changeset
|
141 here = dcode[hold & dmask]; |
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parents:
diff
changeset
|
142 dodist: |
00d788dac91a
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parents:
diff
changeset
|
143 op = (unsigned)(here.bits); |
00d788dac91a
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parents:
diff
changeset
|
144 hold >>= op; |
00d788dac91a
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parents:
diff
changeset
|
145 bits -= op; |
00d788dac91a
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parents:
diff
changeset
|
146 op = (unsigned)(here.op); |
00d788dac91a
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parents:
diff
changeset
|
147 if (op & 16) { /* distance base */ |
00d788dac91a
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parents:
diff
changeset
|
148 dist = (unsigned)(here.val); |
00d788dac91a
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parents:
diff
changeset
|
149 op &= 15; /* number of extra bits */ |
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parents:
diff
changeset
|
150 if (bits < op) { |
00d788dac91a
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parents:
diff
changeset
|
151 hold += (unsigned long)(*in++) << bits; |
00d788dac91a
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parents:
diff
changeset
|
152 bits += 8; |
00d788dac91a
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parents:
diff
changeset
|
153 if (bits < op) { |
00d788dac91a
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parents:
diff
changeset
|
154 hold += (unsigned long)(*in++) << bits; |
00d788dac91a
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parents:
diff
changeset
|
155 bits += 8; |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
156 } |
00d788dac91a
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parents:
diff
changeset
|
157 } |
00d788dac91a
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parents:
diff
changeset
|
158 dist += (unsigned)hold & ((1U << op) - 1); |
00d788dac91a
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parents:
diff
changeset
|
159 #ifdef INFLATE_STRICT |
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parents:
diff
changeset
|
160 if (dist > dmax) { |
00d788dac91a
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parents:
diff
changeset
|
161 strm->msg = (char *)"invalid distance too far back"; |
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parents:
diff
changeset
|
162 state->mode = BAD; |
00d788dac91a
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parents:
diff
changeset
|
163 break; |
00d788dac91a
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parents:
diff
changeset
|
164 } |
00d788dac91a
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parents:
diff
changeset
|
165 #endif |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
166 hold >>= op; |
00d788dac91a
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parents:
diff
changeset
|
167 bits -= op; |
00d788dac91a
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parents:
diff
changeset
|
168 Tracevv((stderr, "inflate: distance %u\n", dist)); |
00d788dac91a
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parents:
diff
changeset
|
169 op = (unsigned)(out - beg); /* max distance in output */ |
00d788dac91a
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parents:
diff
changeset
|
170 if (dist > op) { /* see if copy from window */ |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
171 op = dist - op; /* distance back in window */ |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
172 if (op > whave) { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
173 if (state->sane) { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
174 strm->msg = |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
175 (char *)"invalid distance too far back"; |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
176 state->mode = BAD; |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
177 break; |
00d788dac91a
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parents:
diff
changeset
|
178 } |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
179 #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
00d788dac91a
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parents:
diff
changeset
|
180 if (len <= op - whave) { |
00d788dac91a
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parents:
diff
changeset
|
181 do { |
00d788dac91a
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parents:
diff
changeset
|
182 *out++ = 0; |
00d788dac91a
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parents:
diff
changeset
|
183 } while (--len); |
00d788dac91a
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parents:
diff
changeset
|
184 continue; |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
185 } |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
186 len -= op - whave; |
00d788dac91a
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parents:
diff
changeset
|
187 do { |
00d788dac91a
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parents:
diff
changeset
|
188 *out++ = 0; |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
189 } while (--op > whave); |
00d788dac91a
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parents:
diff
changeset
|
190 if (op == 0) { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
191 from = out - dist; |
00d788dac91a
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parents:
diff
changeset
|
192 do { |
00d788dac91a
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parents:
diff
changeset
|
193 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
194 } while (--len); |
00d788dac91a
Added support for reading gzipped ROMs
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parents:
diff
changeset
|
195 continue; |
00d788dac91a
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parents:
diff
changeset
|
196 } |
00d788dac91a
Added support for reading gzipped ROMs
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parents:
diff
changeset
|
197 #endif |
00d788dac91a
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parents:
diff
changeset
|
198 } |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
199 from = window; |
00d788dac91a
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Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
200 if (wnext == 0) { /* very common case */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
201 from += wsize - op; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
202 if (op < len) { /* some from window */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
203 len -= op; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
204 do { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
205 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
206 } while (--op); |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
207 from = out - dist; /* rest from output */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
208 } |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
209 } |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
210 else if (wnext < op) { /* wrap around window */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
211 from += wsize + wnext - op; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
212 op -= wnext; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
213 if (op < len) { /* some from end of window */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
214 len -= op; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
215 do { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
216 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
217 } while (--op); |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
218 from = window; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
219 if (wnext < len) { /* some from start of window */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
220 op = wnext; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
