rfc1952.txt revision 1.1.1.1.4.2
1 1.1.1.1.4.2 pgoyette 2 1.1.1.1.4.2 pgoyette 3 1.1.1.1.4.2 pgoyette 4 1.1.1.1.4.2 pgoyette 5 1.1.1.1.4.2 pgoyette 6 1.1.1.1.4.2 pgoyette 7 1.1.1.1.4.2 pgoyette Network Working Group P. Deutsch 8 1.1.1.1.4.2 pgoyette Request for Comments: 1952 Aladdin Enterprises 9 1.1.1.1.4.2 pgoyette Category: Informational May 1996 10 1.1.1.1.4.2 pgoyette 11 1.1.1.1.4.2 pgoyette 12 1.1.1.1.4.2 pgoyette GZIP file format specification version 4.3 13 1.1.1.1.4.2 pgoyette 14 1.1.1.1.4.2 pgoyette Status of This Memo 15 1.1.1.1.4.2 pgoyette 16 1.1.1.1.4.2 pgoyette This memo provides information for the Internet community. This memo 17 1.1.1.1.4.2 pgoyette does not specify an Internet standard of any kind. Distribution of 18 1.1.1.1.4.2 pgoyette this memo is unlimited. 19 1.1.1.1.4.2 pgoyette 20 1.1.1.1.4.2 pgoyette IESG Note: 21 1.1.1.1.4.2 pgoyette 22 1.1.1.1.4.2 pgoyette The IESG takes no position on the validity of any Intellectual 23 1.1.1.1.4.2 pgoyette Property Rights statements contained in this document. 24 1.1.1.1.4.2 pgoyette 25 1.1.1.1.4.2 pgoyette Notices 26 1.1.1.1.4.2 pgoyette 27 1.1.1.1.4.2 pgoyette Copyright (c) 1996 L. Peter Deutsch 28 1.1.1.1.4.2 pgoyette 29 1.1.1.1.4.2 pgoyette Permission is granted to copy and distribute this document for any 30 1.1.1.1.4.2 pgoyette purpose and without charge, including translations into other 31 1.1.1.1.4.2 pgoyette languages and incorporation into compilations, provided that the 32 1.1.1.1.4.2 pgoyette copyright notice and this notice are preserved, and that any 33 1.1.1.1.4.2 pgoyette substantive changes or deletions from the original are clearly 34 1.1.1.1.4.2 pgoyette marked. 35 1.1.1.1.4.2 pgoyette 36 1.1.1.1.4.2 pgoyette A pointer to the latest version of this and related documentation in 37 1.1.1.1.4.2 pgoyette HTML format can be found at the URL 38 1.1.1.1.4.2 pgoyette <ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html>. 39 1.1.1.1.4.2 pgoyette 40 1.1.1.1.4.2 pgoyette Abstract 41 1.1.1.1.4.2 pgoyette 42 1.1.1.1.4.2 pgoyette This specification defines a lossless compressed data format that is 43 1.1.1.1.4.2 pgoyette compatible with the widely used GZIP utility. The format includes a 44 1.1.1.1.4.2 pgoyette cyclic redundancy check value for detecting data corruption. The 45 1.1.1.1.4.2 pgoyette format presently uses the DEFLATE method of compression but can be 46 1.1.1.1.4.2 pgoyette easily extended to use other compression methods. The format can be 47 1.1.1.1.4.2 pgoyette implemented readily in a manner not covered by patents. 48 1.1.1.1.4.2 pgoyette 49 1.1.1.1.4.2 pgoyette 50 1.1.1.1.4.2 pgoyette 51 1.1.1.1.4.2 pgoyette 52 1.1.1.1.4.2 pgoyette 53 1.1.1.1.4.2 pgoyette 54 1.1.1.1.4.2 pgoyette 55 1.1.1.1.4.2 pgoyette 56 1.1.1.1.4.2 pgoyette 57 1.1.1.1.4.2 pgoyette 58 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 1] 59 1.1.1.1.4.2 pgoyette 61 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 62 1.1.1.1.4.2 pgoyette 63 1.1.1.1.4.2 pgoyette 64 1.1.1.1.4.2 pgoyette Table of Contents 65 1.1.1.1.4.2 pgoyette 66 1.1.1.1.4.2 pgoyette 1. Introduction ................................................... 2 67 1.1.1.1.4.2 pgoyette 1.1. Purpose ................................................... 2 68 1.1.1.1.4.2 pgoyette 1.2. Intended audience ......................................... 3 69 1.1.1.1.4.2 pgoyette 1.3. Scope ..................................................... 3 70 1.1.1.1.4.2 pgoyette 1.4. Compliance ................................................ 3 71 1.1.1.1.4.2 pgoyette 1.5. Definitions of terms and conventions used ................. 3 72 1.1.1.1.4.2 pgoyette 1.6. Changes from previous versions ............................ 3 73 1.1.1.1.4.2 pgoyette 2. Detailed specification ......................................... 4 74 1.1.1.1.4.2 pgoyette 2.1. Overall conventions ....................................... 4 75 1.1.1.1.4.2 pgoyette 2.2. File format ............................................... 5 76 1.1.1.1.4.2 pgoyette 2.3. Member format ............................................. 5 77 1.1.1.1.4.2 pgoyette 2.3.1. Member header and trailer ........................... 6 78 1.1.1.1.4.2 pgoyette 2.3.1.1. Extra field ................................... 8 79 1.1.1.1.4.2 pgoyette 2.3.1.2. Compliance .................................... 9 80 1.1.1.1.4.2 pgoyette 3. References .................................................. 9 81 1.1.1.1.4.2 pgoyette 4. Security Considerations .................................... 10 82 1.1.1.1.4.2 pgoyette 5. Acknowledgements ........................................... 