[#BN_mod_sub_quick]
= BN_mod_sub_quick
:mrdocs:

Compute `r` = (`a` ‐ `b)` mod `m` assuming 0 <= `a,b` < `m.`

== Synopsis

Declared in `<openssl/bn.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BN_mod_sub_quick(
    xref:BIGNUM.adoc[BIGNUM]* r,
    xref:BIGNUM.adoc[BIGNUM] const* a,
    xref:BIGNUM.adoc[BIGNUM] const* b,
    xref:BIGNUM.adoc[BIGNUM] const* m);
----

== Return Value

1 on success, or 0 on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *r*
| Destination (may alias `a` or `b).`
| *a*
| Minuend already reduced modulo `m.`
| *b*
| Subtrahend already reduced modulo `m.`
| *m*
| Modulus (must be positive).
|===


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