| 1 | // See state defs from inflate.js |
| 2 | var BAD = 30; /* got a data error -- remain here until reset */ |
| 3 | var TYPE = 12; /* i: waiting for type bits, including last-flag bit */ |
| 4 | |
| 5 | /* |
| 6 | Decode literal, length, and distance codes and write out the resulting |
| 7 | literal and match bytes until either not enough input or output is |
| 8 | available, an end-of-block is encountered, or a data error is encountered. |
| 9 | When large enough input and output buffers are supplied to inflate(), for |
| 10 | example, a 16K input buffer and a 64K output buffer, more than 95% of the |
| 11 | inflate execution time is spent in this routine. |
| 12 | |
| 13 | Entry assumptions: |
| 14 | |
| 15 | state.mode === LEN |
| 16 | strm.avail_in >= 6 |
| 17 | strm.avail_out >= 258 |
| 18 | start >= strm.avail_out |
| 19 | state.bits < 8 |
| 20 | |
| 21 | On return, state.mode is one of: |
| 22 | |
| 23 | LEN -- ran out of enough output space or enough available input |
| 24 | TYPE -- reached end of block code, inflate() to interpret next block |
| 25 | BAD -- error in block data |
| 26 | |
| 27 | Notes: |
| 28 | |
| 29 | - The maximum input bits used by a length/distance pair is 15 bits for the |
| 30 | length code, 5 bits for the length extra, 15 bits for the distance code, |
| 31 | and 13 bits for the distance extra. This totals 48 bits, or six bytes. |
| 32 | Therefore if strm.avail_in >= 6, then there is enough input to avoid |
| 33 | checking for available input while decoding. |
| 34 | |
| 35 | - The maximum bytes that a single length/distance pair can output is 258 |
| 36 | bytes, which is the maximum length that can be coded. inflate_fast() |
| 37 | requires strm.avail_out >= 258 for each loop to avoid checking for |
| 38 | output space. |
| 39 | */ |
| 40 | export default function inflate_fast(strm, start) { |
| 41 | var state; |
| 42 | var _in; /* local strm.input */ |
| 43 | var last; /* have enough input while in < last */ |
| 44 | var _out; /* local strm.output */ |
| 45 | var beg; /* inflate()'s initial strm.output */ |
| 46 | var end; /* while out < end, enough space available */ |
| 47 | //#ifdef INFLATE_STRICT |
| 48 | var dmax; /* maximum distance from zlib header */ |
| 49 | //#endif |
| 50 | var wsize; /* window size or zero if not using window */ |
| 51 | var whave; /* valid bytes in the window */ |
| 52 | var wnext; /* window write index */ |
| 53 | // Use `s_window` instead `window`, avoid conflict with instrumentation tools |
| 54 | var s_window; /* allocated sliding window, if wsize != 0 */ |
| 55 | var hold; /* local strm.hold */ |
| 56 | var bits; /* local strm.bits */ |
| 57 | var lcode; /* local strm.lencode */ |
| 58 | var dcode; /* local strm.distcode */ |
| 59 | var lmask; /* mask for first level of length codes */ |
| 60 | var dmask; /* mask for first level of distance codes */ |
| 61 | var here; /* retrieved table entry */ |
| 62 | var op; /* code bits, operation, extra bits, or */ |
| 63 | /* window position, window bytes to copy */ |
| 64 | var len; /* match length, unused bytes */ |
| 65 | var dist; /* match distance */ |
| 66 | var from; /* where to copy match from */ |
| 67 | var from_source; |
| 68 | |
| 69 | |
| 70 | var input, output; // JS specific, because we have no pointers |
| 71 | |
| 72 | /* copy state to local variables */ |
| 73 | state = strm.state; |
| 74 | //here = state.here; |
| 75 | _in = strm.next_in; |
| 76 | input = strm.input; |
| 77 | last = _in + (strm.avail_in - 5); |
| 78 | _out = strm.next_out; |
| 79 | output = strm.output; |
| 80 | beg = _out - (start - strm.avail_out); |
| 81 | end = _out + (strm.avail_out - 257); |
| 82 | //#ifdef INFLATE_STRICT |
| 83 | dmax = state.dmax; |
| 84 | //#endif |