10 83 1.1.1.1.4.2 pgoyette 6. Author's Address ........................................... 10 84 1.1.1.1.4.2 pgoyette 7. Appendix: Jean-Loup Gailly's gzip utility .................. 11 85 1.1.1.1.4.2 pgoyette 8. Appendix: Sample CRC Code .................................. 11 86 1.1.1.1.4.2 pgoyette 87 1.1.1.1.4.2 pgoyette 1. Introduction 88 1.1.1.1.4.2 pgoyette 89 1.1.1.1.4.2 pgoyette 1.1. Purpose 90 1.1.1.1.4.2 pgoyette 91 1.1.1.1.4.2 pgoyette The purpose of this specification is to define a lossless 92 1.1.1.1.4.2 pgoyette compressed data format that: 93 1.1.1.1.4.2 pgoyette 94 1.1.1.1.4.2 pgoyette * Is independent of CPU type, operating system, file system, 95 1.1.1.1.4.2 pgoyette and character set, and hence can be used for interchange; 96 1.1.1.1.4.2 pgoyette * Can compress or decompress a data stream (as opposed to a 97 1.1.1.1.4.2 pgoyette randomly accessible file) to produce another data stream, 98 1.1.1.1.4.2 pgoyette using only an a priori bounded amount of intermediate 99 1.1.1.1.4.2 pgoyette storage, and hence can be used in data communications or 100 1.1.1.1.4.2 pgoyette similar structures such as Unix filters; 101 1.1.1.1.4.2 pgoyette * Compresses data with efficiency comparable to the best 102 1.1.1.1.4.2 pgoyette currently available general-purpose compression methods, 103 1.1.1.1.4.2 pgoyette and in particular considerably better than the "compress" 104 1.1.1.1.4.2 pgoyette program; 105 1.1.1.1.4.2 pgoyette * Can be implemented readily in a manner not covered by 106 1.1.1.1.4.2 pgoyette patents, and hence can be practiced freely; 107 1.1.1.1.4.2 pgoyette * Is compatible with the file format produced by the current 108 1.1.1.1.4.2 pgoyette widely used gzip utility, in that conforming decompressors 109 1.1.1.1.4.2 pgoyette will be able to read data produced by the existing gzip 110 1.1.1.1.4.2 pgoyette compressor. 111 1.1.1.1.4.2 pgoyette 112 1.1.1.1.4.2 pgoyette 113 1.1.1.1.4.2 pgoyette 114 1.1.1.1.4.2 pgoyette 115 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 2] 116 1.1.1.1.4.2 pgoyette 118 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 119 1.1.1.1.4.2 pgoyette 120 1.1.1.1.4.2 pgoyette 121 1.1.1.1.4.2 pgoyette The data format defined by this specification does not attempt to: 122 1.1.1.1.4.2 pgoyette 123 1.1.1.1.4.2 pgoyette * Provide random access to compressed data; 124 1.1.1.1.4.2 pgoyette * Compress specialized data (e.g., raster graphics) as well as 125 1.1.1.1.4.2 pgoyette the best currently available specialized algorithms. 126 1.1.1.1.4.2 pgoyette 127 1.1.1.1.4.2 pgoyette 1.2. Intended audience 128 1.1.1.1.4.2 pgoyette 129 1.1.1.1.4.2 pgoyette This specification is intended for use by implementors of software 130 1.1.1.1.4.2 pgoyette to compress data into gzip format and/or decompress data from gzip 131 1.1.1.1.4.2 pgoyette format. 132 1.1.1.1.4.2 pgoyette 133 1.1.1.1.4.2 pgoyette The text of the specification assumes a basic background in 134 1.1.1.1.4.2 pgoyette programming at the level of bits and other primitive data 135 1.1.1.1.4.2 pgoyette representations. 136 1.1.1.1.4.2 pgoyette 137 1.1.1.1.4.2 pgoyette 1.3. Scope 138 1.1.1.1.4.2 pgoyette 139 1.1.1.1.4.2 pgoyette The specification specifies a compression method and a file format 140 1.1.1.1.4.2 pgoyette (the latter assuming only that a file can store a sequence of 141 1.1.1.1.4.2 pgoyette arbitrary bytes). It does not specify any particular interface to 142 1.1.1.1.4.2 pgoyette a file system or anything about character sets or encodings 143 1.1.1.1.4.2 pgoyette (except for file names and comments, which are optional). 144 1.1.1.1.4.2 pgoyette 145 1.1.1.1.4.2 pgoyette 1.4. Compliance 146 1.1.1.1.4.2 pgoyette 147 1.1.1.1.4.2 pgoyette Unless otherwise indicated below, a compliant decompressor must be 148 1.1.1.1.4.2 pgoyette able to accept and decompress any file that conforms to all the 149 1.1.1.1.4.2 pgoyette specifications presented here; a compliant compressor must produce 150 1.1.1.1.4.2 pgoyette files that conform to all the specifications presented here. The 151 1.1.1.1.4.2 pgoyette material in the appendices is not part of the specification per se 152 1.1.1.1.4.2 pgoyette and is not relevant to compliance. 153 1.1.1.1.4.2 pgoyette 154 1.1.1.1.4.2 pgoyette 1.5. Definitions of terms and conventions used 155 1.1.1.1.4.2 pgoyette 156 1.1.1.1.4.2 pgoyette byte: 8 bits stored or transmitted as a unit (same as an octet). 