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1.1 root 1: .TH CBT 3X
2: .CT 2 data_man
3: .SH NAME
4: bopen, bclose, bseek, bfirst, bkey, breclen, bread,
5: bdelete, bwrite \(mi compressed B-tree subroutines
6: .SH SYNOPSIS
7: .nf
8: .PP
9: .B #include <cbt.h>
10: .PP
11: .B "bfile *bopen(name, typ) char *name;"
12: .PP
13: .B "void bclose(b) bfile *b;"
14: .PP
15: .B "bseek(b, key) bfile *b; mbuf key;"
16: .PP
17: .B "bfirst(b) bfile *b;"
18: .PP
19: .B "mbuf bkey(b) bfile *b;"
20: .PP
21: .B "breclen(b) bfile *b;"
22: .PP
23: .B "bread(b, key, val) bfile *b; mbuf *key, *val;"
24: .PP
25: .B "bdelete(b, key) bfile *b; mbuf key;"
26: .PP
27: .B "bwrite(b, key, val) bfile *b; mbuf key, val;"
28: .fi
29: .SH DESCRIPTION
30: These functions manipulate
31: files of key/value records.
32: Such files are created by
33: .BR "cbt creat" ;
34: see
35: .IR cbt (1).
36: To load the functions use the
37: .IR ld (1)
38: option
39: .BR \-lcbt .
40: .PP
41: The records occur sorted
42: (increasing lexicographical order) by their keys,
43: which must be distinct.
44: Both keys and values are arrays of characters accessed through
45: the structure
46: .EX
47: .ta 8n +15n
48: .nf
49: \fLtypedef struct {
50: \fLchar *mdata;\fR address of data bytes
51: \fLshort mlen;\fP number of data bytes
52: \fL} mbuf;\fR
53: .fi
54: .EE
55: .PP
56: .I "Bopen"
57: attempts to open a named B-tree,
58: and if successful establishes a read pointer
59: pointing to the beginning of the file and
60: returns a pointer to be used
61: in calling the other routines.
62: .I Typ
63: is 0 for read-only or 2 for read-write.
64: .I Bopen
65: returns a descriptor that identifies the file to the other functions.
66: .PP
67: .I "Bclose"
68: closes a B-tree.
69: .PP
70: .I "Bseek"
71: positions the read pointer of the file
72: to the record whose key is
73: the first not less than
74: .IR key .
75: The routine returns 1 if
76: .I key
77: is in the file,
78: .B EOF
79: if
80: .I key
81: is greater
82: than any key in the file,
83: and 0 otherwise.
84: .PP
85: .I "Bfirst"
86: sets the read pointer to the beginning of the file.
87: It has the same error return as
88: .BR bseek .
89: .PP
90: .I "Bkey"
91: returns the current key.
92: The element
93: .I mdata
94: of the returned structure
95: is 0
96: on errors,
97: otherwise it points to a static buffer.
98: .PP
99: .I "Breclen"
100: returns the length of the value part of the current record.
101: .PP
102: .I "Bread"
103: reads the value at the read pointer into the space
104: pointed to by
105: .B val->mdata,
106: places its length in
107: .LR val->mlen ,
108: and advances the read pointer
109: to the record with the next greater key.
110: If
111: .I key
112: is not 0
113: the key of the record is read into the
114: space pointed to by
115: .B key->mdata
116: and its length is placed in
117: .BR key->mlen .
118: .I Bread
119: returns 0
120: if successful.
121: .PP
122: .I "Bdelete"
123: removes the record with the given key,
124: returning 1 if the record was found,
125: \-1
126: if there was an error, and 0
127: otherwise,
128: The read pointer is left undefined.
129: .PP
130: .I "Bwrite"
131: writes the given value with the given key.
132: An existing record with that key will be replaced.
133: The read pointer is left undefined.
134: .SH FILES
135: .F \fIname\fP.T
136: .br
137: .F \fIname\fP.F
138: .SH SEE ALSO
139: .IR cbt (1),
140: .IR dbm (3)
141: .SH DIAGNOSTICS
142: Routines which return pointers return 0
143: on errors,
144: routines which return integers return \-1.
145: .SH BUGS
146: The length of any key is limited to 255.
147: .br
148: The
149: .B mbuf
150: arguments are passed inconsistently to the routines,
151: sometimes by value and sometimes by reference.
152: .br
153: .I Cbt
154: files are not directly portable between big-endian and
155: little-endian machines.
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