asn1_read_value(3)

1asn1_read_value(3)                 libtasn1                 asn1_read_value(3)
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NAME

6       asn1_read_value - API function
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SYNOPSIS

9       #include <libtasn1.h>
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11       int  asn1_read_value(asn1_node_const  root,  const  char * name, void *
12       ivalue, int * len);
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ARGUMENTS

15       asn1_node_const root
16                   pointer to a structure.
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18       const char * name
19                   the name of the element inside a structure that you want to
20                   read.
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22       void * ivalue
23                   vector  that  will contain the element's content, must be a
24                   pointer to memory cells already allocated (may be NULL).
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26       int * len   number of bytes of *value: value[0]..value[len-1]. Initialy
27                   holds the sizeof value.
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DESCRIPTION

30       Returns  the value of one element inside a structure.  If an element is
31       OPTIONAL and this returns ASN1_ELEMENT_NOT_FOUND, it  means  that  this
32       element  wasn't present in the der encoding that created the structure.
33       The first element of a SEQUENCE_OF or SET_OF is named "?1". The  second
34       one  "?2"  and  so  on. If the  root provided is a node to specific se‐
35       quence element, then the keyword "?CURRENT" is also acceptable and  in‐
36       dicates the current sequence element of this node.
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38       Note  that  there  can  be valid values with length zero. In these case
39       this function will succeed and  len will be zero.
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INTEGER

42       VALUE will contain a two's complement form integer.
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44       integer=-1  -> value[0]=0xFF , len=1.  integer=1   ->  value[0]=0x01  ,
45       len=1.
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ENUMERATED

48       As INTEGER (but only with not negative numbers).
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BOOLEAN

51       VALUE will be the null terminated string "TRUE" or "FALSE" and LEN=5 or
52       LEN=6.
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54       OBJECT IDENTIFIER: VALUE will be a null  terminated  string  with  each
55       number separated by a dot (i.e. "1.2.3.543.1").
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57       LEN = strlen(VALUE)+1
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UTCTIME

60       VALUE will be a null terminated string in one of these formats: "YYMMD‐
61       Dhhmmss+hh'mm'" or "YYMMDDhhmmss-hh'mm'".  LEN=strlen(VALUE)+1.
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GENERALIZEDTIME

64       VALUE will be a null terminated string in the same format used  to  set
65       the value.
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67       OCTET  STRING:  VALUE will contain the octet string and LEN will be the
68       number of octets.
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GENERALSTRING

71       VALUE will contain the generalstring and LEN  will  be  the  number  of
72       octets.
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74       BIT  STRING:  VALUE  will contain the bit string organized by bytes and
75       LEN will be the number of bits.
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CHOICE

78       If NAME indicates a choice type, VALUE will specify the alternative se‐
79       lected.
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ANY

82       If  NAME indicates an any type, VALUE will indicate the DER encoding of
83       the structure actually used.
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RETURNS

86       ASN1_SUCCESS if value is returned, ASN1_ELEMENT_NOT_FOUND if   name  is
87       not  a valid element, ASN1_VALUE_NOT_FOUND if there isn't any value for
88       the element selected, and ASN1_MEM_ERROR if The value vector isn't  big
89       enough to store the result, and in this case  len will contain the num‐
90       ber of bytes needed. On the  occasion  that  the  stored  data  are  of
91       zero-length  this function may return ASN1_SUCCESS even if the provided
92       len is zero.
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COPYRIGHT

95       Copyright © 2006-2022 Free Software Foundation, Inc..
96       Copying and distribution of this file, with  or  without  modification,
97       are  permitted in any medium without royalty provided the copyright no‐
98       tice and this notice are preserved.
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