make headers work in C++
add two more variable length integer encoding functionsmaster
leitner
13 years ago
parent
d17c2d1012
commit
4f1e1d300c
@ -0,0 +1,18 @@
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.TH fmt_asn1dertag 3
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.SH NAME
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fmt_asn1dertag \- encode unsigned integer like ASN.1 DER tag
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.SH SYNTAX
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.B #include <fmt.h>
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size_t \fBfmt_asn1dertag\fP(char *\fIdest\fR,unsigned long long \fIsource\fR);
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.SH DESCRIPTION
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fmt_asn1dertag encodes an unsigned integer using the ASN.1 DER for
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encoding tag. This takes one byte for every 7 bits in the number.
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If \fIdest\fR equals FMT_LEN (i.e. is NULL), fmt_asn1dertag returns the
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number of bytes it would have written.
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For convenience, fmt.h defines the integer FMT_ASN1TAG to be big
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enough to contain every possible fmt_asn1dertag output.
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.SH "SEE ALSO"
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scan_asn1dertag(3)
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#include "fmt.h"
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/* write int in least amount of bytes, return number of bytes */
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/* as used in ASN.1 DER tag */
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size_t fmt_asn1dertag(char* dest,unsigned long long l) {
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/* encoding is either l%128 or (0x80+number of bytes,bytes) */
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size_t n=0,i;
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unsigned long long t;
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for (t=l, n=1; t>0x7f; t>>=7) ++n;
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for (i=0; i<n; ++i) {
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if (dest) dest[n-i-1]=((i!=0)<<7) | (l&0x7f);
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l>>=7;
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}
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return i;
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}
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@ -1,20 +1,20 @@
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.TH scan_asn1length 3
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.TH scan_asn1derlength 3
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.SH NAME
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scan_asn1length \- decode an unsigned integer from ASN.1 DER length encoding
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scan_asn1derlength \- decode an unsigned integer from ASN.1 DER length encoding
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.SH SYNTAX
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.B #include <scan.h>
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size_t \fBscan_asn1length\fP(const char *\fIsrc\fR,size_t \fIlen\fR,unsigned long long *\fIdest\fR);
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size_t \fBscan_asn1derlength\fP(const char *\fIsrc\fR,size_t \fIlen\fR,unsigned long long *\fIdest\fR);
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.SH DESCRIPTION
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scan_asn1length decodes an unsigned integer in ASN.1 DER length encoding
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scan_asn1derlength decodes an unsigned integer in ASN.1 DER length encoding
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from a memory area holding binary data. It writes the decode value in
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\fIdest\fR and returns the number of bytes it read from \fIsrc\fR.
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scan_asn1length never reads more than \fIlen\fR bytes from \fIsrc\fR. If the
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scan_asn1derlength never reads more than \fIlen\fR bytes from \fIsrc\fR. If the
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sequence is longer than that, or the memory area contains an invalid
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sequence, scan_asn1length returns 0 and does not touch \fIdest\fR.
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sequence, scan_asn1derlength returns 0 and does not touch \fIdest\fR.
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The length of the longest ASN.1 DER length sequence is 128 bytes. In
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practice the largest sequence is sizeof(*dest)+1.
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.SH "SEE ALSO"
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fmt_asn1length(3)
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fmt_asn1derlength(3)
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.TH scan_asn1dertag 3
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.SH NAME
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scan_asn1dertag \- decode an unsigned integer from ASN.1 DER length encoding
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.SH SYNTAX
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.B #include <scan.h>
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size_t \fBscan_asn1dertag\fP(const char *\fIsrc\fR,size_t \fIlen\fR,unsigned long long *\fIdest\fR);
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.SH DESCRIPTION
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scan_asn1dertag decodes an unsigned integer in ASN.1 DER tag encoding
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from a memory area holding binary data. It writes the decode value in
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\fIdest\fR and returns the number of bytes it read from \fIsrc\fR.
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scan_asn1dertag never reads more than \fIlen\fR bytes from \fIsrc\fR. If the
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sequence is longer than that, or the memory area contains an invalid
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sequence, scan_asn1dertag returns 0 and does not touch \fIdest\fR.
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The length of the longest ASN.1 DER length sequence is 128 bytes. In
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practice the largest sequence is sizeof(*dest)+1.
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.SH "SEE ALSO"
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fmt_asn1dertag(3)
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#include "scan.h"
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size_t scan_asn1dertag(const char* src,size_t len,unsigned long long* length) {
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size_t n;
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unsigned long long l=0;
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for (n=0; n<len; ++n) {
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l=(l<<7) | (src[n]&0x7f);
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if (!(src[n]&0x80)) {
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*length=l;
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return n+1;
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}
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}
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return 0;
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}
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