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field: Document return value of fe_sqrt()

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Co-authored-by: Jonas Nick <jonasd.nick@gmail.com>
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Tim Ruffing 2023-06-15 11:49:35 +02:00
parent 67214f5f7d
commit 5779137457
1 changed files with 4 additions and 2 deletions
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src/field.h
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@ -267,8 +267,10 @@ static void secp256k1_fe_sqr(secp256k1_fe *r, const secp256k1_fe *a);
/** Compute a square root of a field element. /** Compute a square root of a field element.
* *
* On input, a must be a valid field element with magnitude<=8; r need not be initialized. * On input, a must be a valid field element with magnitude<=8; r need not be initialized.
* Performs {r = sqrt(a)} or {r = sqrt(-a)}, whichever exists. The resulting value * If sqrt(a) exists, performs {r = sqrt(a)} and returns 1.
* represented by r will be a square itself. Variables r and a must not point to the same object. * Otherwise, sqrt(-a) exists. The function performs {r = sqrt(-a)} and returns 0.
* The resulting value represented by r will be a square itself.
* Variables r and a must not point to the same object.
* On output, r will have magnitude 1 but will not be normalized. * On output, r will have magnitude 1 but will not be normalized.
*/ */
static int secp256k1_fe_sqrt(secp256k1_fe * SECP256K1_RESTRICT r, const secp256k1_fe * SECP256K1_RESTRICT a); static int secp256k1_fe_sqrt(secp256k1_fe * SECP256K1_RESTRICT r, const secp256k1_fe * SECP256K1_RESTRICT a);