157 1.1.1.1.4.2 pgoyette (For this specification, a byte is exactly 8 bits, even on 158 1.1.1.1.4.2 pgoyette machines which store a character on a number of bits different 159 1.1.1.1.4.2 pgoyette from 8.) See below for the numbering of bits within a byte. 160 1.1.1.1.4.2 pgoyette 161 1.1.1.1.4.2 pgoyette 1.6. Changes from previous versions 162 1.1.1.1.4.2 pgoyette 163 1.1.1.1.4.2 pgoyette There have been no technical changes to the gzip format since 164 1.1.1.1.4.2 pgoyette version 4.1 of this specification. In version 4.2, some 165 1.1.1.1.4.2 pgoyette terminology was changed, and the sample CRC code was rewritten for 166 1.1.1.1.4.2 pgoyette clarity and to eliminate the requirement for the caller to do pre- 167 1.1.1.1.4.2 pgoyette and post-conditioning. Version 4.3 is a conversion of the 168 1.1.1.1.4.2 pgoyette specification to RFC style. 169 1.1.1.1.4.2 pgoyette 170 1.1.1.1.4.2 pgoyette 171 1.1.1.1.4.2 pgoyette 172 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 3] 173 1.1.1.1.4.2 pgoyette 175 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 176 1.1.1.1.4.2 pgoyette 177 1.1.1.1.4.2 pgoyette 178 1.1.1.1.4.2 pgoyette 2. Detailed specification 179 1.1.1.1.4.2 pgoyette 180 1.1.1.1.4.2 pgoyette 2.1. Overall conventions 181 1.1.1.1.4.2 pgoyette 182 1.1.1.1.4.2 pgoyette In the diagrams below, a box like this: 183 1.1.1.1.4.2 pgoyette 184 1.1.1.1.4.2 pgoyette +---+ 185 1.1.1.1.4.2 pgoyette | | <-- the vertical bars might be missing 186 1.1.1.1.4.2 pgoyette +---+ 187 1.1.1.1.4.2 pgoyette 188 1.1.1.1.4.2 pgoyette represents one byte; a box like this: 189 1.1.1.1.4.2 pgoyette 190 1.1.1.1.4.2 pgoyette +==============+ 191 1.1.1.1.4.2 pgoyette | | 192 1.1.1.1.4.2 pgoyette +==============+ 193 1.1.1.1.4.2 pgoyette 194 1.1.1.1.4.2 pgoyette represents a variable number of bytes. 195 1.1.1.1.4.2 pgoyette 196 1.1.1.1.4.2 pgoyette Bytes stored within a computer do not have a "bit order", since 197 1.1.1.1.4.2 pgoyette they are always treated as a unit. However, a byte considered as 198 1.1.1.1.4.2 pgoyette an integer between 0 and 255 does have a most- and least- 199 1.1.1.1.4.2 pgoyette significant bit, and since we write numbers with the most- 200 1.1.1.1.4.2 pgoyette significant digit on the left, we also write bytes with the most- 201 1.1.1.1.4.2 pgoyette significant bit on the left. In the diagrams below, we number the 202 1.1.1.1.4.2 pgoyette bits of a byte so that bit 0 is the least-significant bit, i.e., 203 1.1.1.1.4.2 pgoyette the bits are numbered: 204 1.1.1.1.4.2 pgoyette 205 1.1.1.1.4.2 pgoyette +--------+ 206 1.1.1.1.4.2 pgoyette |76543210| 207 1.1.1.1.4.2 pgoyette +--------+ 208 1.1.1.1.4.2 pgoyette 209 1.1.1.1.4.2 pgoyette This document does not address the issue of the order in which 210 1.1.1.1.4.2 pgoyette bits of a byte are transmitted on a bit-sequential medium, since 211 1.1.1.1.4.2 pgoyette the data format described here is byte- rather than bit-oriented. 212 1.1.1.1.4.2 pgoyette 213 1.1.1.1.4.2 pgoyette Within a computer, a number may occupy multiple bytes. All 214 1.1.1.1.4.2 pgoyette multi-byte numbers in the format described here are stored with 215 1.1.1.1.4.2 pgoyette the least-significant byte first (at the lower memory address). 216 1.1.1.1.4.2 pgoyette For example, the decimal number 520 is stored as: 217 1.1.1.1.4.2 pgoyette 218 1.1.1.1.4.2 pgoyette 0 1 219 1.1.1.1.4.2 pgoyette +--------+--------+ 220 1.1.1.1.4.2 pgoyette |00001000|00000010| 221 1.1.1.1.4.2 pgoyette +--------+--------+ 222 1.1.1.1.4.2 pgoyette ^ ^ 223 1.1.1.1.4.2 pgoyette | | 224 1.1.1.1.4.2 pgoyette | + more significant byte = 2 x 256 225 1.1.1.1.4.2 pgoyette + less significant byte = 8 226 1.1.1.1.4.2 pgoyette 227 1.1.1.1.4.2 pgoyette 228 1.1.1.1.4.2 pgoyette 229 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 4] 230 1.1.1.1.4.2 pgoyette 232 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 233 1.1.1.1.4.2 pgoyette 234 1.1.1.1.4.2 pgoyette 235 1.1.1.1.4.2 pgoyette 2.2. File format 236 1.1.1.1.4.2 pgoyette 237 1.1.1.1.4.2 pgoyette A gzip file consists of a series of "members" (compressed data 238 1.1.1.1.4.2 pgoyette sets). The format of each member is specified in the following 239 1.1.1.1.4.2 pgoyette section. The members simply appear one after another in the file, 240 1.1.1.1.4.2 pgoyette with no additional information before, between, or after them. 241 1.1.1.1.4.2 pgoyette 242 1.1.1.1.4.2 pgoyette 2.3. Member format 243 1.1.1.1.4.2 pgoyette 244 1.1.1.1.4.2 pgoyette Each member has the following structure: 245 1.1.1.1.4.2 pgoyette 246 1.1.1.1.4.2 pgoyette +---+---+---+---+---+---+---+---+---+---+ 247 1.1.1.1.4.2 pgoyette |ID1|ID2|CM |FLG| MTIME |XFL|OS | (more-->) 248 1.1.1.1.4.2 pgoyette +---+---+---+---+---+---+---+---+---+---+ 249 1.1.1.1.4.2 pgoyette 250 1.1.1.1.4.2 pgoyette (if FLG.FEXTRA set) 251 1.1.1.1.4.2 pgoyette 252 1.1.1.1.4.2 pgoyette +---+---+=================================+ 253 1.1.1.1.4.2 pgoyette | XLEN |...XLEN bytes of "extra field"...