221 len -= op; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
222 do { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
223 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
224 } while (--op); |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
225 from = out - dist; /* rest from output */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
226 } |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
227 } |
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 else { /* contiguous in window */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
230 from += wnext - op; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
231 if (op < len) { /* some from window */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
232 len -= op; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
233 do { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
234 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
235 } while (--op); |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
236 from = out - dist; /* rest from output */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
237 } |
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 while (len > 2) { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
240 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
241 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
242 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
243 len -= 3; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
244 } |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
245 if (len) { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
246 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
247 if (len > 1) |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
248 *out++ = *from++; |
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 } |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
251 else { |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
252 from = out - dist; /* copy direct from output */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
253 do { /* minimum length is three */ |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
254 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
255 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
256 *out++ = *from++; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
257 len -= 3; |
00d788dac91a
Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
|
258 } while (len > 2); |
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259 if (len) { |
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260 *out++ = *from++; |
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261 if (len > 1) |
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262 *out++ = *from++; |
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263 } |
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264 } |
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265 } |
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266 else if ((op & 64) == 0) { /* 2nd level distance code */ |
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267 here = dcode[here.val + (hold & ((1U << op) - 1))]; |
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268 goto dodist; |
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269 } |
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270 else { |
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271 strm->msg = (char *)"invalid distance code"; |
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272 state->mode = BAD; |
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273 break; |
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274 } |
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275 } |
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276 else if ((op & 64) == 0) { /* 2nd level length code */ |
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277 here = lcode[here.val + (hold & ((1U << op) - 1))]; |
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278 goto dolen; |
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279 } |
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280 else if (op & 32) { /* end-of-block */ |
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281 Tracevv((stderr, "inflate: end of block\n")); |
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282 state->mode = TYPE; |
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283 break; |
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284 } |
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285 else { |
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286 strm->msg = (char *)"invalid literal/length code"; |
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287 state->mode = BAD; |
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288 break; |
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289 } |
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290 } while (in < last && out < end); |
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291 |
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292 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ |
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293 len = bits >> 3; |
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294 in -= len; |
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295 bits -= len << 3; |
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296 hold &= (1U << bits) - 1; |
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297 |
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298 /* update state and return */ |
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299 strm->next_in = in; |
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300 strm->next_out = out; |
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301 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); |
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302 strm->avail_out = (unsigned)(out < end ? |
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303 257 + (end - out) : 257 - (out - end)); |
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304 state->hold = hold; |
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305 state->bits = bits; |
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306 return; |
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307 } |
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308 |
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309 /* |
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310 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): |
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311 - Using bit fields for code structure |
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312 - Different op definition to avoid & for extra bits (do & for table bits) |
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313 - Three separate decoding do-loops for direct, window, and wnext == 0 |
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314 - Special case for distance > 1 copies to do overlapped load and store copy |
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315 - Explicit branch predictions (based on measured branch probabilities) |
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316 - Deferring match copy and interspersed it with decoding subsequent codes |
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317 - Swapping literal/length else |
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318 - Swapping window/direct else |
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319 - Larger unrolled copy loops (three is about right) |
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320 - Moving len -= 3 statement into middle of loop |
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321 */ |
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322 |
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323 #endif /* !ASMINF */ |