| 85 | wsize = state.wsize; |
| 86 | whave = state.whave; |
| 87 | wnext = state.wnext; |
| 88 | s_window = state.window; |
| 89 | hold = state.hold; |
| 90 | bits = state.bits; |
| 91 | lcode = state.lencode; |
| 92 | dcode = state.distcode; |
| 93 | lmask = (1 << state.lenbits) - 1; |
| 94 | dmask = (1 << state.distbits) - 1; |
| 95 | |
| 96 | |
| 97 | /* decode literals and length/distances until end-of-block or not enough |
| 98 | input data or output space */ |
| 99 | |
| 100 | top: |
| 101 | do { |
| 102 | if (bits < 15) { |
| 103 | hold += input[_in++] << bits; |
| 104 | bits += 8; |
| 105 | hold += input[_in++] << bits; |
| 106 | bits += 8; |
| 107 | } |
| 108 | |
| 109 | here = lcode[hold & lmask]; |
| 110 | |
| 111 | dolen: |
| 112 | for (;;) { // Goto emulation |
| 113 | op = here >>> 24/*here.bits*/; |
| 114 | hold >>>= op; |
| 115 | bits -= op; |
| 116 | op = (here >>> 16) & 0xff/*here.op*/; |
| 117 | if (op === 0) { /* literal */ |
| 118 | //Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ? |
| 119 | // "inflate: literal '%c'\n" : |
| 120 | // "inflate: literal 0x%02x\n", here.val)); |
| 121 | output[_out++] = here & 0xffff/*here.val*/; |
| 122 | } |
| 123 | else if (op & 16) { /* length base */ |
| 124 | len = here & 0xffff/*here.val*/; |
| 125 | op &= 15; /* number of extra bits */ |
| 126 | if (op) { |
| 127 | if (bits < op) { |
| 128 | hold += input[_in++] << bits; |
| 129 | bits += 8; |
| 130 | } |
| 131 | len += hold & ((1 << op) - 1); |
| 132 | hold >>>= op; |
| 133 | bits -= op; |
| 134 | } |
| 135 | //Tracevv((stderr, "inflate: length %u\n", len)); |
| 136 | if (bits < 15) { |
| 137 | hold += input[_in++] << bits; |
| 138 | bits += 8; |
| 139 | hold += input[_in++] << bits; |
| 140 | bits += 8; |
| 141 | } |
| 142 | here = dcode[hold & dmask]; |
| 143 | |
| 144 | dodist: |
| 145 | for (;;) { // goto emulation |
| 146 | op = here >>> 24/*here.bits*/; |
| 147 | hold >>>= op; |
| 148 | bits -= op; |
| 149 | op = (here >>> 16) & 0xff/*here.op*/; |
| 150 | |
| 151 | if (op & 16) { /* distance base */ |
| 152 | dist = here & 0xffff/*here.val*/; |
| 153 | op &= 15; /* number of extra bits */ |
| 154 | if (bits < op) { |
| 155 | hold += input[_in++] << bits; |
| 156 | bits += 8; |
| 157 | if (bits < op) { |
| 158 | hold += input[_in++] << bits; |
| 159 | bits += 8; |
| 160 | } |
| 161 | } |
| 162 | dist += hold & ((1 << op) - 1); |
| 163 | //#ifdef INFLATE_STRICT |
| 164 | if (dist > dmax) { |
| 165 | strm.msg = 'invalid distance too far back'; |
| 166 | state.mode = BAD; |
| 167 | break top; |
| 168 | } |
| 169 | //#endif |
| 170 | hold >>>= op; |
| 171 | bits -= op; |
| 172 | //Tracevv((stderr, "inflate: distance %u\n", dist)); |
| 173 | op = _out - beg; /* max distance in output */ |
| 174 | if (dist > op) { /* see if copy from window */ |
| 175 | op = dist - op; /* distance back in window */ |
| 176 | if (op > whave) { |
| 177 | if (state.sane) { |
| 178 | strm.msg = 'invalid distance too far back'; |
| 179 | state.mode = BAD; |
| 180 | break top; |
| 181 | } |
| 182 | |
| 183 | // (!) This block is disabled in zlib defailts, |
| 184 | // don't enable it for binary compatibility |
| 185 | //#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
| 186 | // if (len <= op - whave) { |
| 187 | // do { |
| 188 | // output[_out++] = 0; |
| 189 | // } while (--len); |
| 190 | // continue top; |
| 191 | // } |
| 192 | // len -= op - whave; |
| 193 | // do { |
| 194 | // output[_out++] = 0; |
| 195 | // } while (--op > whave); |
| 196 | // if (op === 0) { |
| 197 | // from = _out - dist; |
| 198 | // do { |
| 199 | // output[_out++] = output[from++]; |
| 200 | // } while (--len); |
| 201 | // continue top; |
| 202 | // } |
| 203 | //#endif |
| 204 | } |
| 205 | from = 0; // window index |