| (more-->) 254 1.1.1.1.4.2 pgoyette +---+---+=================================+ 255 1.1.1.1.4.2 pgoyette 256 1.1.1.1.4.2 pgoyette (if FLG.FNAME set) 257 1.1.1.1.4.2 pgoyette 258 1.1.1.1.4.2 pgoyette +=========================================+ 259 1.1.1.1.4.2 pgoyette |...original file name, zero-terminated...| (more-->) 260 1.1.1.1.4.2 pgoyette +=========================================+ 261 1.1.1.1.4.2 pgoyette 262 1.1.1.1.4.2 pgoyette (if FLG.FCOMMENT set) 263 1.1.1.1.4.2 pgoyette 264 1.1.1.1.4.2 pgoyette +===================================+ 265 1.1.1.1.4.2 pgoyette |...file comment, zero-terminated...| (more-->) 266 1.1.1.1.4.2 pgoyette +===================================+ 267 1.1.1.1.4.2 pgoyette 268 1.1.1.1.4.2 pgoyette (if FLG.FHCRC set) 269 1.1.1.1.4.2 pgoyette 270 1.1.1.1.4.2 pgoyette +---+---+ 271 1.1.1.1.4.2 pgoyette | CRC16 | 272 1.1.1.1.4.2 pgoyette +---+---+ 273 1.1.1.1.4.2 pgoyette 274 1.1.1.1.4.2 pgoyette +=======================+ 275 1.1.1.1.4.2 pgoyette |...compressed blocks...| (more-->) 276 1.1.1.1.4.2 pgoyette +=======================+ 277 1.1.1.1.4.2 pgoyette 278 1.1.1.1.4.2 pgoyette 0 1 2 3 4 5 6 7 279 1.1.1.1.4.2 pgoyette +---+---+---+---+---+---+---+---+ 280 1.1.1.1.4.2 pgoyette | CRC32 | ISIZE | 281 1.1.1.1.4.2 pgoyette +---+---+---+---+---+---+---+---+ 282 1.1.1.1.4.2 pgoyette 283 1.1.1.1.4.2 pgoyette 284 1.1.1.1.4.2 pgoyette 285 1.1.1.1.4.2 pgoyette 286 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 5] 287 1.1.1.1.4.2 pgoyette 289 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 290 1.1.1.1.4.2 pgoyette 291 1.1.1.1.4.2 pgoyette 292 1.1.1.1.4.2 pgoyette 2.3.1. Member header and trailer 293 1.1.1.1.4.2 pgoyette 294 1.1.1.1.4.2 pgoyette ID1 (IDentification 1) 295 1.1.1.1.4.2 pgoyette ID2 (IDentification 2) 296 1.1.1.1.4.2 pgoyette These have the fixed values ID1 = 31 (0x1f, \037), ID2 = 139 297 1.1.1.1.4.2 pgoyette (0x8b, \213), to identify the file as being in gzip format. 298 1.1.1.1.4.2 pgoyette 299 1.1.1.1.4.2 pgoyette CM (Compression Method) 300 1.1.1.1.4.2 pgoyette This identifies the compression method used in the file. CM 301 1.1.1.1.4.2 pgoyette = 0-7 are reserved. CM = 8 denotes the "deflate" 302 1.1.1.1.4.2 pgoyette compression method, which is the one customarily used by 303 1.1.1.1.4.2 pgoyette gzip and which is documented elsewhere. 304 1.1.1.1.4.2 pgoyette 305 1.1.1.1.4.2 pgoyette FLG (FLaGs) 306 1.1.1.1.4.2 pgoyette This flag byte is divided into individual bits as follows: 307 1.1.1.1.4.2 pgoyette 308 1.1.1.1.4.2 pgoyette bit 0 FTEXT 309 1.1.1.1.4.2 pgoyette bit 1 FHCRC 310 1.1.1.1.4.2 pgoyette bit 2 FEXTRA 311 1.1.1.1.4.2 pgoyette bit 3 FNAME 312 1.1.1.1.4.2 pgoyette bit 4 FCOMMENT 313 1.1.1.1.4.2 pgoyette bit 5 reserved 314 1.1.1.1.4.2 pgoyette bit 6 reserved 315 1.1.1.1.4.2 pgoyette bit 7 reserved 316 1.1.1.1.4.2 pgoyette 317 1.1.1.1.4.2 pgoyette If FTEXT is set, the file is probably ASCII text. This is 318 1.1.1.1.4.2 pgoyette an optional indication, which the compressor may set by 319 1.1.1.1.4.2 pgoyette checking a small amount of the input data to see whether any 320 1.1.1.1.4.2 pgoyette non-ASCII characters are present. In case of doubt, FTEXT 321 1.1.1.1.4.2 pgoyette is cleared, indicating binary data. For systems which have 322 1.1.1.1.4.2 pgoyette different file formats for ascii text and binary data, the 323 1.1.1.1.4.2 pgoyette decompressor can use FTEXT to choose the appropriate format. 324 1.1.1.1.4.2 pgoyette We deliberately do not specify the algorithm used to set 325 1.1.1.1.4.2 pgoyette this bit, since a compressor always has the option of 326 1.1.1.1.4.2 pgoyette leaving it cleared and a decompressor always has the option 327 1.1.1.1.4.2 pgoyette of ignoring it and letting some other program handle issues 328 1.1.1.1.4.2 pgoyette of data conversion. 329 1.1.1.1.4.2 pgoyette 330 1.1.1.1.4.2 pgoyette If FHCRC is set, a CRC16 for the gzip header is present, 331 1.1.1.1.4.2 pgoyette immediately before the compressed data. The CRC16 consists 332 1.1.1.1.4.2 pgoyette of the two least significant bytes of the CRC32 for all 333 1.1.1.1.4.2 pgoyette bytes of the gzip header up to and not including the CRC16. 334 1.1.1.1.4.2 pgoyette [The FHCRC bit was never set by versions of gzip up to 335 1.1.1.1.4.2 pgoyette 1.2.4, even though it was documented with a different 336 1.1.1.1.4.2 pgoyette meaning in gzip 1.2.4.] 