[#BN_mod_lshift]
= BN_mod_lshift
:mrdocs:

Compute r = (a << n) mod m (left‐shift then reduce).

== Synopsis

Declared in `<openssl/bn.h>`

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

== Return Value

1 on success, or 0 on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *r*
| Destination for the result.
| *a*
| Value to shift.
| *n*
| Number of bits to shift left; must be non‐negative.
| *m*
| Modulus; must be non‐zero.
| *ctx*
| BN_CTX for temporary storage.
|===


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