| 206 | from_source = s_window; |
| 207 | if (wnext === 0) { /* very common case */ |
| 208 | from += wsize - op; |
| 209 | if (op < len) { /* some from window */ |
| 210 | len -= op; |
| 211 | do { |
| 212 | output[_out++] = s_window[from++]; |
| 213 | } while (--op); |
| 214 | from = _out - dist; /* rest from output */ |
| 215 | from_source = output; |
| 216 | } |
| 217 | } |
| 218 | else if (wnext < op) { /* wrap around window */ |
| 219 | from += wsize + wnext - op; |
| 220 | op -= wnext; |
| 221 | if (op < len) { /* some from end of window */ |
| 222 | len -= op; |
| 223 | do { |
| 224 | output[_out++] = s_window[from++]; |
| 225 | } while (--op); |
| 226 | from = 0; |
| 227 | if (wnext < len) { /* some from start of window */ |
| 228 | op = wnext; |
| 229 | len -= op; |
| 230 | do { |
| 231 | output[_out++] = s_window[from++]; |
| 232 | } while (--op); |
| 233 | from = _out - dist; /* rest from output */ |
| 234 | from_source = output; |
| 235 | } |
| 236 | } |
| 237 | } |
| 238 | else { /* contiguous in window */ |
| 239 | from += wnext - op; |
| 240 | if (op < len) { /* some from window */ |
| 241 | len -= op; |
| 242 | do { |
| 243 | output[_out++] = s_window[from++]; |
| 244 | } while (--op); |
| 245 | from = _out - dist; /* rest from output */ |
| 246 | from_source = output; |
| 247 | } |
| 248 | } |
| 249 | while (len > 2) { |
| 250 | output[_out++] = from_source[from++]; |
| 251 | output[_out++] = from_source[from++]; |
| 252 | output[_out++] = from_source[from++]; |
| 253 | len -= 3; |
| 254 | } |
| 255 | if (len) { |
| 256 | output[_out++] = from_source[from++]; |
| 257 | if (len > 1) { |
| 258 | output[_out++] = from_source[from++]; |
| 259 | } |
| 260 | } |
| 261 | } |
| 262 | else { |
| 263 | from = _out - dist; /* copy direct from output */ |
| 264 | do { /* minimum length is three */ |
| 265 | output[_out++] = output[from++]; |
| 266 | output[_out++] = output[from++]; |
| 267 | output[_out++] = output[from++]; |
| 268 | len -= 3; |
| 269 | } while (len > 2); |
| 270 | if (len) { |
| 271 | output[_out++] = output[from++]; |
| 272 | if (len > 1) { |
| 273 | output[_out++] = output[from++]; |
| 274 | } |
| 275 | } |
| 276 | } |
| 277 | } |
| 278 | else if ((op & 64) === 0) { /* 2nd level distance code */ |
| 279 | here = dcode[(here & 0xffff)/*here.val*/ + (hold & ((1 << op) - 1))]; |
| 280 | continue dodist; |
| 281 | } |
| 282 | else { |
| 283 | strm.msg = 'invalid distance code'; |
| 284 | state.mode = BAD; |
| 285 | break top; |
| 286 | } |
| 287 | |
| 288 | break; // need to emulate goto via "continue" |
| 289 | } |
| 290 | } |
| 291 | else if ((op & 64) === 0) { /* 2nd level length code */ |
| 292 | here = lcode[(here & 0xffff)/*here.val*/ + (hold & ((1 << op) - 1))]; |
| 293 | continue dolen; |
| 294 | } |
| 295 | else if (op & 32) { /* end-of-block */ |
| 296 | //Tracevv((stderr, "inflate: end of block\n")); |
| 297 | state.mode = TYPE; |
| 298 | break top; |
| 299 | } |
| 300 | else { |
| 301 | strm.msg = 'invalid literal/length code'; |
| 302 | state.mode = BAD; |
| 303 | break top; |
| 304 | } |
| 305 | |
| 306 | break; // need to emulate goto via "continue" |
| 307 | } |
| 308 | } while (_in < last && _out < end); |
| 309 | |
| 310 | /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ |
| 311 | len = bits >> 3; |
| 312 | _in -= len; |
| 313 | bits -= len << 3; |
| 314 | hold &= (1 << bits) - 1; |
| 315 | |
| 316 | /* update state and return */ |
| 317 | strm.next_in = _in; |
| 318 | strm.next_out = _out; |
| 319 | strm.avail_in = (_in < last ? 5 + (last - _in) : 5 - (_in - last)); |
| 320 | strm.avail_out = (_out < end ? 257 + (end - _out) : 257 - (_out - end)); |
| 321 | state.hold = hold; |
| 322 | state.bits = bits; |
| 323 | return; |
| 324 | }; |