337 1.1.1.1.4.2 pgoyette 338 1.1.1.1.4.2 pgoyette If FEXTRA is set, optional extra fields are present, as 339 1.1.1.1.4.2 pgoyette described in a following section. 340 1.1.1.1.4.2 pgoyette 341 1.1.1.1.4.2 pgoyette 342 1.1.1.1.4.2 pgoyette 343 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 6] 344 1.1.1.1.4.2 pgoyette 346 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 347 1.1.1.1.4.2 pgoyette 348 1.1.1.1.4.2 pgoyette 349 1.1.1.1.4.2 pgoyette If FNAME is set, an original file name is present, 350 1.1.1.1.4.2 pgoyette terminated by a zero byte. The name must consist of ISO 351 1.1.1.1.4.2 pgoyette 8859-1 (LATIN-1) characters; on operating systems using 352 1.1.1.1.4.2 pgoyette EBCDIC or any other character set for file names, the name 353 1.1.1.1.4.2 pgoyette must be translated to the ISO LATIN-1 character set. This 354 1.1.1.1.4.2 pgoyette is the original name of the file being compressed, with any 355 1.1.1.1.4.2 pgoyette directory components removed, and, if the file being 356 1.1.1.1.4.2 pgoyette compressed is on a file system with case insensitive names, 357 1.1.1.1.4.2 pgoyette forced to lower case. There is no original file name if the 358 1.1.1.1.4.2 pgoyette data was compressed from a source other than a named file; 359 1.1.1.1.4.2 pgoyette for example, if the source was stdin on a Unix system, there 360 1.1.1.1.4.2 pgoyette is no file name. 361 1.1.1.1.4.2 pgoyette 362 1.1.1.1.4.2 pgoyette If FCOMMENT is set, a zero-terminated file comment is 363 1.1.1.1.4.2 pgoyette present. This comment is not interpreted; it is only 364 1.1.1.1.4.2 pgoyette intended for human consumption. The comment must consist of 365 1.1.1.1.4.2 pgoyette ISO 8859-1 (LATIN-1) characters. Line breaks should be 366 1.1.1.1.4.2 pgoyette denoted by a single line feed character (10 decimal). 367 1.1.1.1.4.2 pgoyette 368 1.1.1.1.4.2 pgoyette Reserved FLG bits must be zero. 369 1.1.1.1.4.2 pgoyette 370 1.1.1.1.4.2 pgoyette MTIME (Modification TIME) 371 1.1.1.1.4.2 pgoyette This gives the most recent modification time of the original 372 1.1.1.1.4.2 pgoyette file being compressed. The time is in Unix format, i.e., 373 1.1.1.1.4.2 pgoyette seconds since 00:00:00 GMT, Jan. 1, 1970. (Note that this 374 1.1.1.1.4.2 pgoyette may cause problems for MS-DOS and other systems that use 375 1.1.1.1.4.2 pgoyette local rather than Universal time.) If the compressed data 376 1.1.1.1.4.2 pgoyette did not come from a file, MTIME is set to the time at which 377 1.1.1.1.4.2 pgoyette compression started. MTIME = 0 means no time stamp is 378 1.1.1.1.4.2 pgoyette available. 379 1.1.1.1.4.2 pgoyette 380 1.1.1.1.4.2 pgoyette XFL (eXtra FLags) 381 1.1.1.1.4.2 pgoyette These flags are available for use by specific compression 382 1.1.1.1.4.2 pgoyette methods. The "deflate" method (CM = 8) sets these flags as 383 1.1.1.1.4.2 pgoyette follows: 384 1.1.1.1.4.2 pgoyette 385 1.1.1.1.4.2 pgoyette XFL = 2 - compressor used maximum compression, 386 1.1.1.1.4.2 pgoyette slowest algorithm 387 1.1.1.1.4.2 pgoyette XFL = 4 - compressor used fastest algorithm 388 1.1.1.1.4.2 pgoyette 389 1.1.1.1.4.2 pgoyette OS (Operating System) 390 1.1.1.1.4.2 pgoyette This identifies the type of file system on which compression 391 1.1.1.1.4.2 pgoyette took place. This may be useful in determining end-of-line 392 1.1.1.1.4.2 pgoyette convention for text files. The currently defined values are 393 1.1.1.1.4.2 pgoyette as follows: 394 1.1.1.1.4.2 pgoyette 395 1.1.1.1.4.2 pgoyette 396 1.1.1.1.4.2 pgoyette 397 1.1.1.1.4.2 pgoyette 398 1.1.1.1.4.2 pgoyette 399 1.1.1.1.4.2 pgoyette 400 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 7] 401 1.1.1.1.4.2 pgoyette 403 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 404 1.1.1.1.4.2 pgoyette 405 1.1.1.1.4.2 pgoyette 406 1.1.1.1.4.2 pgoyette 0 - FAT filesystem (MS-DOS, OS/2, NT/Win32) 407 1.1.1.1.4.2 pgoyette 1 - Amiga 408 1.1.1.1.4.2 pgoyette 2 - VMS (or OpenVMS) 409 1.1.1.1.4.2 pgoyette 3 - Unix 410 1.1.1.1.4.2 pgoyette 4 - VM/CMS 411 1.1.1.1.4.2 pgoyette 5 - Atari TOS 412 1.1.1.1.4.2 pgoyette 6 - HPFS filesystem (OS/2, NT) 413 1.1.1.1.4.2 pgoyette 7 - Macintosh 414 1.1.1.1.4.2 pgoyette 8 - Z-System 415 1.1.1.1.4.2 pgoyette 9 - CP/M 416 1.1.1.1.4.2 pgoyette 10 - TOPS-20 417 1.1.1.1.4.2 pgoyette 11 - NTFS filesystem (NT) 418 1.1.1.1.4.2 pgoyette 12 - QDOS 419 1.1.1.1.4.2 pgoyette 13 - Acorn RISCOS 420 1.1.1.1.4.2 pgoyette 255 - unknown 421 1.1.1.1.4.2 pgoyette 422 1.1.1.1.4.2 pgoyette XLEN (eXtra LENgth) 423 1.1.1.1.4.2 pgoyette If FLG.FEXTRA is set, this gives the length of the optional 424 1.1.1.1.4.2 pgoyette extra field. See below for details. 