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9pcmdbuf 2.1 KB

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  1. .TH 9PCMDBUF 2
  2. .SH NAME
  3. Cmdbuf, parsecmd, respondcmderror, lookupcmd \- control message parsing
  4. .SH SYNOPSIS
  5. .ft L
  6. .nf
  7. #include <u.h>
  8. #include <libc.h>
  9. #include <fcall.h>
  10. #include <thread.h>
  11. #include <9p.h>
  12. .fi
  13. .PP
  14. .ft L
  15. .nf
  16. .ta \w'\fL1234'u +\w'\fL12345678'u
  17. typedef struct Cmdbuf
  18. {
  19. char *buf;
  20. char **f;
  21. int nf;
  22. } Cmdbuf;
  23. typedef struct Cmdtab
  24. {
  25. int index;
  26. char *cmd;
  27. int narg;
  28. };
  29. Cmdbuf *parsecmd(char *p, int n)
  30. Cmdtab *lookupcmd(Cmdbuf *cb, Cmdtab *tab, int ntab)
  31. void respondcmderror(Req *r, Cmdbuf *cb, char *fmt, ...)
  32. .fi
  33. .SH DESCRIPTION
  34. These data structures and functions provide parsing of textual control messages.
  35. .PP
  36. .I Parsecmd
  37. treats the
  38. .I n
  39. bytes at
  40. .I p
  41. (which need not be NUL-terminated) as a UTF string and splits it
  42. using
  43. .I tokenize
  44. (see
  45. .IR getfields (2)).
  46. It returns a
  47. .B Cmdbuf
  48. structure holding pointers to each field in the message.
  49. It is the caller's responsibility to
  50. free this structure when it is no longer needed.
  51. .PP
  52. .I Lookupcmd
  53. walks through the array
  54. .IR ctab ,
  55. which has
  56. .I ntab
  57. entries,
  58. looking for the first
  59. .B Cmdtab
  60. that matches the parsed command.
  61. (If the parsed command is empty,
  62. .I lookupcmd
  63. returns nil immediately.)
  64. A
  65. .B Cmdtab
  66. matches the command if
  67. .I cmd
  68. is equal to
  69. .IB cb -> f [0]
  70. or if
  71. .I cmd
  72. is
  73. .LR * .
  74. Once a matching
  75. .B Cmdtab
  76. has been found, if
  77. .I narg
  78. is not zero, then the parsed command
  79. must have exactly
  80. .I narg
  81. fields (including the command string itself).
  82. If the command has the wrong number of arguments,
  83. .I lookupcmd
  84. returns nil.
  85. Otherwise, it returns a pointer to the
  86. .B Cmdtab
  87. entry.
  88. If
  89. .I lookupcmd
  90. does not find a matching command at all,
  91. it returns nil.
  92. Whenever
  93. .I lookupcmd
  94. returns nil, it sets the system error string.
  95. .PP
  96. .I Respondcmderror
  97. resoponds to request
  98. .I r
  99. with an error of the form
  100. `\fIfmt\fB:\fI cmd\fR,'
  101. where
  102. .I fmt
  103. is the formatted string and
  104. .I cmd
  105. is a reconstruction of the parsed command.
  106. Fmt
  107. is often simply
  108. .B "%r" .
  109. .SH EXAMPLES
  110. This interface is not used in any distributed 9P servers.
  111. It was lifted from the Plan 9 kernel.
  112. Almost any kernel driver
  113. .RB ( /sys/src/9/*/dev*.c )
  114. is a good example.
  115. .SH SOURCE
  116. .B /sys/src/lib9p/parse.c
  117. .SH SEE ALSO
  118. .IR 9p (2)