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flate 4.0 KB

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  1. .TH FLATE 2
  2. .SH NAME
  3. deflateinit, deflate, deflatezlib, deflateblock, deflatezlibblock, inflateinit, inflate, inflatezlib, inflateblock, inflatezlibblock, flateerr, mkcrctab, blockcrc, adler32 \- deflate compression
  4. .SH SYNOPSIS
  5. .B #include <u.h>
  6. .br
  7. .B #include <libc.h>
  8. .br
  9. .B #include <flate.h>
  10. .PP
  11. .ta \w'ulongmm'u
  12. .PP
  13. .B
  14. int deflateinit(void)
  15. .PP
  16. .B
  17. int deflate(void *wr, int (*w)(void*,void*,int),
  18. .br
  19. .B
  20. void *rr, int (*r)(void*,void*,int),
  21. .br
  22. .B
  23. int level, int debug)
  24. .PP
  25. .B
  26. int deflatezlib(void *wr, int (*w)(void*,void*,int),
  27. .br
  28. .B
  29. void *rr, int (*r)(void*,void*,int),
  30. .br
  31. .B
  32. int level, int debug)
  33. .PP
  34. .B
  35. int deflateblock(uchar *dst, int dsize,
  36. .br
  37. .B
  38. uchar *src, int ssize,
  39. .br
  40. .B
  41. int level, int debug)
  42. .PP
  43. .B
  44. int deflatezlibblock(uchar *dst, int dsize,
  45. .br
  46. .B
  47. uchar *src, int ssize,
  48. .br
  49. .B
  50. int level, int debug)
  51. .PP
  52. .B
  53. int inflateinit(void)
  54. .PP
  55. .B
  56. int inflate(void *wr, int (*w)(void*, void*, int),
  57. .br
  58. .B
  59. void *getr, int (*get)(void*))
  60. .PP
  61. .B
  62. int inflatezlib(void *wr, int (*w)(void*, void*, int),
  63. .br
  64. .B
  65. void *getr, int (*get)(void*))
  66. .PP
  67. .B
  68. int inflateblock(uchar *dst, int dsize,
  69. .br
  70. .B
  71. uchar *src, int ssize)
  72. .PP
  73. .B
  74. int inflatezlibblock(uchar *dst, int dsize,
  75. .br
  76. .B
  77. uchar *src, int ssize)
  78. .PP
  79. .B
  80. char *flateerr(int error)
  81. .PP
  82. .B
  83. ulong *mkcrctab(ulong poly)
  84. .PP
  85. .B
  86. ulong blockcrc(ulong *tab, ulong crc, void *buf, int n)
  87. .PP
  88. .B
  89. ulong adler32(ulong adler, void *buf, int n)
  90. .SH DESCRIPTION
  91. These routines compress and decompress data using the deflate compression algorithm,
  92. which is used for most gzip, zip, and zlib files.
  93. .PP
  94. .I Deflate
  95. compresses input data retrieved by calls to
  96. .I r
  97. with arguments
  98. .IR rr ,
  99. an input buffer, and a count of bytes to read.
  100. .I R
  101. should return the number of bytes read;
  102. end of input is signaled by returning zero, an input error by
  103. returning a negative number.
  104. The compressed output is written to
  105. .I w
  106. with arguments
  107. .IR wr ,
  108. the output data, and the number of bytes to write.
  109. .I W
  110. should return the number of bytes written;
  111. writing fewer than the requested number of bytes is an error.
  112. .I Level
  113. indicates the amount of computation deflate should do while compressing the data.
  114. Higher
  115. .I levels
  116. usually take more time and produce smaller outputs.
  117. Valid values are 1 to 9, inclusive; 6 is a good compromise.
  118. If
  119. .I debug
  120. is non-zero, cryptic debugging information is produced on standard error.
  121. .PP
  122. .I Inflate
  123. reverses the process, converting compressed data into uncompressed output.
  124. Input is retrieved one byte at a time by calling
  125. .I get
  126. with the argument
  127. .IR getr .
  128. End of input of signaled by returning a negative value.
  129. The uncompressed output is written to
  130. .IR w ,
  131. which has the same interface as for
  132. .IR deflate .
  133. .PP
  134. .I
  135. Deflateblock
  136. and
  137. .I inflateblock
  138. operate on blocks of memory but are otherwise similar to
  139. .I deflate
  140. and
  141. .IR inflate .
  142. .PP
  143. The zlib functions are similar, but operate on files with a zlib header and trailer.
  144. .PP
  145. .I Deflateinit
  146. or
  147. .I inflateinit
  148. must be called once before any call to the corresponding routines.
  149. .PP
  150. If the above routines fail,
  151. they return a negative number indicating the problem.
  152. The possible values are
  153. .IR FlateNoMem ,
  154. .IR FlateInputFail ,
  155. .IR FlateOutputFail ,
  156. .IR FlateCorrupted ,
  157. and
  158. .IR FlateInternal .
  159. .I Flateerr
  160. converts the number into a printable message.
  161. .I FlateOk
  162. is defined to be zero,
  163. the successful return value for
  164. .IR deflateinit ,
  165. .IR deflate ,
  166. .IR deflatezlib ,
  167. .IR inflateinit ,
  168. .IR inflate ,
  169. and
  170. .IR inflatezlib .
  171. The block functions return the number of bytes produced when they succeed.
  172. .PP
  173. .I Mkcrctab
  174. allocates
  175. (using
  176. .IR malloc (2)),
  177. initializes, and returns a table for rapid computation of 32 bit CRC values using the polynomial
  178. .IR poly .
  179. .I Blockcrc
  180. uses
  181. .IR tab ,
  182. a table returned by
  183. .IR mkcrctab ,
  184. to update
  185. .I crc
  186. for the
  187. .I n
  188. bytes of data in
  189. .IR buf ,
  190. and returns the new value.
  191. .I Crc
  192. should initially be zero.
  193. .I Blockcrc
  194. pre-conditions and post-conditions
  195. .I crc
  196. by ones complementation.
  197. .PP
  198. .I Adler32
  199. updates the Adler 32-bit checksum of the
  200. .I n
  201. butes of data in
  202. .IR buf.
  203. The initial value of
  204. .I adler
  205. (that is, its value after seeing zero bytes) should be 1.
  206. .SH SOURCE
  207. .B /sys/src/libflate