425 1.1.1.1.4.2 pgoyette 426 1.1.1.1.4.2 pgoyette CRC32 (CRC-32) 427 1.1.1.1.4.2 pgoyette This contains a Cyclic Redundancy Check value of the 428 1.1.1.1.4.2 pgoyette uncompressed data computed according to CRC-32 algorithm 429 1.1.1.1.4.2 pgoyette used in the ISO 3309 standard and in section 8.1.1.6.2 of 430 1.1.1.1.4.2 pgoyette ITU-T recommendation V.42. (See http://www.iso.ch for 431 1.1.1.1.4.2 pgoyette ordering ISO documents. See gopher://info.itu.ch for an 432 1.1.1.1.4.2 pgoyette online version of ITU-T V.42.) 433 1.1.1.1.4.2 pgoyette 434 1.1.1.1.4.2 pgoyette ISIZE (Input SIZE) 435 1.1.1.1.4.2 pgoyette This contains the size of the original (uncompressed) input 436 1.1.1.1.4.2 pgoyette data modulo 2^32. 437 1.1.1.1.4.2 pgoyette 438 1.1.1.1.4.2 pgoyette 2.3.1.1. Extra field 439 1.1.1.1.4.2 pgoyette 440 1.1.1.1.4.2 pgoyette If the FLG.FEXTRA bit is set, an "extra field" is present in 441 1.1.1.1.4.2 pgoyette the header, with total length XLEN bytes. It consists of a 442 1.1.1.1.4.2 pgoyette series of subfields, each of the form: 443 1.1.1.1.4.2 pgoyette 444 1.1.1.1.4.2 pgoyette +---+---+---+---+==================================+ 445 1.1.1.1.4.2 pgoyette |SI1|SI2| LEN |... LEN bytes of subfield data ...| 446 1.1.1.1.4.2 pgoyette +---+---+---+---+==================================+ 447 1.1.1.1.4.2 pgoyette 448 1.1.1.1.4.2 pgoyette SI1 and SI2 provide a subfield ID, typically two ASCII letters 449 1.1.1.1.4.2 pgoyette with some mnemonic value. Jean-Loup Gailly 450 1.1.1.1.4.2 pgoyette <gzip (a] prep.ai.mit.edu> is maintaining a registry of subfield 451 1.1.1.1.4.2 pgoyette IDs; please send him any subfield ID you wish to use. Subfield 452 1.1.1.1.4.2 pgoyette IDs with SI2 = 0 are reserved for future use. The following 453 1.1.1.1.4.2 pgoyette IDs are currently defined: 454 1.1.1.1.4.2 pgoyette 455 1.1.1.1.4.2 pgoyette 456 1.1.1.1.4.2 pgoyette 457 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 8] 458 1.1.1.1.4.2 pgoyette 460 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 461 1.1.1.1.4.2 pgoyette 462 1.1.1.1.4.2 pgoyette 463 1.1.1.1.4.2 pgoyette SI1 SI2 Data 464 1.1.1.1.4.2 pgoyette ---------- ---------- ---- 465 1.1.1.1.4.2 pgoyette 0x41 ('A') 0x70 ('P') Apollo file type information 466 1.1.1.1.4.2 pgoyette 467 1.1.1.1.4.2 pgoyette LEN gives the length of the subfield data, excluding the 4 468 1.1.1.1.4.2 pgoyette initial bytes. 469 1.1.1.1.4.2 pgoyette 470 1.1.1.1.4.2 pgoyette 2.3.1.2. Compliance 471 1.1.1.1.4.2 pgoyette 472 1.1.1.1.4.2 pgoyette A compliant compressor must produce files with correct ID1, 473 1.1.1.1.4.2 pgoyette ID2, CM, CRC32, and ISIZE, but may set all the other fields in 474 1.1.1.1.4.2 pgoyette the fixed-length part of the header to default values (255 for 475 1.1.1.1.4.2 pgoyette OS, 0 for all others). The compressor must set all reserved 476 1.1.1.1.4.2 pgoyette bits to zero. 477 1.1.1.1.4.2 pgoyette 478 1.1.1.1.4.2 pgoyette A compliant decompressor must check ID1, ID2, and CM, and 479 1.1.1.1.4.2 pgoyette provide an error indication if any of these have incorrect 480 1.1.1.1.4.2 pgoyette values. It must examine FEXTRA/XLEN, FNAME, FCOMMENT and FHCRC 481 1.1.1.1.4.2 pgoyette at least so it can skip over the optional fields if they are 482 1.1.1.1.4.2 pgoyette present. It need not examine any other part of the header or 483 1.1.1.1.4.2 pgoyette trailer; in particular, a decompressor may ignore FTEXT and OS 484 1.1.1.1.4.2 pgoyette and always produce binary output, and still be compliant. A 485 1.1.1.1.4.2 pgoyette compliant decompressor must give an error indication if any 486 1.1.1.1.4.2 pgoyette reserved bit is non-zero, since such a bit could indicate the 487 1.1.1.1.4.2 pgoyette presence of a new field that would cause subsequent data to be 488 1.1.1.1.4.2 pgoyette interpreted incorrectly. 489 1.1.1.1.4.2 pgoyette 490 1.1.1.1.4.2 pgoyette 3. References 491 1.1.1.1.4.2 pgoyette 492 1.1.1.1.4.2 pgoyette [1] "Information Processing - 8-bit single-byte coded graphic 493 1.1.1.1.4.2 pgoyette character sets - Part 1: Latin alphabet No.1" (ISO 8859-1:1987). 494 1.1.1.1.4.2 pgoyette The ISO 8859-1 (Latin-1) character set is a superset of 7-bit 495 1.1.1.1.4.2 pgoyette ASCII. Files defining this character set are available as 496 1.1.1.1.4.2 pgoyette iso_8859-1.* in ftp://ftp.uu.net/graphics/png/documents/ 497 1.1.1.1.4.2 pgoyette 498 1.1.1.1.4.2 pgoyette [2] ISO 3309 499 1.1.1.1.4.2 pgoyette 500 1.1.1.1.4.2 pgoyette [3] ITU-T recommendation V.42 501 1.1.1.1.4.2 pgoyette 502 1.1.1.1.4.2 pgoyette [4] Deutsch, L.P.,"DEFLATE Compressed Data Format Specification", 503 1.1.1.1.4.2 pgoyette available in ftp://ftp.uu.net/pub/archiving/zip/doc/ 504 1.1.1.1.4.2 pgoyette 505 1.1.1.1.4.2 pgoyette [5] Gailly, J.-L., GZIP documentation, available as gzip-*.tar in 506 1.1.1.1.4.2 pgoyette ftp://prep.ai.mit.edu/pub/gnu/ 507 1.1.1.1.4.2 pgoyette 508 1.1.1.1.4.2 pgoyette [6] Sarwate, D.V., "Computation of Cyclic Redundancy Checks via Table 509 1.1.1.1.4.2 pgoyette Look-Up", Communications of the ACM, 31(8), pp.1008-1013. 510 1.1.1.1.4.2 pgoyette 511 1.1.1.1.4.2 pgoyette 512 1.1.1.1.4.2 pgoyette 513 1.1.1.1.4.2 pgoyette 514 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 9] 515 1.1.1.1.4.2 pgoyette 517 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 518 1.1.1.1.4.2 pgoyette 519 1.1.1.1.4.2 pgoyette 520 1.1.1.1.4.2 pgoyette [7] Schwaderer, W.D., "CRC Calculation", April 85 PC Tech Journal, 521 1.1.1.1.4.2 pgoyette pp.118-133. 522 1.1.1.1.4.2 pgoyette 523 1.1.1.1.4.2 pgoyette [8] ftp://ftp.adelaide.edu.au/pub/rocksoft/papers/crc_v3.txt, 524 1.1.1.1.4.2 pgoyette describing the CRC concept. 525 1.1.1.1.4.2 pgoyette 526 1.1.1.1.4.2 pgoyette 4. Security Considerations 527 1.1.1.1.4.2 pgoyette 528 1.1.1.1.4.2 pgoyette Any data compression method involves the reduction of redundancy in 529 1.1.1.1.4.2 pgoyette the data. Consequently, any corruption of the data is likely to have 530 1.1.1.1.4.2 pgoyette severe effects and be difficult to correct. Uncompressed text, on 531 1.1.1.1.4.2 pgoyette the other hand, will probably still be readable despite the presence 532 1.1.1.1.4.2 pgoyette of some corrupted bytes. 533 1.1.1.1.4.2 pgoyette 534 1.1.1.1.4.2 pgoyette It is recommended that systems using this data format provide some 535 1.1.1.1.4.2 pgoyette means of validating the integrity of the compressed data, such as by 536 1.1.1.1.4.2 pgoyette setting and checking the CRC-32 check value. 537 1.1.1.1.4.2 pgoyette 538 1.1.1.1.4.2 pgoyette 5. Acknowledgements 539 1.1.1.1.4.2 pgoyette 540 1.1.1.1.4.2 pgoyette Trademarks cited in this document are the property of their 541 1.1.1.1.4.2 pgoyette respective owners. 542 1.1.1.1.4.2 pgoyette 543 1.1.1.1.4.2 pgoyette Jean-Loup Gailly designed the gzip format and wrote, with Mark Adler, 544 1.1.1.1.4.2 pgoyette the related software described in this specification. Glenn 545 1.1.1.1.4.2 pgoyette Randers-Pehrson converted this document to RFC and HTML format. 546 1.1.1.1.4.2 pgoyette 547 1.1.1.1.4.2 pgoyette 6. Author's Address 548 1.1.1.1.4.2 pgoyette 549 1.1.1.1.4.2 pgoyette L. Peter Deutsch 550 1.1.1.1.4.2 pgoyette Aladdin Enterprises 551 1.1.1.1.4.2 pgoyette 203 Santa Margarita Ave. 552 1.1.1.1.4.2 pgoyette Menlo Park, CA 94025 553 1.1.1.1.4.2 pgoyette 554 1.1.1.1.4.2 pgoyette Phone: (415) 322-0103 (AM only) 555 1.1.1.1.4.2 pgoyette FAX: (415) 322-1734 556 1.1.1.1.4.2 pgoyette EMail: <ghost (a] aladdin.com> 557 1.1.1.1.4.2 pgoyette 558 1.1.1.1.4.2 pgoyette Questions about the technical content of this specification can be 559 1.1.1.1.4.2 pgoyette sent by email to: 560 1.1.1.1.4.2 pgoyette 561 1.1.1.1.4.2 pgoyette Jean-Loup Gailly <gzip (a] prep.ai.mit.edu> and 562 1.1.1.1.4.2 pgoyette Mark Adler <madler (a] alumni.caltech.edu> 563 1.1.1.1.4.2 pgoyette 564 1.1.1.1.4.2 pgoyette Editorial comments on this specification can be sent by email to: 565 1.1.1.1.4.2 pgoyette 566 1.1.1.1.4.2 pgoyette L. Peter Deutsch <ghost (a] aladdin.com> and 567 1.1.1.1.4.2 pgoyette Glenn Randers-Pehrson <randeg (a] alumni.rpi.edu> 568 1.1.1.1.4.2 pgoyette 569 1.1.1.1.4.2 pgoyette 570 1.1.1.1.4.2 pgoyette 571 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 10] 572 1.1.1.1.4.2 pgoyette 574 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 575 1.1.1.1.4.2 pgoyette 576 1.1.1.1.4.2 pgoyette 577 1.1.1.1.4.2 pgoyette 7. Appendix: Jean-Loup Gailly's gzip utility 578 1.1.1.1.4.2 pgoyette 579 1.1.1.1.4.2 pgoyette The most widely used implementation of gzip compression, and the 580 1.1.1.1.4.2 pgoyette original documentation on which this specification is based, were 581 1.1.1.1.4.2 pgoyette created by Jean-Loup Gailly <gzip (a] prep.ai.mit.edu>. Since this 582 1.1.1.1.4.2 pgoyette implementation is a de facto standard, we mention some more of its 583 1.1.1.1.4.2 pgoyette features here. Again, the material in this section is not part of 584 1.1.1.1.4.2 pgoyette the specification per se, and implementations need not follow it to 585 1.1.1.1.4.2 pgoyette be compliant. 586 1.1.1.1.4.2 pgoyette 587 1.1.1.1.4.2 pgoyette When compressing or decompressing a file, gzip preserves the 588 1.1.1.1.4.2 pgoyette protection, ownership, and modification time attributes on the local 589 1.1.1.1.4.2 pgoyette file system, since there is no provision for representing protection 590 1.1.1.1.4.2 pgoyette attributes in the gzip file format itself. Since the file format 591 1.1.1.1.4.2 pgoyette includes a modification time, the gzip decompressor provides a 592 1.1.1.1.4.2 pgoyette command line switch that assigns the modification time from the file, 593 1.1.1.1.4.2 pgoyette rather than the local modification time of the compressed input, to 594 1.1.1.1.4.2 pgoyette the decompressed output. 595 1.1.1.1.4.2 pgoyette 596 1.1.1.1.4.2 pgoyette 8. Appendix: Sample CRC Code 597 1.1.1.1.4.2 pgoyette 598 1.1.1.1.4.2 pgoyette The following sample code represents a practical implementation of 599 1.1.1.1.4.2 pgoyette the CRC (Cyclic Redundancy Check). (See also ISO 3309 and ITU-T V.42 600 1.1.1.1.4.2 pgoyette for a formal specification.) 601 1.1.1.1.4.2 pgoyette 602 1.1.1.1.4.2 pgoyette The sample code is in the ANSI C programming language. Non C users 603 1.1.1.1.4.2 pgoyette may find it easier to read with these hints: 604 1.1.1.1.4.2 pgoyette 605 1.1.1.1.4.2 pgoyette & Bitwise AND operator. 606 1.1.1.1.4.2 pgoyette ^ Bitwise exclusive-OR operator. 607 1.1.1.1.4.2 pgoyette >> Bitwise right shift operator. When applied to an 608 1.1.1.1.4.2 pgoyette unsigned quantity, as here, right shift inserts zero 609 1.1.1.1.4.2 pgoyette bit(s) at the left. 610 1.1.1.1.4.2 pgoyette ! Logical NOT operator. 611 1.1.1.1.4.2 pgoyette ++ "n++" increments the variable n. 612 1.1.1.1.4.2 pgoyette 0xNNN 0x introduces a hexadecimal (base 16) constant. 613 1.1.1.1.4.2 pgoyette Suffix L indicates a long value (at least 32 bits). 614 1.1.1.1.4.2 pgoyette 615 1.1.1.1.4.2 pgoyette /* Table of CRCs of all 8-bit messages. */ 616 1.1.1.1.4.2 pgoyette unsigned long crc_table[256]; 617 1.1.1.1.4.2 pgoyette 618 1.1.1.1.4.2 pgoyette /* Flag: has the table been computed? Initially false. */ 619 1.1.1.1.4.2 pgoyette int crc_table_computed = 0; 620 1.1.1.1.4.2 pgoyette 621 1.1.1.1.4.2 pgoyette /* Make the table for a fast CRC. */ 622 1.1.1.1.4.2 pgoyette void make_crc_table(void) 623 1.1.1.1.4.2 pgoyette { 624 1.1.1.1.4.2 pgoyette unsigned long c; 625 1.1.1.1.4.2 pgoyette 626 1.1.1.1.4.2 pgoyette 627 1.1.1.1.4.2 pgoyette 628 1.1.1.1.4.2 pgoyette Deutsch Informational [Page 11] 629 1.1.1.1.4.2 pgoyette 631 1.1.1.1.4.2 pgoyette RFC 1952 GZIP File Format Specification May 1996 632 1.1.1.1.4.2 pgoyette 633 1.1.1.1.4.2 pgoyette 634 1.1.1.1.4.2 pgoyette int n, k; 635 1.1.1.1.4.2 pgoyette for (n = 0; n < 256; n++) { 636 1.1.1.1.4.2 pgoyette c = (unsigned long) n; 637 1.1.1.1.4.2 pgoyette for (k = 0; k < 8; k++) { 638 1.1.1.1.4.2 pgoyette if (c & 1) { 639 1.1.1.1.4.2 pgoyette c = 0xedb88320L ^ (c >> 1); 640 1.1.1.1.4.2 pgoyette } else { 641 1.1.1.1.4.2 pgoyette c = c >> 1; 642 1.1.1.1.4.2 pgoyette } 643 1.1.1.1.4.2 pgoyette } 644 1.1.1.1.4.2 pgoyette crc_table[n] = c; 645 1.1.1.1.4.2 pgoyette } 646 1.1.1.1.4.2 pgoyette crc_table_computed = 1; 647 1.1.1.1.4.2 pgoyette } 648 1.1.1.1.4.2 pgoyette 649 1.1.1.1.4.2 pgoyette /* 650 1.1.1.1.4.2 pgoyette Update a running crc with the bytes buf[0..len-1] and return 651 1.1.1.1.4.2 pgoyette the updated crc. The crc should be initialized to zero. Pre- and 652 1.1.1.1.4.2 pgoyette post-conditioning (one's complement) is performed within this 653 1.1.1.1.4.2 pgoyette function so it shouldn't be done by the caller. Usage example: 654 1.1.1.1.4.2 pgoyette 655 1.1.1.1.4.2 pgoyette unsigned long crc = 0L; 656 1.1.1.1.4.2 pgoyette 657 1.1.1.1.4.2 pgoyette while (read_buffer(buffer, length) != EOF) { 658 1.1.1.1.4.2 pgoyette crc = update_crc(crc, buffer, length); 659 1.1.1.1.4.2 pgoyette } 660 1.1.1.1.4.2 pgoyette if (crc != original_crc) error(); 661 1.1.1.1.4.2 pgoyette */ 662 1.1.1.1.4.2 pgoyette unsigned long update_crc(unsigned long crc, 663 1.1.1.1.4.2 pgoyette unsigned char *buf, int len) 664 1.1.1.1.4.2 pgoyette { 665 1.1.1.1.4.2 pgoyette unsigned long c = crc ^ 0xffffffffL; 666 1.1.1.1.4.2 pgoyette int n; 667 1.1.1.1.4.2 pgoyette 668 1.1.1.1.4.2 pgoyette if (!crc_table_computed) 669 1.1.1.1.4.2 pgoyette make_crc_table(); 670 1.1.1.1.4.2 pgoyette for (n = 0; n < len; n++) { 671 1.1.1.1.4.2 pgoyette c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8); 672 1.1.1.1.4.2 pgoyette } 673 1.1.1.1.4.2 pgoyette return c ^ 0xffffffffL; 674 1.1.1.1.4.2 pgoyette } 675 1.1.1.1.4.2 pgoyette 676 /* Return the CRC of the bytes buf[0..len-1]. */ 677 unsigned long crc(unsigned char *buf, int len) 678 { 679 return update_crc(0L, buf, len); 680 } 681 682 683 684 685 Deutsch Informational [Page 12] 686 688
Indexes created Wed Oct 22 13:09:56 GMT 2025